Three previous blogs 123 looked at inspirational videos from the H.O.P.E. Project. In this blog, another video from the same producers covers the story of a 51-year old man, Marc Ramirez, who “cured” his diabetes with a WFPB diet.
He was able to dump all his medications and get rid of all the usual symptoms of diabetes – including the frequently experienced side-effect of erectile dysfunction. All down to the power of plants!
About Marc Ramirez
Marc Ramirez’s family were plagued by diabetes, diagnosed himself in 2002 he was told by his doctor that he’d need to take medication for the rest of his life. After hearing about the benefits of a wholefood plant-based diet in 2011, Marc and his wife Kim decided to give it a go.
His health and their sex life haven’t been the same since…
H.O.P.E. The Project – Healing Of Planet Earth
The H.O.P.E. Project 4 tries to inform people about the endless benefits of a wholefood, plant-based diet and to inspire them to adopt a conscious, sustainable and kind lifestyle.
H.O.P.E.’s 3 main aims
1. Live a healthy and long life
Eating a wholefood plant-based diet without animal products has the potential to prevent and reverse diseases and obesity, which improves our health and longevity.
2. Conserve nature and the environment
A plant-based diet (ideally organic) conserves natural resources, saves biodiversity and helps to reduce our ecological footprint.
3. Protect animals
The lives of countless species of animals are affected by the food we eat. Choosing to eat a WFPB diet goes hand in hand with efforts to promote a more peaceful world in which people understand that all living beings are entitled to compassion, dignity and life.
The above aims seem pretty sound to me and, without too much doubt, appear to be the most effective way each of us can promote optimal health, preserve the environment, and protect animals – all by simply changing our dietary habits.
In Part One we looked at various aspects of how our intestinal microbiota was affected by the food we put in our mouths, particularly with regard to variations that occur between plant- and meat-based diets and in relation to the macronutrient, carbohydrate. In Part Two, we’ll take a look at the microbial effects of the other two macronutrients:
In previous blogs 2345 , we’ve looked in great detail at the effects of protein (both animal and plant) on human health. Studies mentioned in the latter blogs have shown how consumption of animal protein (especially in large quantities) is associated with a wide range of common diseases.
When it comes to the effects of protein on gut microbes, the majority of studies suggest 6 that plant protein consumption has a strongly positive correlation with improved healthy microbial diversity.
The following bacteria are commonly increased in number within the gut microbiota of those individuals consuming a high animal protein diet:
The latter are bile-tolerant microbes11 . Bile increases when animal-protein consumption increases, when compared with increased plant-protein consumption, so it’s no surprise that a meat-based diet will mean that bile-tolerant microorganisms will increase in number 12 .
On the other hand, the following bacteria are commonly decreased in number within the gut microbiota of those individuals consuming a high animal protein diet:
The latter are important for metabolising dietary plant polysaccharides16 . Again, it’s no surprise that these plant polysaccharide-loving bacteria will frequent the guts of plant-eaters.
It’s a zero-sum game
Another factor which needs to be taken into account is that diet is a zero-sum 17 game: the more protein in your diet, the less room there is for healthy plant carbohydrate. The result of this will be a decrease in butyrate-producing bacteria, and thus an increase in the proinflammatory bodily state and an increased risk of colorectal cancer 18 .
When individuals have eaten pea protein, for instance, it’s been shown 6 that there is a corresponding increase in beneficial Bifidobacterium and Lactobacillus, while the pathogenic Bacteroides fragilis and Clostridium perfringens reduce. The result of this is that there is an increase in intestinal SCFA levels (more on SCFAs below). The latter study drew the conclusion that eating plant-derived proteins reduces mortality when compared with eating animal-derived proteins.
Both quantity and quality of consumed fat have been shown 18 to have significant impact on the composition of gut microbiota.
When you eat a plant-based diet (and here we’re talking about whole, unprocessed plant foods), it will be naturally low in fat. This favours the beneficial Bifidobacteria19 .
The fats from a plant-based diet are made up of mainly mono and polyunsaturated fats. On a phyla level, the result of this is that the Bacteroidetes:Firmicutes ratio20 increases, while on the genera level, lactic acid bacteria (Bifidobacteria and Akkermansia muciniphila) increase 6 .
Nuts about gut bacteria
Previous blogs 21 looked at how walnuts are particularly good plant-based sources of omega-3 fatty acids (the ALA within them being converted to DHA and EPA within our bodies); however, it doesn’t stop there. Walnuts, and other nuts in general, have been shown 22 to increaseRuminococcaceae and Bifidobacteria while, at the same time, decreasingClostridium species.
Saturated fat & your guts
Whilst coconut contains unusually high levels of saturated fat for a plant food, saturated fat is almost exclusively found in animal foods.
Studies suggest 23 that saturated fat activates systemic inflammation (by inducing pro-inflammatory cytokines such as IL-1, IL-6 and TNF-α) and thus makes us much more vulnerable to systemic infections 24 and metabolic disorders 25 , such as type 2 diabetes and obesity.
Consuming high levels of saturated and trans fats – something increasingly common in the Western diet – increases the risk of cardiovascular disease and has been shown 626 to:
Polyphenols are secondary metabolites of plants and are generally involved in defence against ultraviolet radiation or aggression by pathogens 30 . These and other naturally occurring plant metabolites in plant foods have been shown to provide cardiovascular protection 6 as well as both anti-inflammatory and anti-pathogenic effects 31 .
In plant foods, polyphenols increase:
Whilst all plants have polyphenols, some of the most common polyphenol-rich foods include:
cocoa products, and
*N.B. The many negatives associated with alcohol consumption per se (for both gut health 32and general health 33) suggest that the small quantities of polyphenols in wine are insufficient reason to drink the stuff.
Spice up you guts
Spices and herbs are also very high in antioxidant polyphenols 34 , although the quantities that one can consume are, of course, limited.
And, of course, it’s widely known that tea contains high levels of polyphenols (including catechins, theaflavins, tannins, and flavonoids). Tea consumption increases Bifidobacterium and Lactobacillus–Enterococcus spp., something which appears 35 to result in increased SCFA production within human microbiota.
Part One introduced this relatively new term. The postbiotics we’ll look at here are SCFAs, phytoestrogens, isothiocyanates, aryl-hydrocarbon receptor ligands, Coprostanol and secondary bile acids, trimethylamine N-oxide (TMAO), and vitamins.
It’s important to understand the difference between prebiotics36 /probiotics37 on the one hand, and postbiotics, on the other. Basically, prebiotics (e.g. indigestible fibre) are put into the mouth and swallowed; probiotics are the microbes themselves which exist within the gut, but can also be consumed as dietary supplements; whilst postbiotics are the products of microbial activity within our guts.
Both prebiotics and postbiotics are, of course, vital for health. And to clarify once again: Probiotics are microbes that exist already in the GI tract, awaiting prebiotics (the substrate or source material). The products resulting from microbial activity are postbiotics – metabolites that research is showing are of fundamental importance for pretty much every functional system within the host (you and me) – from the gut-brain, gut-lung, and gut-liver axes, to immunoprotection38 and mental health. 394041
The various systems within our bodies are linked with each other via communication mechanisms that stem from the microbial products/metabolites (postbiotics) produced from the nutrients we ingest. As it happens, some products are diet-independent (for instance, lipopolysaccharides42 , ribosomally synthesised and post-translationally modified peptides43 etc.). We’ll set aside these diet-independent postbiotics, and look, instead, at the diet-dependent postbiotics mentioned above.
Location, location, location
The complexity of the human digestive system never fails to amaze. Not only do different foods encourage different microbes to produce different end products, but different locations along the intestinal tract result in different bioactive molecules being produced from the different prebiotics and nutrients 3944 .
Diet & postbiotics
The type of food you eat is shown 45 to determines the range of postbiotic positive health effects that you enjoy, including:
Postbiotic effects derive from a range of factors, including:
modulation of gene expression
We’ll now look at the most well-known probiotics – i.e. SCFAs, phytoestrogens, isothiocyanates, aryl-hydrocarbon receptor ligands, Coprostanol and secondary bile acids, trimethylamine N-oxide (TMAO), and vitamins.
Short-Chain Fatty Acids (SCFAs)
The SCFAs acetate, propionate, and butyrate are mostly microbial metabolites of fermented fibre and other carbohydrates, although a tiny fraction does derive from proteins. Levels of these SCFAs significantly increases when a person begins to eat a plant-based diet 48 .
One of the roles of SCFAs is to act as a substrate for the maintenance of healthy colonic epithelium 49 . There is a correlation 50 between plant-based food consumption and improved epithelium health. Maintaining this intestinal barrier prevents endotoxemia51 and subsequent inflammatory effects 5253 .
Specific gut microbes are predisposed to produce SCFAs, and different bacteria produce different SCFAs, such as:
acetate is produced by enteric bacteria54 , such as:
Gluconeogenesis (GNG) is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates, such as protein and fat – and reverses the energy-production process of glycolysis. It provides the body’s cells with energy if carbohydrate stores are depleted. The SCFA, propionate acts as a gluconeogenic substrate in both the liver and intestine 55 . As well as helping to provide energy stores for the body, SCFAs are increasingly thought to play important roles as signalling molecules 65 .
The beauty of butyrate
A previous blog 66 looked in some detail at butyrate. This SCFA, and the bacteria which produce it, are becoming increasingly accepted 55 as being highly beneficial to human health, including:
acting as a major carbon source for colonocytes 67
helping to regulate critical intestinal functions, such as 6869 :
The foregoing barely scratches the surface of the vast range of functions and interactions of SCFAs; but the take-home message is that diets rich in fibre seem to provide huge benefits to both the intestine and overall health.
Phytoestrogens are plant-derived polyphenols that interact with oestrogen receptors with either agonist or antagonist actions 72 . They are found in various plant foods (e.g. seeds, grains, beans) and are concentrated in flax and soy – and, oddly enough, beer – the reason that beer-swilling men develop man boobs 73 .
Phytoestrogens appear 74 to have significant health-promoting properties. Research 757677 has shown them to be:
protective against cardiovascular disease
protective against osteoporosis and amyloid formation78
Phytoestrogens have around a 1% bioavailability 79 , and so lots of them are able to get down to the gut. This is important because increasing evidence 8081 suggests that the above positive health effects are only reached after bioactivation of the polyphenols by gut microbiota.
The players in polyphenol metabolism
As with most aspects of nutritional science, knowledge is limited about how many microbes are involved in polyphenol metabolism. However, the following are currently known 4581 to be involved in the following process:
converting polyphenols to equol82 , urolithins83 , and enterolignans84 :
Coriobacteriaceae, Eubacterium and other species appear to be responsible for various other polyphenol transformations.
It works both ways
There’s a bidirectional relationship between gut microbiota and polyphenols 8586 . That is, gut bacteria produce microbial metabolites (postbiotics) from polyphenols, and, in turn, these postbiotics act as prebiotics for various gut bacteria. The net result of this postbiotic production (especially the production of urolithins) encourages the growth of Lactobacillus and Bifidobacterium.
Sulforaphane, discussed in detail in a previous blog 87 in relation to the incredible health-giving power of broccoli, is perhaps the most extensively studied isothiocyanate – that is, a compound converted enzymatically from particular plant components called glucosinolates88 . Isothiocyanates can be derived from cruciferous89 or brassica90 vegetables. The latter are rich sources of glucosinolate, the precursor of isothiocyanates.
The following gut bacteria are largely responsible for facilitating the conversion of the glucosinolates in plant foods to the isothiocyanates our bodies need:
certain Peptostreptococcus spp., and
These bacteria secrete their own myrosinase enzyme91 in order to metabolise the glucosinolates to isothiocyanates 92 .
Health benefits of isothiocyanates
Isothiocyanates are metabolites which are thought 9394 to have a range of health-benefiting properties, including being:
In terms of diet, intestinal aryl-hydrocarbon receptor96ligands97 are mainly derived from eating plant food, especially cruciferous vegetables. Once again, gut bacteria are responsible for producing these AHRLs.
Using aryl-hydrocarbon receptors, these ligands are able to promote gut homeostasis and intestinal immune function 98 , as well as xenobiotic99 detoxification and maintenance of energy metabolism, including lipid metabolism.
AHRLs and fat
A plant-based diet appears to be better at maintaining an appropriate level of AHRLs, while a high-fat diet appears to decrease the number of aryl-hydrocarbon receptor ligands. A decrease in either aryl-hydrocarbon receptors or in the associated ligands appears to compromise the healthy maintenance of intraepithelial lymphocytes100 and the ability to control microbial load and composition. This can result in increased immune activation which can, in turn, cause epithelial damage 101 .
The result of this negative process can be gut permeability and inflammation. Both of these can promote the development of metabolic syndrome. Interestingly, some research suggests 98102 that when metabolic syndrome is produced because of this process, the condition can be improved by supplementing the diet with a probiotic – namely, a strain of Lactobacillus.
Coprostanol and secondary bile acids
Dietary cholesterol is only found in animal-derived foods and, when consumed, it gets broken down in the gut by bacteria. The two resulting cholesterol metabolites (postbiotics) are coprostanol103 and secondary bile acids.
Coprostanol is poorly absorbed by the human intestine after being isolated from cholesterol by several strains of gut bacteria. This is a good thing as far as cardiovascular disease risk is concerned, since it means that serum cholesterol in the host is reduced, with the coprostanol mostly being excreted in faeces rather than being absorbed back into the bloodstream 104105 .
The situation is somewhat different when it comes to the other cholesterol postbiotic, secondary bile acids. One of the major uses of cholesterol is in the synthesis of bile acids in the liver. Bile acids are, of course, essential for the absorption of fat from the contents of the intestine; however, when the gut microbiota convert the bile acids synthesised from cholesterol into secondary bile acids106 , they can be absorbed into the bloodstream and find their way into various tissues within the body. This is a problem.
Being hydrophobic107 , these secondary bile acids are thought 108 capable of causing direct damage to cell membranes and inducing the generation of reactive oxygen species resulting in DNA damage, apoptosis109 , and necrosis110 . Additionally, it’s believed 10444 that secondary bile acids are involved in maintaining the equilibrium of health and disease – being associated with inflammatory bowel disease, colon and liver cancer.
Trimethylamine N-Oxide (TMAO)
Trimethylamine N-oxide (TMAO) is a molecule generated from choline111 , betaine112 , and carnitine113 via gut microbial metabolism. TMAO is associated with cardiovascular and neurological disorders. Carnitine and choline, precursors of TMAO, are mostly found in foods of animal origin (e.g. eggs, beef, pork), with lower amounts found in beans and fish 114 .
Diets containing animal proteins and fats (particularly red meat) tend to have decreased numbers of Bifidobacterium and increased numbers of L-Ruminococcus, Bacteroides, Alistipes, Ruminococcus, Clostridia, and Bilophila. Such diets are associated with elevated levels of TMAO 48 and, thereby, increased risk of cardiovascular disease and inflammatory bowel disease 236 .
The reason plant-eaters have a different gut microbiota composition to omnivores is that they have a reduced capacity to produce trimethylamine (TMA), the precursor to TMAO 115 . This reduced capacity appears to be due to both a reduction in the number of enzymes responsible for converting TMA to TMAO and to the general remodelling of gut microbiota that results from eating a plant-based diet.
We finally come to the gut microbiota which are essential for producing and maintaining adequate vitamin levels within our bodies.
Not a lot of people know this, but our gut microbes produce or process several vital vitamins 93 :
menaquinone (vitamin K2)
thiamine (vitamin B1)
riboflavin (vitamin B2)
niacin (vitamin B3)
pantothenic acid (vitamin B5)
pyridoxine (vitamin B6)
biotin (vitamin B7)
folate (vitamin B9)
cobalamin (vitamin B12*)
* N.B. vitamin B12, while being produced by gut bacteria, is not absorbed back in to the body. This means that vitamin B12 needs to be taken as a supplement by vegans and, arguably, by most other people irrespective of their dietary choices. This is discussed in great detail in previous blogs116117118119 .
Different bacteria possess specific biosynthetic properties for different vitamins, such as:
Bifidobacterium – vitamins K, B1, B7, B9, and B12
Bacillus subtilis and Escherichia coli – riboflavin120
The latter is by no means a comprehensive analysis of the relationship between intestinal bacteria and vitamin production/processing; but it does provide a brief insight into one more essential role played by the microbes that live within us.
It’s thought that, on average, around 25% of the plasma metabolites resulting from gut microbial activity are different between omnivores and vegans, with current research consistently indicating that diet is the essential factor for the composition and health of human gut microbiota. In turn, this is vital for metabolising the nutrients we consume into postbiotics that our bodies need.
All known research continues to suggest that a plant-based diet may be the most effective way of promoting a diverse ecosystem of beneficial microbes that can support overall health. Nutrition is a complex field, with inter-individual differences abounding. This means that further research is necessary if we are every going to be able to fully characterise the interactions between microbiome, diet and health.
But, in the meantime, it looks like you’d be doing your overall health a huge favour if you choose to…
Prebiotics are compounds in food – largely indigestible fibre – that induce the growth or activity of beneficial microorganisms such as bacteria and fungi. The most common example is in the gastrointestinal tract, where prebiotics can alter the composition of organisms in the gut microbiome. [↩]
Probiotics are live microorganisms intended to provide health benefits when consumed, generally by improving or restoring the gut flora. [↩]
The immune system protects against invasion by foreign substance – and antigen – that can cause the body to produce antibodies. [↩]
Lipopolysaccharides (LPS), also known as lipoglycans and endotoxins, are large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria. [↩]
Ribosomally synthesised and post-translationally modified peptides (RiPPs), also known as ribosomal natural products, are a diverse class of natural products of ribosomal origin. [↩]
Endotoxins are part of the outer membrane of the cell wall of Gram-negative bacteria. Endotoxemia is the presence of endotoxins in the blood. If these are derived from gram-negative rod-shaped bacteria, they may cause haemorrhages, necrosis of the kidneys, shock, etc. [↩]
Microglia are a type of neuroglia (glial cell) located throughout the brain and spinal cord. Microglia account for 10–15% of all cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune defense in the central nervous system (CNS). [↩]
Thermogenesis is a metabolic process during which your body burns calories to produce heat. Several factors induce thermogenesis in your body including exercise, diet and environmental temperature. Thermogenesis can promote weight loss because it increases your body’s calorie burn. [↩]
In general, amyloid formation, or amyloidosis, is caused by the buildup of an abnormal protein called amyloid. Amyloid is produced in bone marrow and can be deposited in any tissue or organ. The antibodies that get produced are deposited in tissues as amyloid, interfering with normal function. [↩]
Equol is an isoflavandiol oestrogen metabolised from daidzein, a type of isoflavone found in soybeans and other plant sources, by bacterial flora in the intestines. While endogenous oestrogenic hormones such as estradiol are steroids, equol is a nonsteroidal oestrogen. [↩]
Urolithins are the major metabolites of polyphenols in the gut, being produced by bacteria when breaking down foods such as pomegranates, nuts and berries. Urolithins have been studied for their antioxidant, antiinflammatory, antioestrogenic properties and their anticancer effects. [↩]
Enterolignans are one of a wide range of lignans found in plants. Plant lignans can be converted by various intestinal bacteria to enterolignans, enterodiol and enterolactone. Enterolignans have a variety of biologic activities, including tissue-specific oestrogen receptor activation, and antiinflammatory and apoptotic effects, that may influence disease risk in humans. [↩]
Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. [↩]
Cruciferous vegetables include plants such as bok choi, broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, kale, kohlrabi, mustard, radish, rutabaga, turnip, and watercress. [↩]
The brassica (or Brassicaceae) family can also be called the Cruciferae family. They are a taxonomic family which includes many genera and cultivars. The brassica family takes its alternative name (Cruciferae, New Latin for “cross-bearing”) from the shape of their flowers, whose four petals resemble a cross. [↩]
Myrosinase enzymes, such as thioglucoside glucohydrolase, sinigrinase, and sinigrase, is a family of enzymes involved in plant defence against herbivores. Its known biological function is to catalyse the hydrolysis of a class of compounds called glucosinolates. [↩]
Cytoprotection is a process by which chemical compounds provide protection to cells against harmful agents. For example, a gastric cytoprotectant is any medication that combats ulcers not by reducing gastric acid but by increasing mucosal protection. [↩]
The aryl hydrocarbon receptor is a protein that in humans is encoded by the AHR gene. The aryl hydrocarbon receptor is a transcription factor within cells to regulate gene expression. [↩]
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. For instance, in protein-ligand binding, the ligand is usually a molecule which produces a signal by binding to a site on a target protein. [↩]
A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual. [↩]
Intraepithelial lymphocytes (IEL) are lymphocytes found in the epithelial layer of mammalian mucosal linings, such as the gastrointestinal (GI) tract and reproductive tract. [↩]
Coprostanol is the major sterol in human faeces, and has been routinely studied as a marker of (modern) sewage pollution in marine and lacustrine sediments. This has led to the search for coprostanol in archaeological soils, in order to detect the presence of faecal material. [↩]
Secondary bile acids (or salts) result from the secretion of primary bile acids into the lumen of the intestine. Bacteria partially dehydroxylate them and remove the glycine and taurine groups. The primary bile acids, cholic acid and chenodeoxycholic acid, are converted into the secondary bile acids, deoxycholic acid and lithocholic acid, respectively. [↩]
Hydrophobic molecules and surfaces repel water. Hydrophobic liquids, such as oil, will separate from water. Hydrophobic molecules are usually nonpolar, meaning the atoms that make the molecule do not produce a static electric field. [↩]
Apoptosis is the death of cells which occurs as a normal and controlled part of an organism’s growth or development. [↩]
Necrosis is the death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply. [↩]
Choline is particularly rich in eggs, liver, and peanuts, and is also found in meat, poultry, fish, dairy foods, pasta, and rice. [↩]
Betaine is a metabolite of choline and is a nonessential nutrient found in numerous food sources, including sugar beets, wheat bran, rye grain, bulgar grain, spinach, quinoa, brown rice, sweet potato, turkey breast, beef, veal and some seafood, such as shrimp. [↩]
Red meat contains the highest level of carnitine. It is also found in smaller amounts in chicken, milk and dairy products, fish, beans, and avocado. Vegans tend to get less carnitine from foods, and their bodies usually produce enough naturally without requiring any from their diet. [↩]
What happens “down below” in our intestines is of such vital importance to our health that I’ve previously covered aspects of this subject in relation to a variety of specific subjects, such as alcohol 1 , obstructive sleep apnea 2 , depression 3 , physical activity 4 , and multiple sclerosis 5 . However, a new review 6 just published puts more meat on the bone – or more fruit on the tree!
The review looks at how the food we put in our mouths determines the type and quantity of our gut flora (also known as gut bacteria, microbes, microbiota or microbiome) and, in turn, how these dietary choices affect the direct and indirect actions performed by these vital microscopic inhabitants of our bodies.
This is Part One of a two part blog on this study. Here, we’ll look at the types and activities of microbes found in the intestinal microbiome of those eating plant- and meat-based diets, finally focusing on the microbial effects of consuming the macronutrient, carbohydrate.
In Part Two, we’ll look at the microbial effects of the other two macronutrients (protein and fat), polyphenols, and the influence on human health of microbiome postbiotics7 derived from such things as vitamins and TMAO.
Definition of terms
“Microbiota”and “microbiome” tend to be used interchangeably; however, “microbiota” refers to the total of all microbial taxa associated with humans (including bacteria, viruses, fungi, protozoa and archaea), while “microbiome” refers to the complete catalogue of microbes plus all their genes.
Each human’s gut microbiota is estimated 8 to consist of over 3 trillion microbes – although I don’t know if anyone has actually sat down and counted them…
The human gut microbiome consists of around 3.3 million non-redundant9 microbial genes. Amazingly, this is much more than our human genome, which only contains around 21,000 genes. So there are around 150 distinct microbial genes in our guts for every one of our human genes 10 .
Omnivore vs plant-based microbiota
Previous blogs 1112 have looked at the evidence for significant differences between the microbiota of meat eaters and plant eaters. Plant-based diets appear to promote the development of more diverse and stable microbial systems, with significantly more Bacteroidetes-related operational taxonomic units compared to omnivores.
Important components of a plant-based diet include:
Fibre (non-digestible carbohydrates that are only found in plants) increase lactic acid bacteria (e.g. Roseburia, Ruminococcus, and E. rectale) while reducing certain pathogenic bacteria (e.g. Clostridium and Enterococcus species). Lactic acid bacteria can help improve lactose digestion, prevent and treat diarrhoea, and act on the immune system, helping the body to resist and fight infection.
SCFAs (short-chain fatty acids) have a plethora of health benefits. A diet high in fibre encourages species that ferment fibre into metabolites in the form of SCFAs (such as acetate, propionate and buyrate). We previously looked in detail at butyrate 13 and saw how such bacteria-produced SCFAs can improve immunity against pathogens, increase the integrity of the blood–brain barrier, provide energy substrates, and regulate critical intestinal functions.
And it’s not just SCFAs that mark the difference between plant- and meat-based diets – for instance, the former contains phytoestrogens, and isothiocyanates such as sulforaphane 14 , whilst the latter contains TMAO 15 and secondary bile acids 16 . These and other basic constituents of each diet will determine the type of gut bacteria that can survive within your body. We’ll look at the latter in more detail in Part Two.
Polyphenols (again, only found in plants) increase bacteria species which can provide anti-pathogenic/anti-inflammatory properties as well as cardiovascular protection (e.g. Bifidobacterium and Lactobacillus).
It’s no surprise, then, that a diet which is high in the foregoing will likely result in a diverse ecosystem of beneficial bacteria that supports the health of the host – that is, you and me.
Diversity & distribution matter
Plant-based diets also appear to promote good health by developing a richer, more diverse gut microbial system, and/or by producing an even distribution of a variety of species 1718 .
Microbiome is a separate “organ”
The range of functions of the human gut microbiome is so wide-ranging (immunity, gastrointestinal, brain, cardiovascular systems, cellular and genetic activity) that it’s increasingly common for researchers to regard it as a distinct “organ” within the human body.
Three basic bacterial enterotypes
Several studies 1920 have suggested that there are three basic bacterial enterotypes21 :
genus Prevotella (largely anti-inflammatory and protective)
genus Bacteroides (more pro-inflammatory and possible associations with heightened risk of metabolic syndrome and other pathological conditions)
genus Ruminococcus (whose biological significance is still largely unclear)
The effects of imbalanced gut microbiota
Imbalanced gut microbiota has been linked 22232425 with a surprisingly large number of conditions, including the following:
Because of the amount of evidence being accumulated in support of the role of our gut microbiota in acting as a mediator of dietary impact on the host metabolic status, an increasing amount of research is being focused on establishing causal relationships in individual people between the food they eat, what it does to their gut microbiota and the consequent effects on their overall health. It’s anticipated that this will allow for the development of therapeutic interventions such as personalised nutrition (18).
One such study concludes: “Convincing accumulating evidence shows that the human gut microbiota contributes to many aspects of human health via molecular pathways that we only begin to understand. The GI microbiota entertains deep mutualistic relationships and co-evolves with the human host, albeit at a much faster rate and demonstrates deep ecological links with the host which are being studied at the interface between Biology, Ecology, and Medicine. Experimental probing of the deep and reciprocal ties characterizing the microbiota-host relationship constitutes a formidable challenge, yet holds the promise to shed light on unknown aspects of human and microbial physiology and novel therapeutic possibilities in the manipulation of microbiota composition via antibiotics, probiotics, and microbial transplantation.” 42
Microbiota and postbiotics
The term “postbiotics” is relatively new. It refers to the vast range of compounds (metabolites) produced by the metabolic activity of our gut bacteria depending, to a large extent, on what nutrients they receive from the diet we eat. These probiotic-produced postbiotic compounds play vital roles in the regulation, not only of the host’s health, but also in the maintenance of a healthy gut microbiome.
The postbiotics produced by probiotic bacteria appear to be responsible for many of the beneficial effects claimed for probiotics.
N.B. In most cases, it can be argued that a healthy and balanced WFPB diet will provide all the natural probiotics you need without having to resort to commercially-produced stuff with dubious effectiveness or, indeed, safety. 4344 Whole plants are covered with bacteria that have been interacting effectively with our bodies for millions of years; and the postbiotics produced by microbes inside vegetarians/vegans have been shown 45 to be particularly effective in reducing various risk factors for chronic inflammation and chronic degenerative diseases.
What determines gut microbiota composition?
Variations in microbiota composition from one person to another are likely to be a combination of the following:
regulation of gene expression of the host and/or his/her microbiota 5145
Gut Microbiota – Why diversity matters
Microbial diversity associated with plant-based diets – particularly seen in research on long-term fruit, vegetable and whole grain intake 5253 – appears to have important associations with many health indicators, including:
Dietary changes are shown 56 to have relatively rapid impact (within a week) on microbial composition and, hence, on the effects of their metabolites. However, it’s important to note that these effects can be modest and reversible if the individual reverts to their prior dietary habits 51 .
One study showed 57 that changes in microbiota and associated immune parameters after just 3 months on a vegetarian (not a WFPB or vegan) diet can be pretty significant; but these changes pale into comparison when compared with the degree of change that occurs with a long-term plant-based diet.
Microbial “stress” and high-fibre diets
Whilst high-fibre diets are excellent for gut health, there is a suggestion that microbes may experience stress at the point when a sudden change from low- to high-fibre diets takes place. One indicator of such stress is an increase in Enterobacteriaceae, known as a pathogenic species of bacteria. Short-term dietary interventions which increase fibre consumption were shown to cause a slight but significant decrease in diversity, possibly associated with a slight but, once again, significant increase in Enterobacteriaceae – a species which is typically lower in vegan compared with omnivorous diets 58 .
This is probably the case because of the fact that longer-term dietary habits that favour high-fibre foods are known to produce greater amounts of butyrate-producing bacteria, which lower the colonic pH and, thus, prevent the growth of pathogenic bacteria, such as Enterobacteriaceae 59 .
Obesity & reduced microbial diversity
Studies have shown 60 reduced microbial diversity in obese individuals. In addition, it was shown that obese individuals have a reduction in the Bacteriodetes:Firmicutes ratio – that is, increased numbers of Bacteriodetes and decreased numbers of Firmicutes (more on this ratio below), an increase in Proteobacteria (a pro-inflammatory phylum), and an increase in C-reactive protein (which is inversely correlated with a healthy Bacteriodetes:Firmicutes ratio – that is, more C-reactive protein means a less favourable Bacteriodetes:Firmicutes ratio).
It’s possible to see quite the opposite results when looking at the ~60,000 participants in the Adventist Health Study-2 61 . The individuals who followed a vegan diet shown the lowest BMI values when compared with vegetarians or omnivores. The suggestion followed that the lower body weight associated with vegan diets might produce a microbial diversity which protects against systemic inflammation.
Why the Bacteroidetes:Firmicutes ratio matters
“Out of thousands of bacterial species-level phylotypes62 inhabiting the human gut, the majority belong to two dominant phyla, the Bacteroidetes and Firmicutes . Members of the Bacteroidetes in particular have been associated with human metabolic diseases.” 63 So, even taking into account the wide range of inter-individual variations in human intestinal microbiomes, it’s known 6465 that these Bacteroidetes and Firmicutes phyla dominate healthy human microbiomes.
However, it’s the actual ratio between them that seems to matter most. Diets heavier in animal fat and protein than in whole grains and plant-based foods (rich in starch, fibre and plant protein) have been shown 66 to cause a significant decrease in Bacteroidetes and increase in Firmicutes.
See the following video by Dr Greger for more information on this important ratio:
In the video, Dr Greger offers a useful way of remembering which bacterial phyla is associated with which body type: Bacteroidetes for bony, and Firmicutes for fat!
Bacteroidetes:Firmicutes ratio and obesity
As the above video explained, a decrease in Firmicutes levels usually favours an increase in Bacteroidetes and Bifidobacteria – something that happens when you eat lots of resistant starches 67 . The typical result of this is that obesity/high BMI can be prevented and treated 68 .
A decreased Bacteroidetes:Firmicutes ratio has a strong negative correlation with BMI 60 . This may be explained by the observation that a 20% increase in Firmicutes with a corresponding decrease in Bacteroidetes abundance is associated with a 150 kcal/day increase in energy harvest69 – something which would, over time, result in weight gain. Thus, an increased Bacteroidetes:Firmicutes ratio (as seen in high-fibre, plant-based diets) could result in weight loss by causing a reduction in the amount of energy being extracted from the diet.
Additional studies are required to decide whether increased energy harvest is caused by the Bacteroidetes:Firmicutes ratio promoting adiposity or by a host-mediated adaptive response to limit energy uptake 70 .
Nothing is plain and simple in the world of microbes, and there are sufficient conflicting results from various studies on the Bacteroidetes:Firmicutes ratio to support the argument that making wide-sweeping statements about which phyla are good and which are bad is likely to be inaccurate and over-generalised. Increased awareness is growing about a need to appreciate the complexity of dynamic interactions between microbes within the microbiome, rather than trying to match one microbe with one health outcome 71527273 .
How gut bacteria enterotypes are affected by diet
As mentioned above, there are three main enterotypes observed in human microbiomes:
1. Prevotella is a genus of the Bacteroidetes phyla. Studies suggest 74757677 that it’s significantly richer in the microbiome of vegans.
Studies with mice have suggested 78 that Prevotella improves glucose metabolism by improving glycogen storage. It has also been observed 79 to confer anti-inflammatory effects, and additional research suggests 80 that it can decrease the growth of other bacteria by competing for fibre as an energy substrate.
2. Bacteroides is another main enterotype and genus of the Bacteroidetes phyla. Whilst still appearing to be affected by the type of diet eaten, Bacteroidetes has been positively associated 8152 with long-term diets high in saturated fat and animal protein.
An explanation of this is that such bacteria are better able to tolerate bile – something common in the gut environments of meat-eaters. It’s no surprise, therefore, that high proportions of Bacteroides are found 76 in the intestinal environments of those who eat the modern Western diet, while the opposite is the case for those eating lots of legumes, fruits and fibre.
3. Ruminococcus is an enterotype and genus also associated with long-term fruit and vegetable consumption. An explanation of this is that species of this genus are specialists in degrading complex carbohydrates (e.g. cellulose and resistant starch which are only found in plants) and, thereby, producing butyrate, an anti-inflammatory SCFA56 .
Increased communities of Ruminococcus have been associated with the following:
lower endotoxemia82 and lower arterial stiffness 55
“A high fat diet increases the absorption of LPS [lipopolysaccharides or LPS are an integral component of Gram negative microorganisms], which, in turn, has been found to be associated with metabolic endotoxemia and to induce inflammation resulting in obesity.” 83
Walnuts, refined grains and Ruminococcus
Studies have shown 65 that eating walnuts appears to enrich the Ruminococcus community within our gut environment.
Interestingly, however, one study showed 84 an increase of Ruminococcus in college students who had low dietary fibre intake in their diets. This may be explained by the ability of these bacteria to also break down resistant starches in the many refined grain products eaten by this group.
How plant food components influence gut microbiota
This final section will look at both nutrient bioavailability and the microbial responses to the consumption of carbohydrates.
It may seem counter-intuitive, but less is more when it comes to certain aspects of nutrient bioavailability85 . When you consume food nutrients with low bioavailability (normally found in intact plant cell walls, larger food particles, and the latter foods without thermal treatment), more nutrients are able to pass through the stomach and small intestine to reach lower in the gastrointestinal tract. This is important since it allows our gut microbiota, lurking down in the colon, to receive a delivery of rich nutrients 86 .
A rich supply of nutrients will help support the normal development and functions of gut microbiota. The modern Western diet has loads of ultra-processed foods and acellular nutrients87 . The small intestine can more easily absorb these components and, thus, deprive the colon of important nutrients. Eating acellular food has been shown 88 to alter the composition and metabolism of the gut microbiota, and induce inflammation in young infants, adolescents, women of child-bearing age, and older adults.
On the other hand, whole plant foods have protective effects, and favour the growth of beneficial fibre-degrading bacteria in the colon.
Both digestible and non-digestible carbohydrates appear able to influence gut microbiota.
Digestible carbohydrates (e.g. glucose, sucrose, and fructose from fruits) have been shown 89 to reduce the following:
The following diagram 92 provides more detail on the absorption of digestible carbohydrates:
Non-digestible carbohydrates (NDCs) generally:
increase the following:
lactic acid bacteria
reduce the following:
The following diagram 93 provides a little more in-depth detail on NDCs.
Both digestible and non-digestible carbohydrates have been shown to increase Bifidobacteria (a genus of the Actinobacteria phylum)
Bifidobacteria are some of the good guys. As a butyrate-producing genus, with known protective properties for the human gut barrier, Bifidobacteria provide effective defences against pathogens and diseases, and increase in number when “fed” with health-giving short-chain fructooligosaccharides (scFOS) and fibre – both forms of carbohydrate found in abundance in natural plant foods, such as bananas, artichokes, onions, etc 94 . On the other hand, high consumption of cholesterol (only found in animal foods), was strongly associated with a lower abundance of Bifidobacteria 95 .
A recent study found 96 that the following fibres have differing prebiotic effects on gut microbiota:
xylo-oligosaccharides (from corn cobs and high-fibre sugar cane)
beta-glucan (from oats)
Inulin and all oligosaccharides have a strong bifidogenic effect97 .
Beta-glucan induces Prevotella and Roseburia growth with associated increase in production of the SCFA, propionate – a good thing, since it’s known 9899 to promote weight loss and provide many other health benefits, including being anti-carcinogenic and anti-inflammatory.
All natural sugars, especially non-digestible forms like inulin and oligosaccharides, increase SCFA levels 100101 .
Prebiotic effects vary depending on which type of bacteria breaks down which type of fibre. The specificity of bacterial activity in relation to fibre is determined by specific gene clusters within the bacterial genome that dictate which saccharolytic102 enzymes the bacteria can produce and, hence, whether they can metabolise the particular prebiotic substrate 103 .
Other protective effects of non-digestible carbohydrates
NDCs don’t just act as prebiotics by promoting the growth of beneficial microorganisms, they are also shown 89 to do the following:
It can be seen from the above that NDCs are, thus, likely to confer significant protective effects against cardiovascular disease as well as central nervous system disorders.
An increasing body of research indicates that diet is the essential factor when it comes to the composition of human gut microbiota. These microbes are then responsible for converting nutrients into active postbiotics that we (the hosts) absolutely need. The weight of evidence is favoured towards a plant-based diet being the most effective way in which we can ensure a diverse ecosystem of beneficial microbes is promoted within us, so that they can support overall health.
Functional redundancy is a characteristic of species within an ecosystem where certain species contribute in equivalent ways to an ecosystem function such that one species may substitute for another. [↩]
An enterotype is a classification of living organisms based on its bacteriological ecosystem in the gut microbiome. The discovery of three human enterotypes was announced in the April 2011 issue of Nature by Peer Bork and his associates. [↩]
Atopy refers to the genetic tendency to develop allergic diseases such as allergic rhinitis, asthma and atopic dermatitis (eczema). Atopy is typically associated with heightened immune responses to common allergens, especially inhaled allergens and food allergens. [↩]
Substrates are the reactants, products, and intermediates of an enzymatic reaction, generally known as metabolites, which are modified by a sequence of chemical reactions catalysed by enzymes. In most cases of a metabolic pathway, the product of one enzyme acts as the substrate for the next. [↩]
The gut microbiota has emerged as an environmental factor that modulates the host’s energy balance. It increases the host’s ability to harvest energy from the digested food, and produces metabolites and microbial products such as short-chain fatty acids, secondary bile acids, and lipopolysaccharides. [↩]
Endotoxemia is essentially an innate immune response that becomes a sub-clinical, persistent, low- grade inflammation because of increased, circulating endotoxins, primarily LPS or lipopolysaccharides. The presence of such endotoxins in the blood, if derived from gram-negative rod-shaped bacteria, like LPS, may cause haemorrhages, necrosis of the kidneys, and shock. Metabolic endotoxemia is a condition that is estimated to affect approximately 33% of the western population. [↩]
Bacteroides fragilis has two main traits that allow it to switch from good to bad – an ability to easily incorporate genes shared by other bacteria and an ability to turn specific genes ‘on’ or ‘off’ as needed. Combined, these traits allow these bacteria to exploit new nutrition pathways, protecting themselves from toxic substrates, and changing the molecules expressed on its
surface. This ‘commensal chameleon’ is the perfect opportunistic pathogen. [↩]
Clostridia are an anaerobic class of Firmicutes. Clostridia are members of normal human flora, present primarily in the intestinal tract and vagina, and are ubiquitous in soil. Generally safe in situ but dangerous if spread through other parts of the body [↩]
The bifidogenic effect is where a bifidus factor (bifidogenic factor) specifically enhances the growth of bifidobacteria in either a product or in the intestines of humans and/or animals. Several products have been marketed as bifidogenic factors, such as several prebiotics and methyl-N-acetyl D-glucosamine in human milk. [↩]
Unfortunately, the standard medical practice for dealing with angina has been a dash to dish out the drugs1 . This may well relieve the symptoms, but it does not deal with the underlying causes. And what’s the main cause? You guessed it, diet. This blog deals with a case study 2 of a 60-year old male who, having been diagnosed with angina, refused both drug therapy and invasive testing in favour of making a dietary change to a WFPB diet. But did it work?
The study subject reported a 12 month history of progressive severe mid-sternal chest discomfort after either walking only half a block, experiencing emotional stress or being out in cold weather. His family history included a mother who had coronary artery bypass surgery and a brother who had an acute myocardial infarction, both while they were in their early sixties.
With medical advice and counselling, he chose to adopt a wholefood plant-based diet (WFPB), which consisted primarily of the following:
Subject’s previous diet
He described his diet as having been a “healthy” diet of the following:
some vegetables, fruits, and nuts
Within just a few weeks of dietary change, his symptoms improved.
After four months, the following biometrics were recorded:
BMI fell from 26 kg/m2 to 22 kg/m2
blood pressure normalised
LDL (low-density lipoprotein) cholesterol decreased from 158 mg/dL to 69 mg/dL
ability to walk one mile without angina symptoms
Two years after starting the WFPB diet, he was able to jog more than 4 miles without incident and remained asymptomatic, off drug therapy for coronary artery disease, and has not required cardiac catheterisation3 .
The study subject’s angina symptoms improved rapidly, as did his weight, blood pressure, and cholesterol levels. And this case study is supported by plenty of evidence that WFPB diets are strongly associated with:
Studies 20 have shown a dose-response-like effect – that is, the greater the adherence to a healthy lifestyle (including a WFPB diet), the greater the apparent benefit.
When less is more
A growing body of evidence suggests that any and all animal-based foods may not be optimal for health 212223 .
Coronary artery disease in plant-eating populations
This case reinforces research showing that great improvements in our “modern” Western NCDs (non-communicable diseases) can be achieved without the need for medications or medical procedures. Previous epidemiological studies24 have documented the near-absence of coronary artery disease in indigenous populations that eat largely or exclusively plant-based diets, including:
“A whole-food plant-based diet helped reverse angina without medical or invasive therapy. It appears prudent that this type of lifestyle be among the first recommendations for patients with atherosclerosis.”
Whilst some people might think it’s too difficult to live a “normal” life while eating a WFPB diet, it’s actually quite achievable within a real-world setting 30 and, with proper education and support, anyone can make the transition 31 . Additionally, a WFPB diet is not associated with markedly increased food costs 32 ; and, in any case, what price can you put on a healthier and longer life?
Whilst the above research only covers one case study, its findings are completely in line with copious research data showing impressive results on the prevention and treatment of cardiovascular diseases through eating a WFPB diet, ideally – and optimally – without any added salt, oils or sugar. Take a look at some of the research links to find out more.
Finally, an excellent explanation of how simple dietary changes can effect such radical health improvements is presented in the following video, where Dr Caldwell B Esselstyn explains how you can make yourself “heart-attack proof”.
References & Notes
Typical angina drugs: Clot-preventing drugs -clopidogrel (Plavix), prasugrel (Effient) ticagrelor (Brilinta); beta blockers – these work by blocking the effects of the hormone epinephrine, also known as adrenaline. As a result, the heart beats more slowly and with less force, thereby reducing blood pressure, they also help blood vessels relax and open up to improve blood flow, thus reducing or preventing angina; statins – these are drugs used to lower blood cholesterol, and work by blocking a substance the body needs to make cholesterol; calcium channel blockers – also called calcium antagonists, relax and widen blood vessels by affecting the muscle cells in the arterial walls. thereby increasing blood flow in the heart, reducing or preventing angina; blood pressure-lowering drugs – if you have high blood pressure, diabetes, signs of heart failure or chronic kidney disease, doctors tend to prescribe a drug to bring the blood pressure down. The two main classes of blood pressure drugs are angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs); finally, a drug called Ranolazine (Ranexa) may be used alone or with other angina medications, such as calcium channel blockers, beta blockers or nitroglycerin. [↩]
Epidemiological studies look at the distribution and determinants of health and disease conditions in defined populations. Such research often forms the cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. [↩]
An April 2019 study 1 looked for dietary reasons that would account for the shockingly high rate of obesity and cardio-metabolic diseases within the US Hispanic and Latino population 2 .
The Adventist Multi-ethnic Nutrition Study (AMEN) enrolled 74 Seventh-day Adventists from five Hispanic and Latino churches within a 20 mile radius of Loma Linda, CA into a cross-sectional study of diet and health. The information analysed was based on questionnaires, anthropometrics3 and biomarkers4 . By comparing US Hispanic and Latino omnivores with a similar plant-based population (namely, Hispanic and Latino vegetarian/vegan Seventh-day Adventists), the researchers hoped to find out whether better health generally found in the latter group could be attributed to their continued adherence to a plant-based diet. Particular attention was paid to differences in adiposity and adiposity-related biomarkers between the two groups.
It appears that the reason US Hispanic and Latino populations experience such high rates of obesity and cardio-metabolic disease is largely down to their transition towards the SAD (Standard American Diet) and away from traditional Hispanic and Latino diets that emphasised whole plant foods, such as were still consumed by the vegetarian/vegan Seventh-day Adventists included in this study.
When compared with the general non-vegetarian Hispanic and Latino population, vegetarian/vegan dietary patterns within the Seventh-day Adventist Hispanic and Latino population were associated with:
significantly lower BMI (24.5 kg/m2 vs. 27.9 kg/m2, p = 0.006) 5
significantly lower waist circumference (34.8 cm vs. 37.5 cm, p = 0.01)
significantly lower fat mass (18.3 kg vs. 23.9 kg, p = 0.007)
Comparative results can be seen in the following table.
These findings are consistent with previous studies that have looked at other populations, including:
There’s a rich cultural tradition of diverse regional plant foods within traditional Latin America cuisine:
the Mexican Tarahumara Indians traditionally ate a diet of beans, corn, and squash and very little meat – a pattern associated with lower risk of cardiometabolic disease 12 . The risks are significantly increased when the Tarahumara change to the typical US diet 13 .
Peruvian and Brazilian populations that follow traditional cultural choices which contain high amounts of plant foods have lower rates of hypertension, dyslipidemia, and obesity when compared to omnivores 14 .
The researchers consider that encouraging populations to re-introduce healthy plant foods, which have long-held and strong roots in their cultural heritage, is a potentially useful means of achieving high impact health interventions.
Plant-based eating as practised by US-based Hispanic and Latino Seventh-day Adventists is associated with relatively healthy BMI15 . The study concludes that further research is needed to characterise the precise type of diet that should be recommended for use in obesity-related interventions among Hispanic and Latinos in the US.
This study adds to the already considerable body of evidence suggesting that naturally-low-fat plant-based diets are the way to go if you want to remain healthy – particularly if you want to ensure that obesity and obesity-related diseases don’t reduce both the quality and length of your life. Of course, the more wholefood, non-processed the diet, the better. This would, I suspect, result in much improved biomarkers when compared, not only with the above omnivores, but also with the vegetarian/vegan group reviewed within this study – a group which included lacto-ovo vegetarians and pescotarians.
Additionally, I could not get a clear picture of whether and how this study drew distinctions between whole and processed plant foods, with the latter consistently failing to provide the health benefits of the former 16 .
From whatever perspective you may look, when it comes to obesity, there’s a weight of truth in the saying: “The fat you eat is the fat you wear.”
Hispanic and Latino are often used interchangeably though they actually mean two different things. Hispanic refers to people who speak Spanish and/or are descended from Spanish-speaking populations, while Latino refers to people who are from or descended from people from Latin America. [↩]
Anthropometry refers to the measurement of the human individual. An early tool of physical anthropology, it has been used for identification, for the purposes of understanding human physical variation. [↩]
The p-value is a number between 0 and 1 and os interpreted in the following way: A small p-value (typically ≤ 0.05) indicates strong evidence against the null hypothesis – that is, that there is no evidence to support a relationship, so you reject the null hypothesis and accept that there is a potentially causal relationship. Basically, the smaller the number, the more evidence there is for some form of relationship between the two or more elements under discussion. In this case, 0.006 indicates that there is a strong probability that a lower BMI is associated with a vegan/vegetarian diet. [↩]
An April 2019 UK study 1 looked at the sort of food, drink and lifestyle choices made by meat-eaters and plant-eaters to see if differences in health outcomes of the two groups were partly the result of these choices.
The researchers analysed data from FFQs (food frequency questionnaires) completed by 30,239 participants involved in the EPIC-Oxford study 2 . They assessed intakes of major protein-source foods and other food groups after dividing the participants into six groups of meat-eaters and non-meat-eaters:
The foods listed in the FFQs were categorised into 45 food groups and the results were analysed for variance in health outcomes between the 6 groups. Figures 1 (men) and 2 (women) give a rough idea of the results:
There are large differences in dietary intakes between meat-eaters and non-meat-eaters:
non-meat-eaters consumed higher amounts of:
nuts and seeds
vegetables and fruits
non-meat-eaters consumed lower amounts of:
sugar-sweetened beverages (SSBs)
other foods high in free sugars (e.g. ice cream)
Contrary to expectations, vegetarians and vegans did not replace meat with higher intakes of animal-sourced protein alternatives (dairy and eggs) and non-animal protein alternatives (including legumes and nuts), respectively.
Vegetarians and vegans were found not to completely replace meat consumption with non-meat protein sources and high protein plant-sources but, rather, they increased their consumption of a large variety of plant-based foods and consumed lower amounts of high protein-sourced foods compared with meat-eaters.
The positive health benefits of lower protein intake (specifically, animal protein) have been discussed previously 3456 .
The proportion of total energy from high protein-sourced foods:
regular meat-eaters – 33%
vegetarians – 25%
vegans – 20%
Compared with the 5 other groups, vegans consumed the highest amount of:
lower amount of dairy and eggs than meat-eaters
highest amount of cheese compared with other 5 groups
Egg consumption was low in all 6 groups, possibly because this study looked at a cohort that might be more ‘health conscious’ than the rest of the population. 7
Compared with regular meat-eaters, all the other groups:
had a higher education level
had a lower socio-economic status
were less likely to smoke and consume alcohol
had higher levels of physical activity
had lower BMI
had higher intakes of carbohydrates
had lower intakes of protein and fat
Table 1 shows more detail on the above:
The findings suggest that non-meat-eaters might be consuming an overall “healthier” diet than meat-eaters.
“In this large study of British men and women, we compared intakes of major protein-source foods and other food groups. …Our results show that meat-eaters and low and non-meat-eaters do not only differ in their meat consumption but in their overall dietary intake…The dietary intakes consumed by low and non-meat-eaters might explain the lower risk for some diseases in these diet groups and can be used as a real-life guide for future work assessing the health impacts of replacing meat intake with plant-based foods or dietary recommendations.”
On the whole, the results are what one would have expected. However, there were some surprises, particularly the findings that non-meat eaters tend to drink less booze, smoke less, and eat less processed and sweetened foods.
It’s often speculated, by those who are unfamiliar with plant-based diets, that life must be more boring when you stop eating animals – I mean, where’s the fun in eating grass?! However, if life were so dull when eating a supposedly buzz-free diet, wouldn’t you imagine that plant-eaters would eat a lot more comfort food 8 (sugary, fried, processed foods) and drink and/or smoke themselves silly whenever they could?
Some clarification is provided by research data showing that, not only does physical health generally improve on a plant-based diet, but mental health 91011 and general outlook on life 12 also tends to improve – obviating the need to get caught in that “pleasure trap” 13 .
It was also interesting to note from this study, that the improved health outcomes for plant-eaters does not just derive from the fact that they eat more healthy foods – it’s also that they generally appear to eat less unhealthy food, exercise more, smoke and drink less. There was also variance by age, socio-economic and educational status between the groups – with the youngest group being vegan, highest socio-economic status being meat-eaters, and the most educated being fish-eaters. Food for thought…
Of course, this is not to say that there are no vegetarians and vegans eating horrendously unhealthy plant-based diets. This is something that’s been covered in previous blogs 141516 . This can probably be seen by the surprisingly low amount of fruit and veg eaten by vegetarians and vegans, when compared with how much rice, pasta and bread they eat.
Since WFPB (especially when non-SOS) would guarantee a maximum amount of fruit and veg, with a minimum amount of the sort of junk foods that can find themselves included in a vegetarian or vegan diet, it would be interesting to see future studies which are able to include the WFPB diet within a list of food groups.
A 2019 Taiwanese study 1 recently reported on the results of two large-scale cohort studies which were analysed in order to establish whether following a vegetarian diet reduces the risk of developing gout, when compared with following a non-vegetarian diet.
What is gout?
This subject has been covered extensively in a previous blog 2 so, in brief terms:
gout is the most common inflammatory joint disease and is an important risk factor for hypertension, diabetes, kidney diseases, cardiovascular diseases, and all-cause and cardiovascular mortality 3456
gout pathogenesis begins with excess serum urate that forms monosodium urate crystals – a salt or ester of uric acid – in the joints, triggering gouty inflammation and resulting in excruciating pain 78
cases of gout have doubled or tripled in many countries in the past decades 910 making it a serious public health threat which desperately requires preventive strategies
Taiwan is particularly affected, with one of the highest incidences and prevalences of gout in the world 11
Two cohort groups, representing almost 14,000 Taiwanese, were followed for between 7 and 9 years. They were divided into vegetarians (n=4684) and non-vegetarians (n=9251), and appropriate tests were undertaken to establish gout occurrence.
the standard therapeutic diet aimed at preventing/managing gout restricts purine intake which is metabolised into urate and contributes to one-third of the body’s total urate pool 12
however, purine exclusion diets have only moderate urate-lowering effects and are generally regarded as an insufficient remedy 13
the researchers considered that the ideal diet for gout prevention/management should be able to simultaneously reduce uric acid and inflammation, while preventing gout-associated comorbidities
they conjectured that a vegetarian diet may be a promising dietary pattern to target multiple pathways in the gout pathogenesis, since:
vegetarians avoid purine-rich meat/seafood, while consuming increased amounts of vegetables, whole grains, seeds and nuts 1415
plant foods contain polyphenols which potentially reduce uric acid via both an inhibition of xanthine oxidase16 activities and the enhancement of uric acid excretion 17
plant foods contain phytochemicals which potentially attenuate the NLRP3 18 inflammatory pathway 1920
vegetarian diets have already been shown to reduce gout associated comorbidities, such as cardiovascular diseases 21 , diabetes 2223 , and hypertension 2425
“In these two prospective cohort studies, a Taiwanese vegetarian diet is associated with lower risk of gout. This association persists after controlling for demographic, lifestyle, cardiometabolic risk factors, and baseline hyperuricemia. This finding does not differ across subgroups of sex, lifestyle factors, or comorbidities.”
it’s most likely that vegetarians experienced a lower risk of gout simply because they had lower uric acid levels since their diets avoid purine-rich meat and seafood – a diet which in prospective studies has been shown to increase gout incidence and recurrence26272829
the results appear to go beyond the single effects of uric acid levels, since they were not consistently wide apart between all vegetarians and all non-vegetarians. The other potential factors influencing the reduction of gout in vegetarians may also be accounted for by the following:
vegetarian diets have higher alkalinity which has been shown to facilitate more effective uric acid excretion than an acidic diet – i.e. one that is fish/meat-based 30
vegetarian diets usually contain lower saturated fat, higher unsaturated fat and phytochemical-rich plant foods 141531
the latter may prevent inflammatory responses which trigger gout attacks by dampening the inflammatory activation of NLRP3 inflammasome 32
fibre (high in plant-based diets) on its own, and when metabolised into short chain fatty acids by gut microbiota, has been shown to resolve inflammatory responses involved in gout attacks in mice 33 and in humans 34
We saw in the previous gout blog 2 that there’s plenty of strong evidence to suggest that the best possible dietary option for gout-avoidance is a WFPB diet (with zero alcohol!). Of course, any diet which favours plant over animal foods will be of some benefit, and the more the latter is replaced with the former, the better in terms of gout-avoidance.
One interesting finding from this Taiwanese study relates to soy. Taiwanese vegetarian diets replace meat and seafood with soy products. But there appears to be a paradox here. Soy has a high purine content and has attracted an infamous reputation – even amongst health professionals – for causing gout 35 . However, contrary to this widely-held belief, the vegetarian diets with high soy content covered in this present Taiwanese study appear to lower gout risk.
And this is not the only study to show this. The researchers’ findings are consistent with the “Singapore Chinese Health Study” which found that soy was protective toward gout 27 .
A potential explanation for this rests in the fact that the potential of soy purines – mainly adenosine36 and guanine37 – to raise uric acid levels is considerably lower than those in meat and fish, which have a higher proportion of their purines in the form of hypoxanthine383940
A 2012 prospective study 41 of gout patients found that the impact of plant purine on gout attacks was significantly less than the purine from animal sources.
Finally, research suggests 42 that soy may have the ability to prevent gout through the inhibition of both the above-mentioned NLRP3 inflammatory pathway and the activity of the caspase-1 enzyme. The latter is an essential effector of inflammation, pyroptosis43 , and septic shock44 .
So, hurrah for the plants, boo hiss for meat and seafood, and don’t be shy about eating soy…
Xanthine oxidase is a type of enzyme that generates reactive oxygen species. These enzymes catalyse the oxidation of hypoxanthine to xanthine and can further catalyse the oxidation of xanthine to uric acid. [↩]
Adenosine is a chemical that is present in all human cells. It readily combines with phosphate to form various chemical compounds including adenosine monophosphate (AMP) and adenosine triphosphate (ATP). [↩]
Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine. [↩]
Hypoxanthine is a naturally occurring purine derivative. It is occasionally found as a constituent of nucleic acids, where it is present in the anticodon of tRNA in the form of its nucleoside inosine. [↩]
(Pyroptosis is a highly inflammatory form of programmed cell death that occurs most frequently upon infection with intracellular pathogens and is likely to form part of the antimicrobial response. [↩]
Septic shock is a potentially fatal medical condition that occurs when sepsis, which is organ injury or damage in response to infection, leads to dangerously low blood pressure and abnormalities in cellular metabolism. [↩]
Asthma is a respiratory condition characterised by spasms in the bronchi of the lungs, resulting in breathing difficulties. It’s normally associated with allergic reactions or other forms of hypersensitivity. This blog will take a brief look at some evidence that suggests a central role for plant-based diets in the treatment of asthma and the prevention of asthmatic attacks.
Healthy body weight and asthma
two 2013 studies on asthma in children found that being overweight increases the risk of developing asthma by 35%, while being obese as a child increases the risk by 50% 1 and losing excess weight in children improves lung function2
this was further supported by a 2018 study: ““There are few preventable risk factors to reduce the incidence of asthma but our data show that reducing the onset of childhood obesity could significantly lower the public health burden of asthma.” 3
Fatty acid intake and asthma
Omega-6 fatty acids are mostly found in animal products. They are also found in margarines and other vegetable oils. The specific amounts of oil-based fats are shown in the chart below 4 . N.B. Consuming any form of oil or fat that’s been separated from its original food source is not to be advised, for reasons covered in previous blogs. 567 .
arachidonic acid (a long-chain omega-6 fatty acid) is found mainly in animal foods and has been shown to be a precursor of leukotrienes which have bronchoconstrictive effects 8 . Leukotrienes are a form of pro-inflammatory molecule released by mast cells during asthma attacks 9
omega-3 fatty acids, on the other hand, have been shown 10 to have anti-inflammatory effects
a higher ratio of omega-6 to omega-3 fatty acids in the diets of children has been shown 10 to have a significant association with an increased risk of asthma
omega-6 fatty acids have been shown 11 to hinder the incorporation of omega-3 fatty acids into tissue lipids and plasma
while some studies suggest 12 that fish-based omega-3 intake improves asthma symptoms in children, there are other studies 13 which contradict this and also suggest that such benefits in adults have not been proven
there are persuasive reasons for getting your omega-3 from walnuts, flaxseeds/chia seeds and/or plant-based omega-3 supplements rather than eating fish or using fish oil supplements 1415
Saturated fat and asthma
evidence suggests 16 that when asthmatics eat diets containing high levels of total and saturated fat, there is an increase in the expression of those genes involved in airway inflammation
a 2010 study concluded 17 that high fat diets are able to inhibit the asthmatic’s response to the asthma medication Ventolin (albuterol)
Dairy products and asthma
a study 18 showed that pregnant women consuming low-fat yogurt once or more a day or low-fat milk 5.5 times or more a week had a 21% and 8% higher risk, respectively, for having a baby which would be diagnosed with asthma, as compared with women consuming no dairy
a 2015 study 19 found roughly 50% greater asthma prevalence in children who consumed butter 3 or more times a week, compared with those who either never consumed butter or only consumed it occasionally
Fast food and asthma
a 2013 study 20 found a ~40% increased risk of severe asthma developing in children and adolescents who consumed fast food 3 or more times a week, as compared with those who either never ate fast food or ate it only occasionally
Nuts, seeds and asthma
although tree nuts and peanuts can be allergenic to some people, a 2012 Danish study 21 found that nut intake during pregnancy was actually inversely related to an asthma diagnosis in their offspring at 18 months of age
a 2009 French study 22 looked at the risk that French women have of frequent asthma attacks (1 or more per week), and found that the risk was lower in women who consumed the highest amount of nuts and seeds (>5.3 g/day) when compared with those with the lowest consumption (≤ 1.0 g/day)
Salt and asthma
whilst there is evidence 23 that consuming a low-sodium (salt) diet appears to reduce bronchoconstriction in asthmatics in response to exercise, there is no strong evidence that a low-sodium diet (of itself) reduces the prevalence or severity of asthma 24
considering that salt is known 25 to be pro-inflammatory, it makes sense that it’s wise to avoid adding salt to your food and, of course, avoiding procesed foods which are known to be high in salt
a 2014 study concluded: “…our findings suggest that higher sodium consumption is associated with greater adiposity, leptin resistance, and inflammation independent of total energy intake and sugar-sweetened soft drink consumption.” 26
Fruits, vegetables and asthma
fruits, vegetables and other foods high in antioxidants have been shown 27 to produce ~45% lower risk for asthma in those children and adults who consume the most amount of fruits and vegetables, as compared with those who eat the least amount
a 2013 study 28 found that individuals who ate the lowest amount of fruit and vegetable (3 servings/day – typical of Western diets) had more than 50% increased risk of asthma exacerbation than those who ate 7 daily servings of fruits and vegetables
the European Academy of Allergy and Clinical Immunology (EAACI) recommended that clinical advice should be to increase the net intake of fruits and vegetables as a way of reducing the risk of asthma, particularly in children 29
a 2017 study concluded “higher intakes of fruits and vegetables may have a positive impact on asthma risk and asthma control.” 30 and provided an interesting schematic that compared the airway effects of the Western diet and a diet high in fruit and veg:
Vegetarian, vegan diets and asthma
a 1994 study 31 of almost 28,000 Seventh-day Adventists found that vegetarian women amongst the group reported a lower incidence of asthma, as compared to women who ate omnivore diets. “The theoretical basis for the value of vegan diets is the absence of potential triggers, particularly dairy products and eggs, as well as a relative lack of arachidonic acid.” 32
although the so-called Mediterranean diet is something of an anathema these days – with the spread of the modern Western diet across the continent – a 2014 review 33 found 7 out of 10 studies noted that there was a protective effect of a Mediterranean diet on the incidence of child asthma
a 1985 study used a vegan diet for 1 year as an alternative therapy to typical asthma drugs for a group of 35 asthma patients. They found a significant decrease in asthma symptoms as a result of this simple dietary intervention: “…71% reported improvement at 4 months and 92% at 1 yr. There was a significant improvement in a number of clinical variables; for example, vital capacity, forced expiratory volume at one sec and physical working capacity, as well as a significant change in various biochemical indices as haptoglobin, IgM, IgE, cholesterol, and triglycerides in blood. Selected patients, with a fear of side-effects of medication, who are interested in alternative health care, might get well and replace conventional medication with this regimen.” 34
Sugar-sweetened beverages and asthma
a 2009 US study 35 found an increased risk of developing asthma in those students who drank soda (fizzy drinks): 2 regular sodas a day meant a 28% increased risk, while 3 or more regular sodas a day meant a 64% increased risk. It was also pointed out that previous studies found asthma symptoms were worsened by regular soda consumption
a follow-up study 36 on non-obese adults found that those who consumed 2 or more sugar-sweetened beverages a day had ~65% increased risk of developing asthma, as compared to those who didn’t consume any such beverages
and it’s not just sodas that are the problem – a further 2016 US study 37 found that asthma risk in children between 2 and 9 years of age was significantly higher when they consumed apple juice or high fructose corn syrup-sweetened beverages 5 or more times a week, as compared to consuming only 1 or no such beverages per month
Alcohol and asthma
a 2012 study 38 found a U-shaped association between alcohol consumption and the development of new onset asthma in adults – that is, moderate weekly intake (1-6 units/week) showed a reduced risk, whilst those who never/rarely drank (<1 unit/month) and heavy drinkers (≥4 units/day) showed an increased risk. The risk of new-onset asthma was also shown to be lower for subjects with wine preference when compared with beer preference. However, the study authors admit that their findings were not statistically significant
contradictory information is provided by other authorities, including Asthma UK 39 , which claims that alcohol does exacerbate asthma symptoms, and a study in The Journal of Allergy and Clinical Immunology 40 , which states that wines are the greatest triggers for asthma attacks
whilst there’s obviously disagreement on this subject, and thus further research would be useful, previous blogs 4142 have explained the reasons why any amount of alcohol intake has been shown to be potentially harmful
Vitamin D status and asthma
a 2014 meta-analysis 43 found that increased vitamin D deficiency was associated both with an increase in the incidence of asthma in general and with a decrease in lung function in asthmatic children in particular
whilst there is some disagreement on the benefits of vitamin D supplementation as a means of treating/preventing asthma in children 44 , an additional study 45 reported that those children who took vitamin D supplements reduced their risk of asthma by ~25%, as compared with children without supplemental vitamin D
Breastfeeding and asthma
a 2004 study 46 on the therapeutic measures for preventing the development of both allergic rhinitis and asthma, made the following suggestions for decreasing the the risk for developing asthma in babies during breastfeeding:
ensure that babies are breastfed for the first 4-6 months of life
avoid dairy products until at least 1 year old
avoid eggs until at least 2 years old
avoid nuts and fish until at least 3 years old
Inhalers and asthma
An interesting article appeared in The Telegraph today 47 entitled “Asthma inhalers as bad for the environment as 180-mile car journey, health chiefs say.” It points out the dangers to the environment of the hydrofluorocarbons (a powerful greenhouse gas) contained in the majority of the asthma inhalers (known as metered dose inhalers of MDI’s) used in the UK.
Nice (The National Institute for Health and Care Excellence) was reported to have calculated that “…five doses from an MDI have the same carbon emissions as a nine-mile trip in a typical car. The devices usually contain 100 doses. By contrast, dry powder inhalers are only around one fifth as bad for the environment.”
more than 5.4 million people in the UK receive treatment for asthma, including 1.1 million children
Britain has some of the highest rates in Europe, with around three people a day dying as a result of the condition
Whilst inhalers do, of course, save lives and users should only consider making changes in consultation with their doctor, they are known 48 to have side effects. Making dietary changes that help to prevent and treat asthma does seem to be a much better alternative, especially since the only side effects appear to be positive ones.
The foregoing appears to suggest that there is, indeed, an important role for plant-based diets in the prevention and treatment of asthma. Such diets (so long as they are based on wholefood plants and avoid processed plant foods) are excellent for the maintenance of healthy weight and can provide the ideal fatty acid profile.
It’s clear that some particular foods are best avoided completely, including dairy products, fast food, sugar-sweetened beverages and, arguably, excessive amounts of salt – especially when contained in processed foods.
If you suffer from asthma, perhaps a useful way to check whether this dietary approach will alleviate your asthma is to stick with your current diet for a specific time, but keep a detailed daily record of asthma symptoms. After this, change to a non-SOS WFPB (no added sugar, salt or oil wholefood plant-based diet) for a similar specific period of time and maintain the daily diary. You would then be able to compare the frequency and intensity of symptoms between the two periods.
Should you decide to do this, and would like to share the results, please feel free to write to me with your findings and I will aim to publish them in a subsequent blog.
In previous blogs, I shared two documentary films produced by the H.O.P.E. project 1 : “What You Eat Matters” 2 and “From Cancer Patient to Plant-Based Strong Man” 3 . H.O.P.E. have just released another short documentary film about Paul Chatlin, a man with heart disease who was saved from surgery by changing to a plant-based diet.
Paul Chatlin’s Story
In 2013, after being diagnosed with heart disease, Paul’s doctor gave him a simple choice – change his diet or undergo major heart surgery.
At the time, Paul was eating a typical Western diet, with cheese and meat being his favourite foods. Having loved pretty much anything fried in oil, he was given a “nutrition prescription” which required him to give up all these foods and cut out the oil – replacing his habitual diet with a low fat, whole food, plant-based diet.
Having spent his whole life eating one way, he found it a struggle to know what he could now eat and how he could prepare it without using oil. Luckily, he came across and attended a seminar on plant-based nutrition by the world-renowned physician and researcher Dr. Caldwell B. Esselstyn 4, a major player in the famous WFPB documentary film, “Forks Over Knives” 5 and author of his must-read book, “Prevent and Reverse Heart Disease: The Revolutionary, Scientifically Proven, Nutrition-Based Cure.” 6 .
As a result of the seminar, Paul was better equipped and motivated to strike out with his new diet and lifestyle. One month on, his heart pain went away completely. Within a year, his cholesterol levels had dropped from 309 to 122. He also lost over 40 lbs (18 kg).
Paul was so amazed with the health impacts of changing to a plant-based diet, that he started The Plant Based Nutrition Support Group (PBNSG) 7 to help others make the transition to the optimally health WFPB diet.
In this second in the series of H.O.P.E. ‘Plant Power Stories’, Paul shares his journey back to health and encourages us all to give back to our communities.
If you consider that plant-based eating is of value to the health and well-being of your friends and family, perhaps you could consider sharing this blog with them.
So many people are facing a lifetime on medications and/or having invasive surgery for conditions that could be avoided and treated with simple dietary changes. But, of course, they have to know that such an alternative exists in the first place!
Whilst anecdotal success stories such as Paul’s are likely to inspire hope, all nutritional claims made on this website are always backed up by peer-reviewed, scientific research.
Diverticulitis is a very unpleasant and potentially lethal condition which is increasingly afflicting populations eating the modern Western diet. This blog will look in some detail at its symptoms, causes and history, as well as potential ways in which you can avoid allowing this often hidden-until-too-late condition to creep up on you.
N.B. THIS BLOG CONTAINS SOME GRAPHIC IMAGES.
What are the symptoms of diverticulitis?
The really dangerous thing about this disease is that there can be no symptoms at all until you drop dead. Indeed, it’s reported 1 that nine out of ten people who die of diverticulitis did so without ever even knowing they had it!
Although it can be an asymptomatic disease, there are a range of symptoms that may appear 23 , including:
abdominal pain, normally on the left side (ranging from slight to excruciating)
The clue is in the word itself – the Latin word dīverticulum means turn aside or divert. This diversion is exactly what can happen to some of the food (called chyme) as it passes through the intestines (usually in the colon – also known as the bowel), the muscular walls of which are “diverted” outwards into the abdomen. Peristalsis is a process where the muscles of the intestinal walls contract and relax so that the chyme gradually gets pushed along to the anus and out of the body.
If weak spots are formed in the outer layer of the intestinal wall, the muscles can push outwards laterally, forming pouches or diverticula (diverticulosis). Although the plural is “diverticuli”, many authorities still use “diverticula” for singular and plural. These diverticula can then become inflamed, infected, and start bleeding (diverticulitis). The greatest danger is that infected diverticula will eventually burst, seeping intestinal contents into the bloodstream. This can lead to sudden death.
It’s obvious, then, that diverticulosis occurs first. This condition is usually completely unnoticed and most people never know they have it unless it’s found on a routine colonoscopy. Diverticulitis comes next, and it’s the reason people end up in hospital. It’s reported that 10-25% of individuals with diverticular disease end up developing symptoms such as abdominal pain, bloating, irregular bowel movements, bleeding, or signs of infection. 67
Doctors often use the analogy of an over-inflated inner tube poking out through the wall of a tyre. Similarly, increased internal pressure can force the gut to balloon out through weak spots in the intestinal wall. The results are pretty obvious and rather unpleasant:
If the pressure builds up so much and the diverticula rupture, intestinal contents can be pushed into the abdomen and end up in the blood stream. 8
The reason internal pressure can increase so much within the intestines (usually in the colon) is related to the type and quantity of food (chyme) that’s passing through. Continuing the inner tube for intestine analogy – imagine your fingers doing the peristalsis movement and squeezing along a lump of soft mashed potato inside the tube. Should be pretty easy. However, replace the mashed potato with thick gooey molasses and it would be much harder to squeeze it along, resulting in increased internal pressure. If, over a long period of time, your colon is having to squeeze small and compacted lumps, rather than gently contract and dilate around large and soft lumps, damage is pretty inevitable. 9
Most diverticula are not particularly large – around 1-2 centimetres in diameter – but, nevertheless, even at this size they can be big enough to cause symptoms and complications in some people. 10
Dietary fibre & diverticulitis
Just as in the previous blog on constipation 11 , it comes down to the amount of fibre in your diet – too little, and our faeces become small and firm. The same thing is happening within our intestines. If there’s not enough ‘bulk’, the intestines have to squeeze really hard to move the chyme along, and this pressure buildup can force out those bulges and eventually lead to the colon literally rupturing itself.
High-fibre diets make for larger and easier movements through the colon. Plant-based diets contribute a considerable range of intestinal health benefits: adding huge amounts of natural prebiotics and probiotics that permit the gut bacteria (the microbiome) to do their magic: providing anti-inflammatory, anti-cancer, anti-obesity and blood sugar control effects; reducing the risk of stroke, high cholesterol and heart disease; helping to prevent hiatal hernia, brain loss, kidney stones, COPD, Parkinson’s disease, and diabetes; aiding weight loss; improving immunity, and ultimately increasing healthy longevity 12 . That our bodies are able to produce sufficient nitric oxide (a powerful antioxidant) is another factor that is of vital importance to the maintenance of health; and, as previous blogs have considered 1314 , the quality and quantity of plant foods within our diet dictates the type of microbiome inhabiting all parts of our bodies – from our mouths and intestines to our bladder.
I came across a nice Australian site which stated the following: “We evolved in tandem with our gut microbiome, the bacteria and other microbes that inhabit our gut. They are just as much a part of our digestive system as our own cells. They feed on dietary components that are not absorbed in the small intestine, such as dietary fibre and resistant starch. The microbiome pays its fare by providing us with energy and nutrients that would otherwise have been lost. The large bowel or colon is essentially a fermentation vat. This explains the gas.” 15 It’s always good to see that on the other side of the planet, these WFPB websites are quoting the likes of Drs McDougall, Greger, Popper and Klaper.
Low-fibre diets are not the only risk factor for diverticulitis. Additional contributing factors include smoking, being obese, and eating a diet which is high in red meat and animal fat. One study on meat intake and risk of diverticulitis in men, concluded: “Red meat intake, particularly unprocessed red meat, was associated with an increased risk of diverticulitis.” 16
This is backed up by a 2017 study:
“During 894,468 person years of follow-up, we identified 1063 incident cases of diverticulitis….The association between dietary patterns and diverticulitis was predominantly attributable to intake of fiber and red meat.” 17
The modern Western diet contains high levels of animal-based and processed foods. Whilst it’s obvious that animal foods are completely devoid of fibre, some people need to be gently reminded that most processed foods are also very fibre-poor, with most fibre being stripped out during the manufacturing process. 18
Medical advice should always be sought if you have any symptoms of diverticulitis. Most diagnoses are during an acute attack of abdominal pain.
Your doctor will normally want to give you a physical examination (checking abdominal tenderness) in order to establish the cause of the pain – and there can be a wide range of causes other than diverticulitis.
Women would also normally have a pelvic examination to rule out pelvic disease. After this, the following are possible diagnostic tests:
blood and urine tests (checking for signs of infection)
pregnancy test for women of childbearing age (ruling out pregnancy as a cause of abdominal pain)
liver enzyme test (ruling out liver-related causes of abdominal pain)
stool test (ruling out infection in patients with diarrhoea)
CT scan (identifying inflamed/infected pouches and to confirm a diagnosis of diverticulitis)
The severity of symptoms will determined the treatment. There are two broad classifications used: uncomplicated diverticulitis (usually mild symptoms treated at home) and complicated diverticulitis (usually severe symptoms treated at hospital):
antibiotics to fight any detected bacterial infection
a liquid diet for a few days until intestines heal naturally
when symptoms improve, gradually add solid food to the diet
over-the-counter pain relief
a tube inserted to drain away any abdominal abscess (if formed)
surgery – this would normally be needed if:
certain complications occurred, such as:
puncture (perforation) in the colon wall
you have a history of multiple episodes of uncomplicated diverticulitis (flare-ups – see below)
you have a weakened immune system
Acute flare-ups are not uncommon. It’s reported 19 that 20% of people with diverticula develop a bout of diverticulitis at some stage in their lives. Best advice – eat lots of fibre and keep hydrated so that you can avoid them developing in the first place.
Two types of surgery for diverticulitis
The two main types of surgery involved with diverticulitis are:
bowel resection with colostomy (when inflammation has been too severe to connect the colon to the rectum, a colostomy will be the option. This involves making an opening in your abdominal wall and connecting it to the still-healthy part of the colon. Waste then passes through the opening into a bag. It’s possible in some cases that the inflammation will reduce and the colostomy can be reversed and the bowel reconnected)
A colonoscopy may be recommended at no less than six weeks after recovering from diverticulitis, particularly if no test was done in the previous year. This might be done in order to exclude any cancer. Some authorities consider 20 that there is no direct link between diverticular disease and colon or rectal cancer. Naturally, a colonoscopy cannot be risked during a diverticulitis attack.
When is eating fibre & a WFPB diet not recommended?
When there’s a flare-up of diverticular disease, especially when hospitalisation was required, it’s generally recommended that a low fibre/liquid-like diet is used as a short-term intervention. Primarily advised as a means of managing gut motility and acute pain, this period of so-called “bowel rest” usually involves abstaining from all solid foods for 2-3 days and consuming only a clear liquid diet, with water or other clear beverages usually being all that’s advised. Once the symptoms have disappeared (that is, when acute pain has subsided) and, of course, under the advice of their doctor, the patient would then be advised to transition to a high-fibre plant diet – ideally of the non-SOS WFPB type.
“An absolute must in treating acute diverticulitis is a high-fibre diet if patients wish to prevent complications and recurrences of disease.” 18
Can diverticulitis be reversed by diet?
Once you’ve been diagnosed with diverticulitis, you are strongly recommended to always liaise with your doctor about any dietary changes. However, to avoid recurrence of symptoms, there is little doubt that reducing the pressure within your intestinal tract is key. This is best achieved through eating a diet high in fibre and ensuring you are always fully hydrated.
How much water and fibre is enough? This is a well-debated topic, and was covered in the previous blog 21 , but my research shows that a person eating a balanced WFPB diet is likely to consume up to 100 grams of fibre daily. This is definitely a healthy level. One UK study suggested 22 that for every 5 gram increase in fibre consumed each day, the result was a 15% reduction in disease risk. The same study found that some whole plant fibre sources were especially protective against the disease, namely whole grains and fruits.
However, if a person chooses not to eat an exclusively WFPB diet, it’s generally advised that over 30 grams of fibre is the lower recommended limit. Personally, I would always suggest that WFPB is the way to go. Best be safe than sorry with something that can kill you quickly without you even knowing you had it in the first place.
In terms of daily liquid (ideally water, or black/green tea) consumption, a minimum of around 7 cups (1.75 litres) of water for women and ll cups (2.75 litres) for men is recommended. Plant foods contain mostly water, and so this will add to liquid intake to make it up to the WHO recommendation of 11 cups (2.75 litres) for women and 15 cups (3.75 litres) for men. 23
It’s been shown 2 that even eating just a standard vegetarian diet (with a high intake of dietary fibre compared with the standard meat-based Western diet), is associated with lowering the risk of getting the disease in the first place, of being admitted to hospital, and of dying from the disease. How much more for a WFPB diet with its higher fibre content? Other studies have shown similar results, stating: “Consuming a vegetarian diet and a high intake of dietary fibre were both associated with a lower risk of admission to hospital or death from diverticular disease.” 24
Dr John McDougall considers that it’s certainly worth changing to a high-fibre diet in order to relieve symptoms and prevent further diverticuli: “Contrary to what was once popular opinion, the addition of fibers in the form of brans or high fiber foods has relieved symptoms in 90% of cases of severe colon disease, even with recurrent pain and bleeding. A high fiber diet will also decrease the likelihood of developing new diverticuli. The diverticuli already formed are permanent herniations of the colon, and will not disappear except by surgical removal, which is rarely indicated.” 25
In the following short video, Dr McDougall also reassures us that the bleeding and infection within diverticuli can, in most cases, disappear by making simple dietary changes. The diverticuli themselves remain, although he considers that they would no longer be a problem, so long as a high-fibre diet is maintained.
Diverticulitis rises as fruit & veg consumption drops
Major studies have shown 626 beyond any doubt that the risk of developing diverticular disease goes down as fruit and vegetable consumption goes up – and, of course, vise versa. These studies produced the following results:
increased diverticular disease is associated with consumption of:
the strongest correlation of disease reduction is associated with consumption of:
consumption of all vegetable fibre also reduces disease risk
A further study 7 looked at the effects of using a high-fibre diet in the cases of 100 patients who had been previously diagnosed with acute diverticulitis. After 5-7 years on this diet, 91% of the patients remained completely symptom-free. The authors pointed out that the following respected organisations endorse and encourage the use of a high-fibre diet to prevent diverticular disease:
Can you eat nuts and seeds if you have diverticulitis?
The usual medical advice around people who have had diverticulitis is that they should avoid eating nuts, seeds, corn, and popcorn. Indeed, some doctors advise that everyone should avoid these foods as a means of avoiding the disease. However, there are at least two recent studies that have blown this unfounded advice out of the water.
A 2009 study 10 stated: “Without any good evidence, certain foodstuffs such as nuts, seeds, popcorn, and corn have long been implicated in the development of diverticulitis and are often advised against by physicians. They were thought to provoke diverticulitis or diverticular bleeding by causing luminal trauma. In a large prospective study of men without known diverticular disease, Strate et al found 31 that nut, corn, and popcorn consumption did not increase the risk of diverticulosis, diverticulitis, or diverticular bleeding.”
A 2012 study 32 stated: “Residue refers to any indigestible food substance that remains in the intestinal tract and contributes to stool bulk. Historically, low-residue diets have been recommended for diverticulosis because of a concern that indigestible nuts, seeds, corn, and popcorn could enter, block, or irritate a diverticulum and result in diverticulitis and possibly increase the risk of perforation. To date, there is no evidence supporting such a practice. In contrast, dietary fiber supplementation has been advocated to prevent diverticula formation and recurrence of symptomatic diverticulosis, although this is based mostly on low-quality observational studies.”
Whilst further research is useful, any advice to avoid nuts & seeds does not appear to be based on anything but unfounded conjecture. And, as shown in the 12-year long Seventh Day Adventist Study published in 2001, vegans who didn’t eat any nuts and seeds didn’t live as long as those vegans who did. This is because of the essential fats that nuts and seeds contain – allowing effective absorption of the phytochemicals and anti-oxidants that both groups are eating 3334
How common is diverticulitis?
“Diverticular disease [including diverticulitis] is the most common intestinal disorder.” 35
One study states: “In industrialized nations, diverticular disease affects up to 70% of individuals by 60 years of age, with symptoms that can range from mild gastrointestinal disturbance to incapacitating pain.” 36
Is diverticulitis age-related?
Whilst it’s been conventionally thought that it is an inevitable age-related condition – with the theory being that the intestinal walls tend to weaken as the years and decades pass – this theory can be shown to be untrue. Back in 1907, guess how many cases were recorded? 25! 36 That’s not 25% of the population, but 25 individual cases had been reported in the medical literature. And, as you can see from the graphic photograph above, any autopsy would have had little difficulty in missing diverticulitis if it had been present.
“Development of diverticular disease is not an inevitable part of growing older. The colons of people living in underdeveloped countries show a virtual absence of diverticular disease. Healthy, low, pressures in the colon happen when the diet is high in starches, vegetables, and fruits, with their generous content of fiber.” 25
Even in 1916, a study 37 reported that diverticulitis was still not sufficiently documented as a morbid disease in medical literature for it to merit medical recognition.
Diverticulitis – a late 20th Century disease
But in a 1971 study, by the WFPB pioneer Denis Burkitt and his team 38 , it was already recognised as the most common intestinal disease in the US population.
How could this have happened so quickly?
Denis Burkitt showed incredible insight by pointing out that it was most probably down to the fact that even by the 1970’s the Western diet had become low in fibre and high in animal products, processed and highly refined foods. Indeed, it took just half a century from the introduction of rolling milling of flour (which greatly reduced the natural fibre content) in the late 1800’s for diverticulitis to become common in the UK by the 1920’s.
Since then, things have gone from bad to worse.
A number of the first researchers to study diverticulitis nicknamed it a “20th century problem” and a “disease of Western civilisation.” 6
Denis Burkitt’s team back in the 1970’s included in their report 38 a simple diagram which they thought explained the process by which diverticula are formed:
It’s probably no surprise that the US and European populations have the highest rates of diverticular disease in the world, whilst it is rarely found in developing countries before, that is, they adopt the Western diet. 397
A 1985 study 40 , again by Denis Burkitt, compared Americans and Africans to see if there were differences in their rates of diverticulitis and other intestinal diseases related to low-fibre diets – namely, hiatus hernia and pelvic phleboliths41 . As Dr Greger pointed out in a video on this subject 42 , Burkitt found a huge difference in diverticulitis rates between the Africans eating the high-fibre diet (less than 1% of the population) and the Americans eating the low-fibre diet (more than 50% of the population):
Your poo can give a clue
This might not be the most tasteful subject, but you can tell a lot about the likely state of your intestines by checking on what your poo (stool or faeces) looks like. If you’re regularly constipated, and diverticula have already formed in the colon, stagnant faecal matter ends up clogged in the diverticula “bubbles”. 39 This can, in turn, trigger inflammation of the intestinal wall, resulting in the above-mentioned symptoms. The following chart is one of the standard charts used to get clues from your poos:
The Bristol Stool Chart provides a graphic version of various stool samples.
Developed by Dr. Ken Heaton from the University of Bristol in the late 1990’s, it’s used primarily as a clinical communication aid in categorising stool types 43 .
It’s only meant to be an unofficial guide, but does allow us to get a general idea of the classification of our poo, providing, thereby, a reasonably good indicator of both the diet we’re eating and the likely state of our intestines.
types 1 and 2 are typical of a constipated individual
type 3 is borderline normal
type 4 is the “gold standard for the perfect stool”
type 5 is heading in the direction of diarrhoea
types 6 and 7 reflect an individual in diarrhoea distress
If you want to delve deeper into the subject of bowel movements and constipation, Dustin Rudolph, PharmD has written a useful article. 44
It’s worth repeating that the balance of gut bacteria can be altered by chronic constipation and eating a low-fibre diet. Rather than a colon full of “good” (healthy) bacteria, there’s an increase in “bad” (infectious) bacteria that populate the colon. And it’s the presence of the latter bacteria that can further increase the chances of an infection developing.
Low-fibre diets do NOT cause diverticulitis!
Just to confuse the issue, a 2012 North Carolina study 45 came up with completely different conclusions than everything else that’s been said above about diverticulitis (and, of course, constipation) being powerfully linked to low-fibre diets. The study concluded:
“In our cross-sectional, colonoscopy-based study, neither constipation nor a low-fiber diet was associated with an increased risk of diverticulosis.”
By understanding the reason that they found no association, we can learn something about the quantity of fibre necessary to make a significant difference to your risk of developing chronic constipation and/or diverticulitis, plus we can learn a lot about how clinical trials can come up with misleading information.
In this study, they took two groups and carefully ensured that one group received only 8 grams of fibre a day while the other group received 25 grams of fibre a day. When they compared the results, there was no significant difference in the rates of diverticulosis and, thus they announced to the world that we do not need to bother eating a high-fibre diet in order to maintain good gut health.
The story was taken up all over the world, with headlines like:
“Diets high in fiber won’t protect against diverticulosis, study finds.“4647
“High-fibre diet may not protect against diverticulosis.”48
“Paleo Diet: More Evidence That Fiber is Not A Good Thing.”49
And not only did the Paleo crowd get involved and believe the study findings, even medical journals jumped on the band wagon, quoting the conclusions of the above study:
“Diverticulosis and dietary fiber: rethinking the relationship…A high-fiber diet does not protect against asymptomatic diverticulosis.” 50
So, what’s going on here?
Firstly, good news about bad habits is always attractive for those who want to justify their own bad dietary habits – tucking into a juicy beefburger and fries with impunity, rather than having to worry about eating all that rabbit food!
However, the fatal flaw in the study was identified pretty quickly by other studies, including the following:
“Most importantly, how this study is interpreted is limited by the overall low-fiber intake within the study population. Although the authors performed analyses stratified by fiber intake and found no significant difference between those in the lowest (2.5–10.1 g) and highest quartiles (18.4–50.3 g) of fiber intake, few patients in the uppermost quartile had a true high fiber intake. An analysis reflecting clinical recommendations of high-fiber (>25 g) vs low-fiber (<14 g) diets may have yielded different results.” 51
To clarify just what this flaw of the study was, Dr Greger 52 drew an excellent analogy with early vitamin C studies. It takes around 10 mg of vitamin C a day to avoid developing scurvy 53 .
Back in the 1700’s, James Lind 54 wondered if scurvy in sailors could be avoided if they were given wedges of lemon each day. So he tested his theory. One group were given one wedge of lemon, and the other group were given three wedges of lemon a day. He found no difference at all between the groups, and the same ratio came down with scurvy.
So, did this prove that low vitamin C levels are not associated with the development of scurvy? Of course not. In order to prevent scurvy, it’s necessary to ingest at least 10 mg of vitamin C, and a single wedge of lemon only has around 2 mg. So, even with three wedges of lemon, you’re still only getting around 6 mg.
See the analogy?
The group eating the highest amount of fibre in the above North Caroline study 45 were only eating around 25 grams of fibre a day, which is less than the US minimum recommended daily allowance of around 32 grams. As Dr Greger says: “They didn’t even make the minimum. So they compared one fiber-deficient diet to another fiber-deficient diet—no wonder there was no difference in diverticulosis rates.”
Whenever looking at any study results that appear “too good to be true”, it’s always worth checking on what was compared with what – after all, even a McDonald’s Big Breakfast is healthy when compared with…smoking tobacco or inhaling asbestos!
As with many things in life, simple is best. The best form of cure for diverticular disease is prevention. And the best form of prevention is undoubtedly provided by eating a high-fibre diet, keeping well-hydrated, and getting plenty of regular daily exercise.
I can’t really think of a better way of ending than by quoting a closing comment by Dustin Rudolph, PharmD, writing for T Colin Campbell’s Center for Nutrition Studies (CNS), made at the end of his article on diverticular disease:
“Eat plants. Get lots of fiber. Live happy. And avoid doctors and pharmacists if at all possible by adopting a whole food, plant-based lifestyle. Your body will thank you for many years to come.” 18
A fistula, in this case, is an abnormal passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs. In this case, it is more commonly between the intestine and the bladder. [↩]
Pelvic phleboliths are are round clusters of calcium that develop in the walls of a vein. They can vary in size but are usually around 5 mm across. They most commonly appear in the veins surrounding the pelvis. They can be caused by constipation and straining, which can damage pelvic veins. [↩]
Scurvy is a disease resulting from a lack of vitamin C (ascorbic acid). Early symptoms include weakness, feeling tired, and sore arms and legs. Without treatment, decreased red blood cells, gum disease, changes to hair, and bleeding from the skin may occur. As scurvy worsens there can be poor wound healing, personality changes, and finally death from infection or bleeding. [↩]