A January 2019 scientific review ¹ by Dr Neal Barnard ² and his team, entitled “Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports“, looked at whether endurance athletes, who are at a higher-than-average risk of developing atherosclerosis and myocardial damage, have reduced health risks and improved performance if they eat a plant-based diet. The results are pretty compelling and should be considered by anyone within any age group who engages in regular physical exercise, not just those who undertake endurance sports.

Diet & exercise

It’s well-accepted ³ that diet in general plays a significant role in maintaining the health and improving the performance of athletes. In previous blogs, we looked in some detail at how plant-based diets may improve sports performance and reduce injury ^{4 5 6} , as well as how options such as the paleo diet ⁷ and consuming whey products ⁸ appear to do quite the opposite. Interestingly, and in relation to cancer risk, some research even showed ⁹ that the blood of a ‘couch potato’ eating a healthier than standard diet is likely to have better cancer-fighting abilities than the blood of someone who exercises regularly and strenuously but eats the standard diet – thus suggesting that diet may play a more significant role in overall health than exercise.

The study covered below deals in more depth with how choosing a plant-based diet can improve athletic performance as well as help avoid, and even reverse, serious and long-term health risks that both athletes and non athletes face.

What the study covers

The study considers that there is sufficient evidence to claim that plant-based regimes can achieve the following:

• reduce cardiovascular risk factors
  • reverse existing atherosclerotic lesions
• reduce plasma lipid concentrations, thereby:
  • reduce blood viscosity, and
  • increase tissue oxygenation
• improve glycaemic control ¹⁰
• reduce body weight (obesity)
• increase glycogen storage
• reduce blood pressure
• reduce oxidative stress
• reduce inflammation

Individually, or in combination, it’s suggested that the above benefits, which may result from plant-based dietary regimes, both protect the health of the athlete and improve athletic performance. The latter are discussed in more detail below.

Cardiovascular risk & plant-based diets

Studies have shown plant-based dietary patterns have particular benefits for heart health:

• being able to reverse arterial plaque ^{11 12 13}
• significantly reducing the likelihood of developing coronary heart disease compared with meat eaters ¹⁴

But surely, you’d think, athletes are more or less immune to developing atherosclerosis ¹⁵ because of all the exercise they do. However, this has been shown ¹⁶ not to be the case. It may seem odd, but it’s been shown in several studies ^{17 18 19 20} that endurance athletes may have more advanced atherosclerosis and more myocardial damage than sedentary individuals, increasing as periods of sports endurance accumulate and as they age.

Even sudden sports-related sudden cardiac deaths among ostensibly ultra fit athletes have been shown ²¹ to be more common than you’d think, especially with increased age.

But is it the diet?

Of course, the question has to be answered: “Is the atherosclerosis and myocardial damage caused by the athletic activity itself or by the foods used to fuel it?”

This study considers that when consumption of animal products is increased, perhaps with the hope of supplying increased energy for increased athletic activity, the associated saturated fat and cholesterol (as well as the relative absence of antioxidants and fibre ²² ) may contribute to the atherosclerotic changes.

Atherosclerosis may also narrow arteries in the legs, brain, and other parts of the body which will reduce blood flow and potentially impair performance. This has certainly been shown ²³ to be the case with diagnosed peripheral artery disease, and is considered as a factor for athletes with undiagnosed (i.e. subclinical) atherosclerotic disease.

Plant-based diets can address the key factors that cause atherosclerosis, namely:

• dyslipidemia ²⁴
• elevated blood pressure
• elevated body weight, and
• diabetes

So it would appear that diet is key to protecting heart health and thus for enhancing athletic performance.

Atherosclerosis – exception or norm?

And while one may think that atherosclerotic disease is the exception rather than the rule, studies have shown ²⁵ that in the modern Western world [with its modern Western diet] atherosclerosis can begin early in life, even in the womb.

A study ²⁶ showed that the majority of American children have fatty streaks in the left anterior descending coronary artery by the age of 10 to 14 years.

Autopsies of U.S. soldiers with a mean age of 20.5 years who died in the Korean War showed that 6.4% of them had coronary atherosclerosis ²⁷ .

Autopsies of soldiers with a mean age of 25.9 years who died in the Iraqi wars between 2001 and 2011 showed that 8.5% of them had coronary atherosclerosis ²⁸ .

And it gets worse. In so-called ‘developed’ countries, by the age of 20, ~10% of the population have advanced atherosclerotic lesions in the abdominal aorta, which reduces blood flow and contributes to disc degeneration and lower back pain ²⁹

So, if you’re from a country where the Western diet is the norm (and, of course, you’ve also eaten that diet), you’re very likely predisposed to such risks even before you run your first marathon.

Plasma lipid concentrations & plant-based diets

Diets rich in saturated fat and, to a lesser degree, dietary cholesterol promote dyslipidemia, and dyslipidemia is a major contributor to arterial disease. With dairy products and meat being the leading sources of saturated fat, removing these has predictably been shown ³⁰ to improve plasma lipid profiles.

By including soluble fibre (e.g. oats, beans, barley), almonds, soy protein, and sterol-containing margarines [the latter being something no WFPB advocate would advocate!], it’s been shown ³¹ that low-density lipoprotein (LDL – the ‘bad’ cholesterol) can be reduced by around 30% in as little as 4 weeks.

It’s also important to point out that trans fats have detrimental effects on plasma lipids and, thus, increase cardiovascular risks ^{32 33} .

Blood viscosity/tissue oxygenation & plant-based diets

Blood viscosity is a key element in oxygen delivery to the muscles ³⁴ – lowering viscosity improves both blood flow and athletic performance, increasing viscosity does the opposite ³⁵ .

During athletic activity, fluid passing from the bloodstream into the tissues leads to haemoconcentration ³⁶ . This gradual rise in blood viscosity results in progressive loss of tissue oxygenation which, of course in turn, degrades athletic performance ³⁷ .

Diet affects this plasma viscosity. Because plants are typically low in saturated fat and have no cholesterol, plant-based diets are considered ^{30 38} to reduce plasma lipid concentrations, and hence reduce viscosity.

Reduced blood viscosity also improves tissue oxygenation, thereby potentially improving athletic performance. In one study ³⁹ , brachial artery flow-mediated vasodilation ⁴⁰ was assessed in a range of diets – low-fat vegetarian, low-carb/high-fat (Atkins), and high-fat (South Beach). The results were that the vegetarian diet improved brachial artery flow-mediated vasodilation compared with the other diets. Basically, the higher the saturated fat intake, the greater the impairment of flow-mediated vasodilation, with arterial compliance being impaired even by a single high-fat meal.

This impairment is not only caused through eating food high in animal fats, added oils appear ^{41 42 43 44} to have similar effects. The latter studies suggest that animal fats as well as meals made with added oils are harmful for arterial flexibility; on the other hand, they make it clear that there is benefit from consuming meals made from vegetables, grains, legumes, and fruits.

The food choices athletes make affect blood viscosity, arterial diameter, arterial compliance and arterial elasticity. All the latter factors can be expected to affect tissue oxygenation, endurance, and performance.

Glycaemic control & plant-based diets

Plant-based diets are known to boost insulin sensitivity ⁴⁵ which, as we’ve seen ⁴⁶ , is important for reducing the risk of type 2 diabetes and improving glycaemic control – a major contributor to atherosclerosis in individuals with diabetes. Indeed, even small amounts of animal food (such as just one cup of non-fat milk) are sufficient to reduce arterial diameter and can thus lead to major changes in blood flow.

Body weight (obesity) & plant-based diets

The risk of developing cardiovascular disease is, naturally, increased by becoming obese. Even when you ditch calorie-counting or portion-control altogether, vegetarian, and especially vegan, diets have been shown ⁴⁷ to reduce body fat and thereby tackle obesity.

In a previous blog ⁴⁸ , we looked at how plant-based diets are the easiest (and healthiest) way to lose weight and then maintain an optimal body weight. This study amplifies this point with reference to how plant-based diets are, thus, able to protect the health of athletes and improve athletic performance. This is achieved via a variety of mechanisms, including:

• the low fat/high fibre content of plant-based diets reduces body fat (thereby reducing atherosclerotic risk and improving performance) ⁴⁹
• the reduced energy density of plant-based meals reduces energy intake (you get fuller quicker on less calories, partly because of the higher proportion of fibre in plants that doesn’t exist in animal-foods)
• postprandial energy expenditure is shown ^{45 50} to be positively influenced by plant-based diets – possibly via changes in mitochondrial activity ⁵¹
• the indirect effects of gut microbiome on cellular metabolism have been shown ⁵² to be negatively affected by a high-fat diet (such as is the norm with a meat-based diet) and positively affected by a low-fat diet (such as is the norm with a plant-based diet), partly through protecting the intestinal barrier and preventing the production of endotoxins which can then enter the bloodstream and, in turn, negatively influence cellular metabolism
• plant-based (vegan more than vegetarian) diets have been shown ^{53 54} to increase sub-maximal/maximal aerobic capacity/endurance and reduce atherosclerotic/metabolic risk through eliminating excess body fat and, thereby, increasing max VO2 ⁵⁵ . This is important since it’s known ^{56 57} that an athlete with a higher VO2 max relative to their body weight will have better endurance and will outperform an athlete with a lower value, and that the effect of diet on VO2 max has a significant effect ⁵⁸

Glycogen storage & plant-based diets

It’s known ⁵⁹ that individuals who start plant-based diets typically increase intake of healthy carbohydrates (the primary energy source during moderate/high-intensity aerobic exercise) and it’s been shown ⁶⁰ that endurance is enhanced by high-carbohydrate intake, not just immediately before athletic events, but also over the long term.

Blood pressure & plant-based diets

We’ve looked previously ⁶¹ at how the risk of atherosclerotic conditions reduces as blood pressure is reduced. This is good news for those on a plant-based diet, since both vegan and vegetarian diets have been shown ⁶² to reduce systolic and diastolic blood pressure. Reduced blood pressure is associated with three other ‘side-effects’ of a (healthy) plant-based diet:

• a reduction in blood viscosity
• an increase in blood potassium, and
• a reduction in body weight

Oxidative stress & plant-based diets

When you exercise, your muscle tissue gets ‘damaged’ and produces reactive oxygen species (free radicals), partly as a result of the normal function of mitochondria and other intracellular organelles ^{63 64} . When your body is overwhelmed by these free radicals, and it can no longer neutralise them, the result is called oxidative stress.

This oxidative stress, in turn, boosts antioxidant defences and immune responses ^{65 66} .

If the amount of free radicals greatly exceeds the neutralising abilities of these defences, the following can occur ⁶⁷ :

• DNA damage – leading to mutations
• plasma lipid damage – leading to atherosclerosis
• protein damage – leading to cell damage and accelerated aging
• muscle fatigue
• reduced athletic performance
• impaired recovery

How can being plant-based help?

When the physiological responses of omnivores and vegans/vegetarians were compared, it was found that vegans and vegetarians have increased antioxidant activity, due to:

• higher intakes of beta-carotene (the precursor of vitamin A), vitamin C, vitamin E, and other antioxidants ⁶⁸
• higher antioxidant enzyme production ⁶⁹

Whilst it’s the combination of plant foods that’s important, specific antioxidant foods have been found to have potentially beneficial effects, including:

• beets ^{70 71}
• allium vegetables (e.g. onions, garlic, and leeks) ⁷²
• cherry juice ⁷³

Inflammation & plant-based diets

Plant-based diets have been shown ⁷⁴ to be helpful in reducing inflammation. This may be due to the following effects produced by plant consumption:

• reduction in serum concentrations of C-reactive protein (a marker of inflammation)
• increased antioxidant content
• absence of products that may be inflammatory or sensitising [animal & processed food products]
• absence of pro-inflammatory fats [mostly found in animal foods]

Again, whilst a healthy variety of plant foods provides the ideal diet, some studies have identified particularly high antioxidant ability within specific foods, including:

• blackcurrants ⁷⁵
• blueberries⁷⁶
• pomegranates ⁷⁷
• tart cherries ⁷⁸
• watermelon ⁷⁹

The above are all thought to decrease post-exercise inflammation and facilitate recovery.

Red meat & inflammation

A major study showed ⁸⁰ that, as total red meat consumption increased, the following also increased:

• C-reactive protein (a marker of inflammation)
• haemoglobin A1c (an indicator of glycaemic control – raised blood sugar levels), and
• stored iron (an excess of iron [specifically haem iron ⁸¹ ] is associated with heart disease, cancer, and diabetes)

Arthritis & plant-based diets

It used to be thought that osteoarthritis was attributable to simple “wear and tear”; however, it’s now known ⁸² that there’s an important inflammatory component which is aggravated by diabetes and by being overweight.

And it’s not just osteoarthritis that’s affected by diet – psoriatic arthritis ⁸³ and many other similar conditions are also now known to be manifestations of inflammatory processes.

In one major ongoing study ⁸⁴ , people who ate meat even once a week had higher levels of both degenerative arthritis and soft tissue disorders than individuals who avoided meat altogether.

A number of studies ^{85 86 87 88 89} on people suffering from rheumatoid arthritis have shown that changing to vegan and vegetarian diets can reduce C-reactive protein, as well as both subjective and objective signs of arthritis.

Whilst vegan diets, in particular, have been shown ^{90 91 92} to have anti-inflammatory effects by reducing C-reactive protein in patients with and without coronary artery disease.

Protein & plant-based diets

The usual red herring about plant-based diets being compromised in terms of protein and/or complete amino acid provision has been covered in considerable detail in previous blogs ^{93 94} ; however, it’s worth pointing out the following:

• changing to plant-based has been shown ⁹⁵ to provide an immediate improvement in nutrition levels (partly because fruits, vegetables, beans, and whole grains tend to be high in vitamins, minerals, and fibre, very low in saturated fat, and devoid of cholesterol)
• pretty much every endurance athlete tested ⁹⁶ met recommended protein intake
• a varied plant-based diet is known ⁵⁹ to easily provide adequate amounts of all essential amino acids for athletes

Calcium & plant-based diets

Another fallacy, addressed in previous blogs ^{97 98} , is that plant-based diets, because they don’t contain cow’s milk, will lack sufficient bone-building calcium for athletes and others.

However, calcium is abundant in many plant foods, especially green leafy vegetables and legumes ⁹⁹ .

Iron and plant-based diets

As mentioned above, plants contain non-haem iron, which is considered to be a healthier form of iron than the haem iron in animal foods. It may come as a surprise that iron intake is often higher in those who eat plant-based diets than in those who eat meat-containing diets, with serum ferritin levels being typically within the normal range ¹⁰⁰ . This is because of the large iron content of green vegetables and legumes. However, iron storage tends to be lower – a good thing since you don’t want rust inside your body! ^{101 102}

Vitamin B12 & plant-based diets

Vitamin B12, covered in previous blogs ^{103 104 105} , is another area where confusion reigns. Whilst, of course, B12 is absolutely vital for nerve function and blood cell formation, and must be supplemented when on a plant-based diet ⁵⁹ , B12 deficiency/insufficiency is surprisingly common throughout whole populations, regardless of their dietary regime. Thus, it’s advisable for everyone, particularly as we age ¹⁰⁶ , to take B12 supplementation.

Study conclusions

“Plant-based diets play a key role in cardiovascular health, which is critical for endurance athletes…and, as part of a healthful lifestyle, have been shown to reverse atherosclerosis. The possibility that such diets may also contribute to improved performance and accelerated recovery in endurance sports is raised by their effects on blood flow, body composition, antioxidant capacity, systemic inflammation, and glycogen storage. These attributes provide a scientific foundation for the increased use of plant-based diets by endurance athletes.”

Final thoughts

When we looked at obesity and plant-based diets above, it was pointed out that calorie-counting and portion-control were not needed in order to reduce body fat and, thereby, reduce body weight and avoid the risk of becoming obese. In relation to this, there was a BBC documentary ¹⁰⁷ recently by Hugh Fearnley-Whittingstall at the end of which he drew the unfortunate (in my opinion) conclusion that, whilst calorie-counting was not the way to go, the best way to keep the weight down was to apply strict control to portion size.

I tend to disagree with this approach. Just as it’s been shown that calorie-counting ¹⁰⁸ and exercise alone ¹⁰⁹ are ineffective means of maintaining a healthy body weight, I suspect that, in spite of some studies’ somewhat optimistic conclusions ¹¹⁰ , portion-control (or portion-sizing) is also a dietary method destined to fail in most cases ¹¹¹ , albeit that it’s a whole lot better than doing nothing at all.

When you eat a non-SOS WFPB diet, you never need to worry about how many calories you are eating nor about what size your plate is. The very nature of the food itself will be regulated by your body’s appetite and requirement for nutrients, whether or not you’re an Olympic athlete.

Ever seen anyone becoming overweight who consistently eats a WFPB diet? If you do, let me know, since I haven’t come across one yet…

---

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