A recent prospective cohort study and meta-analysis was published in the Lancet ¹ . It looked at dietary carbohydrate intake and mortality. This study acts as a perfect example of why it’s so important to look at the detail rather than simply read and believe the headline messages you read in the media.

Study background

This study was a serious and well-presented piece of research, spanning three decades and covering large groups of subjects spread across different continents. It’s aim was to find out whether a person’s risk of mortality is determined by their intake of carbohydrates.

Study findings

This chart comes from the study and is the main item I want to discuss with you.

What it basically shows is a U-shaped curve, indicating that you are likely to have a premature death (Hazard Ratio) whether you eat too little or too much carbohydrate as a percentage of your diet.

The other macronutrients would, of course, be proteins and fats.

On the face of it, you would think therefore that the ideal amount of carbs to consume would be around 50% of your total calorie intake. This would mean that you’d then be getting the remaining 50% from proteins and fats.

So what’s the problem?

The problem is that, if the above summation is the truth, the whole truth, and nothing but the truth, then much of what I’ve been writing in previous blogs is up the swanny! ²

We’ve seen how Dr T Colin Campbell and others claim ³ we should be aiming for 8-12% protein and 10-15% fat, with the lower figures being ideal. So, you don’t need to be a mathematician to realise that this leaves 77-82% carbohydrates.

The latter figure would be in the upper end of the right hand side of the U-shaped curve, which would make it as unhealthy (higher mortality rate) as the bottom part of the left hand side, where carbs are around 20% – basically the amount in a really heavy-duty Paleo/Atkins-type diet, which we’ve seen has been shown ^{4 5 6} to be a strikingly unhealthy option…

Naturally, if a person just looked at that one chart and derived their opinion of the study researchers’ conclusions from that alone, they could be misled into believing that something like the WFPB diet (which ideally has the 77-82% carb content mentioned above) is not the way to go. Far better to follow the age-old mantra “Moderation in all things“.

However, the U-shaped curve above does not tell the whole story.

So where’s the solution?

The solution to this quandary lies in both the type and source of carbohydrate, and not so much in the simple percentage of carbs in the diet. Not all carbohydrates are the same… ^{7 8}

The researchers in this study state, for instance, that much of the data regarding the highest levels of carbohydrate consumption are in populations (e.g. China and Japan) which consume huge quantities of white rice, which not only forms the major type of carbohydrate consumed, but also represents pretty much the only food some of these communities eat:

“…high carbohydrate diets, which are common in Asian and less economically advantaged nations, tend to be high in refined carbohydrates, such as white rice; these types of diets might reflect poor food quality ^{9 10} and confer a chronically high glycaemic load that can lead to negative metabolic consequences ¹¹ .”

Additionally, the authors state:

“…There are limitations to this study that merit consideration. This study represents observational data and is not a clinical trial…Our study focused on general carbohydrate intake, which represents a heterogeneous group of dietary components. Any number and combination of dietary components could have been considered and adjusted for in this analysis; therefore, some confounders might have been unadjusted for.”

Thus, it appears that the vast majority of group eating high levels of carbohydrate (above the 50% which would appear to be the optimum from the U-shaped curve) were actually eating the sort of refined carbohydrates (white rice etc) which would never be considered as part of an optimal WFPB diet.

It’s also useful to note that the study does not look at how much of the recorded carbohydrate intake derives from so-called Frankenfoods ¹² – the typical highly-processed, pre-packed, junk food which increasingly comprises the ever-spreading SAD (standard american diet).

In their conclusion, the authors are very clear on one matter, which is in line with findings from studies covered in previous blogs ^{13 14 15} , indicating that protein and fat from animal sources are more harmful to human health than protein and fat from plant sources:

“Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality.”

And whilst they don’t mention the problems with protein and fat (as well as PCBs, heavy metals, pesticides, diotoxins, etc) from dairy and fish, previous blogs certainly have covered them ^{16 17} .

There are some caveats about saturated fats from the likes of coconut oil ¹⁸ and all isolated vegetable fats/oils ^{19 20} , but the general picture of the higher health benefits of unprocessed whole plant proteins and fats is clear from previous studies, as well as from the above study:

“…animal-based low carbohydrate diets should be discouraged. Alternatively, when restricting carbohydrate intake, replacement of carbohydrates with predominantly plant-based fats and proteins could be considered as a long-term approach to promote healthy ageing.”

The position is made even more apparent when you consider that eating a balanced and varied diet of whole unrefined plant foods provides the natural macronutrient balance ²¹ – which just happens to be in line with the 10:15:75 (or 10:10:80) protein:fat:carbohydrate ratio recommended by the likes of Drs Campbell, Klaper, Esselstyn, Greger, Fuhrman, McDougall, et al.

The above chart ²² shows the sort of diet that helps Chinese centenarians to live long and healthy lives.

Final thoughts

There’s limited long-term research yet available on the relationship between mortality and the type of carbohydrate consumption a WFPB diet recommends – that is, whole vegetables, fruits, legumes, nuts, seeds and mushrooms without any (or, at least, with very low quantities of) added salt, oil or sugar.

When we look at the so-called Blue Zones ^{23 24 25} , we see a consistently high pattern of low animal-sourced consumption and a high level of unrefined plant-sourced consumption. And it’s important to emphasise the unrefined aspect of these healthy diets.

So to advocate that we “Believe half of what we see but none of what we hear” might make it seem as though we have to be critical and unbelieving – but that’s how we need to be in this society of soundbites and truncated attention-spans if, that is, we want to wrestle fact from fiction.

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References

1. Lancet Public Health. 2018 Sep;3(9):e419-e428. doi: 10.1016/S2468-2667(18)30135-X. Epub 2018 Aug 17. Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. Seidelmann SB, Claggett B, Cheng S, Henglin M, Shah A, Steffen LM, Folsom AR, Rimm EB, Willett WC, Solomon SD. [↩]
2. Urban Dictionary Definition of ‘Up the swanny’ [↩]
3. Fat and Plant-Based Diets [↩]
4. Our Grandchildren Suffer From Our Meat Consumption [↩]
5. Want Heart Failure? Try the Atkins Diet… [↩]
6. The Problem with Protein [↩]
7. Pritikin: Good Carbs vs Bad Carbs – What Are You Eating? [↩]
8. Low Carb Hot Air—Again, again and again! [↩]
9. Ramsden CE, Domenichiello AF. PURE study challenges the definition of a healthy diet: but key questions remain. Lancet. 2017; 390: 2018-2019 [↩]
10. Nakamura Y, Okuda N, Okamura T et al. Low-carbohydrate diets and cardiovascular and total mortality in Japanese: a 29-year follow-up of NIPPON DATA80. Br J Nutr. 2014; 112: 916-924 [↩]
11. Augustin LS, Kendall CW, Jenkins DJ et al. Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC). Nutr Metab Cardiovasc Dis. 2015; 25: 795-815 [↩]
12. Dr Fuhrman: Frankenfoods [↩]
13. Nutrients in Plant and Animal Foods [↩]
14. Animal Foods Are The Smoking Gun [↩]
15. Animal Protein & Your Kidneys [↩]
16. Cow’s Milk – But It Looks So Innocent… [↩]
17. But I thought Fish Was Good For Me! [↩]
18. Coconut Oil is ‘Pure Poison’ says Harvard Professor [↩]
19. Olive Oil Injures Endothelial Cells [↩]
20. Macronutrients in a Healthy Balanced Diet [↩]
21. Macronutrients in a Healthy Balanced Diet [↩]
22. Diet of Chinese Centenarians. [↩]
23. The Blue Zones, Second Edition: 9 Lessons for Living Longer From the People Who’ve Lived the Longest by Dan Buettner. [↩]
24. Chen J, Campbell TC, Li J, Peto R. A Study of Diet Nutrition and Disease in the People’s Republic of China. University of Oxford Press, Cornell University Press, China Publishing House, 1988. [↩]
25. Diet, nutrition and cancer: Executive summary. Cancer Research 1983;43:3020. [↩]