Despite its modern resurgence, vegetarian diets are far from new.  Since the 6th century BCE humans have abstained from consuming animals (and often their products) for ethical, ascetic, spiritual and even health reasons. There is something to be said for first of these aforementioned motives; principally through moral questions that have long been posed such as: how much do animals suffer?  Do they have emotional lives?  What is the level of their consciousness? Further to that, the ecological impact of animal husbandry cannot be ignored.  Research suggests that agriculture is the leading contributor to global warming and many scientists predict it will have disastrous effects on our survival as a species.  These questions are best answered by the relevant scientists and philosophers, however, what I would like to explore is the impact of a vegetarian – and specifically a vegan – diet on health and performance.  If for both moral and ecological reasons a shift to a lower (or non-existent) intake of animal products is necessary, what impact will it have on our health, and can we predict any evolutionary changes?

Diet & Evolution (Protein for Brains)

It is well documented that the regular consumption of meat enabled early humans to evolve large brains.  Research out of the University of Sydney in 2015 showed that starchy carbohydrates were also crucial to brain development, providing a key argument against Paleo and “keto” dietary advocates; however, what cannot be refuted is the necessity of meat in getting the human race to where it is today [1].  It is quite ironic that the consumption of meat has allowed our brains to develop to a point where we can now decide that we no longer wish to do so.  Is it now possible that after an estimated 800,000 years of meat consumption, the human race can not only survive, but thrive off an animal free diet?  Given the ecological and moral issues around meat consumption, vegetarianism may provide a way forward.  However, before we begin to pose it as a serious species-wide option, its impact on health and performance must be well-established.

Disease Risk and Mortality

In any conversion about vegetarianism and nutritional risk, two diseases are guaranteed to come up: osteoporosis and anaemia.  The former appears to be more than a genuine concern on the surface; dairy has long (although in evolutionarily terms, short) been our greatest source of calcium.  Whilst vegans (who do not consume animal products) will sometimes profess that spinach has as much calcium as milk, this is far from true.  However, most research shows that low bone mineral density, and consequently osteoporosis, is not as common in vegetarians as one might think.  This absence can be explained by the low acid loads of these diets [2].  Perhaps dairy is not as essential as we once thought? – Asking the question feels considerably blasphemous, as I can remember happily sculling milk from the jug after footy, as I’m sure almost every Aussie kid did.

In regards to overall health, a 2015 study comparing the impact of different vegetarian diets (including vegan) with omnivorous diets on metabolic markers over a 14 year period found that non-vegetarians had a much higher rate of abnormalities.  However, they stressed the importance of cautioning against diets high in refined carbohydrates and fructose whilst mentioning the need to monitor HDL and triglyceride levels [3].

Given the lower intake of key nutrients such as protein, vitamin D, vitamin A, B6, B12, niacin, iodine, zinc and selenium in vegan diets, awareness of food intake and nutrient deficiency risk needs to be addressed [4, 5].  Still, if these deficiency risks are moderated the overall benefits could possibly outweigh the risks.  A recent study coming out of the UK this year found no difference in all-cause mortality between vegetarians and omnivores [6].  However, reduced incidence of cancer (particularly in vegans), and reduced incidence and mortality from ischemic heart disease has been found in vegetarian populations [7].   Reduced incidence of metabolic abnormalities, cancer and ischemic heart disease is certainly reason to consider a switch.

The research is clear that vegetarian diets have better health outcomes when compared to typical omnivorous diets.  However the question needs to be asked, would a vegetarian based diet with low meat consumption (to fix nutritional gaps) be even more optimal?  I would hypothesise “yes” but this is purely speculative.


Research into vegetarianism and performance is relatively thin on the ground compared to its effect on morbidity.  There are several key factors that we can postulate to have an effect on performance: the low intake of iron, B-complex vitamins, selenium, protein and quite possibly, lowered testosterone production due to reduced intake of saturated fat.  A systematic literature review published in 2015 found that consuming a predominantly vegetarian-based diet had no adverse effect on performance.  However, given only 8 studies were identified they pointed out the need for more research [8].  If mild deficiency in some key nutrients – as indicated above – did in fact decrease performance, supplementation may provide a suitable option.

In regards to supplementation, the higher quality of dairy proteins as compared to vegetable based proteins is well established.  However, if the difference in body composition or performance from consuming vegetable proteins vs dairy proteins was negligible, would the reward of reduced disease risk, reduced ecological impact, and overcoming ethical issues, outweigh the reward of negligibly higher performance and body composition?

The jury is still out here and may be for quite some time.  It is probably worth noting that protein intake across the health and fitness industry is generally higher than necessary.  There are several cases of athletes who eat vegan diets and perform at a high level (most notably Nate Diaz of late*), but it is hard to say whether or not the addition of a few weekly servings of meat would be more optimal.

Editors Note: It has come to my attention that Nate Diaz actually follows a Pescatarian diet; that is the first and last time I shall be using Internet memes as a source of information.  This fact change bares no significance to the argument.


The Future for Humanity

The human species has quite a dilemma on its hands.  The majority of scientists agree that global warming is a major danger to the planet.  If a species-wide shift to a predominantly vegetarian (or completely plant-based) diet would save the planet and improve overall health, it would be ludicrous and self-destructive if the shift didn’t happen.

However, in our industry of health and fitness, performance and body composition is of considerable individual importance.  Even if the benefits of general health were well established, most athletes do not perform at the standards of “general” humans.  Can a high level of performance be expected from a vegan diet?  We still do not know for sure.

Vaclav Smil, author of Should We Eat Meat?: Evolution and Consequences of Modern Carnivory, suggests that going completely vegan is not only against our evolved fundamental diets, but also wasteful.  This is “because both grasslands and croplands produce plenty of phytomass that is not digestible by humans and that would be, if not regularly harvested, simply wasted and left to decay”.  What he does stress though is that the current level of meat production is not only completely unsustainable, but far beyond what both current and future populations would need to thrive.

As far as I am concerned, the current research on vegetarian diets suggests that whilst it goes against our evolutionary history, if proper attention is paid to meeting minimum requirements for micronutrients and macronutrients, it may be a viable alternative.  It is far from clear as to whether or not maximal performance and body composition may be achieved following a completely animal product-free diet though.  What is beyond doubt, is that if something isn’t done soon regarding global meat consumption, our biosphere is up for one hell of a change; principally through the possible extinction of our own species amongst others.


1.            Hardy, K., et al., The Importance of Dietary Carbohydrate in Human Evolution. Q Rev Biol, 2015. 90(3): p. 251-68.

2.            Burckhardt, P., The role of low acid load in vegetarian diet on bone health: a narrative review. Swiss Med Wkly, 2016. 146: p. w14277.

3.            Chiu, Y.F., et al., Cross-sectional and longitudinal comparisons of metabolic profiles between vegetarian and non-vegetarian subjects: a matched cohort study. Br J Nutr, 2015. 114(8): p. 1313-20.

4.            Kristensen, N.B., et al., Intake of macro- and micronutrients in Danish vegans. Nutr J, 2015. 14: p. 115.

5.            Schupbach, R., et al., Micronutrient status and intake in omnivores, vegetarians and vegans in Switzerland. Eur J Nutr, 2015.

6.            Appleby, P.N., et al., Mortality in vegetarians and comparable nonvegetarians in the United Kingdom. Am J Clin Nutr, 2016. 103(1): p. 218-30.

7.            Dinu, M., et al., Vegetarian, vegan diets and multiple health outcomes: a systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr, 2016: p. 0.

8.            Craddock, J., Y. Probst, and G.E. Peoples, Vegetarian and Omnivorous Nutrition – Comparing Physical Performance. Int J Sport Nutr Exerc Metab, 2015.