Over the past several months I came across a number of debates between vegetarians/vegans and people sticking to carnivorous or predominantly animal-based diets. As curious these debates were, I was surprised that there is still so much confusion and mix up around this subject. So, I would like to share my own, "doctor's", take on this – I believe that we are omnivores, but I would like to examine this statement as well as the both ideas of us being herbivores and carnivores.
I must make a couple of disclaimers. First of all, I am not a zoologist or anthropologist, not even historian, and there are lots of things that I simply don't know, but I would be open to discussion about them. For example, just recently I learnt that gorillas are eating plants all day long and their gut microflora converts fiber into fatty acids – that would be an important argument for justifying plant-based nutrition for some people as we are great apes and there are some parallels to be made in respect to that. In fact, there are indications that we can digest some fiber in the same manner1. I assume that there is much more to learn for me and I acknowledge this limitation of mine (happy to learn more, so feel free to leave comments and to make suggestions).
Also, I would like to say that quite often the discussion about us being herbivores or carnivores is conflated with veganism or other specific diets and nutritional styles as well as with the health effects of certain nutrients such as, for example, cholesterol and the risk of heart disease2 and oxalates and kidney stones3. I would like to separate these questions and focus only on one thing – the natural dietary patterns for human beings.
The historical context:
In order to understand these natural patterns, I must take a look at the historical, preagricultural, dietary patterns. Again, I'm not an anthropologist, so it's a little bit difficult, but I hope I'll be able to make a reasonable argument here. Which, essentially, is based on the fact that due to the development of agriculture and technology in general, currently we have an unlimited access to a variety of foods that would not be normally accessible to us whereas our physiology and genetics remained principally the same as they were in pre-agricultural times, the historical period when we were tribal hunter-gatherers.
Are we omnivores?
As I said before, I believe that we are omnivores. My point of view is based on the assumption that as hunters-gatherers, which we were for the vast majority of our existence as a species, we had access to limited sources of nutrition and we had to take the best from what was available. As gatherers we could find some wild berries, fruit, roots, mushrooms, but these plant-based foods were quite scarce, mostly seasonal and also, we would have to compete with other animals for them. As a practical way of looking at this, I would suggest just going to a random forest and trying to live there for several days off the ground – you will see that plant-based foods are very hard to come by and that many items like berries and mushrooms might turn out to be poisonous. Nevertheless, we still could incorporate at least some plant-based foods into our rations in order to survive. The animal-based foods would also be hard to come by, but the way I see it, they are much easier to get your hands on – we could eat some eggs, hit a bird or a small animal with a stone, we could catch a fish, eat some worms or insects (sounds disgusting, I know, but Bear Grylls does it). These products are much more nutritionally dense and, again, from my point of view, they are much easier to find or catch, especially if you hunt as a tribe and you have been doing it all your life.
I think that this description of the food items we could come across is pretty accurate and that's the main reason why I think that we are omnivores i.e. animals that can live off both plant- and animal-based products. Moreover, I think that as omnivores we have an evolutionary advantage over both strict herbivores and carnivores – we can rely on broader spectrum of foods available in nature. Let's examine the idea that we are not omnivores i.e. we're either herbivores or carnivores.
Can we survive as herbivores?
I would like to stress again that I have nothing against the idea of being vegan or vegetarian. Moreover, I believe that nowadays we can easily get everything we need from a plant-based diet as we have access to all kinds of foods and dietary supplements. But I don't think it was the case for millennia preceding modern civilization. As hunters-gatherers, or just gatherers in this case we would face not only the scarcity of plant-based foods, but also, we would have a huge problem with finding certain micronutrients such as vitamin D or B12 and heme iron to name a few. I don't know how a gatherer would solve this problem then, but also, I'm not sure why they would choose to limit their nutritional choices to plant-based foods when the survival of the species is essentially at stake. An additional argument against us being herbivores (i.e. animals primarily or exclusively relying on plant-based foods) is based on our anatomy and physiology – our gastrointestinal tracts are not equipped to process vast majority of plants – we can't digest fiber (or at least we are not very efficient in that), so the "herb" in "herbivore" is effectively the food that we can't process. We have shorter intestines, smaller stomachs (in comparison to gorillas or cows), the digestion time is shorter, the structure of our jaws is not really the best fit for plant-based foods etc. The fact that we can process some plant-based foods doesn't make us herbivores and the fact that we can process all kinds of animal-based foods shows that we aren't. As a matter of fact, I don't know of any prehistorical tribe that would survive off exclusively plant-based foods (It doesn't mean that they didn't exist, so if you know of such a tribe or society, please let me know in comments).
Can we survive as carnivores?
At the same time, I know of several tribes or societies that relied exclusively on hunting and animal-based foods and managed to survive for multiple generations. A great example would be Inuit people – they eat exclusively meat, animal organs, fish and seafood and miraculously do not have any clinical deficiencies of vitamins or micronutrients we would expect normally. One of the major conundrums I had is the vitamin C deficiency – one would expect that in the absence of plant-based foods we would quickly develop scurvy, but it clearly doesn't happen among Inuit people. The best explanation for this phenomenon is that some organ foods contain vitamin C and consuming foods like liver would give us enough of vitamin C supply4. The problem with that is that we have to consume these organs raw in order to preserve the vitamin (it's mostly destroyed while cooking). I can see how it works, but again, I don't think that it would be acceptable for the majority of people these days and, again, I don't know why hunter-gatherers would choose to limit their sources of nutrition – if something is available and consumable, it would likely be consumed – if just 100 grams of raw broccoli would yield a daily supply of vitamin C why would be discard it? Thus, in my understanding, a completely animal-based diet would be used only if the plant-based foods are not available. Some people would argue that animal-based foods are rich in cholesterol and saturated fat, which are associated with a number of health problems, but I would prefer discussing it in a separate blog as I have a lot to say in this respect.
The bottom line:
Overall, I think that it's quite obvious that as a species we could and did survive mostly as universal consumers of a variety of foods (aka omnivores) and while it looks like we could survive exclusively on animal-based food sources, it happened only in extreme conditions. Also, it's clear that we definitely aren't herbivores. Again, it doesn't mean that plant-based diets do not have health benefits or that a vegan lifestyle is unsustainable in modern society. It actually is, but both the sustainability of specific diets and their health effects are a subject for another review.
As I said in the very beginning, there are lots of things I don't know and I would be very curious if you could share your thoughts on this subject, I'm open to new information or even a debate and I'm always happy to see your comments. So, feel free to ask questions, to make comments, to explore my website and to subscribe to my YouTube channel for updates.
1. Holloway WD, Tasman-Jones C, Lee SP. Digestion of certain fractions of dietary fiber in humans. The American journal of clinical nutrition. 1978;31(6):927-930.
2. Shekelle RB, Shryock AM, Paul O, et al. Diet, Serum Cholesterol, and Death from Coronary Heart Disease. New England Journal of Medicine. 1981;304(2):65-70.
3. Taylor EN, Curhan GC. Oxalate Intake and the Risk for Nephrolithiasis. Journal of the American Society of Nephrology. 2007;18(7):2198-2204.
4. Fediuk K, Hidiroglou N, Madère R, Kuhnlein HV. Vitamin C in Inuit Traditional Food and Women's Diets. Journal of Food Composition and Analysis. 2002;15(3):221-235.