Are Humans Vegans or Omnivores? The Answer is All in Your Head

Studies reveal what bad gut bacteria do_How to feed your good gut bacteria and still eat red meat

Today, we welcome internationally acclaimed keto and ancestral nutrition specialist Nora Gedgaudas, CNS, NTP, BCHN as a guest author on the Bulletproof Blog. You can listen to her chat live with Dave at PaleoFX on this episode of Bulletproof Radio (iTunes). 

Are Humans Vegans or Omnivores? The Answer is All in Your Head

by Nora Gedgaudas, CNS, NTP, BCHN

After experiencing detrimental health and mental health effects from my own foray into veganism, I became determined to find out what foods worked best for my biology.

My interests ultimately shifted toward studying the foundational roots of prehistoric ancestral diets, along with the various selective pressures that served to shape our physiological makeup and most basic nutritional requirements as humans. I sought to answer the question: Is human health enhanced or best supported by a strictly (or mostly) herbivorous diet?

Keep reading to find out how I found veganism, why I gave it up, and how a close examination of the human ancestral diet over thousands of years helped me realize that my body’s cravings for animal products weren’t a personal failure — they were biological.

Instantly download the Bulletproof Diet Roadmap, your cheat sheet to finding out which foods work with your unique biology. 

Why I became vegan in the first place

12 Best Vegetables and Fruit to Eat Right Now_farmers market_headerAround forty years ago, I bought into the mainstream perception that dietary animal fat was bad, and that animal source foods in general (especially red meat) should be consumed sparingly, if at all. Most of the propaganda in the health food stores I frequented in those days were rife with books and pamphlets on the many lofty virtues of vegetarianism and veganism as some established ideal.

For a time, I fully attempted adopting these approaches in the best quality and strictest possible way, which resulted in a near catastrophic failure in my health and well being. What began with positive effects rapidly led over the course of a year or two to woefully diminishing returns. My struggles with depression deepened to the point of near suicidality, and I even developed an eating disorder for a time. For the first time, I began experiencing panic attacks. What started out as some potentially positive early detoxification effects eventually gave way to a complete loss of vitality and mental clarity.

RELATED: Things You Should Know Before Going Vegan

Persistent cravings for animal source foods left me feeling guilty. I felt like a complete failure when I finally succumbed to those cravings. Eventually, I abandoned what was then my ideal for what I begrudgingly had to concede worked far better for me. I automatically assumed the fault lay with some odd abnormality in my biochemical makeup or perhaps just an intrinsic weakness of my own self-discipline and character. I struggled internally with my failure. But I soon realized that this was faulty thinking.

Historical diets of primates and early humans

The vegetarian and vegan communities seem to be under the impression that our species has evolved from an herbivorous line, and that leaves and bananas are meant to be our most natural dietary staple. Conversely, nowadays meat eating is popularly perceived by many as being more of a modern-day aberration (or abomination, according to the most passionate proponents of the vegan diet).

The only problem with this notion is that our closest great ape ancestors never quite got that memo. It turns out that all great apes (with one notable exception) regularly hunt, kill and consume some meat (comprising up to 20% of their diets).[ref url=”,+Craig+B.+%22The+Hunting+Apes:+Meat+Eating+and+the+Origins+of+Human+Behavior.%E2%80%9D++Princeton+University+Press+(February+25,+2001)&ots=qNqibQ1OO_&sig=rgfZp7fgqGIHKq1BPzflgkuZcIA#v=onepage&q&f=false”] With a cursory search on YouTube, you’ll find a plethora of very strong and difficult to watch footage clearly showing just that.

Dietary changes and brain size changes

Some attribute cooking as the practice that made us human. Others say it was our increased consumption of starchy roots and tubers (much less grains or legumes) along the way. The most impactful practice that led to the brain architecture and capacity that we have today was our consistent consumption of the dietary fat of animals.

The notable exception to this meat-eating rule among our simian brethren includes herbivorous gorillas. The rub there is that these herbivorous gorillas also have a smaller brain-to-body ratio then would be expected for their size.[ref url=”″] In fact, a gorilla weighing about the same as a human has a brain just one-third of the size.

RELATED: What “The China Study” Gets Wrong About Vegan Diets

We can also turn to the chimpanzee for comparison. The size and sophistication of the chimpanzee’s brain really has not changed much at all in about seven million years. Why? In general terms, chimpanzees continued on to live as they always had, and kept persistently noshing on those leaves and bananas, along with the occasional meat of small and relatively lean animals. No real changes there.

Somewhere along the way, an intrepid primate ancestor began to do things a bit differently. Profound physiological changes, like the development of opposable thumbs, allowed them to more effectively cleave meat and marrow from the scavenged bones of animals. Eventually, they used new abilities, like the ability to grip and walk upright, to band together to hunt with the tribe, creating and grasping spears and other weaponry to hunt more efficiently.

Animal fat and rapid brain growth (encephalization)

the china study criticismAround 2 million years ago, we first emerged as the genus, ‘Homo’, standing fully upright and having by then established a fully hunting-based dietary economy.[ref url=”″][ref url=””] By this time, our brains were already double to triple that of our closest primate ancestor (the chimpanzee). From there, our hominid brain nearly doubled again by roughly 200,000 years ago when we finally emerged as Homo sapiens for the first time.[ref url=””]

This rapid rate of brain enlargement and sophistication, aka encephalization, is wholly unprecedented among the evolutionary lineages of any other species. What is also unique about us as human primates is our additionally unprecedented taste for fat — particularly animal fat — which we pursued voraciously along the way.[ref url=”″] We had available to us the meat of massive, fatty herbivores we now refer to as megafauna all the way from 2.6 million years ago—at the outset of the Quaternary Ice Age all the way to 13,000 or so years ago.

And this, more than any other single factor, has led to what is arguably our most unique and defining human characteristic: our unusually large brain. And unlike any other primate, the fatty acids responsible for our unique human cognition — both 20- and 22-carbon fatty acids: arachidonic acid (AA) and docosahexaenoic acid (DHA)—are both found within the human food supply exclusively within animal source foods.[ref url=”″]

It is the effect of dietary fat on brain growth that we have to thank for advanced human achievement: art, poetry, music, culture, mathematics, language, literary works, science and technology, and arguably even human spirituality. And it’s worth pointing out that we didn’t require fire in order to make excellent and consistent dietary use of that precious dietary commodity. We are meant as humans first and foremost to be fat-heads, not potato heads or grain brains.

Humans in reverse: more grains, smaller brains

The cataclysmic birth of the Holocene tragically led to the sudden mass extinction of more than half of the planet’s megafauna species (particularly the largest and fattiest of them), leaving us with much smaller, leaner prey that was much more fleet of foot. Even so, our Neolithic hunting ancestors never lost their preference for animal fat as their most coveted dietary staple.

Nevertheless, the advent of agriculture (and a diet increasingly based upon sugars, starches, and grains) has led not to any continued brain enhancement and evolution, but instead a loss of close to 11% of our brain volume over the last 10,000 years.[ref url=”″][ref url=””] Let’s just say that evolution has not continued in quite the direction we might have hoped, or as is popularly advertised.

Your brain is energy-hungry

An adult human brain utilizes an estimated 20-30% of our total human caloric energy demand,[ref url=”″] making it very, very expensive in energy terms. A baby’s brain requires closer to 85% of total energy, the brains of young children require 45-50% of total energy. For perspective, consider that the brains of other primates use no more than about 8% of their total caloric energy demands.

Fat supplies more than twice the caloric value of glucose, and in the form of ketones, can supply literally FOUR times the energy!

As understood by most anthropologists today, it was likely our dependence on the meat, and especially fat, of the animals we hunted that not only allowed us to survive, but to develop the structure and function of the human brain.

The fact is, compared to large-bodied apes, we humans have an enhanced capacity and a fundamentally optimized physiology toward digesting and metabolizing higher animal fat diets. We are unique among all animals in our capacity of our brains to make full time use of almost nothing but ketones, full time. I think we need to view this as a significantly meaningful adaptation. Without it, our species could not have evolved such large brains.[ref url=”″]

Stay tuned for Part 2, where we dig into the human digestive system and the guts of our primate ancestors. Read more from Nora at her web site, Primal Body, Primal Mind





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