MEAT AND EGGS, OR VEGETABLES?

Veganism not our heritage

Animal-based foods remain superior, nutritionally, to plant-based foods.

In Summary
  • The increased energetic demands of a relatively large brain are balanced by the reduced energy demands of a relatively small GI tract.
  • Our early ancestors were a large-bodied species. It would have been challenging to provide themselves with sufficient quality food to permit the necessary reduction of the gut. It is highly unlikely that veganism would have been adequate.
Veganism not our heritage
Veganism not our heritage
Image: STAR ILLUSTRATED

Veganism seems to have evolved to become much more about a belief system, than what people chose to eat.

It’s main spheres – the nutrition, moral and environmental arguments – often entangle when in deep conversation. Most vegans start off in one sphere, then strengthen their belief by adopting the others. Vegans adopt a plant-based diet, avoiding all animal foods such as meat (including fish, shellfish and insects), dairy, eggs and honey; as well as products such as leather and anything tested on animals.

This is my attempt to disentangle the sphere that I feel most confident to engage in – the nutrition argument. I do not believe that one can be optimally healthy, long-term, on an exclusively plant-based diet.

The human diet must contain essential fatty acids (derived from fats). It must also contain essential amino acids (derived from protein). These acids are essential, because they cannot be synthesised (made) by the body, ie, they must come from our food. There are no essential carbohydrates – not a single one.

A good place to start this three-part piece is to try to determine, anatomically and physiologically, whether we, humans, are carnivores, herbivores or omnivores.

Over the past 4 million years, our brains have undergone immense increases in size; from 400cc to 1,400cc. We know that all living things have a finite energy budget. We also know that the brain is a very expensive organ, in metabolic terms. How does a brain get bigger in the context of finite energy allocation? A large brain is a considerable metabolic investment. Where did the energy come from to fuel the growing brain?

The Expensive Tissue Hypothesis seeks to explain this apparent paradox. This hypothesis, first proposed by Aiello and Wheeler in 1995, states “an increase in the size of a metabolically expensive tissue is offset by a decrease in the size of other metabolically expensive tissues”. It is proposed that the increase in brain size in humans was balanced by an equivalent reduction in the size of the GI (gastro-intestinal) tract.

If dietary quality determines the size of the gut, a high-quality diet must be essential for a large brain. It therefore follows that to permit the necessary reduction of the gut, our early ancestors would have had to increasingly rely on animal-based foods, which are less voluminous and more rapidly absorbed.

In other words, the increased energetic demands of a relatively large brain are balanced by the reduced energy demands of a relatively small GI tract. Our early ancestors were a large-bodied species. It would have been challenging to provide themselves with sufficient quality food to permit the necessary reduction of the gut. It is highly unlikely that veganism would have been adequate.

When human organs are compared to those of a similarly sized primate, the heart and kidneys are sized about the same. However, the GI tract is only 60 percent of that expected. It appears that the increase in mass of the human brain is balanced by an almost identical reduction in the size of the GI tract; and that these changes evolved simultaneously. And in the context of a finite energy supply, it was proposed, and demonstrated, that the energy saved by having a smaller gut was almost the same as that required for a larger brain. 

This theory is fascinating, as it suggests that from a metabolic point of view, a primate either has a large brain, or a small gut – but not both.

Unlike the heart, liver, and kidneys, the size and structure of the gut is strongly determined by the diet. This further supports the Expensive Tissue Hypothesis. It made sense for the gut to be ‘sacrificed’ and explains its inverse relationship to brain size.

If dietary quality determines the size of the gut, a high-quality diet must be essential for a large brain. It therefore follows that to permit the necessary reduction of the gut, our early ancestors would have had to increasingly rely on animal-based foods, which are less voluminous and more rapidly absorbed.

It is, therefore, highly probable that we developed a large brain by evolving a smaller gut. Veganism, therefore, is not our heritage, and cannot be our destiny.

The inescapable conclusion that I came to when studying human nutrition was that we are designed to consume animal foods. Yet again, science, not dogma, elegantly explains why meat and eggs should feature front and centre in our diets. Animal-based foods remain superior, nutritionally, to plant-based foods. This is a matter of fact, not a matter of opinion.

Next week, I’ll posit that although we are well adapted to a predominantly carnivorous (meat-based) diet, we have thrived as a species by being opportunistic omnivores. Plant and animal foods should be viewed as complementing, rather than competing sources of nutrition.

UK-based consultant physician and obesity management expert.

www.insulean.co.uk/ [email protected]/ Facebook: Nyambura Mburu Svendsen, or @insuleanmedical