Scientific Walkthrough: Paleo Diet Considerations

Homo Sapiens appeared around 200,000 years ago and their anatomy and genetic make-up is essentially the same as modern humans of today. Evolution that changes anatomy and molecular mechanisms takes place over millions of years and not much has changed over the hundred thousand years of human existence bringing in to question the notion that we are better evolved for a pure hunter Paleolithic diet that emphasizes meat and fat rather than the gatherer’s predominantly low energy density vegetarian diet relied upon by our homo-anthropoid ancestors for 20-30 million years or so of anthropoid primate evolution.

Phylogenetic Classification of Anthropoid primates

[A widely-used phylogenetic taxonomy recognizes all apes as the superfamily Hominoidea, great apes asHominidae, gorillas, chimps, and humans as three genera in the subfamily Homininae, and orangutans as Ponginae].

Popovich et al studied the diet of the Western Lowland Gorilla and argued that our anthropoid human ancestors’ diets for millennia of evolution have relied on short chain fatty acids for greater than 50% of their energy requirements.

“On analysis of the food eaten by the gorillas: Average nutrient content as percentage of dry weight was fat 0.5%, protein 11.8%, available carbohydrate 7.7% and dietary fiber 74.0%. The energy macronutrient profile of this diet was: 2.5% energy as fat, 24.3% protein, 15.8% available carbohydrate, with potentially 57.3% of metabolizable energy from short-chain fatty acids (SCFA) derived from colonic fermentation of fiber. Gorillas would therefore obtain considerable energy through fiber fermentation. We suggest that humans also evolved consuming similar high foliage, high fiber diets, which were low in fat and dietary cholesterol. The macronutrient and fiber profile of the gorilla diet is one in which the colon is likely to play a major role in overall nutrition. Both the nutrient and fiber components of such a diet and the functional capacity of the hominoid colon may have important dietary implications for contemporary human health. Popovich et al: J. Nutr. 127: 2000–2005, 1997.”

It is noteworthy that despite very low fat consumption, the gorilla would nevertheless be in a ketogenic state most of the time because of the paucity of glucose and the need for almost constant gluconeogenesis.

The human colon is strikingly similar to other hominoids and well suited for fiber fermentation and importantly the fermentation product butyrate is essential for normal colon cell function in humans as well as other hominoids that in captivity are highly susceptible to intestinal malfunction (bloat) when fed low fibre “Western Diets”.

What is good for growth, development and sexual maturation is often counterproductive to successful aging. Lessons on human aging from evolution can be misleading as “The Blind Watchmaker” of evolution could care less what happens after successful rearing of offspring. In fact, quite the opposite as evolution benefits from short generational intervals. For us after middle age, aging is a random deterioration more likely accelerated by the environmental factors that favor rapid growth and reproduction (a note of caution to the body building fraternity regarding high protein diets). We know that calorie restriction benefits longevity and the mechanisms are related to the influence of glucose and amino-acids on cell stress resistance and activation of the pathways involving insulin, akt and mTOR that negatively regulate autophagy (the cell detoxification mechanisms) that also favor a more pro-inflammatory immune system.

For those looking for health clues from evolution should look much further than the appearance of our genetically equivalent modern humans, back in our evolutionary history to 10 or more million years on a low energy density vegetarian-omnivorous diet that relied on hind gut fibre fermentation for a major proportion of energy needs. In any event most estimates of Paleolithic man’s likely diet would have involved up to 100 grams fibre per 1000 Calories which would provide 20% of energy needs from short chain fatty acids that are also involved in regulating immune function and gut permeability. Our serious deficiency of SCFA is likely a major factor in the high incidence of chronic inflammation from increased gut permeability, food intolerance and auto-immune diseases.

Today it is a challenge to reproduce a nutritional profile of a typical hunter gatherer’s diet (see Table below from Eaton et al). They estimate paleolithic intake amounted to 3000 kcalories, 1.7 kg of vegetables and 900g of meat, 104 g/day of fiber, 5 to 10 times current US intake and even the US RDA. Recent studies using intensive counselling urging higher fiber intake to prevent diabetes have been unable to achieve target levels without added fiber supplements.

Estimated daily paleolithic intake of selected nutrients compared to recommended and current levels