What Is Mankind's Natural Diet?

Few Paleolithic human hunters lived long enough to develop heart disease but today it kills more people than any other disease.

Evolution has played a role in determining the nutritional requirements of all animals. The cat family is metabolically adapted to a carnivorous, whereas horses and rabbits evolved to consumed a plant-based diet. Other animals such as pigs and rats evolved to consume a mix of both plant and animal foods. Human beings like other omnivorous animals evolved to be able to consume a wide variety of plant and animal material as food. Most nutritionists agree that the typical modern diet high in fatty animal products, added salt, and refined carbohydrates and fats is neither natural nor optimal nutritionally for human beings. What diet mix is the most natural and optimal nutritional for most people today?Some researchers have argued that what our ancestors were eating during the Paleolithic period is optimal for meeting our nutritional requirements and promoting optimal health. However, as near as nutrition science can determine there are few differences in the nutritional requirements of humans or chimpanzees. Indeed, if chimpanzees are fed what modern humans eat they get fat, develop insulin resistance, dyslipidemia, atherosclerosis, hypertension, type 2 diabetes, and numerous other ills associated with modern Western diet. When humans and chimps are fed more meat both see increases in their LDL-cholesterol levels and the development of atherosclerosis. By contrast, chimps and humans fed more whole grains and beans see their LDL-cholesterol levels drop and their risk of developing coronary heart disease fall. So it is hard to argue that man has adapted physiologically to a diet high in meat. Where humans and chimps do differ metabolically these differences appear more related to metabolic changes that have occurred since the end of the Paleolithic period.For example, many modern day humans unlike their ancient primate ancestors or even their Paleolithic ancestors can digest lactose as adults. All primates (indeed all mammals) not surprisingly produce lactase (the enzyme needed to digest milk sugar lactose) as babies. However, after weaning nearly all primates except a large proportion of humans lose their ability to make lactase. This made perfect sense biologically. Why retain metabolic machinery to digest something that would never be consumed? However, a few thousand years ago some human tribes started to domesticate goats, sheep, and cattle. Some started using their milk as a source of food. Given the large amount of the energy in dairy products coming from lactose this provided a strong selective advantage to humans who retained their ability to make lactase as they grew older - especially in grasslands where hunting was difficult and other food sources were limited. Today if you look around the world it is clear that a genetic mutation allowing better utilization of milk as a food source has spread widely primarily in human populations most reliant on human milk as a food source.Bottom Line: While one could argue that human beings did not evolve on a diet composed of large amounts of whole grains and legumes and nonfat dairy products there are thousands of studies demonstrating that such a diet is optimal or close to it for a large proportion of modern day people. By contrast, given the known adverse effects of diets high in meat and particularly red meat it seems unwise to advocate such a diet based on evidence that Paleolithic human hunters often ate a lot meat. Back then few of our ancestors lived long enough to die of coronary heart disease, but today it kills more people than other disease.By Dr. James J Kenney, PhD, FACN