Our epidemics of dietary disease have prompted a great deal of research into what humans are meant to eat for optimal health. In 1985, an influential article was published, proposing that our chronic diseases stem from a disconnect between what our bodies evolved eating during the Stone Age, or the Paleolithic period, during the last two million years and what now makes up our diet, and advocating for a return towards a hunter-gatherer type of diet of lean meat, fruits, vegetables, and nuts, also known as the so-called Paleo Diet.
It might be reasonable to assume our nutritional requirements were established in the past, but why the Paleolithic period? Why only the last two million years of human evolution?
We have been evolving for about 20 million years since we split off from our last common great ape ancestor, during which time our nutrient requirements and digestive physiology were relatively set and likely little affected by our hunter-gatherer days at the tail end. So what were we eating for the first 90 percent of our time on Earth? What the rest of the Great Apes were eating: more than 95 percent plants. Indeed, for the vast majority of our evolution, it appears we, like our Great Ape cousins, ate primarily leaves, stems, and shoots (in other words, vegetables), and fruit, seeds, and nuts.
In modern times, populations where many of our deadliest diseases were practically unknown, such as rural China and rural Africa, were reportedly eating huge amounts of whole plant foods, up to 100 grams of fiber every day, which is what researchers have estimated our Paleolithic ancestors were getting based on dietary analyses of modern-day primitive hunter-gatherer tribes and by analyzing coprolites, human fossilized feces. (Yes, we’re talking about paleopoop.) In contrast, today in the United States, we tend to get fewer than 20 grams of daily fiber, which is about half the minimum recommended intake and only one-fifth the amount of rural Chinese and Africans, and our Paleolithic ancestors.
Advocates of the Paleo diet are certainly right in railing against the consumption of dairy and refined, processed junk, as well as encouraging high fruit, nut, and vegetable intake, but do they fail in promoting excess meat-eating, particularly products that bear little resemblance to the flesh of prehistoric wild animals? A review published in Meat Science, for example, catalogued the laundry list of contaminants, including arsenic, mercury, lead, cadmium, and veterinary drugs such as antibiotic residues.
What about following a Paleo-type diet and exercising? In one study, young, healthy subjects were put on a Paleolithic diet along with a Crossfit-based, high-intensity circuit training exercise program. As has been shown with exercise, stomach-stapling surgery—and tuberculosis and chemotherapy, for that matter—losing weight typically causes a drop in cholesterol levels no matter the diet. Researchers found the opposite in this case: After ten weeks of a Paleo diet with hard-core workouts and weight loss, participants’ LDL (bad) cholesterol levels rose and did so more dramatically in those who started the study the healthiest. Exercise is supposed to improve health and well-being, not compromise it.
There have been some studies published in the last two decades that have shown health benefits of Paleo-type diets, but questions have been raised regarding their methodology. For example, some were conducted without a control group, for an extremely short duration, with very few participants, or on pigs instead of humans.