Paleolithic diet

This article is about a modern-day diet. For information on the dietary practices of Paleolithic humans, see Paleolithic § Diet and nutrition.

Wild fruit is an important feature of the diet.

The paleolithic diet (sometimes called the paleo diet, caveman diet or stone-age diet) is a fad diet based on the foods that proponents believe paleolithic humans might likely have eaten, such as meat, nuts, and berries, and excludes food which proponents think paleolithic humans did not eat, like dairy.

A number of scientists have debunked the ideas underlying the paleolithic diet. It is based on the misconception that human digestive abilities today are identical to those of our paleolithic ancestors. Proponents of the diet say that modern human metabolism has been unable to adapt fast enough to handle many of the foods that have become available since the advent of agriculture. Thus, they conclude that modern humans are maladapted to eating foods such as grain, legumes, and dairy, and in particular the high-calorie processed foods that are a staple of most modern diets. Proponents claim that modern humans' inability to properly metabolize these comparatively new types of food has led to modern-day problems such as obesity, heart disease, and diabetes. They claim that followers of the Paleolithic diet may enjoy a longer, healthier, more active life.

Critics of the diet have pointed out that although little is known about the diet of Paleolithic humans, it is very likely that they consumed wild grains and legumes. Additionally, during the 2.6 million year long Paleolithic era, the highly variable climate and worldwide spread of human population meant that humans were, by necessity, nutritionally adaptable, in stark contrast to the claims made by Paleo diet supporters.

Proponents of the diet make a number of health claims for it, but these are not backed by good medical evidence; following the diet can lead to nutritional deficiency.

Health effects

A 2015 systematic review of the effects of paleolithic nutrition on metabolic syndrome concluded that there was insufficient evidence for the diet's supposed beneficial effects and treatment potential. As of 2014, there was no conclusive evidence the paleo diet is effective in treating inflammatory bowel disease.

The British Dietetic Association judged the paleo diet a "Jurassic fad" and listed it as one of the five worst celebrity-endorsed diets of 2015, saying it was "unbalanced, time consuming, [and] socially isolating" and so "a sure-fire way to develop nutrient deficiencies". David L. Katz and Stephanie Meller have written that the paleo diet presents a "scientific case" in part because of its anthropological basis, but that there is comparatively limited evidence supporting its health benefit over other popular contemporary diets.

History and terminology

The idea of a paleolithic diet can be traced to the work in the 1970s by gastroenterologist Walter Voegtlin. The idea was later developed by Stanley Boyd Eaton and Melvin Konner, and popularized by Loren Cordain in his 2002 book The Paleo Diet. The terms caveman diet and stone-age diet are also used, as is Paleo Diet, trademarked by Loren Cordain.

In 2012, the paleolithic diet was described as being one of the "latest trends" in diets, based on the popularity of diet books about it; in 2013 the diet was Google's most searched-for weight-loss method. The diet is one of many fad diets that have been promoted in recent times, and draws on an appeal to nature and a narrative of conspiracy theories about how nutritional research, which does not support the supposed benefits of the paleo diet, is controlled by a malign food industry.

Foods

Cordain has said the diet requires:

Seeds such as walnuts are rich sources of protein and micronutrients

• More protein and meat: meat, seafood, and other animal products represent the staple foods of modern-day paleo diets, since advocates claim protein constituted 19–35% of the calories in hunter-gatherer diets.
• More fats: advocates recommend that paleo diet adherents should have moderate to higher fat intake, relative to contemporary diets. The fat intake should consist mainly of monounsaturated, polyunsaturated, and omega-3 fatty acids, and avoiding trans fats, and Omega-6 fatty acids.
• Less carbohydrates: non-starchy vegetables. The diet recommends the consumption of non-starchy fresh fruits and vegetables to provide 35–45% daily calories and be the main source of carbohydrates. According to the United States Department of Agriculture, the acceptable macronutrient distribution range for carbohydrates is 45 to 65 percent of total calories. A typical modern diet mostly provides carbohydrates from grains and dairy products, but both these are excluded in the paleo diet.
• More fiber: a high fiber intake not from grains, but from non-starchy vegetables and fruits.

Exclusions

Food that advocates claim were rarely or never consumed by humans before the Neolithic agricultural revolution are excluded from the diet. These include green tomatoes, rice, bread and potatoes.

Rationale and counter-arguments

Paleolithic carving of a mammoth. Hunting by humans may have been a factor in its extinction, causing resource scarcity which may in turn have contributed to the development of agriculture.

Adaptation

The rationale for the Paleolithic diet derives from proponents' claims relating to evolutionary medicine. Advocates of the diet state that humans were genetically adapted to eating specifically those foods that were readily available to them in their local environments. These foods therefore shaped the nutritional needs of Paleolithic humans. The physiology and metabolism of modern humans have changed little, if at all, since the Paleolithic era. Natural selection is a long process, and the cultural and lifestyle changes caused by westernized culture have occurred much more quickly. Thus, modern humans have not yet been able to adapt to the new circumstances. The agricultural revolution brought the addition of grains and dairy to the diet.

According to the model from the evolutionary discordance hypothesis, "many chronic diseases and degenerative conditions evident in modern Western populations have arisen because of a mismatch between Stone Age genes and recently adopted lifestyles." Advocates of the modern Paleolithic diet, including Loren Cordain, take the evolutionary discordance hypothesis for granted, and form their dietary recommendations on its basis. They argue that modern humans should follow a diet that is as nutritionally close to that of their Paleolithic ancestors as possible.

The validity of the evolutionary discordance hypothesis has been brought into doubt by recent research. Studies of a variety of populations around the world show that humans can live healthily with a wide variety of diets; humans have evolved to be flexible eaters. Lactose tolerance is an example of how humans have adapted to the introduction of dairy into their diet. While the introduction of grains, dairy, and legumes during the Neolithic revolution may have had some adverse effects on modern humans, if humans were not nutritionally adaptable, these technological developments would have been dropped.

Evolutionary biologist Marlene Zuk writes that the idea that our genetic makeup today matches that of our ancestors is misconceived, and that in debate Cordain was "taken aback" when told that 10,000 years was "plenty of time" for an evolutionary change in human digestive abilities. On this basis Zuk dismisses Cordain's claim that the paleo diet is "the one and only diet that fits our genetic makeup".

Diseases of affluence

Advocates of the diet argue that the increase in diseases of affluence after the dawn of agriculture was caused by the change in diet, but it may be that pre-agricultural hunter-gatherers did not suffer from the diseases of affluence because they did not live long enough to develop them. Based on the data from recent hunter-gatherer populations, it is estimated that at age 15, life expectancy was an additional 39 years, for a total age of 54. At age 45, it is estimated that average life expectancy was an additional 19 years, for a total age of 64 years. That is to say, in such societies, most deaths occur in childhood or young adulthood; thus, the population of elderly - and the prevalence of diseases of affluence - was much reduced. Excessive food energy intake relative to energy expended, rather than the consumption of specific foods, may underlie the diseases of affluence. "The health concerns of the industrial world, where calorie-packed foods are readily available, stem not from deviations from a specific diet but from an imbalance between the energy humans consume and the energy humans spend."

Historical diet

Adoption of the Paleolithic diet assumes that modern humans can reproduce the hunter-gatherer diet. Molecular biologist Marion Nestle argues that "knowledge of the relative proportions of animal and plant foods in the diets of early humans is circumstantial, incomplete, and debatable and there are insufficient data to identify the composition of a genetically determined optimal diet. The evidence related to Paleolithic diets is best interpreted as supporting the idea that diets based largely on plant foods promote health and longevity, at least under conditions of food abundance and physical activity". Ideas about Paleolithic diet and nutrition are at best hypothetical.

Brassica oleracea, an edible wild plant

The data for Cordain's book only came from six contemporary hunter-gatherer groups, mainly living in marginal habitats. One of the studies was on the !Kung, whose diet was recorded for a single month, and one was on the Eskimos. Due to these limitations, the book has been criticized as painting an incomplete picture of the diets of Paleolithic humans. It has been noted that the rationale for the diet does not adequately account for the fact that, due to the pressures of artificial selection, most modern domesticated plants and animals differ drastically from their Paeleolithic ancestors; likewise, their nutritional profiles were very different from their modern counterparts. For example, wild almonds produce potentially fatal levels of cyanide, but this trait has been bred out of domesticated varieties using artificial selection. Many vegetables like broccoli "did not ... exist in the Paleolithic period". Broccoli and many other genetically similar vegetables (like cabbage, cauliflower, kale, etc.) are in fact modern cultivars of the ancient species Brassica oleracea, a wild plant also known as wild mustard.

Trying to devise an ideal diet by studying contemporary hunter-gatherers is difficult because of the great disparities that exist; for example, the animal-derived calorie percentage ranges from 25% for the Gwi people of southern Africa to 99% for the Alaskan Nunamiut. Recommendations to restrict starchy vegetables may not be an accurate representation of the diet of relevant Paleolithic ancestors.

Not all processed foods were introduced after the agricultural revolution; there is evidence early humans processed plant food and possibly prepared flour 30,000 years ago. Researchers have proposed that cooked starches met the energy demands of an increasing brain size, based on variations in the copy number of genes encoding for amylase.

See also

• Inuit diet
• Leaky gut syndrome
• Low carbohydrate diet
• Modern primitive
• Nutritional genomics
• Paleolithic lifestyle