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The paleolithic diet (also called the paleo diet, caveman diet or stone-age diet) is a diet based mainly on foods presumed to be available to paleolithic humans. It includes vegetables, fruits, nuts, roots, meat, and organ meats while excluding foods such as dairy products, grains, sugar, legumes, processed oils, salt, and alcohol or coffee. Proponents of the diet recommend avoiding modern processed foods that humans began eating after the agricultural revolution.

With regard to the ideas behind the diet, which can be traced to Walter Voegtlin, the digestive abilities of modern humans are somewhat different from those of paleolithic humans, undermining the diet's core premise. 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 contrast to the claims about them made by supporters of the ideas behind the diet. It has been described as an "ideology" and its core assumptions as "only superficially plausible".

History and terminology

The idea of a paleolithic diet can be traced to a 1975 book by gastroenterologist Walter Voegtlin which in 1985 was further 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 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

It includes vegetables, fruits, nuts, roots, meat, organ meats. Cordain has said the diet requires:

• 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. It also excludes foods such as dairy products, grains, sugar, legumes, processed oils, salt, and alcohol or coffee. The diet is based on avoiding modern processed foods that humans began eating after the agricultural revolution.

Health effects

A 2015 review suggested that the paleolithic diet could be a useful alternative to the unhealthy Western diet. A 2015 systematic review of the effects of paleolithic nutrition on metabolic syndrome concluded that there was moderate evidence for better short-term improvements than the various guideline-based diets that were used as controls in the trials. 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:

A diet with fewer processed foods, less sugar and salt is actually a good idea, but unless for medical reason, there is absolutely no need to cut any food group out of your diet. In fact, by cutting out dairy completely from the diet, without very careful substitution, you could be in danger of compromising your bone health because of a lack of calcium. An unbalanced, time consuming, socially isolating diet, which this could easily be, is a sure-fire way to develop nutrient deficiencies, which can compromise health and your relationship with food.

David L. Katz and Stephanie Meller have written that while there is comparatively little evidence for the diet, and "any of the plant foods and nearly all of the animal foods consumed during the remote Stone Age are now extinct", the evidence that exists "suggest[s] benefits of the Paleo diet over the prevailing Western diet in measures of both body composition and metabolic health".

Rationale and counter-arguments

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. They argue that the physiology and metabolism of modern humans have changed little since the Paleolithic era. Natural selection is a long process, and the cultural and lifestyle changes introduced by western culture have occurred quickly. The argument is that modern humans have therefore not 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 Paleo diet form their dietary recommendations on its basis. They argue that modern humans should follow a diet that is nutritionally closer to that of their Paleolithic ancestors.

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.

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

References

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Further reading

• Bijlefeld M, Zoumbaris SK (2014). Paleo Diet (2nd ed.). ABC-CLIO. pp. 164–166. ISBN 978-1-61069-760-6. {{cite book}}: |work= ignored (help)
• Gorski D (18 March 2013). "It's a part of my paleo fantasy, it's a part of my paleo dream". Science-Based Medicine. Retrieved February 2015. {{cite web}}: Check date values in: |accessdate= (help)

• Diets
• Raw foodism