Paleolithic diet

Fruits and vegetables represent an important feature of forager diets.

The paleolithic diet, also known as the paleo diet or caveman diet, is a diet based on the food humans' ancient ancestors might likely have eaten, such as meat, nuts and berries.

The diet is based on several premises. Proponents of the diet posit that during the Paleolithic era — a period lasting around 2.5 million years that ended about 10,000 years ago with the advent of agriculture and domestication of animals — humans evolved nutritional needs specific to the foods available at that time, and that the nutritional needs of modern humans remain best adapted to the diet of their Paleolithic ancestors. Proponents claim that 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, modern humans are said to be 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 Paleolithic diet have pointed out a number of flaws with its underlying logic, including the fact that there is abundant evidence that paleolithic humans did in fact eat grains and legumes,^[1] that humans are much more nutritionally flexible than previously thought, that the hypothesis that Paleolithic humans were genetically adapted to specific local diets remains to be proven, that the Paleolithic period was extremely long and saw a variety of forms of human settlement and subsistence in a wide variety of changing nutritional landscapes, and that currently very little is known for certain about what Paleolithic humans ate.

Terminology and etymology

The term Paleolithic (/ˌpeɪliəˈlɪθɪk/) describes a cultural period circa 2 million BC and 10,000 BC 'characterized by the use of flint, stone, and bone tools, hunting, fishing, and the gathering of plant foods'.^[2] The term was coined by archaeologist John Lubbock in 1865.^[3] It derives from Greek: παλαιός, palaios, "old"; and λίθος, lithos, "stone", meaning "old age of the stone" or "Old Stone Age."^[4][5]

The terms caveman diet and stone-age diet are also used,^[6] with paleo diet by 2002.^[7][8] Loren Cordain trademarked the term "Paleo Diet".^[9]

History

The roots of the idea of a paleolithic diet can be traced to the work in the 1970s by gastroenterologist Walter Voegtlin.^[7] The idea was later popularized by Loren Cordain in his best-selling 2002 book, The Paleo Diet.^[7][8]

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;^[10] in 2013 the diet was Google's most searched-for weight-loss method.^[11] 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 paleo diet, is controlled by a malign food industry.^[12]

Foods

Cordain has said the diet requires:^[13]

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 comprises 19-35% of the calories in hunter-gatherer diets.^[14] The Centers for Disease Control and Prevention, the national public health institute of the United States, recommends that 10-35% of calories come from protein.^[15] Advocates recommend, relative to modern diets, that the Paleolithic diet have moderate to higher fat intake dominated by monounsaturated and polyunsaturated fats and omega-3 fats, but avoiding trans fats, and omega-6 fats.^[14]
• Fewer 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.^[14] According to the United States Department of Agriculture, the acceptable macronutrient distribution range for carbohydrates is 45 to 65 percent of total calories.^[16] A typical modern diet gets a lot of carbohydrates from dairy products and grains, but these are excluded in the Paleolithic diet.
• High fiber: High fiber intake not from grains, but from non-starchy vegetables and fruits.^[14]

Exclusions

Food groups that advocates claim were rarely or never consumed by humans before the Neolithic agricultural revolution are excluded from the diet.^[17] These include:

• dairy products
• grains, for example wheat, rye, canary seed, and barley, which make it a gluten-free diet
• legumes, for example beans and peanuts
• processed oils
• refined sugar
• salt
• Neither alcohol^[18] nor coffee is considered "paleo" as human ancestors could not produce these drinks.

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.

The rationale for the Paleolithic diet derives from evolutionary medicine,^[19] specifically the evolutionary discordance hypothesis. which states that "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."^[20] 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.

However, the validity of the evolutionary discordance hypothesis has been brought into doubt by recent research.^[21]

Adaptation

The following are claims which advocates of the paleodiet make. Paleolithic 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 time of their Paleolithic ancestors.^[22] The extreme changes in human diets due to the agricultural and industrial revolutions occurred over less than 200 years ago, which is not enough time for genetic adaptation.

By using applied Darwinian medicine, the use of modern evolutionary theory to understand health and disease, one can see that the human genome today was chosen by natural selection for the ancestral Paleolithic environment. Natural selection took time and the cultural and lifestyle changes to westernized culture occurred too quickly for the gene pool to evolve with the environmental changes.^[23] Between 5,000 and 10,000 years ago the agricultural revolution brought about the replacement of certain uncultivated foods from the Paleolithic diet with grains and dairy.^[24] The industrial revolution, in combination with the development of agriculture, brought about significant changes to the diet less than 200 years ago as well.^[24] This revolution brought about crop manipulation, animal-rearing practices, and food processing, thus further changing the Westernized diet.^[24] Both of these major instances occurred recently enough that the human genome did not have time to adapt to the changed environment. Alleles that were selected for or were neutral in the hunter-gatherer environment now promote diseases in modern environments and diets.^[25] Some of the alleles selected for in the past had positive effects for survival and reproduction, but may cause health problems in the post-reproductive years.^[23] Selection processes that were made in post agricultural alleles were due to pathogens in the environment, not diet, lifestyle, or environmental changes.^[23]

Counter-argument

Studies of traditionally living populations show that humans can live healthily with a wide variety of diets. Humans have evolved to be flexible eaters.^[26] Additionally, this flexibility in diet rather illustrates the resiliency with which humans have adapted to post-agricultural society. The assumption that humans have been entirely maladapted to these changes undermines this fact, as well as the fact that much more research needs to be done in regards to evolutionary changes in order to understand the actual harm or good done by the introduction of grains, processed foods, and dairy into the modern diet. Lactose intolerance serves as a perfect example of how humans have adapted to the introduction of dairy, demonstrating one of the ways that humans have actually adapted to their environment rather than deteriorated from it. It must also be kept in mind that while the idea behind the Paleo diet is that humans should eat like human ancestors, humans will never be able to do so in today's society, as every species of plant and animal that humans consumed has completely evolved to fit the dietary needs of a much larger population that must be sustained in modern society. While the introduction of grains, dairy, and legumes has not necessarily been easy for the modern human, especially the Westernized one, it is safe to say that if humans could only survive in environments similar to that of their ancestors, then the society that humans have would not be in existence today.^[27]

Historical diet

It is often argued that pre-agricultural foragers did not suffer from the diseases of affluence simply because they did not live long enough to develop them.^[28] 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.^[29] At age 45, it is estimated that average life expectancy was an additional 19 years, for a total age of 64 years.^[30][31] Food energy excess, 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."^[32]

Counter-argument

The data for Cordain's book only came from six groups, mainly living in marginal habitats.^[33] One of the studies was on the !Kung, whose diet was recorded for a single month,^[34] and one was on the Eskimos.^[35] Due to these limitations, the book has been criticized as painting an incomplete picture of what the diets of Paleolithic ancestors may have looked like.^[33] It has been noted that the rationale for the diet does not take adequate account of the fact that, due to the pressures of artificial selection, most modern domesticated plants and animals differ drastically from their Paeleolithic ancestors, whose nutritional profiles often differed drastically from their modern counterparts. For example, wild almonds produce potentially fatal levels of cyanide, but this harmful poison has been bred out of domesticated varieties by artificial selection. Moreover, many vegetables like Broccoli "did not ... exist in the Paleolithic period".^[36] 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.

With regard to attempts to emulate the "ideal" 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".^[37] Ideas about Paleolithic diet and nutrition are at best hypothetical.^[38]

Trying to devise an ideal diet by studying contemporary hunter-gatherers is difficult because of the great disparities that exist, for example with the animal-derived calorie percentage ranging from 25% in the Gwi people of southern Africa to 99% in Alaskan Nunamiut.^[39] Recommendations to restrict starchy vegetables may not be an accurate representation of the diet of relevant Paleolithic ancestors.^[40]

Reception

The British Dietetic Association named the paleo diet as among the five worst celebrity-endorsed diets of 2015, saying it risks being "unbalanced, time consuming, [and] socially isolating" and so "a sure-fire way to develop nutrient deficiencies".^[41]

David L. Katz and Stephanie Meller have written that the paleolithic 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.^[42] According to S. Jay Olshansky and Bruce Carnes, "there is neither convincing evidence nor scientific logic to support the claim that adherence to a Paleolithic diet provides a longevity benefit."^[43]

A ranking by U.S. News & World Report, involving a panel of experts, evaluated the diet based on factors including health, weight loss, and ease of following. In 2014, it tied for last place out of 32 with the Dukan Diet.^[44]

There is no good evidence the paleo diet is effective in treating inflammatory bowel disease.^[45]

See also

• Inuit diet
• Modern primitive
• Nutritional genomics
• Paleolithic lifestyle
• Low carbohydrate diet

References

Further reading

• Bijlefeld M, Zoumbaris SK (2014). Paleo Diet. Encyclopedia of Diet Fads: Understanding Science and Society (2nd ed.) (ABC-CLIO). pp. 164–166. ISBN 978-1-61069-760-6. 
• 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. 
• Zuk M (2013). Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live. W.W. Norton & Co. ISBN 978-0-393-08137-4. 
• George Bryant (2014). The Paleo Kitchen: Finding Primal Joy in Modern Cooking. Victory Belt. ISBN 978-1-628-60010-0. 

External links

• "Paleo isn't a fad diet, it's an ideology that selectively denies the modern world"