The Paleolithic diet, also popularly referred to as the caveman diet, Stone Age diet and hunter-gatherer diet, is a modern nutritional diet designed to emulate, insofar as possible using modern foods, the diet of wild plants and animals eaten by humans during the Paleolithic era. Proponents of the diet therefore recommend avoiding any foods that they claim were not available to humans at that time, including dairy products, grains, legumes, processed oils, and refined sugar. The Paleolithic diet has been referred to as a fad diet; it has gained popularity in the 21st century.
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 also 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 part 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, 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. Average life expectancy was significantly lower than the one found in subsequent ages, and food and diet composition are among the main reasons for its increase, adding additional questions about the effectiveness of the Paleo Diet in terms of longevity and health.
- 1 History
- 2 The diet
- 3 Rationale and counter-arguments
- 4 Reception
- 5 See also
- 6 References
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.
Major advocates of the diet believe that this includes eating:
- 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. 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. 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.
- 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. 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 gets a lot of carbohydrates from dairy products and grains, but these are excluded in the Paleolithic diet.
- High fiber: High fiber intake not via grains, but via non-starchy vegetables and fruits.
Food groups that advocates claim were rarely or never consumed by humans before the Neolithic agricultural revolution are excluded from the diet. 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
- Neither alcohol nor coffee is considered "paleo" as our ancestors could not produce these drinks.
Rationale and counter-arguments
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The rationale for the Paleolithic diet derives from evolutionary medicine, 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." 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.
Humans are adapted to a paleolithic diet
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. 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. 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. The industrial revolution, in combination with the development of agriculture, brought about significant changes to the diet less than 200 years ago as well. This revolution brought about crop manipulation, animal-rearing practices, and food processing, thus further changing the Westernized diet. 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. Some of the alleles selected for in the past had positive effects for survival and reproduction, but caused health problems in the post-reproductive years. Selection processes that were made in post agricultural alleles were due to pathogens in the environment, not diet, lifestyle, or environmental changes.
Studies of traditionally living populations show that humans can live healthily with a wide variety of diets. We have evolved to be flexible eaters.
Human health has been in decline since the agricultural revolution because of dietary changes
Paleolithic humans had relative health and longevity, and less obesity, atherosclerosis, pulmonary disease, type 2 diabetes, certain types of cancer, and dental cavities. The advent of agriculture and industrialization has led to the availability of foods to which humans are not genetically adapted, and these detrimental foods (particularly carbohydrate-rich starches like wheat and maize) have now largely replaced beneficial foods (like lean animal protein) in human diets. Diseases of affluence and lifestyle diseases are modern afflictions that have arisen in part from the eating of foods to which humans are not genetically adapted.
The Paleolithic diet followed the macronutrient compositions of 25-29% protein, 39-40% carbohydrates, and 30-39% fats. Today’s Westernized diets generally follow the macronutrient compositions of 15% protein, 49% carbohydrates for men, 52% carbohydrates for women, and 33% fats. The amount of protein in humans’ diets drastically decreased, while carbohydrates increased. Even in the short amount of time from 1972 to 2000, the carbohydrate values in the United States increased for men from 42% to 49% and for women from 45% to 52%. The higher percentage of carbohydrates in the diet essentially took away a percentage of the fats intake, which decreased the amount of fats for men from 37% to 33% and for women from 36% to 33%. Following these patterns of increasing amounts of carbohydrates in the human diet will have a continuation of decreasing amounts of proteins and fats in the human diet, which could in turn continue encouraging negative health affects on the human populations.
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. 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. 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 we consume and the energy we spend."
We understand and can imitate the paleolithic diet
Most Paleolithic communities were organized around some form of hunter-gatherer or forager-gather subsistence, which implies that they regularly ate wild plants and root vegetables, fruits and nuts, and the considerable quantities of the flesh of wild animals (including fish and shellfish). They did not eat (because they could not cultivate in large enough quantity) legumes, grains, salt, the milk of other animals, and large quantities of animal fat. It is currently possible to discover (through palaeontology, archaeology, and the study of modern hunter-gatherer societies) what the diet of Paleolithic humans consisted of and to reproduce or at least emulate it using foods readily available today. The Paleolithic Prescription, published in 1988 by S. Boyd Eaton, Melvin Konner, and Marjorie Shostak, attempted to reconstruct a Paleolithic forager diet based on average values from hunter-gatherer diets that were available in the literature.
The data for the book only came from six 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 what the diets of Paleolithic ancestors may have looked like. 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". 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". Ideas about Paleolithic diet and nutrition are at best hypothetical.
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. Recommendations to restrict starchy vegetables may not be an accurate representation of the diet of relevant Paleolithic ancestors.
Five recent studies examining the isotope analysis of fossilized tooth enamel from scores of human ancestors and baboons in Africa show that human ancestors expanded their menu 3.5 million years ago, adding C4 tropical grasses and sedges to an ape-like diet. While the consumption of animals grazing on C4 pastures can contribute to C4 isotopic signatures, the magnitude of 13C enrichment—used to infer C3/C4 ratios—in early hominid fossils suggests that the carbon in their diet was derived mainly from C4 plants rather than the tissues of animals grazing on C4 grasses. Very high proportions of animal food are not considered plausible for hominids given that even modern hunter gatherers armed with bows and arrows tend to have dismal hunting success, and hominids lack the appropriate dental morphology of a high meat diet. Expanding on those findings, Oxford University researchers observed that baboons today eat large quantities of starchy C4 tiger nut tubers and the wear patterns on the tooth enamel from these sedge tubers are a perfect match with the wear patterns on the enamel of Paranthropus boisei ('Nutcracker Man')—a hominid, with a high C4 isotopic signature, who lived in East Africa between 2.4 million and 1.4 million years ago. The Oxford University study therefore concluded that Paranthropus boisei survived mainly on a diet of starchy tiger nut tubers. Dr Gabriele Macho, a lead researcher on the study from the School of Archaeology at Oxford University, said "I believe that the theory—that 'Nutcracker Man' lived on large amounts of tiger nuts—helps settle the debate about what our early human ancestor ate. On the basis of recent isotope results, these hominins appear to have survived on a diet of C4 foods, which suggests grasses and sedges. Yet these are not high quality foods. What this research tells us is that hominins were selective about the part of the grass that they ate, choosing the grass bulbs at the base of the grass blade as the mainstay of their diet." Incidentally, tiger nut tubers were among the earliest plants cultivated by humans, including ancient Egyptians and Paleo-Indians. Additionally, recent understanding of the human genome has shown that modern humans typically have many copies of the AMY1 gene for starch digestion—suggesting widespread evolutionary adaptation to starch consumption by humans. Furthermore, the restriction of starchy plants, by definition, severely limits the dietary intake of microbiota-accessible carbohydrates (MACs) and may negatively affect the microbiome in ways that contribute to disease. Starchy plants, in particular, are a main source of resistant starch — a dietary fiber with strong prebiotic properties. Resistant starches are not digestible by mammals and are fermented and metabolized by gut flora into short chain fatty acids, which are well known to offer a wide range of health benefits. Resistant starch consumption has been shown to improve intestinal/colonic health, blood sugar, glucose tolerance, insulin-sensitivity and satiety. Public health authorities and food organizations such as the Food and Agricultural Organization, the World Health Organization, the British Nutrition Foundation recognize resistant starch as a beneficial carbohydrate. The Joint Food and Agricultural Organization of the United Nations/World Health Organization Expert Consultation on Human Nutrition stated, "One of the major developments in our understanding of the importance of carbohydrates for health in the past twenty years has been the discovery of resistant starch."
A ranking by U.S. News & World Report, involving a panel of experts, evaluated 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.
Evidence for the effect of the switch to agriculture on general life expectancy is mixed, with some populations exhibiting an apparent decrease in life expectancy and others an apparent increase. And 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."
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Most apes eat leaves and fruits from trees and shrubs. But new studies show that human ancestors expanded their menu 3.5 million years ago, adding tropical grasses and sedges to an ape-like diet. The change set the stage for consuming more modern fare: grains, grasses, and meat and dairy from grazing animals. In four studies of carbon isotopes in fossilized tooth enamel from scores of human ancestors and baboons in Africa from 4 million to 10,000 years ago, researchers found a surprise increase in the consumption of grasses and sedges--plants that resemble grasses and rushes but have stems with triangular cross sections.
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