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Fruits and vegetables, rich in vitamins, potassium and fiber, represent an important feature of forager diets.
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 is a fad diet that became popular in the late 2000s.
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. Nutritionists have stated that the diet may be less effective than other popular diets in promoting good health.
An early book on the topic was The Stone Age Diet, self-published in 1975 by Walter Voegtlin. In 1985, Boyd Eaton and Melvin Konner published a paper on Paleolithic nutrition in the New England Journal of Medicine followed in 1988 by the book, with Marjorie Shostak, The Paleolithic Prescription. The evolutionary discordance hypothesis was first articulated by Eaton and Konner in their 1985 article "Paleolithic Nutrition: A Consideration of Its Nature and Current Implications". Since the late 1990s many others have published books and articles promoting the diet, including Staffan Lindeberg, Mark Sisson, and Arthur De Vany.
The diet was overshadowed by regimens such as the Atkins diet and South Beach Diet until the publication of a popular book by Loren Cordain. Cordain holds a bachelor degree in health science, a masters and doctoral degree in exercise physiology, and has studied nutrition professionally for over twenty years. His web site styles him as "Dr Loren Cordain, world's leading expert on paleolithic diets and founder of The Paleo Movement". He is the owner of the trademark "The Paleo Diet". The paleolithic diet has grown greatly in popularity since the publication of Cordain's book, and in 2013 was Google’s most searched-for weight loss method.
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, 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
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. 
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
It is often argued that preagricultural 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 and the U.S. National Academy of Sciences 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."
Major advocates of the diet believe that this includes eating:
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. 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.
Neither alcohol nor coffee is considered "paleo" as our ancestors could not produce these drinks.
Nutritionists agree that the Paleolithic diet is beneficial in that it cuts processed foods that have been highly modified from their raw state such as white bread, artificial cheese, certain cold cuts and packaged meats, potato chips, and sugary cereals. These often offer less nutrients than their unprocessed equivalents, and may be packed with calories, sodium and preservatives that may increase the risk of heart disease and certain cancers.
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."
^Konner M.; Eaton, S. Boyd (2010). "Paleolithic Nutrition: Twenty-Five Years Later". Nutrition in Clinical Practice25 (6): 594–602. P. 594.
^Elton, S (2008). "Environments, Adaptation, and Evolutionary Medicine: Should We be Eating a Stone Age Diet?". In S. Elton, P. O'Higgins (ed.), Medicine and Evolution: Current Applications, Future Prospects. Boca Raton, FL: CRC Press. P. 9. ISBN 978-1-4200-5134-6.
^Eaton, S. Boyd; Konner, M (1985). "Paleolithic Nutrition: A Consideration of Its Nature and Current Implications". New England Journal of Medicine 312: 283–289. P. 283 et passim.
^Eaton, S. Boyd; Eaton III, S. Boyd (2000). "Paleolithic vs. Modern Diets: Selected Pathophysiological Implications". European Journal of Nutrition39(2): 67–70. P. 67, et passim.
^Konner M.; Eaton, S. Boyd (2010). "Paleolithic Nutrition: Twenty-Five Years Later". Nutrition in Clinical Practice25 (6): 594–602. Pp. 594–95.
^Eaton, S. Boyd; Eaton III, S. Boyd (2000). "Paleolithic vs. Modern Diets: Selected Pathophysiological Implications". European Journal of Nutrition39(2): 67–70. P. 67.
^Ramsden, Christopher E.; Faurot, Keturah R.; Carrera-Bastos, Pedro; Cordain, Loren; De Lorgeril, Michel; Sperling, Laurence S. (2009). "Dietary Fat Quality and Coronary Heart Disease Prevention: A Unified Theory Based on Evolutionary, Historical, Global, and Modern Perspectives". "Current Treatment Options Cardiovascular Medicine" 289-301.
^Leonard, William R. "Food for Thought: Dietary change was a driving force in human evolution". Scientific American.Missing or empty |url= (help)
^Eaton, S. Boyd; Konner, M (1985). "Paleolithic Nutrition: A Consideration of Its Nature and Current Implications". New England Journal of Medicine 312: 283–289. Pp. 287–88.
^ abEaton, S. Boyd; Konner, M.; Shostak, M. (1988). "Stone Agers in the Fast Lane: Chronic Degenerative Disease in Evolutionary Perspective". The American Journal of Medicine84:739–49.
^Eaton, S. Boyd; Eaton III, S. Boyd (2000). "Paleolithic vs. Modern Diets: Selected Pathophysiological Implications". European Journal of Nutrition39(2): 67–70. P. 68.
^ abEaton, S. Boyd; Konner, M (1985). "Paleolithic Nutrition: A Consideration of Its Nature and Current Implications". New England Journal of Medicine 312: 283–289. P. 284.
^Eaton, S. Boyd; Konner, M (1985). "Paleolithic Nutrition: A Consideration of Its Nature and Current Implications". New England Journal of Medicine 312: 283–289. Pp. 284, 285, 286.
^ abEaton, M.D., S. Boyd; Shostak, Marjorie; Konner, M.D., Ph.D., Melvin (1988). The Paleolithic Prescription: A Program of Diet and Exercise and a Design for Living. Harper and Row. p. 79. ISBN978-0060916350.
^Dybas, Cheryl; Siegel, Lee; Scott, Jim (2013-06-03). "A Grassy Trend in Human Ancestors' Diets". National Science Foundation (National Science Foundation). Retrieved 2014-08-31. "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."
^Retica, Aaron (2007-12-09). "Starch Made Us Human". The New York Times (New York, NY: The New York Times Company). Retrieved 2014-08-31. "In a paper published in September in Nature Genetics, George Perry, a graduate student at Arizona State University, Nathaniel Dominy, an anthropology professor at the University of California, Santa Cruz, and their colleagues demonstrate something significant: unlike our fellow primates, modern humans have many copies of a gene that makes a protein in our saliva that is crucial for breaking down starch into glucose."
^ abBird AR, Brown IL, Topping DL (March 2000). "Starches, resistant starches, the gut microflora and human health". Curr Issues Intest Microbiol1 (1): 25–37. PMID11709851.|accessdate= requires |url= (help)