Paleolithic diet
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Paleolithic-style dish: A traditional seafood stew (Bouillabaisse served without bread).
The Paleolithic diet (or Paleolithic nutrition), also popularly known as the paleo diet (paleodiet), caveman diet, Stone Age diet and hunter-gatherer diet, is a dietary regimen which emulates the diet of wild plants and animals that humans and their close relatives habitually consumed during the Paleolithic (the Old Stone Age), a period of about 2.5 million years duration that ended around 10,000 years ago when Homo sapiens developed agriculture.[1] Based upon commonly available modern foods, the Paleolithic diet consists mainly of lean meat, fish, vegetables, fruit, roots and nuts, and excludes grains, legumes, dairy products, salt, refined sugar and processed oils.[1][2]
First popularized in the mid 1970s by a gastroenterologist named Walter L. Voegtlin,[3] this nutritional concept has been expounded and adapted by a number of authors and researchers in several books[4][5][6] and academic journals.[7] Building upon the principles of evolutionary medicine,[8] it is based on the premise that modern humans are genetically adapted to the diet of their Paleolithic ancestors and that human genetics have scarcely changed since the dawn of agriculture, and therefore that an ideal diet for human health and well-being is one that resembles this ancestral diet.[9][10]
This dietary approach is a controversial topic amongst nutritionists[11][12] and anthropologists.[13][14] Advocates argue that modern human populations subsisting on traditional diets similar to those of Paleolithic hunter-gatherers are largely free of diseases of affluence,[15][16] and that such diets produce beneficial health outcomes in controlled medical studies.[17] Supporters point to several potentially therapeutic nutritional characteristics of preagricultural diets.[10] Critics of this nutritional approach have taken issue with its underlying evolutionary logic,[18][19] and have disputed certain dietary prescriptions on the grounds that they pose health risks[18][20] and may not reflect real Paleolithic diets.[19][21] It has also been argued that such diets are not a realistic alternative for everyone,[22] and that meat-based diets are not environmentally sustainable.[23]
History
Gastroenterologist Walter L. Voegtlin was one of the first to suggest that following a diet similar to that of the Paleolithic era would improve a person's health. In 1975, he published a book[3] in which he argued that humans are carnivorous animals and that the Paleolithic diet was that of a carnivore—chiefly fats and protein, with only small amounts of carbohydrates.[24][25] His dietary prescriptions were based on his own medical treatments of various digestive problems, namely colitis, Crohn's disease, irritable bowel syndrome and indigestion.[26]
In 1985, Melvin Konner and S. Boyd Eaton, an associate clinical professor of radiology and an adjunct associate professor of anthropology at Emory University, published a key paper on Paleolithic nutrition in the New England Journal of Medicine.[7] Three years later, S. Boyd Eaton, Marjorie Shostak and Melvin Konner published a book about this nutritional approach,[4] which was based on achieving the same proportions of nutrients (fat, protein, and carbohydrates, as well as vitamins and minerals) as were present in the diets of late Paleolithic people, not on excluding foods that were not available before the development of agriculture. As such, this nutritional approach included skimmed milk, whole-grain bread, brown rice, and potatoes prepared without fat, on the premise that such foods have the same nutritional properties as Paleolithic foods.[24][27] In 1989, these authors published a second book on Paleolithic nutrition.[28][29]
Since the end of the 1990s, a number of medical doctors and nutritionists[30][31][32] have started to advocate a return to a so-called Paleolithic (pre-agricultural) diet.[14] Proponents of this nutritional approach have published books[5][6][33] and created websites[34][35] to promote their dietary prescriptions.[36][37][38][39][40] They have synthesized diets from commonly available modern foods that would emulate the nutritional characteristics of the ancestral Paleolithic diet, some allowing specific foods that would have been unavailable to preagricultural peoples, such as certain processed oils and beverages.[5][6][41][34][42]
[edit] Practices
Paleolithic-style dish: A raw tomato sauce with olives, celery, spinach and walnuts on courgette 'pasta' noodles.
The Paleolithic diet is a modern dietary regimen that seeks to mimic the dietary practices of Paleolithic hunter-gatherers.[1] Based upon commonly available modern foods, it includes cultivated plants and domesticated animal meat as an alternative to the wild sources of the original preagricultural diet.[1][2][43] The ancestral human diet is inferred from historical and ethnographic studies of modern-day hunter-gatherers as well as archaeological finds and anthropological evidence.[10][44][45]
The Paleolithic diet consists of foods that can be hunted and fished, such as meat, offal and seafood, and that can be gathered, such as eggs, insects, fruit, nuts, seeds, vegetables, mushrooms, herbs and spices.[1][2] Practitioners are advised to eat only the leanest cuts of meat, free of food additives, preferably wild game meats, such as quail, rabbit, and venison, as well as grass-fed beef, since they contain relatively high levels of omega-3 fats compared with grain-produced domestic meats.[1][2][43][46] Food groups that were rarely or never consumed by humans before the Neolithic revolution are excluded from the diet, mainly grains, legumes (e.g. peanuts), dairy products, salt, refined sugar and processed oils,[1][2] although some advocates consider the use of oils with low omega-6/omega-3 ratios, such as olive oil and canola oil, to be healthy and advisable.[43] Practitioners are permitted to drink mainly water, and some advocates recommend tea as a healthful drink,[43] but alcoholic and fermented beverages are restricted from the diet.[2][43] Furthermore, eating a wide variety of plant foods is recommended to avoid high intakes of potentially harmful bioactive substances, such as goitrogens, which are present in certain roots, vegetables and seeds.[1][44][47] Unlike raw food diets, the Paleolithic diet does not limit the consumption of cooked foods.[1] Cooking is widely accepted to have been practised by at least 250,000 years ago, in the Middle Paleolithic.[48]
Loren Cordain, a professor in the Department of Health and Exercise Science at Colorado State University, recommends that practitioners derive about 56–65% of their food energy from animal foods and 36–45% from plant foods. He advocates a diet high in protein (19–35% energy) and relatively low in carbohydrates (22–40% energy), with a fat intake (28–58% energy) similar to or higher than that found in Western diets.[43][49][50] Moreover, according to Cordain, root vegetables that exhibit high glycemic indices, such as potatoes, should be excluded from the diet.[2] Staffan Lindeberg, an associate professor in the Department of Medicine at the University of Lund, advocates a Paleolithic diet without recommending any particular proportions of plants versus meat or macronutrient ratios.[1][44] According to Lindeberg, calcium supplementation may be considered when the intake of green leafy vegetables and other dietary sources of calcium is limited.[1]
Scientific basis
Over 70% of our dietary calories come from foods that our Paleolithic ancestors rarely, if ever, ate, such as grains, dairy products and cooking oils.
[10] (
USDA's
Food Pyramid)
According to S. Boyd Eaton, "we are the heirs of inherited characteristics accrued over millions of years; the vast majority of our biochemistry and physiology are tuned to life conditions that existed prior to the advent of agriculture some 10,000 years ago. Genetically our bodies are virtually the same as they were at the end of the Paleolithic Era some 20,000 years ago."[51]
Paleolithic nutrition has its roots in evolutionary biology and rests on the principles of evolutionary medicine.[8][52] The reasoning underlying this nutritional approach is that natural selection had sufficient time to genetically adapt the metabolism and physiology of the various human species living during the Paleolithic to the varying dietary conditions of that era. But in the 10,000 years since the invention of agriculture and its consequent major change in the human diet, natural selection has had too little time to make the optimal genetic adaptations to the new diet.[1] Physiological and metabolic maladaptations result from the suboptimal genetic adaptations to the contemporary human diet, which in turn contribute to many of the so-called diseases of civilization.[9]
Loren Cordain argues that "today more than 70% of our dietary calories come from foods that our Paleolithic (Stone Age) ancestors rarely, if ever, ate. The result is epidemic levels of cardiovascular disease, cancer, diabetes, osteoporosis, arthritis, gastrointestinal disease, acne, and more."[35] According to Staffan Lindeberg, the "Paleolithic diet", basically meat, fish, vegetables, fruit and nuts, prevents heart disease, stroke and some forms of cancers and it has a beneficial effect on overweight, digestive problems and more;[34] it may have benefits even compared with prudent diets based on whole-grain cereals and low-fat milk.[53]
Interpretation of medical research
Based on the subsistence patterns and biomarkers of hunter-gatherers studied in the last century, advocates argue that modern humans are well adapted to the diet of their Paleolithic ancestors.[54] The diet of modern hunter-gatherer groups is believed to be representative of patterns for humans of 50 to 25 thousand years ago,[54] and individuals from these and other technologically primitive societies,[55][56] including those individuals who reach the age of 60 or beyond, seem to be largely free of the signs and symptoms of chronic disease (such as obesity, high blood pressure, nonobstructive coronary atherosclerosis, and insulin resistance)[B] that universally afflict the elderly in western societies (with the exception of osteoarthritis, which afflicts both populations).Moreover, when these people adopt western diets, their health declines and they begin to exhibit signs and symptoms of "diseases of civilization".[15][54] In one clinical study, stroke and ischaemic heart disease appeared to be absent in a population living on the island of Kitava, in Papua New Guinea, where a subsistence lifestyle, uninfluenced by western dietary habits, was still maintained.
The results of controlled medical studies on the Paleolithic diet have also been interpreted as evidence of the health benefits of such diets.[60][61][62] The first animal experiment on a Paleolithic diet suggested that this diet, as compared with a cereal-based diet, conferred higher insulin sensitivity, lower C-reactive protein and lower blood pressure in domestic pigs.[62] Subsequently, a short-term intervention with such a diet in healthy volunteers showed some favourable effects on cardiovascular risk factors.[63] In the first controlled human trial on a Paleolithic diet, researchers found that the diet improved glucose tolerance more than a Mediterranean diet in individuals with ischaemic heart disease.[17]
Nutritional factors
The novel foods introduced as staples during the Neolithic and Industrial Eras, namely dairy products, beans, cereals, refined cereals, refined sugars, refined vegetable oils, alcohol, salt and fatty domestic meats,[C] are believed to have fundamentally altered several key nutritional characteristics of the human diet since the Paleolithic period, and these dietary compositional changes have been implicated as risk factors in the pathogenesis of many of the so-called "diseases of civilization",[9][10][64][65] including obesity, cardiovascular disease,[66] diabetes, osteoporosis,[67][68] autoimmune-related diseases,[69] certain cancers,[70][71] and acne, as well as many diseases related to vitamin and mineral deficiencies.
According to Cordain et al., seven crucial nutritional characteristics of ancestral hominin diets that have been fundamentally altered by food staples and food-processing procedures introduced during the Neolithic and Industrial Periods serve to inhibit the development of diseases of affluence in modern-day hunter-gatherers:
- Glycemic load: Unrefined wild plant foods like those available to contemporary hunter-gatherers typically exhibit low glycemic indices.[77] Moreover, their diets are devoid of dairy products, such as milk, yoghurt, and cottage cheese, which have low glycemic indices, but are highly insulinotropic, with an insulin index similar to that of white bread.[78][79] These dietary characteristics may lower risk of diabetes, obesity and other related syndrome X diseases by placing less stress on the pancreas to produce insulin, and preventing insulin insensitivity.[80]
- Fatty acid composition: Hunter-gatherer diets generally maintain relatively high levels of monounsaturated and polyunsaturated fats, moderately low levels of saturated fats (10–15% of total food energy[81]) as well as a low omega-6:omega-3 fatty acid ratio. Moreover, they are devoid of artificial trans fat. These nutritional factors may serve to inhibit the development of cardiovascular disease.[10]
- Macronutrient composition: Dietary protein is characteristically elevated (19–35% of energy) at the expense of carbohydrate (22–40% of energy).[49][50] High protein diets may have a cardiovascular protective effect and may represent an effective weight loss strategy for the overweight or obese.[10] Furthermore, carbohydrate restriction may help prevent obesity and type 2 diabetes,[82][83] as well as atherosclerosis.[66]
- Micronutrient density: Fruits, vegetables, lean meats, and seafood, which are staples of the hunter-gatherer diet, are more nutrient-dense than refined sugars, grains, vegetable oils, and dairy products. Consequently, the vitamin and mineral content of the diet is very high compared with a standard diet, in many cases a multiple of the RDA.[2]
- Acid-base balance: Because of the absence of cereals and energy-dense, nutrient-poor foods, foods that displace base-yielding fruits and vegetables, the diet produces a net base load on the body, as opposed to a net acid load. Net acid producing diets may contribute to the development of osteoporosis and renal stones, loss of muscle mass, and age-related renal insufficiency.[67][84]
- Sodium-potassium ratio: Since no processed foods or added salt are included the sodium intake (~726 mg) is lower than average U.S. values (3,271 mg) or recommended values (2,400 mg). Further, since potassium-rich fruits and vegetables comprise ~30% of the daily energy, the potassium content (~9,062 mg) is nearly 3.5 times greater than average values (2,620 mg) in the U.S. diet.[2] Diets containing high amounts of salt induce and sustain increased acidity of body fluid, which may contribute to the development of osteoporosis and renal stones, loss of muscle mass, and age-related renal insufficiency. Moreover, the inverted ratio of potassium to sodium in the U.S. diet compared with preagricultural diets adversely affects cardiovascular function and contributes to hypertension and stroke
- Fiber content: Contemporary diets devoid of cereal grains, dairy products, refined oils and sugars, and processed foods have been shown to contain significantly more fiber (~42.5 g/d) than either current or recommended values.[2]
Objections to the Paleolithic diet
Comparative life expectancy
One of the most frequent criticisms of this nutritional approach is that it is unlikely that Paleolithic hunter-gatherers suffered from the diseases of modern civilization simply because they did not live long enough to develop these illnesses, which are typically associated with old age.[12][16][86][87][88] Advocates state in response that human populations with lifestyles resembling that of our pre-agricultural ancestors have no or little diseases of affluence, despite sufficient numbers of elderly.[16][89]
Criticism of evolutionary logic
The evolutionary assumptions upon which the Paleolithic diet is based have been disputed.[13][19][27] According to Alexander Ströhle, Maike Wolters and Andreas Hahn,[19] with the Department of Food Science at the University of Hannover, the statement that the human genome evolved during the Pleistocene (a period from 1,808,000 to 11,550 years ago) is resting on an inadequate, but popular gene-centered view of evolution. They argue that evolution of organisms cannot be reduced to the genetic level with reference to mutation and that there is no one to one relationship between genotype and phenotype.
They further question the notion that 10,000 years since the dawn of agriculture is a period not nearly sufficient to ensure an adequate adaptation to agrarian diets. Ströhle et al. argue that the number of generations that a species existed in the old environment is irrelevant, and that the response to the change of the environment of a species would depend on the hereditability of the traits, the intensity of selection and the number of generations that selection acts. They state that if the diet of Neolithic agriculturalists had been in discordance with their physiology, then this would have created a selection pressure for evolutionary change and modern humans, such as Europeans, whose ancestors have subsisted on agrarian diets for 400–500 generations should be somehow adequately adapted to it. In response to this argument, Wolfgang Kopp states that "we have to take into account that death from atherosclerosis and cardiovascular disease (CVD) occurs later during life, as a rule after the reproduction phase. Even a high mortality from CVD after the reproduction phase will create little selection pressure. Thus, it seems that a diet can be functional (it keeps us going) and dysfunctional (it causes health problems) at the same time."Moreover, S. Boyd Eaton and colleagues have indicated that "comparative genetic data provide compelling evidence against the contention that long exposure to agricultural and industrial circumstances has distanced us, genetically, from our Stone Age ancestors."[According to Kopp, the implementation of high-glycemic and high-insulinogenic food, like refined cereals and sugars, into human nutrition only about 200 years, or 10 generations, ago, occurred too recently on an evolutionary time scale for the human genome to adjust.
According to Ströhle et al. "whatever is the fact, to think that a dietary factor is valuable (functional) to the organism only when there was ‘genetical adaptation’ and hence a new dietary factor is dysfunctional per se because there was no evolutionary adaptation to it, such a panselectionist misreading of biological evolution seems to be inspired by a naive adaptationistic view of life."
No evidence of adaptation to Paleolithic diets
Katharine Milton, a professor of physical anthropology at the University of California, has also disputed the evolutionary logic upon which is based the Paleolithic diet. She questions the premise that the metabolism of modern humans must be genetically adapted to the dietary conditions of the Paleolithic.[13] According to Milton,[13] "there is little evidence to suggest that human nutritional requirements or human digestive physiology were significantly affected by such diets at any point in human evolution."[95][96][97][98]
Food energy excess causes diseases of affluence
According to Geoffrey Cannon, science and health policy advisor to the World Cancer Research Fund, humans are designed to work physically hard to produce food for subsistence and to survive periods of acute food shortage, and are not adapted to a diet rich in energy-dense foods.[99] These are, in his view, the crucial evolutionary principles that underly the diseases of affluence. Similarly, William R. Leonard, a professor of anthropology at Northwestern University, states that the health problems facing industrial societies stem not from deviations from a specific ancestral diet but from an imbalance between calories consumed and calories burned, a state of energy excess uncharacteristic of ancestral lifestyles.[100]
Objections to low-carbohydrate and high-protein versions
The high protein and low-carbohydrate diet[A] recommended by Loren Cordain and colleagues based on worldwide modern hunter-gatherer diets has attracted a number of criticisms, including the following:
No superior therapeutic merits
It has been argued that relative freedom from degenerative diseases was, and still is, characteristic of all hunter-gatherer societies irrespective of the macronutrient characteristics of their diets. Katharine Milton states that "hunter-gatherer societies, both recent and ancestral, displayed a wide variety of plant-animal subsistence ratios, illustrating the adaptability of human metabolism to a broad range of energy substrates. Because all hunter-gatherer societies are largely free of chronic degenerative disease, there seems little justification for advocating the therapeutic merits of one type of hunter-gatherer diet over another."
Marion Nestle, a professor in the Department of Nutrition and Food Studies at New York University, states that based on research relating nutritional factors to chronic disease risks, and to observations of exceptionally low chronic disease rates among people eating vegetarian, Mediterranean and Asian diets, plant-based diets are most associated with health and longevity.
According to Ströhle, Wolters and Hahn,[19] hunters like the Inuit, who traditionally obtain most of their dietary energy from wild animals and therefore eat a low-carbohydrate diet,seem to have a high mortality from coronary heart disease and many populations of horticulturists, pastoralists and simple agriculturists living today are ingesting a high-carbohydrate diet without having signs and symptoms of CHD.In response to this criticism, Wolfgang Kopp states that "carbohydrate food, consumed by hunter-gatherers, is high in fiber and low-glycemic in effect, eliciting small amounts of insulin only. [...] Are high-carbohydrate diets atherogenic per se? Not if they have a low glycemic load. In this point, Stroehle et al. are right. However, it is the question, whether diets high in low-glycemic plant food (which is relatively high in indigestible fiber and relatively low in carbohydrate) should be labeled as “high-carbohydrate” diets." Kopp also says that it is very likely that diets with only a moderately increased glycemic load are atherogenic to some degree.
At odds with evidence of Paleolithic diets
It has also been argued that there are insufficient data to identify the relative proportions of animal and plant foods in the diets of Paleolithic humans.
Furthermore, according to Katharine Milton, "data from ethnographic studies of nineteenth and twentieth century hunter-gatherers, as well as historical accounts and the archeological record, suggest that ancestral hunter-gatherers enjoyed a rich variety of different diets. Thus estimates of nutrient proportions for "the Paleolithic diet" are hypothetical, at best."Echoing Milton's criticism, Ströhle et al.[19] argue that it is questionable if all hunter-gatherers living between 150,000 and 10,000 years ago in different geographical regions ate a low-carbohydrate diet.[ They indicate that, because the plant–animal subsistence ratios of contemporary hunter-gatherers vary in a remarkable manner (0–90% food from gathering; 10–100% food from hunting and fishing), it is likely that the macronutrient intake of preagricultural humans varied enormously.
They also refer to a hypothesis (the 'Plant underground storage organs hypotheses') that suggests that carbohydrate tubers were eaten in high amounts by our preagricultural ancestors.[113][119][120][121] They add: "Provided that humans are incapable of metabolizing high amounts of dietary protein and given the fact that wild African mammals are relatively low in fat, a diet supplemented with carbohydrates from tubers seems to be more efficient in meeting the energy requirements of early hunters and gatherers than a diet based on lean meat."
Ströhle et al. further mention that Staffan Lindeberg, an advocate of a "Paleolithic diet", has accounted for a plant-based diet rich in carbohydrates as being consistent with the human evolutionary past.
Comparative life expectancy
According to Geoffrey Cannon, "relatively carnivorous diets high in fat, and extremely high in protein evolved with physically very active populations who usually did not live long enough to suffer from chronic diseases. This does not mean us." In response to this argument, S. Boyd Eaton and colleagues state that while Paleolithic humans did have a shorter average life expectancy than we do, studies of modern hunter-gatherer populations suggest that ancestral foragers that reached the age of 60 or beyond were almost completely free from manifestations of most chronic degenerative diseases.
Possible contraindications
According to Erica Frank, professor of health care at the University of British Columbia, eating an animal also involves absorbing the toxins stored in its body fat. She quotes the EPA: "The average American intake is between 300 and 500 times the safe daily dose of dioxin."She argues that dioxin, which is stored in animal fat, is a cancer-causing substance and disrupts hormones and the immune system. "People would be in error if they think they're doing themselves a service by eating bison."
Sustainability concerns
The Paleolithic diet has been criticized on the grounds that it cannot be implemented on a worldwide scale. According to Loren Cordain, if such a diet was widely adopted, it would compromise the food security of populations dependent on cereal grains for their subsistence. However, he says that where cereals are not a necessity, as in most western countries, reverting to a grain-free diet can be highly practical in terms of cutting long-term healthcare costs. Barry Bogin, a professor of anthropology at the University of Michigan, argues that less intensive farming techniques, such as pasture-grazed cattle, will not produce sufficient meat to feed the world’s population.
Concerns have also been raised about the detrimental effects of meat-based diets on the environment.According to Anthony J. McMichael, director of the National Centre for Epidemiology and Population Health at the Australian National University, "in order to achieve a world nutritional state that is health-supporting, equitable and ecologically sustainable, we can learn much from consideration of the interplay between the evolutionary, environmental and ecological realms." He further indicates that the level of per-person meat consumption need only be moderate for dietary optimisation in accordance with human evolutionary biology.
