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*THIS IS THE CURRENT (21/9) PALEO ARTICLE*

The Paleolithic diet, Paleo diet, caveman diet, or stone-age diet is a modern fad diet consisting of foods thought to mirror those eaten during the Paleolithic era.

There are different variants of the diet; some are predominantly plant-based but the most recent popular variants focus on animal products. The diet avoids processed food and typically includes vegetables, fruits, nuts, roots, and meat and excludes dairy products, grains, sugar, legumes, processed oils, salt, alcohol, and coffee. The ideas behind the diet can be traced to primitive diets advocated in 19th century. In the 1970s Walter L. Voegtlin popularized a meat-centric "Stone Age" diet, and in the 21st century, the Paleo Diet was popularized in the best-selling books of Loren Cordain. the paleo diet industry was worth approximately US$500 million.

In the 21st century the sequencing of the human genome and DNA analysis of the remains of early humans has found evidence that humans evolved rapidly in response to changing diet. This evidence undermines a core premise of the paleolithic diet, that human digestion has remained essentially unchanged over time. Anthropological science has found that the paleolithic human diet was more varied and less meat-centric than had been assumed.

The paleolithic diet is promoted as a way of improving health. There is some evidence that following it may lead to improvements in body composition and metabolism compared with the typical Western diet or compared with diets recommended by some European nutritional guidelines. On the other hand, following the diet can lead to nutritional deficiencies such as an inadequate calcium intake, and side effects can include weakness, diarrhea, and headaches.

History and terminology
Adrienne Rose Johnson writes that the idea that the primitive diet was superior to current dietary habits dates back to the 1890s with such writers as Emmet Densmore and John Harvey Kellogg. Densmore proclaimed that "bread is the staff of death", while Kellogg supported a diet of starchy and grain-based foods in accord with "the ways and likings of our primitive ancestors". Arnold DeVries advocated an early version of the Paleolithic diet in his 1952 book, Primitive Man and His Food. In 1958, Richard Mackarness authored Eat Fat and Grow Slim, which proposed a low-carbohydrate "Stone Age" diet.

In his 1975 book The Stone Age Diet, gastroenterologist Walter L. Voegtlin advocated a meat-based diet, with low proportions of vegetables and starchy foods, based on his declaration that humans were "exclusively flesh-eaters" until 10,000 years ago.

In 1985 Stanley Boyd Eaton and Melvin Konner published a controversial article in the New England Journal of Medicine proposing that modern humans were biologically very similar their primitive ancestors and so "genetically programmed" to consume pre-agricultural foods. Eaton and Konner proposed a "discordance hypothesis" by which the mismatch between modern diet and human biology gave rise to lifestyle diseases, such as obesity and diabetes.

The diet started to become popular in the 21st century, where it attracted a largely internet-based following using web sites, forums and social media.

These diet's ideas were further popularized by Loren Cordain, a health scientist with a Ph.D. in physical education, who trademarked the words "The Paleo Diet" and who wrote a 2002 book of that title.

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 and 2014 the Paleolithic diet was Google's most searched weight-loss method.

The paleolithic or paleo diet is also sometimes referred to as the caveman or stone-age diet.

Foodstuffs
The basis of the diet is a re-imaging of what paleolithic people ate, and different proponents recommend different diet compositions. Eaton and Konner, for example, wrote a 1988 book The Paleolithic Prescription with Marjorie Shostak, and it described a diet which is 65% plant-based. This is not typical of more recently devised paleo diets; Loren Cordain's – probably the most popular – instead emphasizes animal products and an avoidance of processed food. Diet advocates concede the modern paleolithic diet cannot be a faithful recreation of what paleolithic people ate, and instead aim to "translate" that into a modern context, avoiding such likely historical practices as cannabalism.

Foodstuffs that have been described as permissible include:
 * "vegetables, fruits, nuts, roots, meat, and organ meats";
 * "vegetables (including root vegetables), fruit (including fruit oils, e.g., olive oil, coconut oil, and palm oil), nuts, fish, meat, and eggs, and it excluded dairy, grain-based foods, legumes, extra sugar, and nutritional products of industry (including refined fats and refined carbohydrates)"; and
 * "avoids processed foods, and emphasizes eating vegetables, fruits, nuts and seeds, eggs, and lean meats".

The diet forbids the consumption of all dairy products. This is because milking did not exist until animals were domesticated after the Paleolithic era.

Ancestral 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 that 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 Inuit. 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 Paleolithic ancestors; likewise, their nutritional profiles are very different from their ancient 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, such as broccoli, did not exist in the Paleolithic period; broccoli, cabbage, cauliflower, and kale are modern cultivars of the ancient species Brassica oleracea.

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. Descendants of populations with different diets have different genetic adaptations to those diets, such as the ability to digest sugars from starchy foods. Modern hunter-gatherers tend to exercise considerably more than modern office workers, protecting them from heart disease and diabetes, though highly processed modern foods also contribute to diabetes when those populations move into cities.

A 2018 review of the diet of hunter-gatherer populations found that the dietary provisions of the palelothic diet had been based on questionable research, and were "difficult to reconcile with more detailed ethnographic and nutritional studies of hunter-gatherer diet".

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 amylase.

Health effects
The paleolithic diet is controversial in part because of the exaggerated health claims made for it by its supporters. In general, research into the diet has been of poor quality.

The aspects of the paleolithic diet that result in eating fewer processed foods and less sugar and salt are consistent with mainstream advice about diet. Diets with a paleolithic nutrition pattern have some similarities to traditional ethnic diets such as the Mediterranean diet that have been found to be healthier than the Western diet. Following the paleolithic diet, however, can lead to nutritional deficiencies such as those of vitaminD and calcium, which in turn could lead to compromised bone health; it can also lead to an increased risk of ingesting toxins from high fish consumption.

Research into the weight loss effects of the paleolithic diet has generally been of poor quality. There is some evidence the diet helps achieve weight loss, possibly because of the increased satiety from the foods typically eaten. One trial of obese postmenopausal women found improvements in weight and fat loss after six months, but the benefits had ceased by 24 months; side effects among participants included "weakness, diarrhea, and headaches". As with any other diet regime, the paleolithic diet leads to weight loss because of overall decreased caloric intake, rather than a special feature of the diet itself.

There is no good evidence that following a paleolithic diet lessens the risk of cardiovascular disease or metabolic syndrome. As of 2014 there was no evidence the paleolithic diet is effective in treating inflammatory bowel disease.

The paleolithic diet similar to the Atkins diet encourages the consumption of large amounts of red meat, especially meats high in saturated fat. This has a negative effect on health in the long run as medical studies have shown that it can lead to increased incidence of cardiovascular disease.

Genetics


The stated rationale for the paleolithic diet is that human genes of modern times are unchanged from those of 10,000 years ago, and that the diet of that time is therefore the best fit with humans today. Loren Cordain has described the paleo diet as "the one and only diet that ideally fits our genetic makeup".

The argument is that modern humans have not been able to adapt to the new circumstances. According to Cordain, before the agricultural revolution, hunter-gatherer diets rarely included grains, and obtaining milk from wild animals would have been "nearly impossible". Advocates of the diet argue that the increase in diseases of affluence after the dawn of agriculture was caused by these changes in diet, but others have countered that 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.

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 modern lifestyles." Advocates of the modern paleo diet have formed their dietary recommendations based on this hypothesis. They argue that modern humans should follow a diet that is nutritionally closer to that of their Paleolithic ancestors.

The evolutionary discordance is incomplete, since it is based mainly on the genetic understanding of the human diet and a unique model of human ancestral diets, without taking into account the flexibility and variability of the human dietary behaviors over time. Studies of a variety of populations around the world show that humans can live healthily with a wide variety of diets and that humans have evolved to be flexible eaters. Lactose tolerance is an example of how some 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 had not been nutritionally adaptable, these technological developments would have been dropped.

Since the publication of Eaton and Konner's paper in 1985, analysis of the DNA of primitive human remains has provided evidence that evolving humans were continually adapting to new diets, thus challenging the hypotheis underlying the paleothic diet. 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 to have taken place. On this basis Zuk dismisses Cordain's claim that the paleo diet is "the one and only diet that fits our genetic makeup".

Paleoanthropologist Peter Ungar has written that the paleo diet is a "myth", on account both of its invocation of a single suitable diet when in reality humans have always been a "work in progress", and because diet has always been varied because humans were spread widely over the planet.

Anthropological geneticist Anne C. Stone has said that humans have adapted in the last 10,000 years in response to radical changes in diet. In 2016 she was quoted as saying "It drives me crazy when Paleo-diet people say that we've stopped evolving — we haven't".

Melvin Konner has said the challenge to the hypothesis is not greatly significant since the real challenges to human non-adaptation have occurred with the rise of ever-more refined foodstuffs in the last 300 years.

Environmental impact
An 2019 analysis of diets in the United States ranked consumption of a paleolithic diet as more environmentally harmful than consumption of an omnivorous diet, though not so harmful as a ketogenic diet.

Elizabeth Kolbert has written the paleolithic's emphasis on meat consumption is a "disaster" on account of meat's comparatively high energy production costs.

Culture and society
A lifestyle and ideology have developed around the diet. "Paleolithic" products include clothing, smartphone apps, and cookwear, and many paleolithic cookery books have been bestsellers.

the market for products with the word "Paleo" in their name was worth approximately $US500&thinsp;million, with strong growth prospects despite pushback from the scientific community. Some products were taking advantage of the trend by touting themselves as "paleo-approved" despite having no apparent link to the movement's tenets.

Like many other diets, the paleolithic diet is promoted by some by an appeal to nature and a narrative of conspiracy theories about how nutritional research, which does not support the supposed benefits of the palelithic diet, is controlled by a malign food industry. Paleolithic diet advocate John Durant has blamed suppression of the truth about diet in the United States on "the vegetarian lobby".

Politically, the paleolithic diet has found favour with the alt-right as a point of opposition to what is seen as more left-wing veganism.

*THIS IS THE CURRENT (21/9) PALEO ARTICLE*