The paleolithic diet is a diet based on the food humans' ancient ancestors might likely have eaten, such as meat, nuts and berries, and excludes food to which they had not yet become familiar, like dairy. The Paleolithic era was a period lasting around 2.5 million years that ended about 10,000 years ago with the advent of farming. It was characterized by the use of flint, stone, and bone tools, hunting, fishing, and the gathering of plant foods.
The diet is based on the premise that Paleolithic 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 argue that this is because modern 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 raised a number of objections, including that paleolithic humans did eat grains and legumes, that humans are much more nutritionally flexible than Paleolithic advocates claim, that Paleolithic humans were not genetically adapted to specific local diets, that the Paleolithic period was extremely long and saw a variety of forms of human sustenance, or that little is known for certain about what Paleolithic humans ate.
A 2015 systematic review on paleolithic nutrition and its effects on measurable components of metabolic syndrome found that the paleo diets used in the studies led to short-term improvements that had statistical significance for waist circumference, triglycerides, and blood pressure and that there was no statistical significance for changes in HDL cholesterol and fasting blood sugars; it concluded: "Although there is moderate quality evidence from randomized controlled intervention studies to suggest that the Paleolithic diet can improve metabolic syndrome components, we believe that more studies are required before Paleolithic nutrition can be recommended in future guidelines.”
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".
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.
According to evolutionary biologist Marlene Zuk of the University of Minnesota: "Those who follow the [paleo] diet may be missing out on vital nutrients, and it is believed that could create long term health problems, in particular for adolescent girls who may be at risk of developing osteoporosis later in life as a result of not getting enough calcium."
History and terminology
The idea of a paleolithic diet can be traced to the work in the 1970s by gastroenterologist Walter Voegtlin. The idea was later developed by Stanley Boyd Eaton and Melvin Konner, and popularized by Loren Cordain in his 2002 bookThe Paleo Diet.
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. 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.
Cordain has said the diet requires:
- More protein and meat: Meat, seafood, and other animal products represent the staple foods of modern-day Paleo diets, since advocates claim protein constitutes 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 from grains, but from 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 human ancestors could not produce these drinks.
Rationale and counter-arguments
The rationale for the Paleolithic diet derives from evolutionary medicine. Advocates of the diet state that 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. 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. The agricultural revolution brought the addition of grains and dairy to the diet.
According to 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 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. Studies of traditionally living populations show that humans can live healthily with a wide variety of diets. Humans have evolved to be flexible eaters. Lactose tolerance is an example of how humans have adapted to the introduction of dairy. 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.
Diseases of affluence
Advocates of the diet argue that the increase in diseases of affluence after the dawn of agriculture was caused by the change in diet. However, it may be that pre-agricultural foragers did not suffer from the diseases of affluence 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 humans consume and the energy humans spend."
Adoption of the diet assumes that we 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 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 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. 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.
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.
Not all processed foods are a post agricultural introduction, there is evidence early humans processed plant food and possibly prepared flour 30,000 years ago. 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 for amylase.
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