The Paleo Diet
The Paleolithic diet (also called the paleo diet, caveman diet or stone-age diet) is based mainly on foods presumed to have been available to Paleolithic humans. Wide variability exists in the way the diet is interpreted. However, the diet typically includes vegetables, fruits, nuts, roots, meat, and organ meats while excluding foods such as dairy products, grains, sugar, legumes, processed oils, salt, and alcohol or coffee. The diet is based on avoiding not just modern processed foods, but rather the foods that humans began eating after the Neolithic Revolution when humans transitioned from hunter-gatherer lifestyles to settled agriculture. The ideas behind the diet can be traced to Walter Voegtlin, and have been popularized more recently in the best-selling books of Loren Cordain.
Like other fad diets, the Paleo diet is promoted as a way of improving health. Limited data exist on the metabolic effects on humans eating the diet, though the available data suggest following this diet may lead to improvements in terms of body composition and metabolic effects as compared to the typical Western diet or as compared to diets recommended by national nutritional guidelines. Following the Paleo diet can lead to an inadequate calcium intake.
The digestive abilities of modern humans are different from those of Paleolithic humans, undermining the diet's core premise. Although little is known about the diet of Paleolithic humans, it is very likely that they consumed wild grains and legumes. During the 2.6 million year long Paleolithic era, the highly variable climate and worldwide spread of human population meant that humans were, by necessity, nutritionally adaptable; in contrast, supporters of the diet assume that human digestion has remained essentially unchanged over time.
The diet advises eating only foods presumed to be available to Paleolithic humans; there is wide variability in the way this is interpreted. There is a debate surrounding the specific foods eaten by our ancestors.
In the original description of the paleo diet in Cordain's 2002 book, he advocated eating as much like Paleolithic people as possible, which meant:
55% of daily calories from seafood and lean meat, evenly divided
15% of daily calories from each of fruits, vegetables, and nuts and seeds
no dairy, almost no grains (which Cordain described as "starvation food" for Paleolithic people), no added salt, no added sugar
The diet is based on avoiding not just modern processed foods, but also the foods that humans began eating after the Neolithic Revolution.
The scientific literature generally uses the term "Paleo nutrition pattern", which has been variously described as:
"Vegetables, fruits, nuts, roots, meat, and organ meats";
"vegetables (including root vegetables), fruit (including fruit oils, e.g.,olive oil, coconut oil, and palmoil), 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".
Seeds such as walnuts are rich sources of protein and micronutrients.
The aspects of the Paleo diet that advise eating fewer processed foods and less sugar and salt are consistent with mainstream advice about diet. Like other low carb or high protein diets,[not in citation given] the Paleo diet's focus on protein from lean meat and seafood makes people feel full more quickly and so can help people eat less. Diets with a paleo nutrition pattern have some similarities to traditional ethnic diets like the Mediterranean diet that are healthier than the Western diet; however, following the Paleo diet can lead to nutritional deficiencies such as those of vitamin D and calcium, which in turn could lead to compromised bone health. There is also a risk of toxins from high fish consumption.
As of 2016 there are limited data on the metabolic effects on humans eating a Paleo diet, based on a few clinical trials that have been too small to have a statistical significance sufficient to allow the drawing of generalizations. These preliminary trials have found that participants eating a paleo nutrition pattern had better measures of cardiovascular and metabolic health than people eating a standard diet, though the evidence is not strong enough to recommend the Paleo diet for treatment of metabolic syndrome. As of 2014 there was no evidence the paleo diet is effective in treating inflammatory bowel disease.