Paleo Diet

Definition

The Paleo diet is an eating plan that is intended to mimic as closely as possible the way that human ancestors ate more than 10,000 years ago, before the introduction of agricultural foods. It is also known as the Paleolithic or caveman diet. Supporters of this diet maintain that Paleolithic people did not suffer from contemporary conditions such as heart disease, cancer, and type 2 diabetes; others point out, however, that Paleolithic people had a much shorter lifespan than 21st century humans and so did not live long enough to develop these conditions.

Origins

The Paleolithic period, also known as the Old Stone Age, began about two million years ago. It ended at various times around the world, concluding about 10,000 years ago in Europe and the Middle East. The period is associated historically with modern humans, and the era is the basis of the modern Paleolithic diet.

During the Paleolithic period, human ancestors were hunters and gatherers, eating foods that they found in the wild, hunting for animals that they killed for meat, and gathering foods such as fruits and vegetables. At this time, agriculture and raising animals for food had not yet evolved.

During the Neolithic period (New Stone Age) that followed, people formed villages and started to cultivate plants, domesticate animals, cook food, and farm. The first crops included grains, leading to the increased consumption of grain-based foods. These post-Paleolithic foods are generally not allowed when eating a Paleo diet.




The Paleo diet includes only foods that could have been hunted or gathered during the Paleolithic era.





The Paleo diet includes only foods that could have been hunted or gathered during the Paleolithic era.
(WIS Bernard/Getty Images)

Since 1985, different versions of the Paleo diet have been marketed. Though they are all based on Paleolithic eating patterns, there is generally some variation. For example, some proponents recommend eating a variety of very lean meats from animals raised as much as possible like those in the wild, while others encourage eating a large quantity of red meat with high fat content.

Description

Although many people use Paleolithic diets to lose weight, they are intended as lifelong eating plans to promote good health. Portion control or counting calories and fat grams are not part of these plans. People are allowed to eat permitted foods until they feel full. The food choices allowed in these high-protein, low-carbohydrate diets are based on prehistoric nutrition.

The Paleo diet permits fruits, vegetables, meats, fish, eggs, nuts, and certain oils. Cereal grains, legumes (including peanuts and soy), dairy, and processed foods should be eliminated or severely reduced. When beginning the Paleo diet, it is advisable to slowly begin the transition to Paleo, gradually including more meals from the eating plan. Guidelines are relaxed during this transition period, which is intended to help the dieter maintain the diet over the long term.

Diet basics

Although wild grains existed during the Paleolithic period, many were very different than the grains grown today. They were unlikely to have been as robust and would have provided little nutrition, so grains, including rice, wheat, and corn, are forbidden with most Paleo diets.

Starchy vegetables such as potatoes are also forbidden, as are legumes. Many diets make exceptions for yams and sweet potatoes, especially for athletes, as they are a good source of carbohydrates for energy and post-workout recovery.

No dairy products are allowed on this diet. Milking did not occur until animals were domesticated, sometime after the Paleolithic age, so milk, cheese, butter, or anything else that comes from milking animals is not permitted. Alternatives for cow's milk include almond and coconut milks. Eggs are allowed, because eggs could have been found in bird's nests during foraging and hunting.

The other basic premise of Paleo diets is that nothing that requires technology can be eaten. Technology encompasses activities as diverse as agricultural methods to complex processing and canning. This rule excludes all forms of refined sugars and other processed foods. The Paleo Diet website ( http://thepaleodiet.com ) advises consumers to avoid food “if it contains salt or comes in a package, can, or box.”

HUNTER-GATHERER MEATS. Although some foods that Paleolithic people ate are still available in the 21st century, modern diets focus on more common meats, such as beef and chicken. Some versions of the Paleo diet suggest eating meats higher in fat to promote a feeling of fullness, but others recommend selecting lean meats. Loren Cordain, author of The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat, believes that Paleolithic humans ate meat that was leaner because animals raised in the wild tended to have less fat and leaner muscle. Regardless of the type of meat selected, an emphasis is placed on choosing free-range and grass-fed products, which are considered by some to be healthier than meat from animals fed corn and grains.

EXERCISE. Different versions of the Paleo diet vary in their recommendations about the role of exercise. Some versions do not make recommendations, while others encourage significant amounts of exercise, especially outdoor exercise. This is because Paleolithic humans spent most of their time hunting and gathering food, which would have required significantly more physical activity than average humans engage in during the 2010s.

Function

Paleo diets are intended to improve overall health and promote weight loss, if needed. Advocates of the diets believe that the human body is not designed to process foods that were not consumed during the Paleolithic age, and that avoiding post-Paleolithic foods will lead to a decreased risk of many of the diseases prevalent in the industrialized world, such as obesity, type 2 diabetes, and heart disease.

Benefits

In addition to weight loss, Paleo diets may provide other health benefits. Fresh fruits and vegetables are high in many vitamins and minerals, which are important for overall good health. Free-range, grass-fed lean meats may contain higher levels of omega-3 fatty acids, which are believed to have positive effects on the heart and cardiovascular system. Eliminating processed foods reduces exposure to artificial ingredients and chemicals that may cause sensitivity reactions in some individuals.

Advocates of Paleo diets maintain that people who follow these plans experience an immediate increase in energy, because their blood sugar and insulin concentrations stabilize on the low–glycemic load carbohydrates found in fruits and vegetables. Foods and drinks that contain carbohydrates are ranked on a glycemic index based on how they affect blood sugar levels. Low rankings start at 0, with the highest foods ranked at 100. Foods and beverages considered low rank at 55 or less. Examples of low-ranking foods include spinach, asparagus, broccoli, tomatoes, grapefruit, and apples.

Cordain claims that following a Paleo diet helps resolve conditions such as diabetes, high blood pressure, high cholesterol, acne, and irritable bowel syndrome. Further research is needed to substantiate these assertions, but some studies have shown promise that Paleo diets may help regulate blood glucose levels in people with type 2 diabetes.

The Paleo diet is the foundation for a stricter diet called the Autoimmune Protocol, which eliminates food that irritates the gut mucosa. It has been theorized that this diet reduces inflammation and helps heal the immune system, thereby reducing symptoms of autoimmune diseases. Although anecdotal reports from followers of the Paleo and Autoimmune Protocol diets suggest health benefits, research studies are limited, and benefits have not been definitively proven.

Precautions

Anyone thinking about beginning a new diet should first consult a medical practitioner. Requirements for calories, fat, and nutrients could differ significantly from person to person, depending on gender, age, weight, and the presence of any diseases or conditions. Pregnant or breastfeeding women should be especially cautious, because deficiencies of vitamins or minerals could have a significant negative impact on a developing baby.

Dairy products and grains are part of traditionally accepted nutritional eating plans. The two food groups are recommended in the 2015–2020 Dietary Guidelines for Americans issued by the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (HHS). Grains and dairy products are also recommended by organizations such as the Academy of Nutrition and Dietetics (formerly the American Dietetic Association). Health experts recommend that people consume low-fat dairy products because they are rich in calcium, the primary mineral used for the body to build and maintain strong bones and teeth. Dairy products, especially milk, and grain products are major sources of iodine, a trace element essential for thyroid functioning and skeletal and central nervous system development in foetuses and infants. In addition, grains are a source of dietary fiber, which not only provides the bulk needed for a healthy digestive system but also has been linked to reduced risk of cardiovascular disease and cancer.

A diet consisting primarily of meat will be more expensive than diets based on a more traditional food plan. In addition, more plant-based diets are increasingly being recommended for both health benefits and sustainability. Critics of the various versions of the Paleo diet also regard it as a fad diet, one that is nutritionally lacking and could be difficult to maintain on a long-term basis. Furthermore, they point out that although Paleolithic people did not have chronic conditions like diabetes and heart disease, the life expectancy of Stone Age people was 30 years old. Not only is that much shorter than the life expectancy today, but type 2 diabetes and heart disease are more likely to develop later in life.

Risks

Any diet poses some risks, and the Paleo is no exception. It can be difficult to get enough of some vitamins and minerals when eating a limited variety of foods. All versions of the Paleo diet exclude all milk and other dairy products. Because these foods are excellent sources of calcium and iodine, people following a Paleo diet will need to ensure that they are getting enough of these in their diet. A lack of calcium can lead to many different diseases and conditions such as osteoporosis and rickets. Iodine deficiency can adversely affect thyroid functioning, as well as fetal and infant development. Anyone beginning this diet should consult with a physician about whether or not it is safe and to discuss the need for any vitamins or supplements.

KEY TERMS
Blood glucose—
The main sugar that the body makes from the food in the diet.
Carcinogen—
A cancer-causing substance.
Diabetes mellitus—
A condition in which the body either does not make or cannot respond to the hormone insulin. As a result, the body cannot use glucose (sugar). There are two types, type 1, or juvenile onset, and type 2, or adult onset.
Dietary supplement—
A product, such as a vitamin, mineral, herb, amino acid, or enzyme that is intended to be consumed in addition to an individual's diet with the expectation that it will improve health.
Glycemic index (GI)—
A measurement of the speed at which the body converts carbohydrates in foods to blood glucose. The more rapidly a food's carbohydrates are converted to glucose, the higher its GI.
Ketones—
Chemicals produced during the breakdown of fat.
Ketosis—
An abnormal increase in the number of ketones in the body, produced when the liver breaks down fat into fatty acids and ketone bodies. Ketosis is a common side effect of low-carbohydrate diets or very low-calorie diets. If continued for a long period of time, ketosis can cause serious damage to the kidneys and liver.
Mineral—
An inorganic substance found in the earth that is necessary in small quantities for the body to maintain health (e.g., zinc, copper, iron).
Vitamin—
A nutrient that the body needs in small amounts to remain healthy but that the body cannot manufacture for itself and must acquire through diet.

Eating unlimited amounts of foods could pose a health risk. Eating food high in calories without exercising could result in weight gain and put a person at risk medically. Versions of the Paleo diet that allow and encourage the consumption of large quantities of high-fat red meat could pose this danger. High-fat diets, especially diets high in animal fats, have been shown to increase the risk of cardiovascular disease. Versions of the diet that encourage the consumption of lean meats may not have this increased risk.

Diets that recommend large amounts of red meat and eggs and encourage the consumption of fattier meats are extremely controversial. High-fat, low-carb diets, such as the Atkins diet, have gained many followers, but physicians, registered dietitians, and other health and science professionals continue to debate their various health benefits and risks. It is generally accepted that regularly eating a diet high in saturated fats, which are often found in high quantities in red meat, has a detrimental effect on health and can lead to increased incidence of cardiovascular disease. High intake of red meat is also associated with increased risk of colorectal cancer, thought to be due to N-nitroso compounds produced when the heme iron in meat breaks down. N-nitroso compounds may be carcinogenic.

Although fatty fish is a source of omega-3 fatty acids, the Academy of Nutrition and Dietetics and other organizations caution that it is also high in calories. Some types of seafood, such as tuna, may also contain mercury or other toxins.

Research and general acceptance

In a 2010 article titled “Paleolithic Nutrition: Twenty-Five Years Later,” authors Konner and Eaton reviewed the research conducted during the 25 years following the publication of their first article about Paleolithic nutrition in 1985. The authors stated that initial results from studies were consistent with their original predictions.

The research they cited included a noncontrolled challenge study of nine sedentary but healthy volunteers who were not obese. Volunteers ate their usual diets for three days followed by three days of “ramp-up” diets. The volunteers then ate meat, fruit, vegetables, and nuts for ten days and did not consume grains, dairy products, and legumes. The authors stated that the group experienced “modest but significant” drops in blood pressure.

Another study involved 29 patients with ischemic heart disease (coronary heart disease) and either glucose intolerance or type 2 diabetes. During the 12-week study, 14 people followed a Paleolithic-based diet consisting of lean meat, fish, fruit, vegetables, root vegetables, eggs, and nuts. The remaining 15 people followed a Mediterranean-style diet that included whole grains, lowfat dairy products, vegetables, fruits, fish, oils, and margarines. After 12 weeks, the AUC (area under the curve) glucose level decreased by 26% in the Paleolithic group and 7% in the Mediterranean group. Waist circumference dropped 2.20 inches (5.6 cm) in the Paleolithic group and 1.14 inches (2.9 cm) in the Mediterranean group.

QUESTIONS TO ASK YOUR DOCTOR

Both of these studies were extremely small and do not provide enough support for the diet's purported benefits. Studies since then have not proven definitive health benefits compared to other diets for health conditions such as type 2 diabetes and metabolic syndrome. Further research is needed. There is, however, strong research indicating that a healthy, varied diet that incorporates many different fruits and vegetables is important for good overall health. In addition, health benefits are associated with eating fewer processed foods that contain high amounts of fat, sugar, and salt.

See also Coronary heart disease ; High-fat, low-carb diets .

Resources

BOOKS

Cordain, Loren. The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat. Hoboken, NJ: J. Wiley, 2010.

Wolf, Robb, and Loren Cordain. The Paleo Solution: The Original Human Diet. Expanded, updated ed. Las Vegas: Victory Belt, 2017.

PERIODICALS

Bastide, Nadia M., Fabrice H. F. Pierre, and Denis E. Corpet. “Heme Iron from Meat and Risk of Colorectal Cancer:

A Meta-Analysis and a Review of the Mechanisms Involved.” Cancer Prevention Research 4, no. 2 (2011): 177–84.

Eaton, S. Boyd, and Melvin Konner. “Paleolithic Nutrition: A Consideration of Its Nature and Current Implications.” New England Journal of Medicine 312 (January 31, 1985): 283–89.

Fenton T. R., and C. J. Fenton. “Paleo Diet Still Lacks Evidence.” American Journal of Clinical Nutrition 104, no. 3 (2016): 844.

Jew, Stephanie, Suhad S. AbuMweis, and Peter J. H. Jones. “Evolution of the Human Diet: Linking Our Ancestral Diet to Modern Functional Foods as a Means of Chronic Disease Prevention.” Journal of Medicinal Food 12, no. 5 (October 2009): 925–34.

Konner, Melvin, and S. Boyd Eaton. “Paleolithic Nutrition Twenty-Five Years Later.” Nutrition in Clinical Practice 25, no. 6 (December 2010): 594–602.

Lindeberg, Staffan. “Paleolithic Diets as a Model for Prevention and Treatment of Western Disease.” American Journal of Human Biology 24, no. 2 (2012): 110–5.

Lindeberg, Staffan, Tommy Jönsson, Yvonne Granfeldt, et al. “A Palaeolithic Diet Improves Glucose Tolerance More than a Mediterranean-Like Diet in Individuals with Ischaemic Heart Disease.” Diabetologia 50, no. 9 (September 2007): 1795–807.

Manheimer, Eric W., Esther J. van Zuuren, Zbys Fedorowicz, et al. “Paleolithic Nutrition for Metabolic Syndrome: Systematic Review and Meta-Analysis.” American Journal of Clinical Nutrition 102, no. 4 (2015): 922–32. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4588744 (accessed May 19, 2018).

WEBSITES

Cordain, Loren. “The Paleo Diet.” ThePaleoDiet.com . http://www.thepaleodiet.com (accessed May 19, 2018).

Mayo Clinic Staff. “Paleo Diet: What Is It and Why Is It So Popular?” MayoClinic.com . https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/paleo-diet/art-20111182 (accessed May 19, 2018).

Mayo Clinic Staff. “Low-Carb Diet: Can It Help You Lose Weight?” MayoClinic.com . http://www.mayoclinic.com/health/low-carb-diet/NU00279 (accessed May 19, 2018).

USDA Center for Nutrition Policy and Promotion (CNPP). “ ChooseMyPlate.gov .” U.S. Department of Agriculture. http://www.choosemyplate.gov (accessed May 19, 2018).

U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2015–2020. Health.gov . http://health.gov/dietaryguidelines/2015/guidelines (accessed May 19, 2018).

U.S. News & World Report. “Paleo Diet.” Health.USNews.com . http://health.usnews.com/best-diet/paleo-diet (accessed May 19, 2018).

ORGANIZATIONS

Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, amacmunn@eatright.org, http://www.eatright.org .

American Society for Nutrition, 9211 Corporate Blvd., Ste. 300, Rockville, MD, 20850, (240) 428-3650, Fax: (240) 404-6797, http://www.nutrition.org .

Center for Food Safety and Applied Nutrition, Food and Drug Administration, 5001 Campus Dr., HFS-009, College Park, MD, 20740-3835, (888) 723-3366, https://www.fda.gov .

Center for Nutrition Policy and Promotion, U.S. Department of Agriculture, 3101 Park Center Dr., 10th Fl., Alexandria, VA 22302, (202) 720-2791, support@cnpp.usda.gov, http://www.cnpp.usda.gov .

Helen M. Davidson,
Revised by Jennifer E. Van Pelt, MA

  This information is not a tool for self-diagnosis or a substitute for professional care.