Paleo diets are a set of eating patterns that limit or exclude foods that were unavailable to our Paleolithic ancestors. Randomized trials suggest well-formulated paleo diets may be as effective as other healthy diets for weight loss and improving markers of metabolic health. Risks of a well-formulated paleo diet are minimal, but more restrictive versions can cause nutrient deficiencies and health issues.
What is a paleo diet?
What are other names for the paleo diet?
The paleolithic diet goes by many other names, including paleo diet, ancestral diet, primal diet, hunter-gatherer diet, evolutionarily appropriate diet, caveman diet, Stone Age diet, evolutionary eating, and, simply, paleo.
Some of these (e.g., the Stone Age diet, primal diet, and original The Paleo Diet™) offer different dietary recommendations but resemble each other enough to be categorized as paleo diets.
What are other versions of the paleo diet?
Related diets include the Paleo Autoimmune Protocol and the Wahls Protocol.
The Paleo Autoimmune Protocol is a two-stage elimination diet. First, foods typically excluded on a paleo diet are removed. Then, after a period, the eliminated foods are added back one by one to see if they cause negative symptoms.
The Wahls Protocol is another restrictive diet that aims to address autoimmunity issues and is sometimes referred to as a modified paleo diet.
Carnivore diets and raw-food diets share some philosophical principles with the modern paleo lifestyle — namely, their premise on the evolutionary discordance hypothesis. Carnivore diets are completely (or almost completely) animal-based diets. Raw-food diets range from vegan to carnivore, but no processing or heat treatment is permitted. When these diets are more paleo than not, they are often labeled “carnivore paleo” or “raw paleo” in colloquial usage. These diets have not been studied in interventional trials.
Low-carbohydrate paleo diets can cause nutritional ketosis; some paleo diets are ketogenic diet, and some keto diets are paleo.
|Cultural periods||Approximate dates||Important dietary developments|
|Paleolithic period*||2.5 million ya to 10,000 – 12,000 ya||2.5–2.6 million ya - first use of stone tools for processing meat  30–250 kya - earliest fire and hearth structures  100–130 kya - earliest evidence of seed and wheat-predecessor consumption 44–100 kya - possible first evidence of bean consumption * 30 kya - early evidence of starchy root vegetable processing |
|Mesolithic period||10,000 – 12,000 ya to 8,000 – 5,500 ya||2.5–2.6 million ya - first use of stone tools for processing meat  30–250 kya - earliest fire and hearth structures  100–130 kya - earliest evidence of seed and wheat-predecessor consumption 44–100 kya - possible first evidence of bean consumption * 30 kya - early evidence of starchy root vegetable processing |
|Neolithic period||8,000 – 5,500 ya to the beginning of the Bronze Age (depending on location)||* Widespread agrarian practices (e.g., domestication of plants and animals, food production practices) mark the beginning of the Neolithic period|
|ya = years ago kya = thousand years ago||*Anatomically modern humans first appeared around 200 kya and dispersed out of Africa around 50 ka. Many of the dietary developments in the Paleolithic Period occurred among pre-human ancestors or evolutionary cousins, not modern humans.|
How does paleo compare with other diets?
Compared with standard Western diets and healthy eating guidelines, paleo diets include more calories from protein and fat and fewer from carbohydrates, according to the dietary intake data in interventional studies.
Compared with some Westerners’ baseline diets, paleo diets generally provide more polyunsaturated (i.e., omega-3s) and monounsaturated fatty acids and carotenoids, as well as potentially more fiber and potassium, while providing less sodium, less saturated fat, and less sugar.
Compared with national healthy eating guidelines, however, paleo diets have been shown to be lower in calcium and iodine. Theoretically, they may also provide less potassium and fiber and more saturated fat than healthy diet guidelines.
Are paleo diets healthy?
A moderate, sensible, nonrestrictive paleo diet that generally fits within the contemporary, evidence-based ideas of paleo nutrition is likely to be healthy. A highly restrictive, unsustainable paleo diet, on the other hand, can lead to adverse health outcomes.
More studies have been conducted on paleo diets for their effects on weight and markers of cardiometabolic health than on any other outcome. Averaged across studies, paleo diets appear to have a positive effect on these outcomes, comparable to other healthy diets. Conclusions on long-term outcomes are impossible to make, but one epidemiological study that watched people’s disease rates over time suggests that people with a diet closer to paleo may have a lower risk of death from all causes, compared with people whose diet is furthest from paleo.
Paleo diets typically include more animal protein and fewer grains, dairy products, and legumes than recommended by official organizations, which could contribute to ill health. On the other hand, paleo diets also encourage lean meats, fruits, and vegetables and restrict alcohol, refined grains, added sugars, and ultraprocessed foods, which jibes with many of the requirements for healthy diets outlined by the FDA, American Institute for Cancer Research, and American Cancer Society.
Paleo diets are sometimes misconstrued as being high in saturated fat. Although that’s certainly a possibility, the results of rigorous studies suggest that paleo diets generally lead to a decrease in saturated fat and increase in unsaturated fat intake.
Overall, the diet that works is the one you can stick to, and some studies suggest that people have a hard time sticking to paleo, with only 3 out of 4 participants able to adhere to it for 2 years. Restrictive paleo diets, such as the paleo autoimmune protocol and popularized fad versions, entail even greater dietary restriction, which increases the risk and difficulty. Adopting a more restrictive paleo diet should be supervised by a qualified healthcare professional to ensure the diet is supportive of — not damaging to — your health.
What are the benefits of a paleo diet?
Most interventional studies comparing a moderate paleo diet to a typical Western diet show marked health improvements with a paleo diet, whereas comparison to one of any number of national healthy eating guidelines reveals comparable positive effects among the groups studied.
A modest body of research shows that a typical paleo diet may help people lose weight and may promote health, including studies showing positive outcomes for body composition; markers of metabolic syndrome, markers of diabetes and insulin resistance; blood lipid markers of heart disease; and observational data for oxidative stress and cancer. The scant evidence available for autoimmune conditions suggests minor, potentially irrelevant, improvements for multiple sclerosis and inflammatory bowel diseases. The evidence suggests a consistent, if not always significant, decrease in blood pressure across studies.
Is paleo good for weight loss?
Paleo diets can lead to greater weight loss than other healthy diets in the short term, but after 6 months, their effect on weight is comparable to other healthy diets.
The longest paleo diet study (2 years) shows that it can lead to greater weight loss over 6 months compared with other healthy diets, but this beneficial effect may not extend to a year or longer, which may be due to an adaptation effect or issues with long-term adherence. (Additionally, for low-carb paleo diets, part of the initial weight loss may be due to glycogen depletion. Several meta-analyses have found that paleo diets reduce weight by 1.4–3.9 kg (3.1 –8.5 pounds), reduce BMI by 1.1–1.7 kg/m2, and decrease waist circumference by 2.5–3.1 centimeters (1–1.25 inches) more than control diets.
Trials using the gold standard for fat mass measurements, dual-energy X-ray absorptiometry (DXA), showed no difference in fat loss between participants who ate a paleo diet versus another healthy diet. Trials that used the less reliable method of bioelectrical impedance analysis (measured using the rate at which an electrical current runs through the body) found that a paleo diet reduced fat mass more than a control diet did.
Paleo diets lead to weight loss because people tend to eat fewer total calories, even though most studies tell participants to not intentionally restrict calories. Eating a paleo diet may result in consuming 108–451 fewer kilocalories daily than on a control diet. 
The effect on reducing calorie intake may be attributed to the high quantities of protein, fats, and fiber in most paleo diets, which contribute to a high level of satiety (feeling full). Compared with healthy eating guidelines, paleo meals lead to a relative increase in the satiety hormones glucagon-like peptide-1 (GLP-1) and peptide YY,  or a decrease in the fat hormone leptin, but probably not due to ghrelin, the hunger hormone. On the flip side, other diets (e.g., low-fat or high-unsaturated-fat diets) are associated with greater before-meal hunger compared with a paleo diet. Over the long run, this satiating effect may translate to reduced calorie intake, greater weight loss, and a reduction in the risk of related cardiometabolic diseases.
Is paleo good for people with type 2 diabetes?
Paleo appears to be effective for managing markers of diabetes, at least in the short term and to a similar extent as diets based on other healthy eating guidelines that also lead to weight loss.
In people with diabetes, paleo diets have a greater effect on reducing insulin resistance (using the homeostatic model assessment for insulin resistance, or HOMA-IR) and blood insulin compared with other healthy diets. Among people with, or at high risk of, diabetes, paleo appears to have a similar, but not superior, effect on lowering elevated hemoglobin A1c (HbA1c, an average blood sugar measurement over 3 months), glucose, and HOMA-IR as other healthy diets.
Paleo diets have a small effect on levels of the inflammation marker C-reactive protein (CRP) among people with type 2 diabetes and people at high cardiometabolic risk. 
The positive effects of weight loss on blood sugar and insulin regulation are well established, regardless of the diet used to achieve it. Since people on a paleo diet tend to lose weight, the diet also tends to show favorable effects on markers of type 2 diabetes. The low-glycemic sources of carbohydrates and lower total carbohydrate content in paleo diets may also play a role in glycemic regulation, but whether the diet’s beneficial effect is due to its specific composition or its effect on weight loss has not been directly studied.
Is paleo good for blood pressure, cholesterol, and other heart health markers?
Overall, paleo seems to have small, mostly positive effects on markers of cardiometabolic health, including weight, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides. Positive effects on blood pressure are seen less consistently across studies.
Paleo may lead to a consistent (but not always significant) decrease in blood pressure across short-term studies when compared with other healthy diets. The variable effect of paleo on blood pressure may be due to the different makeup of individual paleo diets. Eating less sodium and more potassium lowers blood pressure; more magnesium and a higher ratio of unsaturated fat to saturated fat may also contribute.
When it comes to blood lipids, randomized studies suggest that a paleo diet decreases triglycerides and LDL-C, though one nonrandomized, noncontrolled trial showed that an unrestricted paleo diet can raise LDL-C. The positive effect on HDL-C is less clear.
The effect on lowering triglycerides is likely due to eating less total refined carbohydrates, in particular, sugar. A decrease in LDL-C and increase in HDL-C may be attributed to paleo’s high omega-3 fatty acid content and favorable ratio of unsaturated to saturated fats. On the other hand, LDL-C may rise when dietary saturated fat is eaten in place of carbohydrates or unsaturated fats. This relationship might not hold true for paleo diets that are also ketogenic.
Does the paleo diet affect cancer?
No interventional trials have looked at the relationship between a paleo diet and cancer development, progression, or recurrence. In one retrospective case-control study, people without endoscopy-confirmed colorectal cancer were marginally more likely to eat a diet that adhered to general paleo principles compared with people who followed a diet least similar to paleo. A more rigorous prospective observational study showed that participants who ate a diet most similar to paleo were less likely to die of cancer than those who followed a diet most removed from paleo.
Is paleo good for inflammatory autoimmune conditions?
Paleo Autoimmune Protocol and inflammatory bowel diseases
The Paleo Autoimmune Protocol (AIP) is an elimination diet based on paleo and developed by biologist researcher Sarah Ballantyne, PhD. The one before-and-after study on people with Crohn’s disease or ulcerative colitis used the “SAD to AIP in Six” — SAD standing for the standard American diet — diet transition program, in which participants went through an elimination phase followed by a highly restricted maintenance phase. Negative symptoms decreased, and 73% of participants achieved and maintained clinical remission during the study. The downward trend in fecal calprotectin (a marker of inflammation in inflammatory bowel disease) was not significant, and researchers observed no effect on CRP or any other biomarker.
Paleo AIP and Hashimoto’s thyroiditis
Only a single before-and-after study has been conducted on the paleo AIP’s effect on Hashimoto’s thyroiditis. Compared to baseline, mild improvements in quality of life were reported.
Wahls Protocol and multiple sclerosis
Another paleo-based dietary protocol, developed by Terry Wahls, MD, has been studied for its effect on multiple sclerosis with and without a lifestyle component. Each randomized study showed a modest improvement in quality of life and level of fatigue but no change in disease activity when compared to a typical American diet, MCT oil-based ketogenic diet, or low-fat diet.
What is the history of the paleo diet?
For almost a century, diets informed by evolutionary biology and paleoanthropology have enjoyed a presence in popular media. Weston A. Price’s “Nutrition and Physical Degeneration: A Comparison of Primitive and Modern Diets and Their Effects” in 1937 is one early example, but only since Walter Voegtlin’s 1975 chiefly carnivorous “The Stone Age Diet” have these ancestral diet theories come together to form the popular “paleolithic diet” recognized today.
The next wave of paleo diet science came in 1985. S. Boyd Eaton, MD, and Melvin Konner, MD, analyzed data from George Murdock’s 1967 “Ethnographic Atlas” and suggested that typical paleolithic diets completely excluded dairy, potentially included tiny amounts of grains, and often included roots, beans, nuts, tubers, and fruits. Eaton and Konner estimated that in the average paleolithic diet, 33% of calories came from protein, 21% from fat, and 44% from carbohydrates, but they noted that variation in macronutrient composition was the rule.. From these investigations, Eaton published “Paleolithic Prescription” to reach popular audiences in 1988. By 1997, the authors had expanded their data set and showed that a model of the diets of small, traditional societies were more nutrient dense than modern diets.
In 2002 the paleo diet’s eponymous book by Loren Cordain, PhD, ushered in a new level of popular interest in evolutionary eating. Going off the (mistaken) perspective that human digestion and genetics have remained unchanged for more than 10,000 years, and the then-current paleoanthropological research which suggested that animal foods made up the majority of Paleolithic diets, Cordain’s paleo is heavy on meat and excludes all grains, dairy, and legumes.
In subsequent years, paleo protocols have multiplied, resulting in a dizzying variety of paleo diets. Emerging from this trend, the paleo-esque AIP and Wahls Protocol are evidence-based, medically supervised elimination diets that restrict foods commonly discouraged by paleo diets.
As proponents of paleo update their evidence base, contemporary paleo diets are becoming more flexible and more able to suit individual needs. “Paleo”-branded products proliferate, blurring the line between what is and is not paleo. The history of the paleo movement shows that if there is one thing we know about paleo, it’s that the paleo diet doesn’t exist: there was no single diet of our Paleolithic ancestors, and there is no single paleo diet today.
What did Paleolithic humans actually eat?
The diverse dietary patterns of hunter-gatherers were largely determined by geography. Notwithstanding the claims made by popular paleo diet doctrines, grains (including wheat), tubers, roots, and legumes were all consumed by our Paleolithic ancestors. In addition, nuts, seeds, animal products, honey, and other plants were all regular features of a Paleolithic-era diet, and milk consumption emerged in the Mesolithic and Paleolithic periods.
Contemporary evidence reveals that early notions of the Paleolithic diet were inadequately informed and excessively restrictive. Insights from dietary paleoanthropology show that diversity is the rule when it comes to defining the diet of hunter-gatherers. Geography and climate strongly correlate to the sources of calories in ancestral peoples’ diets. The proportion of calories from plant sources versus animal sources is correlated to geographic latitude, with equatorial populations consuming more calories from plants.
Evidence of grain and legume consumption has been documented in Paleolithic archaeological sites. Dairy was widely consumed around 6,000 years ago, and human genetics have changed since then to accommodate the digestion of lactose. Some foods available today provide fewer nutrients than those available only 70 years ago, calling into question whether it is even possible to eat like a Paleolithic human.
The development of lactase persistence — the continued activity of the lactase enzyme in adulthood — which allows adults to consume lactose in dairy with no digestive ill effects, has been documented as an evolutionary adaptation in some populations starting about 5,000–10,000 years ago by at least two research groups. Even if this evidence supports the idea that dairy is a Mesolithic or Neolithic addition to the human diet, it refutes the principle that human genetics have not changed since the Paleolithic age. Whereas evidence suggests digestion-related genes have changed as recently as 5000 years ago among some humans, the Paleolithic period ended about 8,000–12,000 years ago among those populations who developed lactase persistence.
The emphasis on meat in early conceptions of paleo was supported by the scientific literature available then (i.e., Murdock's “Ethnographic Atlas”). However, an absence of evidence, rather than evidence of absence, may have led to the unwarranted exclusion of plant foods. More systematic, recent investigations on the teeth, fecal remains, and stone tools of early humans suggest that almost all small-scale Paleolithic societies gathered, processed, cooked, and consumed a variety of grains, including grass-seed predecessors to modern wheat and other grains, as well as other seeds, roots, and beans.
Together, this research suggests that rather than one paleo diet, the diets of Paleolithic humans differed by location and culture and included a variety of foods. Additionally, evidence for recent evolutionary adaptations to Neolithic foods casts doubt on the belief held by many paleo doctrines that genetics are rigid.
How safe is a paleo diet?
Are there any major side effects or adverse events with paleo diets?
Paleo diets are safe for most people. Reports of adverse events are rare in research studies, but they’re not always monitored, which may reflect a lack of evidence. Most adverse events are found in one-off case reports of people using a highly restrictive version of the diet, which limits the ability to apply these observations to other settings.
One trial that rigorously followed adverse events found little evidence of negative effects with a moderate paleo diet.  However, when implementing a more restrictive paleo AIP diet, one study participant with a preexisting bowel stricture dropped out due to a bowel obstruction caused by the diet. 
Case studies have drawn a connection between ketoacidosis (a harmful level of acid in the blood) and calorie- or carbohydrate-restricted paleo diets among lactating women. Additionally, excessive urination (polyuria) was linked to a low-carbohydrate paleo diet in a 2-year-old boy. In another case study, a low-carb paleo diet was connected to a red rash called prurigo pigmentosa in a middle-aged woman who had lost significant weight. In all cases, adverse symptoms resolved when the affected individual reintroduced carbohydrates to their diet, suggesting that the level of carbohydrate restriction, not the paleo diet itself, was the cause.
When implemented improperly (e.g., without adequate seafood, iodized salt, or dairy), paleo can lower iodine intake, which may impair thyroid function. Additionally, low calcium intake on a paleo diet may be problematic for bone health.
Are there long-term risks with a paleo diet?
Long-term consequences of a paleo diet have not been studied. The longest randomized trial is 24 months and did not show an increase in side effects in the long term.
Some observational studies found a link between an increased risk of cardiovascular disease, cancer, and kidney disease and a higher intake of red meat. High-protein diets may be associated with risk of kidney problems as well, but this association has been inconsistent. Low-carbohydrate diets are independently associated with an increased risk of adverse effects such as kidney stones, elevated LDL-C, and (rarely) ketoacidosis.
Is paleo safe for your kidneys?
Moderate paleo diets appear to be safe for healthy kidneys, but paleo diets that are very high in protein may impair kidney function, and ketogenic paleo diets that are very low in carbs may increase risk for kidney stones. These risks are elevated in people whose kidney function is already impaired.
Unfortunately, no randomized clinical trials have tested the effect of a paleo diet on renal function. People with renal disease are sometimes excluded from paleo clinical trials, which limits the conclusions we can draw from the research literature. Additionally, no kidney-related adverse events have been reported in paleo diet clinical trials.
The effect a paleo diet has on your kidneys must be interpreted from research on similar dietary patterns, such as high-protein or low-carb diets, which have been studied for their effects on renal function.
In one before-and-after study, participants at a stable weight on a low-carb, high-protein diet (33% of calories from protein) had a high renal acid load, which increased their risk factors for kidney stone formation.
Epidemiological evidence shows an inconsistent link between diets higher in animal protein and risk for kidney stones and renal impairment. Among people with type 2 diabetes, a paleo diet produced lower estimated net acid excretion, which is associated with a higher risk of kidney disease progression, than an American Diabetes Association diet. On the other hand, estimated net acid excretion may not accurately represent true net acid excretion in the context of a diet high in protein, fruit, and vegetables, since some fruits may counteract the metabolic effects of animal protein.
Moderate protein diets — around 0.8 g/kg of body weight — have been shown to be safe among people at risk for kidney disease, and protein intake as high as 1.1 g/kg may be safe for people with diabetes-induced kidney damage. Among people who have a stable weight, diets that include 10–20% of calories from protein for people below age 65 or 15–20% for people above age 65 are safe. Higher-protein weight-loss diets, in which 20–30% of calories come from protein, may have a net-positive effect among people with metabolic dysregulation (e.g., overweight, type 2 diabetes) considering how important protein is for successful calorie restriction. Eating more plant-based proteins, which may be excluded in some popular paleo diets, is associated with lower risk of kidney damage than eating more protein from animal sources. Conversely, diets high in animal protein may be linked to an increased risk of kidney damage compared with diets low in animal protein.
For healthy individuals, the risk of moderate-to-high protein consumption on kidney function appears to be insignificant in the context of an otherwise healthy diet (i.e., a moderate diet low in sugar and salt). In studies mostly 6 months or shorter on healthy individuals, protein intake on the higher side but still within the recommended range (1.8–2.5 grams of protein/kg/day) was associated with elevated glomular filtration rate within the range of normal kidney function.
Is paleo safe for children and pregnant or nursing women?
Though generally considered safe, extreme paleo diets may pose risks for children and pregnant women. Low-carbohydrate, low-calorie paleo diets have been connected with lactation ketoacidosis in multiple case studies. This rare condition may arise when a lactating woman’s calorie needs are not being met through diet. Whether acidosis was caused chiefly by calorie restriction, carbohydrate restriction, an element of the paleo diet itself, or the patients’ own metabolic or genetic abnormalities is unknown, but these case studies showed that the condition always resolved with the reintroduction of dietary carbohydrates.
One other case report connected a low-carbohydrate paleo diet with excessive urination in a 2-year-old boy. Ketogenic diets, which sometimes include paleo, may delay growth in children.
Does the paleo diet lead to any nutrient deficiencies?
A well-formulated paleo diet is unlikely to lead to any stark nutrient deficiencies. When they do occur, the nutrients most likely to be insufficient are iodine, calcium, and vitamin D. Iodine is one of the more likely insufficiencies because much of itin Western diets comes from fortified foods like iodized salt and iodine used in producing cow’s milk.
Evidence from clinical trials shows that iodine intake may be lower, and the rate of iodine deficiency higher (from a prevalence of 15% to 73% over 6 months),  among people on a paleo diet compared with people adhering to healthy eating guidelines. Paleo-friendly iodine sources include seafood, particularly seaweed, cod, and oysters.
Calcium, typically from dairy products, is another potential nutrient insufficiency on a paleo diet. The best paleo source of calcium is bone-in canned fish, which may not be permitted in more strict versions that disallow all processed foods. Otherwise, some leafy greens of the cabbage family and bonemeal are good sources of calcium on paleo.
Vitamin D, a nutrient in which people are commonly deficient regardless of diet, may theoretically be hard to come by in a paleo diet. On the other hand, vitamin D deficiency in connection with a paleo diet has not been reported in scientific literature. This may be because it has not been measured, either because fish-forward paleo diets provide sufficient vitamin D or because appropriate sun exposure — from which the body generates vitamin D — is a component of some paleo lifestyle recommendations.
Should you take supplements on a paleo diet?
Since iodine, calcium, vitamin D, and other essential nutrients may be low in a paleo diet, talk to your healthcare provider to see if you should take supplements to meet your nutritional needs. Kelp, bone meal, and fish liver oil are paleo-friendly supplements that address the nutritional needs of people on a paleo diet.