Carnivore diet

The carnivore diet is not a formal guideline developed by a hospital or academic society. Rather, it is an eating pattern that spread as people following it shared their experiences. Beef, lamb, pork, chicken, fish, and eggs are its main foods, and most versions allow salt and water. Because carbohydrate intake is nearly zero, many people enter ketosis, a state in which the body uses ketones produced by breaking down fat as an energy source.

Former orthopedic surgeon Shawn Baker's book *The Carnivore Diet* (2019) helped popularize it. Psychologist Jordan Peterson and his daughter Mikhaila Peterson also drew public attention by discussing their experiences.

What people actually eat under the name “carnivore” varies. The categories below are names used among people following the diet, not official classifications established by the academic community.

These differences also matter when reading research findings. If participants eat different foods, it is difficult to determine which diet the results should be attributed to. In a survey of 2,029 people, participants' actual dietary intake also varied. In addition, a key part of an elimination diet is the reintroduction phase: after excluding foods for a set period, foods are added back one at a time to identify which ones did not agree with the person. How to incorporate this phase is also discussed when trying the Lion Diet.

• To simplify their diet — They think that greatly reducing the variety of foods they eat makes it easier to identify which foods agree with them.
• Because of digestive, skin, or joint discomfort — Many personal accounts describe symptoms improving after changing the diet.
• For fullness and blood glucose — People cite prolonged fullness from eating mainly protein and fat, and smaller fluctuations in blood glucose after meals, as advantages. These features are also shared by low-carbohydrate and ketogenic diets.
• To reduce the burden of food choices — The short list of permitted foods keeps things simple.

Supporters also point out that plant compounds such as oxalic acid, lectins, and phytic acid cause discomfort for some people (antinutrients). The possibility that these compounds can affect certain individuals under particular conditions is also a topic addressed in nutrition science.

There are not yet any long-term randomized clinical trials specifically examining the carnivore diet. The available evidence mainly consists of surveys and case reports.

One prominent study is a survey by a Harvard research team (Lennerz et al.) published in *Current Developments in Nutrition* in 2021. The researchers recruited 2,029 adults online who had followed a carnivore diet for at least 6 months. About 95% reported improved health, and satisfaction was high. This was preliminary evidence based on participants' responses, without a control group. Subsequent critiques noted that people who were successfully maintaining the diet may have been more likely to respond.

A scoping review published in *Nutrients* in 2026 (2026;18(2):348) brought together the available evidence. It concluded that further research is needed on long-term effects and safety because most studies had small samples and short durations.

Some studies have also calculated the diet's nutritional composition. Riboflavin, niacin, phosphorus, zinc, vitamins B6 and B12, selenium, and vitamin A generally met reference levels, while thiamine, magnesium, calcium, and vitamin C fell short, and dietary fiber was far below the recommended intake. Studies of very-low-carbohydrate ketogenic diets in people with type 2 diabetes have reported reductions in fasting blood glucose, glycated hemoglobin, triglycerides, and blood pressure. However, those findings concern ketogenic diets that do not completely exclude plant foods.

When a diet is highly restrictive, it becomes important to look at which foods contain particular nutrients and in what amounts. Although effects are difficult to assess from personal accounts, nutrient content can be calculated.

Vitamin C and scurvy. Vitamin C is essential for forming stable collagen. Humans cannot make vitamin C in the body and must obtain it from food. Prolonged deficiency can weaken newly formed collagen and cause scurvy, with bleeding gums, small pinpoint areas of bleeding in the skin, delayed wound healing, and joint and muscle pain. Animal foods contain vitamin C, but in small amounts, particularly in muscle meat. Organ meats contain relatively more. People following the diet explain that avoiding carbohydrates reduces vitamin C requirements because glucose and vitamin C no longer compete for entry into cells. More human research is needed to determine how much requirements actually decrease.

Thiamine (vitamin B1). Thiamine helps enzymes at several steps in converting glucose into energy. Prolonged deficiency can cause beriberi, which affects the peripheral nerves and heart, or Wernicke encephalopathy, an acute neurological condition. Thiamine content varies by type of meat, with pork containing relatively more. This difference is also relevant to the thiamine shortfalls found in calculations of beef-centered diets. Meanwhile, because thiamine requirements have been expressed in proportion to calorie intake, particularly carbohydrate intake, some suggest that requirements may be lower on a diet containing almost no carbohydrates.

Studies calculating nutritional composition do not measure actual blood levels, so they do not account for absorption rates or individual nutrient stores. They only indicate potential shortfalls. Nutrient deficiencies may also cause no symptoms at first, so blood tests are one way to assess nutritional status if this diet is continued for a long time.

Because the carnivore diet involves eating large amounts of meat, the IARC (International Agency for Research on Cancer) classifications concerning meat and cancer are often discussed alongside it.

IARC Group 1 carcinogens

Since 1971, IARC has used its Monographs series to evaluate the carcinogenicity of various exposures, including chemicals, foods, occupational environments, and infectious agents. This evaluation is hazard identification: determining whether something can cause cancer under any conditions. It differs from risk assessment, which calculates how many cancers actually occur at everyday exposure levels.

• Group 1 (carcinogenic to humans) — Sufficient evidence exists from human studies. This group includes tobacco smoking, asbestos, alcoholic beverages, solar radiation, benzene, hepatitis B and C viruses, Helicobacter pylori, and processed meat.
• Group 2A (probably carcinogenic to humans) — Limited associations have been observed in human studies, supported by animal experiments and mechanistic studies. Examples include red meat, very hot beverages at 65°C or higher, and night shift work.
• Group 2B (possibly carcinogenic to humans) and Group 3 (not classifiable) — Group 3 does not mean safe; it means that a judgment cannot yet be made.
• Group 4 (probably not carcinogenic to humans) contained only one substance and was discontinued in 2019 because proving an absence of carcinogenicity is inherently difficult.

These classifications indicate the certainty of the evidence. The magnitude of risk is expressed through separate measures, such as relative risk, and varies with exposure level and population. The inclusion of both tobacco smoking and solar radiation in Group 1 illustrates that the list is not a ranking by magnitude of risk.

Processed meat

Processed meat refers not to a cooking method but to meat processed to preserve it or enhance its flavor. Pork belly grilled at home is not processed meat, but bacon that has been cured and then smoked is. Common processing methods include curing, smoking, fermentation, and drying.

In 2015, after reviewing more than 800 studies in Monograph Volume 114, IARC classified processed meat as Group 1 in relation to colorectal cancer. A frequently cited estimate is that each additional 50g of processed meat eaten daily increases colorectal cancer risk by about 18%. This 18% is an increase relative to the original risk. It does not mean an increase of 18 percentage points, so when the baseline risk is small, the absolute increase is also small. Potential pathways discussed include N-nitroso compounds formed from curing agents and components of meat, heme iron, substances formed during high-temperature or direct-flame cooking, and high sodium content.

Red meat

Red meat is classified by its content of myoglobin, an oxygen-storing protein in muscle, rather than by culinary traditions. Beef, pork, and lamb are red meats. Pork becomes pale when cooked and may look like white meat, but nutritional epidemiology classifies it as red meat. IARC classified red meat as Group 2A in 2015 because some associations had been observed in human studies and were supported by mechanistic research. The Group 2A classification means the evidence is less certain than for processed meat.

Most evidence on this topic comes from observational studies. Dietary surveys rely on memory, and other factors are intertwined: for example, groups that eat less meat tend to smoke less and exercise more. Researchers therefore differ in how they interpret these findings and what recommendations should follow. In 2019, the NutriRECS consortium rated the certainty of the evidence as low and issued a weak recommendation that people could maintain their current intake. Several academic societies expressed different views in response.

• Your body needs time to adapt to dietary changes. Abruptly reducing carbohydrates may initially cause low energy or headaches. Many people make a point of getting enough water and salt.
• There is almost no dietary fiber. Vegetables, fruit, and grains are major food sources for gut microorganisms, so the effects on gut health are a subject of research. (See Gut microbiota.)
• Cholesterol levels may change. The extent of change varies from person to person, so checking blood markers before and after the dietary transition can help with comparison.
• If you have a pre-existing medical condition, take medication, or are pregnant or breastfeeding, consult a healthcare professional first. The diet may affect medication effects, blood glucose, or blood pressure.
• If you decide to try it, set a time frame. One approach is to follow it for a set period, record how your body responds, and, if needed, add foods back one at a time while observing changes.