The carnivore diet, a highly restrictive eating plan centered around animal products and the elimination of plant-based foods, has garnered considerable attention. Proponents of this diet suggest various health benefits, including weight loss, improved mental clarity, and management of chronic conditions. However, it also raises numerous concerns regarding potential nutrient deficiencies and long-term health risks. This article examines the available evidence on the carnivore diet, exploring both the purported benefits and potential dangers.
What is the Carnivore Diet?
The carnivore diet involves consuming only animal-sourced foods, effectively excluding fruits, vegetables, grains, legumes, and nuts. The suggested menu typically includes beef, pork, poultry, fish, seafood, wild game, eggs, and limited full-fat dairy products like cheese and butter. This approach goes beyond other protein-heavy diets like keto and Atkins, which allow for at least some carbohydrate intake.
Motivations and Reported Outcomes
A social media survey conducted in 2020 among 2029 adults who self-identified as following a carnivore diet for at least six months revealed that the primary motivation for adopting this diet was health-related (93%). Participants reported consuming the diet for a median of 14 months. Red meat was a staple, consumed daily or more often by 85% of respondents. Less than 10% reported consuming vegetables, fruits, or grains more than monthly, and 37% did not use vitamin supplements.
Interestingly, the prevalence of adverse symptoms was low, ranging from <1% to 5.5%. Reported symptoms included gastrointestinal issues (3.1%-5.5%), muscular complaints (0.3%-4.0%), and dermatologic issues (0.1%-1.9%). The majority of participants reported high satisfaction levels and improvements in overall health (95%), well-being (66%-91%), and various medical conditions (48%-98%). The median BMI also decreased from 27.2 to 24.3.
However, among a subset reporting current lipid levels, LDL-cholesterol was markedly elevated (172 mg/dL), while HDL-cholesterol (68 mg/dL) and triglycerides (68 mg/dL) were within optimal ranges.
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Historical Context and Early Observations
The concept of animal-based diets is not new. Historical reports from Arctic and nomadic societies indicate that these populations consumed diets with little to no plant matter for extended periods, often associated with good health and longevity. Inspired by these observations, Arctic explorers participated in a study involving a meat-only diet for a year, reporting good health and no clinical evidence of vitamin deficiency, although a negative calcium balance was noted. These diets typically included both lean and fatty meats, as well as organ meats, which were often boiled or consumed raw.
In 1797, Dr. John Rollo successfully treated diabetes patients with a diet consisting solely of meat and fat, advocating for the near-complete elimination of plant foods. This approach was widely adopted in the 19th century to manage diabetes, with some physicians allowing low-carbohydrate vegetables while others promoted a strict meat- and fat-based approach.
Potential Benefits of the Carnivore Diet
Proponents of the carnivore diet often cite the following potential benefits, primarily supported by anecdotal accounts:
- Weight Loss: Eliminating carbohydrates forces the body to burn fat for energy, potentially leading to increased metabolism and weight loss.
- Blood Sugar Management: By removing carbohydrates, the diet can stabilize blood sugar levels, preventing spikes associated with carbohydrate consumption.
- Chronic Disease Control: Some argue that reducing carbohydrate intake, particularly from sugars, can mitigate risk factors associated with chronic diseases.
- Better Mental Health: Certain studies suggest a connection between meat consumption and lower rates of depression and anxiety, with some individuals reporting improved mental clarity on the diet.
Risks and Concerns
Despite the reported benefits and satisfaction among some individuals, the carnivore diet raises several health concerns:
- Nutrient Deficiencies: Excluding entire food groups can lead to deficiencies in essential vitamins, minerals, and fiber, which are vital for overall health. The carnivore diet overlooks entire food groups that offer many health benefits. Eating only meat and animal-based products can leave your body nutritionally deficient in some areas.
- Cardiovascular Disease: The high saturated fat content of the carnivore diet may increase LDL-cholesterol levels, potentially raising the risk of heart disease.
- Cancer Risk: High consumption of red and processed meats has been linked to an increased risk of colorectal and other cancers.
- Digestive Problems: The lack of fiber can lead to constipation and other digestive issues. Meat takes longer to digest, and slowing down that process can lead to constipation. Plus, the carnivore diet lacks fiber to help keep things moving along.
- Muscle Cramps and Electrolyte Imbalances: The absence of key nutrients can cause electrolyte imbalances, leading to muscle cramps, dizziness, fatigue, and weakness.
- Kidney Stress: A high intake of animal protein can place added stress on the kidneys, potentially affecting their long-term function and contributing to kidney stone formation.
Long-Term Health Implications: Mortality Risks
A study from the NIH-AARP Diet and Health Study cohort, involving half a million people aged 50-71 years, examined the relationship between meat intake and mortality. Over a 10-year follow-up period, the study found that individuals in the highest quintile of red and processed meat intake had elevated risks for overall mortality, cancer mortality, and cardiovascular disease mortality.
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Specifically, men and women in the highest quintile of red meat intake had hazard ratios (HRs) of 1.31 and 1.36, respectively, for overall mortality. For processed meat intake, the HRs were 1.16 for men and 1.25 for women. These findings suggest that higher intakes of red and processed meats are associated with increased mortality risks.
Conversely, the study also noted an inverse association between white meat intake and total mortality, and cancer mortality.
The study calculated population attributable risks (PAR), estimating the percentage of mortality that could be prevented if individuals adopted intake levels of participants within the first quintile. The results indicated that 11% of deaths in men and 16% of deaths in women could be prevented if they decreased their red meat consumption to the level of intake in the first quintile. The impact on CVD mortality was an 11% decrease in men and a 21% decrease in women if red meat consumption was reduced to the amount consumed by individuals in the first quintile.
The Role of Fiber and Plant Compounds
Harvard T.H. Chan School of Public Health highlighted the potential adverse health effects of the carnivore diet, emphasizing the lack of fiber and essential plant compounds. By skipping fruits and vegetables, individuals likely won’t get enough fiber in their diets, which can affect gut health. They also will miss out on carotenoids and polyphenols, substances with antioxidant properties that have been linked to lower risk of chronic diseases such as Type 2 diabetes and some types of cancer.
Case Studies and Anecdotal Evidence
While some individuals report positive outcomes on the carnivore diet, such as weight loss and improved energy levels, case studies also highlight potential risks. One case report in JAMA Cardiology described a patient who developed xanthelasma (yellow deposits on the eyelids) and dramatically increased cholesterol levels after following the carnivore diet for eight months.
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Considering the Extremes
The carnivore diet stands as one of the most extreme examples of low-carbohydrate diets, weaving together ideas associated with paleo and keto diets. It assumes that some human ancestors relied heavily on animal products and that carbohydrates are not our bodies’ preferred fuel source. However, these assumptions often ignore decades of observational studies linking nutrition to health outcomes and selectively disregard intervention studies that do not support its claims.
Expert Opinions and Recommendations
Registered dietitians and health experts generally do not recommend the carnivore diet due to its restrictive nature and potential health risks. They emphasize the importance of a balanced diet that includes a variety of whole foods like fruits, vegetables, grains, and lean meats. The key is moderation, rather than eliminating entire food groups.
Understanding the Science
The claims made by proponents of the carnivore diet often lack rigorous scientific evidence. While some argue that plants contain defense chemicals that are harmful to human digestion, research suggests that plant-based diets contain thousands of other compounds that counteract these potential effects. Additionally, what have been referred to as “anti-nutrients” may, in fact, be therapeutic agents for various conditions.
Survey Limitations and Considerations
A survey of over 2,000 carnivore dieters revealed limitations, including the fact that participants were recruited from social media communities frequented by carnivore dieters and had been on the diet for at least six months. This suggests that the survey captured only those who were the most dedicated to the diet, potentially skewing the results. Additionally, pre-diet food intake was not reported, making it impossible to determine how healthy the individuals’ diets were before switching to the carnivore diet.