TLDR - Contrary to common expectations, adults consuming a carnivore diet experienced few adverse effects and instead reported health benefits and high satisfaction. Cardiovascular disease risk factors were variably affected. The generalizability of these findings and the long-term effects of this dietary pattern require further study.
Background: The “carnivore diet,” based on animal foods and excluding most or all plant foods, has attracted recent popular attention. However, little is known about the health effects and tolerability of this diet, and concerns for nutrient deficiencies and cardiovascular disease risk have been raised.
Objectives: We obtained descriptive data on the nutritional practices and health status of a large group of carnivore diet consumers.
Methods: A social media survey was conducted 30 March–24 June, 2020 among adults self-identifying as consuming a carnivore diet for ≥6 mo. Survey questions interrogated motivation, dietary intake patterns, symptoms suggestive of nutritional deficiencies or other adverse effects, satisfaction, prior and current health conditions, anthropometrics, and laboratory data.
Results: A total of 2029 respondents (median age: 44 y, 67% male) reported consuming a carnivore diet for 14 mo (IQR: 9–20 mo), motivated primarily by health reasons (93%). Red meat consumption was reported as daily or more often by 85%. Under 10% reported consuming vegetables, fruits, or grains more often than monthly, and 37% denied vitamin supplement use. Prevalence of adverse symptoms was low (<1% to 5.5%). Symptoms included gastrointestinal (3.1%–5.5%), muscular (0.3%–4.0%), and dermatologic (0.1%–1.9%). Participants reported high levels of satisfaction and improvements in overall health (95%), well-being (66%–91%), various medical conditions (48%–98%), and median [IQR] BMI (in kg/m 2 ) (from 27.2 [23.5–31.9] to 24.3 [22.1–27.0]). Among a subset reporting current lipids, LDL-cholesterol was markedly elevated (172 mg/dL), whereas HDL-cholesterol (68 mg/dL) and triglycerides (68 mg/dL) were optimal. Participants with diabetes reported benefits including reductions in median [IQR] BMI (4.3 [1.4–7.2]), glycated hemoglobin (0.4% [0%–1.7%]), and diabetes medication use (84%–100%)
From the journal of Current Developments in Nutrition.
- Full text at above link
Notes:
What little evidence exists for the sustainability of carnivore diets derives from historic reports on Arctic or nomadic societies, clinical case studies, and accounts on nutrition therapy for diabetes mellitus in the preinsulin era c.1920
Using an online survey, we collected self-reported data from respondents who self-identified as following a carnivore diet for a minimum of 6 mo
Weekly or more frequent consumption was reported for organ meat by 42%, and for nonmilk dairy by 72%.
Most participants reported eating 1–3 times daily (differentiation between meals and snacks was not queried), including 16% three times per day, 64% twice per day, and 17% once per day.
Generally, more participants reported choosing cuts of meat with high (61%) or moderate (37%) fat content as opposed to lean cuts (2%).
Reported prevalence of adverse effects or symptoms consistent with nutritional deficiency was generally low, as shown in Supplemental Table 1, and commonly preceded the diet.
Consistent with other low-carbohydrate diet studies (40–45), respondents reported a mixed blood lipid pattern: LDL-cholesterol, a major conventional cardiovascular disease risk factor, was markedly elevated whereas HDL-cholesterol and TG were favorable. However, LDL-cholesterol elevation, when associated with low TG, may reflect large, buoyant lipoprotein particles, possibly comprising a relatively low-risk subtype
Food allergies and sensitivities are common, and predominantly related to plant foods (51). Some plant chemicals may produce adverse effects through other mechanisms, such as lecithin in beans, cyanogenic glycosides in certain seeds, and glycoalkaloids in potatoes. Indeed, >50% of survey participants started the carnivore diet to improve allergic, skin, or autoimmune conditions, or digestive health, and many reported improvements in inflammatory conditions and related symptoms.
dietary intake may be low for vitamins that are typically derived from plant foods (e.g., fruits, vegetables, nuts, seeds, and grains) or from nutritional fortification of staple foods (e.g., milk, juices, cereals, pastas, and other grain products) (52, 53). In addition, often unquantified phytochemicals (e.g.,polyphenols, alkylresorcinols, phytosterols) are largely absent from the diet. Although these phytochemicals do not have DRIs, they have been linked to cardiometabolic benefits (54, 55). In people who eat meat only with exclusion of dairy (∼30% in this survey), calcium intake might also be low, as illustrated by the low intake and negative calcium balance in 2 Arctic explorers (28)
Although essential nutrients can presumably be derived in sufficient amounts from animal foods (34), they are present in less commonly consumed parts of the animal, such as fat and organ meats (vitamins A and D), or bone (calcium), or may be reduced during food preparation (vitamin C)
Whereas meat is more expensive than grains and starchy foods, it may be less expensive on a caloric basis, depending on location and specific comparisons, than fresh fruits and nonstarchy vegetables (59), and cost may be in addition offset by decreased expenditure for diabetes and other medications.
the generalizability of the findings is unknown owing to the existence of selection bias, because individuals who experienced adverse effects or lack of health benefits are likely to have abandoned the diet and would therefore not have been captured in this survey. Adults adhering to a carnivore diet and responding to this online survey represent a special subpopulation with high levels of motivation and other health-related behaviors (e.g., physical activity, consumption of relatively whole, unprocessed foods). Therefore, respondents likely differ from the general population in ways that could influence the effectiveness, practicality, and safety of a carnivore diet.
Thoughts:
This is an epidemiological study, which is the weakest form of scientific evidence. Patients volunteered into the study, so we have healthy patient bias, and we don’t see patients who didn’t respond well. This was based on food frequency questionnaires, which has issues with patient honesty, recall, etc. Online surveys also have issues with honesty and data integrity.
The increase in LDL may be concerning to some, but my understanding of current literature is that undamaged LDL (as seen in lean mass hyper responders to ketogenic diets) are quite healthy and at very low risk of cardiovascular events. It’s damaged LDL (glycated and oxidized damage) thats the problem.
Differentiating the effect of a Carnivore diet vs a Omnivore ketogenic diet (or vegan keto even) would be very interesting.
Almost all of the positive effects reported in this paper are also seen (perhaps to a lesser degree) on ketogenic diets - Even gut issues and inflammation to a much lesser degree.
My current understanding of literature is there is a very strong case for a ketogenic diet being optimal for human health, but inside of that domain (omnivore, plant-keto, carnivore) it’s unclear which is “best”. They are all probably “good enough” for a long and happy life for most people without other issues.
Though plant-keto will forever be in the domain of highly food available societies, somewhat on the luxury spectrum, given the high quantity, quality, and breadth of different plants required. i.e. it wouldn’t be good for developing countries with poor logistics and weak economies which account for 40% of the worlds population right now.