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There is no shortage of different approaches to nutrition and the best ways to achieve optimal health through food. One of the most well-studied dietary approaches is the Mediterranean diet; however, there are others, such as the DASH diet, the Traditional Japanese (Okinawan) diet, the ketogenic diet, vegan/vegetarian diets, and even the elimination diet. While many of these approaches have a common focus on eating more plants, the latest trending diet, the carnivore diet, focuses on eating fewer plants – and in more stringent formats, no plants at all.

What is the Carnivore Diet?

The carnivore diet encourages the consumption of animal products while limiting or eliminating plant foods. Common features of the carnivore diet include:

• All or most nutrition is derived from animal sources.
• Plant foods are excluded as much as possible.
• Fruits and vegetables may be occasionally consumed.

However, this diet differs from the ketogenic (keto) diet, a high-fat diet that allows regular consumption of low-carbohydrate fruits and vegetables, nuts, and seeds to achieve nutritional ketosis. Ketosis involves a metabolic state in which ketone bodies from fat metabolism are used as a primary fuel source rather than glucose.

While a keto diet – especially a therapeutic keto diet – is high in fat and relatively low in protein, the carnivore diet may have a higher protein intake and does not necessarily track ketones. In a study that surveyed 2,029 individuals following a carnivore diet, only 41% aimed to achieve nutritional ketosis and tracked ketones.

The carnivore diet may feel like a new fad, but it’s not new at all – Inuits, for example, consumed a predominantly meat-based diet, and researchers have been interested in this way of eating since the early 1900s.

However, traditional indigenous populations, including the Inuit, have also been shown to forage for wild berries and even kelp while maintaining a diet high in protein and fat from animal sources.

Is There Science to Support the Carnivore Diet?

Followers of the carnivore diet commit to it for many reasons: to improve energy, relieve digestive discomfort, increase testosterone levels, reduce inflammation, improve insulin resistance, reduce “anti-nutrients,” and help with weight loss.

The previously mentioned study involving 2,029 individuals following a carnivore diet used descriptive data from a social media survey to explore the participants’ eating habits, nutrition, and health. The respondents were predominantly male (67%), and the median time on the carnivore diet was 14 months. Of these respondents, less than 10% consumed carbohydrates (fruits, vegetables, and grain products) monthly. Red meat, eggs, and non-milk dairy, in that order, were the most consumed foods.

Of the respondents, 93% were motivated to do so for health reasons, and the perceived health-related outcomes included overall health, chronic illness, and general well-being aspects of sleep, cognition, and energy. Additionally, <1% to 5.5% reported adverse symptoms, which included gastrointestinal, muscular, and dermatologic symptoms. The low prevalence of complaints may imply satisfaction with the diet, though the study authors did note the limitations of the study, which included reporting bias, selection bias, and a lack of information about respondents’ diets before beginning the carnivore diet.

The carnivore diet boasts high bioavailability of nutrients since animal proteins do not contain “anti-nutrients,” for example, lectins, oxalates, goitrogens, phytoestrogens, phytates, and tannins that decrease the bioavailability of nutrients. But do you need to be concerned about anti-nutrients?

As it turns out, anti-nutrients may not impact nutrient status as much as was once thought, and they even have some health benefits. Lectins are a common anti-nutrient of concern and are found in plant foods such as legumes and whole grains. While high doses of raw legume flours and isolated legume lectins can impact the intestinal lining  and comprise nutrient absorption, lectin content can be significantly reduced by proper preparation, including soaking, sprouting, and boiling. Further, lectins demonstrate anti-proliferative activity and are being researched for therapeutic uses. Another anti-nutrient known as tannins, which have the potential to reduce iron absorption, are associated with a decreased risk of type 2 diabetes and may also lower cardiovascular risk.

Possible Advantages of the Carnivore Diet

Improvement in insulin resistance. The carnivore diet and its positive impact on insulin resistance dates back to the 19th century when a diet consisting of meat and fat (and minimal plant foods) was used as an approach to managing diabetes. However, this approach is no longer commonly used, and the approach instead favors a less restrictive diet with a mix of macronutrients. We know that in those with diabetes, controlling blood sugar is important, and blood sugar rises when consuming simple sugars and starchy carbohydrates. Yet, many carbohydrate food sources are high in fiber, another dietary factor in blood sugar control.

Alleviation of digestive symptoms. Some individuals who adopt the carnivore diet hope to reduce digestive symptoms, including constipation. In one study, individuals who adopted a low or no-fiber diet had significant improvement in their symptoms, including constipation and bloating. In the study, researchers narrowly defined constipation as difficulty in evacuating feces and reported that participants who decreased fiber had more frequent bowel movements with less straining to evacuate. Certainly, removing the fibers that ferment in the colon and create gas can decrease bloating. However, taking this approach may not address the underlying causes of constipation. Other studies defined constipation more broadly as a variety of bowel disturbances, including infrequent bowel movements as a symptom of constipation. The Bristol Stool Form Scale is often used as a part of diagnosing constipation and tracking treatment outcomes.

Increase in testosterone. Healthy testosterone levels are known to improve muscle mass, bone density, libido, and even mood in both men and women. But can the carnivore diet increase testosterone? A carnivore diet is relatively high in fat, which tends to increase cholesterol. Both fat and cholesterol are building blocks for testosterone, and it is suggested that a high-fat diet can increase testosterone levels regardless of whether or not ketosis is achieved. The carnivore diet may also be relatively higher in vitamin D and zinc, which are key nutrients involved in healthy testosterone levels.

Additionally, a 2014 study on college-aged, resistance-trained men showed that a very low carbohydrate and high-fat diet, which is aligned with the carnivore diet, can improve testosterone levels as well as insulin sensitivity. However, many modifiable factors impact testosterone, including nutrition, sleep hygiene, stress levels, alcohol consumption, and resistance training, so a carnivore diet may not be the ideal place to start if increasing testosterone is the primary goal. Additionally, low energy availability, which involves a higher energy expenditure compared to energy intake, can negatively affect testosterone synthesis and should be considered when addressing low testosterone levels.

Modification in body composition. It’s debated whether a low-carbohydrate diet or even a keto diet is the most effective approach to favorably modifying body composition. On one hand, a low-carbohydrate diet emphasizing protein can be more satiating since protein considered to be one of the most satiating macronutrients, which can reduce cravings. However, rapid weight loss may be more reflective of water and glycogen loss associated with low-carbohydrate diets. Regardless of carbohydrate content, a high-protein diet has been shown to improve body composition, though not necessarily weight, by increasing lean body mass and decreasing fat mass in both trained female athletes and females with normal-weight obesity, which is defined as having a normal body mass index (BMI) with a body fat percentage greater than 30. Notably, neither of these studies considered a carnivore diet but rather focused on the effects of different protein intakes on body composition.

Improvement in amino acid intake. Protein plays many roles in the body, including catalyzing chemical reactions, regulating gene expression, regulating the immune system, and serving as neurotransmitters and hormones. Of course, protein is primarily known for its role in maintaining and improving muscle mass. Research shows that proteins from animal sources are more effectively synthesized because of their essential amino acid content and digestibility. Diets that rely on plant proteins tend to be lower in branched-chain amino acids, which include leucine, isoleucine, and valine. Leucine, in particular, is a protein anabolism regulator that “stimulates protein synthesis and inhibits protein degradation” (p. 5). Therefore, those following a plant-based diet who wish to gain muscle mass may benefit from an increase in overall protein intake and diversification or “blending” of plant proteins.

Elimination of common problematic foods. Since the carnivore diet relies solely on animal products, it naturally eliminates problematic foods, including alcohol, sugar, and common food allergens and sensitivities such as gluten, corn, and soy. The carnivore diet may provide relief for those who are sensitive to any of these foods. However, eliminating problematic foods from other eating styles would achieve similar results, and common allergens also include animal sources such as shellfish, dairy, eggs, and fish.

Exposure to a wide range of nutrients. Finally, animal proteins are rich in many nutrients, including vitamin B12, iron, and zinc, and organ meats, such as liver or heart, are particularly nutritious. While organ meats are less popular in today’s diet, they were once a prized food and are often emphasized in the carnivore diet. All kinds of animal liver are rich in minerals, including iron, copper, zinc, chromium, and selenium, and vitamins A, B2 (riboflavin), vitamin B12, folate, niacin, and pantothenic acid. This is why liver has earned the nickname “nature’s multivitamin.”

Disadvantages of the Carnivore Diet

Lack of phytochemicals. Phytochemicals are plant compounds that are found in plant-based foods, such as fruits, vegetables, nuts, seeds, legumes, grains, herbs, spices, teas, and coffee, and confer antioxidant, anti-inflammatory, and anticarcinogenic benefits. More specifically, phytochemicals such as anthocyanins can have a beneficial effect on inflammation associated with ulcerative colitis, whereas glucoraphanin, a sulforaphane precursor, can improve liver function. Consuming only animal proteins eliminates the dietary benefits of phytochemicals.

Potential nutrient deficiencies. While all essential nutrients can be found in some capacity in animal-sourced foods, calcium and vitamin C are two nutrients of concern in the carnivore diet. On the one hand, it’s speculated that a diet high in animal protein could have a vitamin C-sparing effect. Because vitamin C is used to synthesize carnitine endogenously, its need may be reduced for a person who consumes higher amounts of carnitine in their diet via animal sources.

On the other hand, carnitine may be in greater demand in a higher-fat diet since it’s used for fatty acid oxidation. Besides a carnivore diet lacking quality food sources of calcium, low carbohydrate diets may decrease calcium balance. However, another study found that increased calcium absorption in a high-protein diet compensated for increased excretion. More research on nutrient deficiencies associated with the carnivore diet is needed.

Impaired digestive health. Digestive health and fiber have a complicated relationship as fiber may cause digestive symptoms, such as gas and bloating. However, a high-fiber diet may significantly lower one’s risk for developing various diseases, such as cardiovascular disease, hypertension, Type II diabetes, gastrointestinal dysbiosis, gastroesophageal reflux disease (GERD), and diverticulitis.

Additionally, prebiotic fibers found in many fruits and vegetables, such as asparagus, apples, and garlic, enhance immune function. And finally, polyphenols found in plants support a healthy gut microbiome. Those unable to tolerate fiber should consult with their doctor to rule out underlying causes.

Exposure to lipophilic toxins (POPs). The original “dirty dozen” list included 12 persistent organic pollutants (POPs), which were used in pest management. Though the production of most POPs has been banned, they do persist in the environment. POPs are lipophilic, allowing them to accumulate in adipose tissue and increase in concentration as they move up the food chain, potentially “biomagnifying” to dangerous levels as they do so. Humans are primarily exposed to POPs through fatty foods, including meat, fish, and dairy. Because of their lipophilic properties, adipose tissue in both humans and animals is generally where the toxins are stored. While the accumulation of POPs in adipose tissue may be protective by reducing blood concentration and availability to other cells and tissues, research has found that POPs in adipose tissue may contribute to increased risk for certain diseases due to their role in inflammatory processes.

Environmental impact. Animal production involves large-scale greenhouse gas emissions, land degradation, and water use, which have implications for the environment and exacerbate climate change. For example, animal production, particularly red meat, is responsible for greenhouse gas emissions including carbon dioxide, methane, and nitrous oxide, mostly being generated on-farm vs. activities after agricultural production, such as processing and transport. While plant-based foods generally produce fewer greenhouse gasses, production, processing, and transport can vary by product, with some transport methods (e.g., air-freighted) and cultivation strategies (e.g., continuous flooding for rice) significantly impacting total energy use, resource use, and emissions.

Impaired relationship with food. Finally, it’s important to consider the psychological impact of a restrictive diet, as this can increase anxiety around food choices, limit cultural and religious experiences, and even increase feelings of loneliness. The carnivore diet may not be appropriate for those with a history of disordered eating.

Should You Try a Carnivore Diet?

The answer will depend on your health and dietary needs. Animal proteins contain many nutrients, including zinc, vitamin B12, iron, and selenium. But enjoying a diverse diet with a variety of colorful plant-based foods could also provide enough of these nutrients. The eating style that is best for you is a personalized approach.

Indeed, the carnivore diet is likely a drastic change from the typical mainstream diet. Of course, before making any decisions about one’s diet, it’s best to understand what a carnivore eating approach is and to discuss any dietary changes with your healthcare practitioner for personal options based on your health circumstances.