The carnivore diet, a highly restrictive eating plan primarily consisting of animal products, has garnered attention for its purported health benefits. However, its impact on cardiovascular health remains a subject of debate. This article delves into the carnivore diet, examining its potential benefits and risks, particularly from a cardiologist's perspective, incorporating insights from experts and research findings.
What is the Carnivore Diet?
The carnivore diet, also known as the "zero carb" diet, is a restrictive eating plan that advises the consumption of only animal products and a few other items. Avid fans of the carnivore diet say it has a range of benefits. The carnivore diet is among the latest and most extreme examples of the low-carbohydrate fad, weaving together several ideas generally associated with the paleo and keto diets specifically: that some of our human ancestors relied heavily on animal products (and that animal products must, therefore, be optimal for our health), that carbohydrates are not our bodies’ preferred fuel source, and that the evidence linking meat-heavy diets with increased incidence of chronic disease is fatally flawed. There are a few variations of the carnivore diet-for example, one popular variety allows fruit consumption-but generally, it is exactly what it sounds like: a diet exclusively centered on animal products.
Challenging Conventional Wisdom: Dr. Ovadia's Perspective
Advice on how to avoid heart disease has stayed relatively the same for decades with one common recommendation being to avoid sources of saturated fat such as red meat-but Florida-based heart surgeon Dr. Philip Ovadia challenges this as a "misconception." Ovadia argues against the long-standing recommendation to avoid saturated fats like red meat. He posits that insulin resistance and inflammation, often triggered by sugar and ultra-processed foods, are the primary culprits behind heart disease.
"The majority of what I eat, the basic framework that I construct what I'm eating around, is things from the animal world, mostly animal protein," Ovadia told Newsweek. Instead of cutting out red meat and other sources of saturated fat, he said: "A whole real food, low carbohydrate dietary approach is the best way to deal with insulin resistance and inflammation, which are the true root causes of heart disease."
Insulin resistance is a condition that is the precursor to diabetes. When we eat carbohydrates, the body turns this food into glucose, and the hormone insulin is released to take the glucose out of the bloodstream to be used as energy. Individuals who eat a lot of sugar and refined carbohydrates-such as white bread, pasta, and rice-may develop insulin resistance, where the body gradually struggles to cope with high levels of glucose in the blood.
Read also: The Carnivore Diet: An Autoimmune Solution?
"Things like diabetes, things like cancer, high blood pressure, Alzheimer's disease-all of these things tie back to insulin resistance and inflammation," said Ovadia. "The carnivore diet in particular-but more broadly, low-carbohydrate diets-have now been demonstrated to be particularly effective at dealing with insulin resistance and improving or preventing inflammation." That's why I think they're so powerful when it comes to heart disease and these other chronic diseases."
Ovadia's approach involves eliminating processed foods and focusing on whole, real foods, particularly animal protein. He believes this dietary strategy can effectively combat insulin resistance and inflammation, which he identifies as the root causes of heart disease. He emphasizes that surgery addresses the symptoms, but not the underlying causes of heart disease. "What I tell [my patients] is the surgery, it will address the problem, right?" he said. "They're not getting enough blood flow to their heart, and the surgery deals with that, but the surgery doesn't change why they got the heart disease." If we don't address that, they're going to continue to have problems with heart disease throughout their life."
Concerns and Counterarguments
Despite anecdotal reports of positive outcomes, the carnivore diet faces criticism from some experts. Dietitian Nichola Ludlam-Raine, author of How Not to Eat Ultra-Processed, told Newsweek: "Although short-term benefits might be reported, the high intake of red meat and lack of carbohydrates in a carnivore diet are concerning for long-term heart and gut health." A more balanced, varied diet including lean proteins-with fresh red meat featuring around twice a week-heart healthy fats, and fiber from plant foods is better supported by evidence for cardiovascular protection."
One of the primary concerns is the potential for increased LDL cholesterol levels due to the high saturated fat content in animal products like red meat, butter, and cheese. Saturated fats have been shown to increase LDL cholesterol, which can build up in the blood vessels, narrowing them. This narrowing can restrict blood flow to the heart and other organs, raising a person’s risk of a heart attack or stroke.
Another area of concern is the lack of dietary fiber in the carnivore diet. Lisa said, “The higher the consumption of fiber, the lower the risk of colon cancer". If you are trying the carnivore diet, you may also experience vitamin and mineral deficiencies due to the restrictive nature of what you are eating. Consuming a large amount of animal protein can lead to unwanted stress on the kidneys, especially if you already experience kidney issues.
Read also: The Carnivore Diet's Impact on Sleep
Research Findings and Limitations
While there is a lack of extensive research on the carnivore diet, some studies have explored its effects. A 2021 study conducted a social media survey and gathered self-reported data from 2,029 people following a carnivore diet for 14 months. Of the participants, 67% were male, and the median age was 44 years. The majority of the diets in this study consisted of red meat other than pork, such as beef, lamb, venison, buffalo, or goat. Eggs and nonmilk dairy were the most commonly consumed foods, followed by pork, poultry, and seafood. Out of the participants, 85% reported consuming red meat daily or more frequently. Less than 10% consumed plant-based foods such as vegetables, fruits, or grains monthly, while 37% did not use any vitamin supplements.
Despite the researchers’ concerns about nutrient deficiencies and cardiovascular risks, the participants reported minimal negative effects. Of the participants, 95% reported experiencing health improvements and high satisfaction with the carnivore diet. While the researchers observed higher LDL cholesterol levels in the participants, other heart health markers were positive. Their high-density lipoprotein (HDL), or “good” cholesterol levels, were optimal. Participants also reported a reduction in body mass index (BMI), while those with diabetes reported reductions in glycated hemoglobin (HbA1c) and diabetes medication use. The main adverse effects that the participants reported with the carnivore diet were gastrointestinal effects, including diarrhea and constipation. However, this study has limitations. For example, the data came from self-reported perceptions of people’s health. Alcohol and fast food consumption were also minimal, differing from typical Western diets. Still, over half of the participants reported improvements in allergies, skin issues, and digestive health, possibly due to eliminating allergenic or inflammatory foods.
Experts need to conduct further research on the carnivore diet and how it can affect long-term health. Some research suggests there are possible negative effects of following this eating regimen.
The American College of Cardiology's Stance
While the carnivore diet emphasizes red meat, evidence from large-scale studies by the American College of Cardiology (ACC) raises concerns about its potential cardiovascular effects. A systematic review of 7,446 studies found that both processed and unprocessed red meat consumption has links to a higher risk of cardiovascular disease (CVD), CVD subtypes, and diabetes, with stronger associations in Western populations. Another ACC analysis of data from 29,682 participants reported significant associations between red meat intake and both CVD incidence and all-cause mortality. However, consuming fish and poultry, especially lean and unprocessed, had no links to these risks. Although these studies did not specifically examine the carnivore diet, they provide strong objective evidence for reducing red meat consumption and favoring diets rich in fruits, vegetables, nuts, legumes, fish, and dairy. At this time, the ACC does not recommend the carnivore diet, emphasizing instead balanced dietary patterns for cardiovascular health and longevity.
Animal-Based Diets and Cardiovascular Disease: A Deeper Dive
Cardiovascular disease (CVD) is the leading cause of death in the United States, and diet plays an instrumental role in CVD development. Plant-based diets have been strongly tied to a reduction in CVD incidence. In contrast, animal food consumption may increase CVD risk. While increased serum low-density lipoprotein (LDL) cholesterol concentrations are an established risk factor which may partially explain the positive association with animal foods and CVD, numerous other biochemical factors are also at play. Thus, the aim of this review is to summarize the major cellular and molecular effects of animal food consumption in relation to CVD development. Animal-food-centered diets may (1) increase cardiovascular toll-like receptor (TLR) signaling, due to increased serum endotoxins and oxidized LDL cholesterol, (2) increase cardiovascular lipotoxicity, (3) increase renin-angiotensin system components and subsequent angiotensin II type-1 receptor (AT1R) signaling and (4) increase serum trimethylamine-N-oxide concentrations. These nutritionally mediated factors independently increase cardiovascular oxidative stress and inflammation and are all independently tied to CVD development.
Read also: Troubleshooting Carnivore Diet Diarrhea
The Role of Toll-Like Receptors (TLRs)
Toll-like receptors (TLRs) are involved in innate immunity, and a number of isoforms exist from TLR1-10 in humans. The evolutionary purpose of TLRs are to appropriately respond to pathogens by inducing an inflammatory immune response. All of these TLRs can bind to a number of bacterial components: for example, TLR4 to lipopolysaccharides (LPS), a component of the outer membrane of Gram-negative bacteria; TLR2 to lipopeptides, and TLR3 to double-stranded RNA. In macrophages, LPS can trigger an inflammatory response at very low concentrations, such as 100 pg/mL, which is a physiologically relevant concentration in human serum following certain nutritional interventions, such as high-fat feeding with animal products. TLRs are found ubiquitously across most tissue and cell types, including the cardiovascular system. Their role in driving the pathogenesis of CVD is recognized as a critical component of the molecular disease process, driving both atherosclerosis and heart failure, particularly TLR2 and TLR4. While tuned to pathogenic stimuli, a number of exogenous and endogenous ligands which are mediated by diet appear to also lead to their activation or upregulation. For example, TLR2 and TLR4 can be upregulated or activated by oxidized low-density lipoproteins (oxLDL), while angiotensin (Ang) II can mediate TLR4, all of which can be regulated by diet (to be discussed).
Examining the Carnivore Diet Through Different Lenses
A variety of dietary approaches have emerged in recent years aimed at addressing the chronic disease epidemic , including cardiovascular disease (CVD). However, the spectrum of these diets varies extensively with respect to their composition. For example, diets such as the ketogenic diet advocate for the near elimination of carbohydrates while simultaneously encouraging the consumption of copious amounts of fat and moderate intake of protein . Other low carbohydrate diet models replicate aspects of this with changes in protein or fat proportionally, such as the paleolithic diet, the Atkins diet or the “carnivore” diet. In contrast, a whole-food, plant-based diet tends to be higher in carbohydrates and lower in fat with moderate-to-lower protein intake . Macronutrients, however are not consumed in isolation of the food from which they are derived; diets which favor high protein or fat consumption tend to also be animal-based, with far fewer (or near-absent) calories, derived from plant foods. While humans are an adaptable species nutritionally, our nutritional biology is not wildly different. This is evident in the study of the “Blue Zones”, which illustrate common dietary themes among the most long-lived populations from different regions of the world who have very low CVD incidence. Individuals in these groups tend to eat diets higher in plant foods derived from unprocessed carbohydrates and also consume fewer animal products. Illustrative of the Blue Zone diets, the Okinawans in the 20th century had the highest number of centenarians per capita. Their diet was 85% percent carbohydrates derived from whole plant foods, such as sweet potatoes (69% of total calories), grains (19% of total calories) and legumes (6% of total calories), while animal foods comprised 1-2% of total calories of their diet. In 1995, the Okinawan CVD-associated mortality in males was nearly one-sixth the rate of male counterparts in the United States, and among Okinawan woman, CVD-associated mortality was less than one-twelfth the rate of female counterparts in the United States. Similarly, the Seventh-Day Adventists in the United States consume a mostly plant-based diet, and vegetarian men and woman have life expectancies that are 9.5 and 6.1 years greater than their Californian counterparts, respectively . It appears that animal food intake is significantly tied to CVD mortality among males. Compared to omnivores, ischemic heart disease and overall CVD mortality was associated with a 24% and 23% reduction in vegetarian Adventists (dairy and eggs, but no meats), respectively, while vegan males (no animal products) had a 55% and 42% reduction in ischemic heart disease and overall CVD mortality, respectively . It is recognized that genetic factors are not primary drivers of the extended lifespans observed, as Westernization, characterized by the consumption of fewer plants and more meat, has resulted in a stark increase in CVD incidence among Japanese with traditionally low CVD incidence . Migration studies also indicate that integration into Western societies among Okinawan and Japanese individuals results in a shift towards the increased prevalence of CVD risk factors, which were once nearly absent from these cultures . In contrast to the Blue Zones, the Arctic Inuit consume significantly more meat, particularly seafood, compared to their Western counterparts, and their diet is, by definition, lower in carbohydrate content . However, the lifespan of Inuit is 10 years less on average than their Western counterparts, with twice the mortality, due to a high incidence of stroke .
The Importance of Fiber and Plant-Based Nutrients
Animal-based diets tend to be much lower in fiber, and indeed, the consumption of fiber, which is inexorably linked to unprocessed plant-food consumption, is associated with reduced CVD incidence in the most rigorous of systematic analyses . Additionally, carbohydrate consumption observed at the low end of the spectrum (~≤20% of calories) is associated with increased mortality, while carbohydrates at the high end of the spectrum (~≥70% of calories) is also associated with increased mortality . However, an important caveat must be noted, in that this association observed with high-carbohydrate consumption is not evident in those consuming unprocessed carbohydrates (e.g., whole grains rather than refined grains). Indeed, the evidence which supports whole grain consumption (a rich source of carbohydrates) is compelling , as not a single study can be identified in the literature which demonstrates that whole grain consumption is associated with increased mortality or biomarkers classically associated with CVD. The same is true of the consumption of fruit, which collectively contain even greater percentages of calories derived from carbohydrates than grains . In addition to fiber, a major nutritional aspect unique to plants is their polyphenol content, secondary metabolites found strictly in plants which have bioactive properties. My prior work with colleagues (Feresin, Turner and Wong ) defined a number of molecular pathways involved in CVDs which polyphenols could beneficially target. In limited clinical investigations, my prior work with colleagues (Montgomery and Moore ) demonstrated that a plant-based diet could reduce blood pressure more efficaciously than hypertension-managing drugs , reduce atherogenic lipoproteins and inflammatory markers with high efficacy , and, based on data from a case series of three patients , potentially treat heart failure adjunctly. Jenkins et al. demonstrated that a weight-maintaining plant-based diet very high in raw fruits, vegetables and nuts could reduce low-density lipoproteins (LDL) by ~33% , a reduction comparably as effective as statin treatment . Other investigators have shown that a plant-based diet could treat atherosclerosis, an outcome previously thought improbable through dietary means .
The Impact of Low-Carbohydrate Diets
Despite compelling population studies, epidemiological data and promising clinical data regarding the efficacy of consuming more plants for cardiovascular health, meat-based and classically high-protein/high-fat diets, such as the Atkins, paleolithic or ketogenic diet, have gained popularity in American culture. In practice, the restriction of carbohydrates will concomitantly reduce the proportion of calories derived from plants, since carbohydrates are exclusively found in plant-based foods (with the exception of small amounts found in dairy) . Thus, a low-carbohydrate diet is almost always a high-animal-product diet. Interestingly however, low-carbohydrate diets which are more plant-based tend to be associated with reduced CVD mortality (21% reduction in risk) compared to more animal-based (22% increased risk) , illustrating that it is indeed animal-based foods which are the problem. In fact, a fully vegan, low-carbohydrate, low-saturated fat diet (26% carbohydrates, 31% protein, and 43% fat) rich in soy, wheat gluten, nuts and oils was more effective than a higher carbohydrate lacto-ovo-vegetarian diet in reducing LDL cholesterol and triglycerides after four weeks with energy restriction and 6 months ad libitum . In contrast, low-carbohydrate animal-based diets inherently lead to increased saturated fatty acid consumption, which results in a predictable rise in serum LDL cholesterol concentrations . The American Heart Association (AHA) presidential panel position statement on the link between serum LDL cholesterol and cardiovascular events identified this link as causal . Further, the consumption of animal proteins, but not plant proteins, is associated with increased CVD events . It is interesting to note that a number of clinical trials which have utilized animal-product-rich diets (low-carbohydrate, high-protein or high-fat diets) in comparison to more mixed diets that are higher in carbohydrate and lower in fat demonstrate benefit in CVD risk factors, despite inherently reduced plant food consumption and increased saturated fat intake . While this may seem paradoxical based on the aforementioned literature, no paradox truly exists. It is important to note the following two dominant methodological features which drive the appearance of benefit with poor societal extrapolation: (1) the low-carbohydrate diets are not intended to meet energy needs, and are instead designed to substantially reduce caloric consumption, leading to inherently more favorable lipid and metabolic profiles as well as blood pressure, due to reduced body weight, although LDL may be increased in some cases despite body weight reductions due to increased saturated fat intake , and (2) the low-fat, higher-carbohydrate dietary group which acts as the control comparison tends to be of low dietary quality, as evidenced by very low fiber intake (~15 g/day), a clear indication of processed food consumption, and is thus not designed to be health promoting. For example, sugary cereal, such as frosted flakes and white bread are 93% and 76% carbohydrates, respectively, compared to black beans, sweet potatoes and oats, which are 73%, 93% and 74% carbohydrates, respectively . Even for lay individuals, one would consider the nutritional quality of these latter foods to be far superior compared to the former, despite similar carbohydrate contents. Illustrative of this concept, it has been demonstrated that unprocessed, plant-based diets, characterized by increased fruits, vegetables, nuts, legumes and whole grains are associated with reduced CVD mortality, but not plant-based diets with more processed foods such as refined grains, fruit juices, potatoes (French fries, potato chips, mashed potatoes) and desserts (cakes, candy, pastries) . Thus, one cannot determine the nutritional quality of a moderate-to-high carbohydrate diet without knowing what foods the diet is comprised of. To conclude that animal-product-rich diets are healthy or efficacious in treating CVD would be erroneous based on the aforementioned literature. Additionally, animal-product-rich diets tend to impair vascular function , increase LDL cholesterol and inflammation compared to an isocaloric unprocessed high-carbohydrate diet , and reduce myocardial blood flow compared to a plant-based diet, which had the opposite effect . While increased saturated fat consumption and subsequently increased serum LDL cholesterol are a well-known and plausible physiological mechanism by which these diets are associated with CVD risk, there is far greater complexity and a multitude of other biochemical mechanisms involved that exacerbate or are independent of these effects. To date, these mechanisms have not been well-defined or discussed.
Dr. Shawn Baker's Perspective on the Carnivore Diet
Shawn Baker is a doctor, an accomplished athlete, and the author of the 2019 book The Carnivore Diet. Athletically, he’s played professional rugby, won strongman competitions, set records as a Highland Games participant, and most recently, he became an indoor rowing world champion. Shawn has gained notoriety as a leading proponent of the carnivore diet-where participants get nutrition from animal-sourced foods and severely limit or eliminate all plants from their diet.
Baker shares his personal journey toward adopting a carnivore diet. He recounts how he initially believed he could eat anything as long as he exercised. However, as he entered his forties, he gained weight and developed health issues. He experimented with various diets, including low-calorie, low-fat, and paleo diets, before discovering the carnivore diet. After trying it for 30 days, he noticed improvements in his health and well-being.
Baker emphasizes the importance of individuals identifying the foods that work best for their bodies. He criticizes the reliance on population-based studies in nutrition science, arguing that they provide poor-quality evidence. He points out the limitations of food frequency questionnaires and the challenges of extrapolating animal studies to humans. Baker advocates for a more personalized approach to nutrition, focusing on individual health outcomes rather than broad dietary recommendations.
Baker notes what he identifies as dogma in the nutrition realm. He questions the assumption that humans must eat a variety of foods and maintain a balanced diet. He argues that this notion is not supported by the history of human eating habits or the dietary patterns of other animals. Baker also challenges the reverence for fiber, suggesting that it may be a marker for other healthy behaviors rather than an essential nutrient.
Practical Considerations and Recommendations
With all the various diet trends promoted today, it can be difficult to know what is the safest or healthiest. “The best diet is the one you can sustain the longest. A gradual lifestyle change approach is more manageable than tackling a trendy diet that is drastically different than your usual diet.
If you’re considering a major diet change, especially one as extreme as the carnivore diet, talk with your primary care doctor or a registered dietitian. They can help you find a plan that aligns with your health goals-without putting your heart at risk.
tags: #carnivore #diet #cardiologist