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. Its popularity owes to the influence of a few prominent social media personalities, authors, and bloggers, including Mikhaila Peterson, daughter of popular psychologist Jordan Peterson, and orthopedic surgeon Shawn Baker, whose 2019 The Carnivore Diet is something of a holy book for the community.

Like most similar books, The Carnivore Diet downplays or dismisses decades of observational studies linking nutrition to health and disease outcomes, selectively ignores intervention studies that do not suit its agenda, and substitutes its own favorite form of evidence: individual success stories. The carnivore diet website features over a thousand examples of such success stories, incredible stories of individuals overcoming the worst symptoms of Lyme disease, asthma, depression, autoimmune disorders, and so much more.^[1]

“Think about it from a plant’s point of view….” writes Paul Saladino, another well-known proponent of animal-based diets and the author of The Carnivore Code.^[2] “They simply do NOT want to be eaten, and they contain MANY defense chemicals that are designed to mess with your digestion [. . .] The fact is, the vast majority of plants are inedible if not toxic to humans.”

Inedible if not toxic? Are we sure? Inflammatory, aggressively obtuse claims are a dime a dozen in the popular nutrition sphere, but suppose we give Saladino the benefit of the doubt and seriously consider what he’s saying. Is there anything in the scientific literature to substantiate such a claim? In a 2020 review of perceived problematic plant compounds, so-called antinutrients like those that Saladino loosely speculates about, authors Petroski and Minich have this to say:^[3]

“Plant-based diets which contain these compounds also contain thousands of other compounds in the food matrix, many of which counteract the potential effects [. . .] Therefore, it remains questionable as to whether these compounds are as potentially harmful as they might seem in isolation [. . .] In some cases, what has been referred to as ‘anti-nutrients’ may, in fact, be therapeutic agents for various conditions. More exploration and research are required to know for certain.” (For those interested in learning more, another recent article published in the Journal of Functional Foods essentially echoes this review: antinutrients, to the extent that such things exist, do not behave in the body as simplistically as plant fearmongers suggest they do.^[4])

But that’s only one sliver of the research contradicting only one claim commonly made by proponents of the carnivore diet. What does the research on this diet more broadly indicate? Here, we run into a problem:

The Supporting Evidence Does Not Exist

According to Amber O’Hearn, the phrase carnivore diet did not even appear in the title of a scientific paper until 2020, when she published a paper in Current Opinion in Endocrinology, Diabetes and Obesity.^[5][6] O’Hearn has spent at least a decade studying the carnivore diet, organizing a carnivore conference, and writing blog posts on the subject, but by her own admission, the scientific literature on the subject has been lacking; it wasn’t until she—an outsider without scientific research credentials—took the initiative that the subject even appeared in an article’s title.^[7]

I highlight O’Hearn’s lack of credentials not to belittle her enthusiasm or knowledge. Critical outsiders who work hard to deeply engage with a subject can offer unique insights; sometimes, their perspectives might be even more valuable than what we have learned from established, credentialed experts. But her example proves what many carnivore dieters would rather not admit: the rigorous scientific evidence supporting this diet does not exist. Beyond a century-old case study of two Arctic explorers and speculation about the diets of Inuit or Mongolian nomads, the only evidence is anecdotal.^[6]

Does that mean people should not be allowed to go all in on the carnivore diet? Of course not. Although the loudest voices from this corner commonly appeal to values of freedom, insisting on the importance of protecting free choice and free thinking, as far as I can tell, no one is trying to stop them. If someone decides to make potentially life-or-death decisions based on such a thin body of evidence, that’s their prerogative. Everyone should weigh the potential risks and benefits and make their own decisions. However, given the glaring absence of evidence, I am wary of anyone claiming this is the healthiest choice.

Seemingly positive survey data published in 2021 did find that the diet was well tolerated and that dieters experienced few adverse effects.^[8] However, there were several obvious issues with the survey design:

• Participants were recruited from social media communities commonly frequented by carnivore dieters, and anyone who had been on the diet for less than six months was excluded. This means the survey captured only those who were the most dedicated to the diet (just over 2,000 subjects, less than .000025% of the population); of course that group will report that the diet is tolerable—they are the ones who have already tolerated it. It remains unproven whether the diet is, or ever could be, tolerable to everyone else.
• Because it was an email survey without rigorous verification, there is a reasonably high likelihood that the provided health data was skewed by self-report bias.
• Pre-diet food intake was not reported, so it is impossible to know how healthy (or likelier, how unhealthy) these individuals’ diets were before switching to a carnivore diet. Even though the carnivore diet is unproven, with unknown long-term consequences, we should not overlook the possibility that these individuals might have felt better simply by ditching an unhealthy standard American diet.

This final point is supported by the self-reported weight loss data: the median pre-diet BMI was 26.4, squarely in the overweight range, whereas the median BMI at the time of the survey was 23.7. (Unsurprisingly, they also reported significant increases in serum LDL cholesterol levels, a measure many carnivore dieters insist is unimportant.) In other words, they lost weight on average. And at the time of the survey, nearly all the respondents reported consuming very little or no candy, desserts, alcohol, or fast food meats. Is it possible they were feeling less junky only as a result of consuming less processed food and losing excess weight? We cannot say for sure, because the survey failed to include any information about their pre-diet choices.

You might be unsurprised—given the survey’s shortcomings—to read the acknowledgments section, which credits Shawn Baker (The Carnivore Diet author mentioned above) and Travis Statham (another advocate for the carnivore diet) “for input in developing the survey instruments, online distribution of the survey, and critical review of the manuscript.”

Meanwhile, there is a mountain of evidence suggesting the carnivore diet is likely unhealthy:

• Countless large-scale observational studies consistently show that plant-predominant diets are associated with a lower incidence and mortality of numerous chronic diseases, including several cancers.^[9]–[16]
  Reasonable skeptics understand that observational studies alone are generally considered a weaker form of evidence—correlations, we know, do not prove causation—but these correlations are reliably backed up by a combination of other forms of evidence.
• Several intervention studies have shown that replacing animal-based foods with whole plant-based foods can improve health outcomes, particularly in heart disease patients.^[17]–[20] On a molecular level, “[Numerous] nutritionally mediated factors independently increase cardiovascular oxidative stress and inflammation and are all independently tied to CVD development.”^[21]
• Laboratory experiments (animal studies) help to explain the association between animal protein and disease progression; these findings provide evidence of biological plausibility. For example, in rodent models, animal protein has been shown to increase the binding of a carcinogenic metabolite, decrease voluntary energy expenditure, and increase the formation of reactive oxygen molecules that promote cancer development.^[22]–[26]
• Numerous additional studies highlight the potential benefit of shifting away from animal-based foods to prevent or treat kidney disease, type 2 diabetes, obesity, Alzheimer’s, osteoporosis, and more.^[27]–[34]
• Finally, the many benefits of choosing plant-forward diets “dovetail with their lower environmental impact, which must be considered when designing an optimal diet.”^[35]

(Learn more about the extensive science supporting a plant-based diet.)

So, long-term research on the carnivore diet is, as I’ve already written, completely absent. In light of the research supporting a plant-based diet—much less a plant-inclusive diet—the problem that carnivore dieters face now is that even short-term research is difficult to justify funding. Why? Because, like the flat-Earth theory, their hypothesis flies in the face of essentially all the established research. No sufficient preliminary evidence suggests such research efforts would be worthwhile.

Finally, in the absence of short- and long-term studies on the carnivore diet, what do the anatomical clues tell us? The editor-in-chief of the American Journal of Cardiology put it well in 1990: “Although we think we are one and we act as if we are one, human beings are not natural carnivores. When we kill animals to eat them, they end up killing us because their flesh [. . .] was never intended for human beings, who are natural herbivores.”^[36] Whereas carnivores do not develop atherosclerosis from consuming meat, herbivores do. Humans respond to animal foods more similarly to rabbits (natural herbivores) than they do to dogs or cats.

You might wonder how the carnivore diet has become so trendy, given the lack of rigorous evidence. Why are people so compelled by this idea? What lessons might we learn from its popularity? These are just a few of the questions we’ll be answering—soon! Keep your eyes trained on this space for more updates.

References

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3. Petroski W, Minich DM. Is There Such a Thing as “Anti-Nutrients”? A Narrative Review of Perceived Problematic Plant Compounds. Nutrients. 2020;12(10):2929. Published 2020 Sep 24. doi:10.3390/nu12102929
4. López-Moreno M, Garcés-Rimon M, Miguel M. Antinutrients: Lectins, goitrogens, phytates and oxalates, friends or foe? Journal of Functional Foods. 2022;89. doi:10.1016/j.jff.2022.104938
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