The meat eaters have arrived with a fervour to stake their spot as the next big dietary trend. Hundreds of thousands are discussing the aptly named carnivore diet on social media platforms, many of them avid supporters. As it gains momentum, the diet is challenging one of humanity’s most universal nutritional paradigms, our shared belief in the necessity of plant consumption for human health.

Carnivorism — A Response to Veganism?

If you’re still adjusting to veganism, you’re not alone. As recently as the early 2010s, veganism was still a countercultural obscurity. In 2015, veganism was deemed “a thing.” These days, it’s really a thing.

Despite its mainstream newness, veganism isn’t surprising. With “eat your veggies” as the longtime nutritional mantra of mothers everywhere (followed by “starving children in Africa would eat that”), even the dietarily illiterate can comprehend how a veggie-centric diet might be desirable.

The same can’t be said for carnivorism. Nobody grew up with reminders to eat their meat. Meat was the thing you just ate. Fatty, salty, satiating — we knew meat was good for bodybuilders because of protein, or whatever, but mostly we ate it because it filled us up and it tasted good.

If somebody told you a couple years ago that the next big dietary trend would be carnivorism, you’d laugh: Oh, I get it. It’s like the opposite of veganism. That could be, like, a South Park episode or something. Except it’s 2018 and we’re living in a South Park episode, with the carnivore diet as a subplot.

Instinctually, it makes sense to label carnivorism as a response to the now-mainstream and often dogmatic veganism, but supporters of the diet aren’t generally espousing an anti-vegan sentiment. Mostly, they are posting pictures of meat and boasting about the glorious health effects from their newfound carnivorous lifestyles.

The Carnivore Cure-All

At its extreme, the carnivore diet is promoted as a radical health intervention for people who can’t seem to eat anything else. The most noteworthy case is probably Mikhaela Peterson, daughter of the popular (and polarizing) academic Jordan Peterson. As detailed in Jordan’s book and referenced several times in interviews, Mikaela is the lifelong victim of an aggressive autoimmune disorder causing severe arthritis and forcing her to receive multiple joint transplants before the age of twenty. When her elimination diet strategy led her to carnivorism, the story goes, all of her symptoms — including severe depression — vanished.

“She is doing so well now it is absolutely beyond comprehension,” Dr. Peterson reports, “She’s just glowing with health. All of her autoimmune symptoms are gone. All of them.”

Furthermore, Jordan, who suspects Mikhaela’s autoimmune disorder is hereditary and was inherited in part from himself, has adopted the diet with similarly fantastic results. He says he’s in the best mental and physical shape of his life since switching to a beef-only diet. And he looks great — a noticeable transformation from the pale, tired-looking man who first hit the spotlight in 2016.

This isn’t an article about the Petersons but they do offer a perfectly surreal example of carnivorous triumph, which prompts us to ask: Could the carnivore diet be right for some people? And, if so, why?

Let’s visit the opinions of some experts to figure out why the carnivore diet works, and why it also might kill you.

Part 1 — Why The Carnivore Diet Works

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Less is More

Experts agree that the carnivore diet probably works by helping people to eat less.

Meat is satiating — it causes us to feel full. It tastes good but we’re typically not tempted to overeat it. Unlike delicious temptations like pizza and ice cream, we don’t get carried away and “accidentally” eat a family pack of ribeyes.

Dr. Layne Norton agrees, “If I give you a plate of french fries, like 200 grams of french fries, you can get a lot of calories from that. If I give you 200 grams of meat, even a real fatty meat, it’s not nearly the same. You’re going to be much more satiated from the protein. You can only eat so much meat.”

“I think it’s [probably] a calorie restriction effect,” says Dr. Dom D’Agostino, a researcher and advocate of the popular (and also controversial) ketogenic diet.

Like the ketogenic diet, a carnivorous diet is naturally high in protein and low in carbs, a combination which has been observed to suppress appetite by affecting key hunger hormones such as leptin and ghrelin.

Additionally, dietary monotony — eating the same food repeatedly — has been shown to reduce caloric intake by increasing what’s called “food habituation”. The more often we’re presented with the same type of food, the less that food excites us and the less likely we are to binge, causing us to eat less.

These three factors combined make a good case for the caloric restriction hypothesis:

Meat is satiating and hard to overeat. A high protein, low carb diet suppresses our appetite at the hormonal level. A monotonous diet reduces our caloric intake at the habitual level.

For most participants, the carnivore diet seems to coincide with one or more fasting strategies which have proven benefits, including Dr. Valter Longo’s fasting mimicking diet and Dr. Satchin Panda’s time-restricted feeding strategy.

For Mikhaela Peterson and the many others who are drawn to the carnivore diet because of autoimmune issues, there’s an important connection here:

“One thing that’s really known to affect autoimmunity is caloric restriction and fasting,” says Dr. Rhonda Patrick, “It’s probably one of the most well known technologies that you can intervene and have improvements in autoimmune disease.”

Dr. Patrick points to research by Dr. Longo which showed selective replacement of autoimmune cells by healthy cells in mice fed a fasting mimicking diet, as well as symptomatic improvement in humans with multiple sclerosis (MS) who used a fasting mimicking diet for one week.

Caloric Restriction and the Microbiome

Similar research showed that intermittent fasting (IF) altered the gut microbiome, improving symptoms in mice and humans with MS. The study concluded, “IF has potent immunomodulatory effects that are at least partially mediated by the gut microbiome.”

Dr. Patrick continues, “The microbiome has been linked to immunity in multiple, multiple studies. It’s been linked to arthritis, it’s been linked to multiple sclerosis… There’s actually been a few animal studies which have led to phase one, phase two, and phase three clinical trials that have been done in humans.”

One such trial treated MS patients with minocycline, an antibiotic which was observed to improve MS symptoms by clearing “bad bacteria” from the gut. The positive effects lasted about two years before stopping, “Probably because you’re wiping out the microbiome,” says Dr. Patrick, “and eventually you’re also getting rid of the good bacteria.”

Finally, both Jordan and Mikhaela Peterson report relief from chronic depression as a result of their meat-only diet. With several studies linking systemic inflammation and the gut microbiome to depression, and linking caloric restriction to a reduction of inflammation and improvements to the microbiome, caloric restriction and its effect on the gut microbiome emerge as a likely mechanism behind the carnivore diet’s positive effects.

The effects aren’t all positive, though. Keeping the microbiome in focus, let’s move onto potential negative effects of the carnivore diet.

Part 2 — Why the Carnivore Diet Might Kill You

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Bad Bacteria

While your gut might benefit from a foray into carnivorism, science suggests you can only thrive without plants for a limited time.

In the Cell Metabolism study referenced above, the positive effects of caloric restriction on immunity were attributed to increased “gut bacteria richness” and “gut microbial diversity.” In another study, we learned that the benefits of minocycline for MS patients stopped after about two years, which Dr. Patrick believes is due to the microbiome being depleted.

These results suggest that wiping the microbiome is a positive short-term health intervention, so long as the gut is replenished with a diversity of bacteria. However, with a diet as restricted as the carnivore diet, we observe restricted gut bacteria.

“It’s been shown that people who go from a more high-fibre to a high-protein diet — they have changes to their microbiome,” Dr. Patrick explains, “…a lot of the microbiome bacteria that are fermenting a variety of fermentable fibres start to leave and you actually start to get bacteria cropping up that ferment amino acids.”

These amino acid fermenting bacteria are known as putrefactive bacteria. Two products of putrefactive bacteria, putrescine and cadaverine, are best known for literally smelling like death. They are also genotoxins known to damage the DNA inside your colon cells.

In the Nature study referenced by Dr. Patrick, the authors write, “…high intake of red meat relative to fruits and vegetables appears to associate with outgrowth of bacteria that might contribute to a more hostile gut environment,” and, “Together, our results suggest venues through which a diet low in fruits and vegetables relative to meats select for outgrowth of putrefactive bacteria, which might help promote colorectal carcinoma.”

These findings contribute to an ongoing discussion regarding the potential link between meat consumption and colon cancer. Other studies have focused on heterocyclic amines, which are formed when meat is cooked at high temperatures, nitrates, which are used to preserve processed meats, and N-nitroso compounds, carcinogens linked to red meat consumption and colorectal cancer risk.

As the names suggest, there is a connection between nitrates and N-nitroso compounds (specifically, nitrosamine). Connections are also observed between nitrosamine and putrecine, one of the genotoxins mentioned above. But we don’t need to get lost in the science to understand the most important connection at play here.

Why No Veggies?

For you and I, if we’re inclined to eat meat — especially red meat — the most relevant connection isn’t between meat and cancer but, rather, between cancer (and other illnesses) and the absence of dietary plants and fibre.

If we’re answering the question, “Why would a person only eat meat?” we can produce a sensible answer — to create a caloric restriction. The more relevant question confounding experts is, “Why wouldn’t a person eat vegetables?”

“There’s some really tight meta-analyses that have been done looking at colorectal cancer and low fibre intake, and I would not be comfortable recommending people not eat enough vegetables and fibre,” warns Dr. Norton.

“I feel uncomfortable eating a steak or a burger without something like broccoli or salad,” adds Dr. D’Agostino, “I think you negate many of the potentially carcinogenic compounds that are in red meat [with vegetables].”

As cited above, one Nature study linked colon cancer risk to “a diet low in fruits and vegetables relative to meats.” The Cancer Research study referenced above observed significantly elevated levels of genotoxic N-nitroso compounds (NOC) in the study group who were fed a diet of red meat compared to those who were fed a vegetarian diet. Interestingly, the group who were fed a high-meat, high-fibre diet showed only intermediate levels of NOC.

One possible explanation for these findings is the inhibitory effect of lactic acid on putrefactive bacteria. If you’re eating plants, Dr. Patrick explains, “…you’re going to limit the growth of putrefactive because they can’t grow with lactic acid.”

“Bifidobacteria, lactobacillus, S. mutans, S. thermophilus — those strains of bacteria are lactic acid producing bacteria which you’d be facilitating the growth of if you’re eating plants.”

Numerous similar relationships have been observed between plant and fibre intake and decreased colorectal cancer risk, including the preventative action of vitamin C on nitrosamine formation, among many others.

In her discussion, Dr. Patrick transitions to the necessity of micronutrients for human health, detailing vital nutrients such as vitamin C, vitamin E, magnesium, folate, and manganese that you can’t get in meaningful quantities from a meat-only diet.

“Twenty two percent of all enzymes in your body require a micronutrient to function,” says Dr. Patrick, “There’s about thirty of them [that] you have to get from your diet because you don’t make them in your body, and if you don’t get them from your diet it can lead to health problems and death.”

Some micronutrients are most concentrated in plants and others in meat, Dr. Patrick explains, and it’s near-impossible to get all of your vital micronutrients from food alone when you eliminate one of these sources. While proponents of veganism and carnivorism both have ways of reasoning around this simple truth, it’s naive and risky to think that a carnivore diet could possibly provide a complete micronutrient profile.

With all that said, regarding colorectal cancer and other risks, the case against eating meat starts to sound a lot like the case for eating fruits and vegetables. Other factors found to be significant include body fat, whole grain intake, alcohol consumption, and exercise.

Meat, Cancer, and Aging

Finally on the “Why The Carnivore Diet Might Kill You” side is a more general relationship between meat and age-related disease involving the IGF-1 pathway.

It’s a popular notion among anti-meat communities that meat causes cancer, as evidenced by a growing body of research. Despite the evidence, the connection between meat and cancer isn’t as clear as some meat opponents would have you believe.

In a podcast episode titled “Does Meat Consumption Cause Cancer?” Dr. Patrick discusses possible mechanisms that could link meat consumption to cancer risk. She begins by referencing a massive JAMA study titled “Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality” which linked animal protein intake with higher all-cause mortality and cancer mortality.

Though significant, this finding did not hold up to an important control. “A more careful analysis within the paper revealed something interesting,” states Dr. Patrick, “This pattern only held up for participants with at least one other factor associated with an unhealthy lifestyle, like being obese, or being a heavy consumer of alcohol, or having a history of smoking, or being physically inactive.”

“Meat consumers that were healthy by not having any of these aforementioned unhealthy lifestyle factors did not have a higher mortality rate or higher cancer mortality rate.”

To explain this, Dr. Patrick turns to research involving insulin-like growth factor-1 (IGF-1), a hormone with unique consequences for human health. A primary function of IGF-1 is helping damaged cells stay alive. In early-life development, the maintenance of muscle tissue, and neuronal function, IGF-1 is your ally. However, some damaged cells, such as those that have become cancerous, are not meant to be kept alive. In these cases, IGF-1 is your enemy.

Damaged cells are a part of life. When our cells create energy through “respiration”, they also create damaging byproducts known as reactive oxygen species. We have a built-in mechanism for this called programmed cell death, or apoptosis. In ordinary circumstances damaged cells self-destruct, preventing further damage.

Unhealthy lifestyle factors such as those mentioned above increase the rate of damage and compromise our ability to repair DNA. In a high-damage environment, apoptosis can become disabled and damaged cells are left to live and multiply, spawning further generations of damaged cells. As damaged cells reproduce, the genes responsible for growth and proliferation can become mutated so they are constantly active, transforming them into what are known as oncogenes. Conditions vary but multiple oncogenes in combination with mutated apoptotic and tumor suppressor genes are what we generally refer to as cancer.

How does this relate to meat? Dr. Patrick says, “Meat, unlike plants, is of course extremely rich in protein. And protein — especially the amino acids found in protein — directly affect our IGF-1 levels by increasing them. Moreover, essential amino acids which are disproportionately found in meat have more of an effect on increasing serum IGF-1 compared to non-essential amino acids.”

As mentioned above, IGF-1 is a cancer enabler because it allows damaged cells to stay alive. In many cases, Dr. Patrick explains, damaged cells can’t survive our body’s natural defence mechanisms on their own. They need growth factor to do this. That’s why multiple studies have found a strong connection between IGF-1 (or lack thereof), cancer, and longevity. For example, leveraging animal studies that showed a direct relationship between lifespan and IGF-1 activity, one study identified an overrepresentation among female centenarians of mutations to the IGF-1 receptor gene, resulting in reduced IGF-1 receptor activity and above-average lifespans.

So, low IGF-1 equals lower cancer incidence and increased lifespan. But, given the beneficial functions of IGF-1, we don’t want to eliminate it entirely. Instead, we can mitigate the risks of IGF-1 by avoiding excess cellular damage from unhealthy lifestyle factors and by limiting meat consumption to avoid excess IGF-1 levels. Additionally, we can exercise to increase the uptake of IGF-1 in our muscles.

Given the relationship between IGF-1 and animal protein, eating a diet of only meat is probably an unwise longevity decision, regardless of your lifestyle.

Part 3 — Conclusions and Considerations

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In Defence of Carnivores

Despite an absence of studies, the positive effects of the carnivore diet can be plausibly validated using existing science. With high protein content and virtually zero carbs, the carnivore diet is likely the most satiating, least calorie-dense diet a person could eat, making it conducive to sustained caloric restriction. It’s not surprising that carnivore diet newcomers are enjoying rapid weight loss and the associated benefits.

If a person is reporting relief from the carnivore diet, especially in severe cases like that of Mikhaela Peterson, it would be contentious to suggest they return to their suffering. However, given the potentially hazardous repercussions of abstaining from plant fibre, it’s worth investigating the mechanisms beneath the carnivore diet to attain the same result through safer means.

The Keto Connection

Mentioned only briefly in the “Why The Carnivore Diet Works” section but highly relevant is the connection between the carnivore diet and the ketogenic diet.

The ketogenic diet is extremely low carb but with only moderate protein intake and a priority on healthy fats. With a combination of caloric restriction and the optimal fat-to-carb ratio, the body goes into ketosis, converting fat into ketones and using them as its primary energy source.

Being in ketosis offers some distinct benefits, making the diet popular for weight loss, athletic and cognitive performance, and the management of several chronic illnesses. It’s shown to have antioxidant, anti-inflammatory, and neuroprotective effects. The ketogenic diet lowers blood glucose and improves insulin sensitivity, as well as suppressing hunger hormones.

For these reasons, the ketogenic diet has found applications in the management or prevention of heart disease, cancer, Alzheimer’s disease, epilepsy, Parkinson’s disease, and more.

While this all sounds great, the ketogenic diet is notoriously hard to follow and more research is needed to verify its long term efficacy and safety in the applications listed above.

There’s reason to think that some carnivores might be in ketosis, despite the tendency of excess protein to pull the body out of ketosis. Although it’s surprisingly restrictive, the ketogenic diet allows for a variety of food sources including some vegetables. This fact, combined with the known benefits of ketones themselves, suggest that the ketogenic diet might be an attractive alternative to the carnivore diet.

It appears that keto and carnivore advocates are well-aware of this connection, as evidenced by the significant overlap in their online communities. This author wonders if the carnivore diet is attractive because it offers some of the benefits of ketosis without the complications of tracking macronutrients and ketone levels. It doesn’t get much simpler than only eating meat.

Lifestyle Matters

According to JAMA’s massive associative study, meat consumption won’t increase the likelihood of early death unless it’s combined with at least one unhealthy lifestyle factor, in which case it appears it will.

Obesity, physical inactivity, alcohol abuse, and smoking cigarettes — among other unhealthy lifestyle factors — will turn the meat on your plate into a liability.

Our hunter-gatherer ancestors would have typically enjoyed protein-dense meals after a period of deprivation and exertion. Mostly they grazed on plants and nuts. These circumstances might explain how our bodies evolved to best metabolize meat — in combination with plants and exercise.

Everybody is Different

There’s no one-size-fits-all diet. People vary greatly in their metabolic needs and adaptations. People can be more protein or fat or carb adapted than others and our genes and microbiome significantly dictate how we respond to certain foods.

Much of what’s healthy for the human body is actually stress. Exercise, starvation, heat and cold exposure — these all evoke a stress response from our body which offers a net benefit. The phytochemicals in plants are another mild stressor that we benefit from.

Except, what if the mild stress from plants is actually severe stress? What if a genetic polymorphism or an imbalance in the microbiome causes your body to attack itself after eating a serving of vegetables? It’s reasonable to believe this is the case for some people.

The important question is, if a person reacts negatively to plants, could this be fixed by modifying the microbiome?

Listen To Your Gut

I’m not a doctor and this is not medical advice, but if I was facing a situation similar to Mikhaela Peterson’s — knowing what I’ve learned researching this article — I’d be inclined to focus on the microbiome.

Could an initial test reveal some abnormality? What might happen after a supervised water fast or the administration of an antibiotic like minocycline? Under professional supervision, would it be possible to re-introduce some fermented foods? Given the desirability of dietary plants, it would be worth exhausting every opportunity to integrate them back into the diet.

Genetic testing such as 23andMe would also be vitally helpful in discovering why your body reacts positively to a meat-only diet.

Seriously Though, Just Eat Your Greens

Unless plants are wreaking obvious havoc on your body, there’s no excuse not to eat them. Regular plant consumption is directly associated with longevity.

Comfortingly and annoyingly, when we investigate topics like the carnivore diet, the conversation is complex but the conclusions are simple. What we learn about healthy living is what we’ve known for a long time. Get rest, get exercise, don’t smoke, don’t drink excessively, eat fruits and vegetables, and consume in moderation.

Final Thought

Could the carnivore diet, or a version of it, be safe? Could the caloric restriction that accompanies it be so beneficial that it supplants the need for plants altogether? Maybe. Probably not. We won’t know until more research is done.

Until then, it’s probably wise not to take your chances.