You may be familiar with the carnivore diet through Mikhaila Peterson, daughter of best-selling author and professor of psychology Jordan B. Peterson. In her first YouTube video , she narrates a long history of health issues: juvenile arthritis, chronic depression, hypomania, chronic fatigue, numerous skin problems. She started eliminating foods from her diet and, through trial and error, arrived at the solution: all beef, all the time. And she reports her health has dramatically improved. And not just hers.

Her dad’s depression is under control, his gum disease went away. And her mom’s inflammatory colon disease is apparently nowhere to be seen since she joined the all-meat club.

The carnivore diet has variants. Some will eat any meat; others have eliminated everything but beef. Some add salt, while others have cut it out. But generally, it means getting rid of vegetables, fruits, grains, dairy, sweets, and processed food. Imagine eating two ribeye steaks a day. This is the keto diet on testosterone.

Some people adopt it as a way to lose weight. Others hope to be cured of their chronic affliction. It’s an act of rebellion against the medical establishment for some, a way to reassert one’s masculinity for others. For a few, it’s culinary libertarianism in the face of an alleged vegan agenda. A “don’t tread on me” flag the colour of a rare steak.

Is there any scientific evidence behind the claims of contemporary carnivory? And what are the risks associated with such a drastic dietary regimen?

Let’s first address many of the assertions made by the diet’s promoters.

Claim #1: You will lose weight

Any diet on which you burn more calories than you consume will lead to weight loss. If you consume fewer calories by eating steaks all day long, you will lose weight.

The problem is always sustainability. Losing weight initially is relatively easy, but most people on a diet will regain much if not all of the lost weight.

Extreme diets are almost always untenable: even Mikhaila’s dad, Jordan Peterson, when recently asked if he was still on the diet , replied, “Unfortunately, yes. […] It isn’t something I would lightly recommend. […] And it’s dull as hell.”

Claim #2: Plant food is actually toxic

We are told that many plants have defence mechanisms and that ingesting these toxins could very well precipitate inflammation and disease. Specifically, lectins, gluten, and phytic acid are, according to some proponents of the diet, responsible for many human diseases.

“When it comes to lectins, we know very little about them in human nutrition,” says Kevin Klatt , Ph.D. in Molecular Nutrition when I asked him about these claims of toxicity. “It’s recommended to soak and boil beans, destroying the active lectin.” Heidi Bates , a Registered Dietitian and the director of the Integrated Dietetic Internship at the University of Alberta, tells me some people can experience gas or stomach upset if they eat a lot of lectin-rich foods (like beans, bell peppers, and rice). “But there is no research to suggest that we should avoid all of these nutrient-rich foods.”

Gluten, however, is responsible for an autoimmune condition called celiac disease which affects 0.5 to 1% of North Americans , but its danger to the rest of us has been greatly exaggerated . “There is no evidence to suggest,” Bates says, “that the general population needs to avoid gluten-containing foods.”

As for phytic acid, its affinity for minerals like iron and zinc is a theoretical concern, because it could lead to poor absorption of these minerals in the body. While this is important in developing countries where these deficiencies are more commonplace, phytic acid is not a concern in the developed world, Klatt tells me. Case in point: “Vegetarians and vegans do not typically have higher rates of anemia. Phytic acid is a common bogeyman in circles trying to demonize any plant-based food.”

Claim #3: No constipation despite the lack of dietary fibre

Eating only meat means a drastic reduction in your fibre intake, and we’ve been told that fibre is good for us. Indeed, not getting enough fibre can cause constipation… but many carnivores are quick to prop up a study that seems to prove the opposite .

However, it’s hard to simply dismiss the many trials out there, systematic reviews and meta-analyses that show that fibre can work to relieve constipation. But it’s not tolerated by everyone. It turns out that some constipated patients do experience distention and increased bloating on a high-fibre diet. How a patient responds to fibre seems to be associated with the type of constipation they have.

Moreover, people with active inflammatory bowel disease or Crohn’s disease may need to limit their intake of some vegetables, says Bates. And some vegetables contain FODMAPs, small sugars and alcohols that can cause bloating for certain people.

Vegetables are not to be demonized. “There is no body of evidence that suggests that vegetables cause illness,” Bates tells me. “In fact, the opposite is true. There is an excess of evidence linking vegetable consumption to reductions in the risk for heart disease, stroke, diabetes, obesity and certain types of cancer.”

Claim #4: No more brain fog

Is there any evidence that an all-beef diet can increase mental clarity? “No causal evidence,” says Klatt. The best link he can imagine is that, if you have a food sensitivity or allergy that is affecting your gut, and if your carnivore diet removes the nasty trigger, you might see an improvement in mental clarity because of the crosstalk between the gut and the brain. “But,” he points out, “we barely understand how diet might affect mental health and clarity for the foods and nutrients we regularly eat.” We commonly hear that low-carb diets give you mental clarity. “A common claim for almost every diet, though,” he says, “is mental clarity.”

Claim #5: This diet cured Mikhaila Peterson of her juvenile arthritis

The carnivore diet is not the first dietary regimen to be linked to a miraculous remission; it’s only the latest. Mikhaila Peterson, who reports having tried drugs like naproxen, Enbrel, methotrexate, immunosuppressants, and cortisone injections for her arthritis, concludes, “The beef thing has treated my problems” . And I am happy that her symptoms have gone away and that her quality of life has improved. But before jumping to conclusions, we must zoom out of this particular testimonial and look at the bigger picture.

Juvenile arthritis has a remission rate with treatment. A cohort study of over 1,000 Canadian children with the disease reported that the probability of achieving remission within five years of diagnosis was 50%. A systematic review of the phenomenon looking at multiple studies calculated this remission rate to be 47% by 10 years after diagnosis. So remission from juvenile arthritis is not rare.

Even though it is tempting to link remission with our last major lifestyle change, it’s more of a manifestation of the saying that “the brain abhors a vacuum” than a legitimate explanation.

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Now that we’ve addressed many of the claims surrounding the diet, let’s look at some genuine concerns.

Concern #1: Vitamin deficiency

“If you are excluding all fruits and vegetables,” says Dr. Christopher Labos , cardiologist and associate with our Office, “this might be one of the rare circumstances where you might be deficient in certain vitamins and minerals.”

But some carnivores will point to the Inuit and their all-meat diet and lack of vitamin deficiency. AsPopular Science writer Sara Chodosh highlights, however, they also eat whale skin , which is rich in vitamin C. I suspect you won’t see many trendy carnivores shopping for whale skin at their favourite butcher, so vitamin supplements become hard to avoid.

Another counter-argument is that the amount of vitamin prescribed to us is based on diets filled with junk food. If we only eat meat, we are told, our vitamin requirements will go down dramatically. Some have even stated that, since you essentially don’t consume glucose anymore, your vitamin C requirement is very, very small.

As Klatt tells me, however, this claim comes from the observation that very high glucose levels in cells can limit the ability for these cells to uptake vitamin C. “This does not mean that not eating carbohydrates will lead to vitamin C not being a vitamin. Even if you don't eat glucose, you'll still have glucose in your blood and you'll still need vitamin C for its vitamin properties. It's a cofactor for a number of enzymatic reactions in the body.”

When it comes to scurvy, however, it does take surprisingly little vitamin C to prevent the disease, about 10 mg, “much lower than the recommended daily allowance,” says Klatt.

Concern #2: Protein and uric acid overload

“Eating a lot of meat, especially organ meats, can increase your uric acid levels which can cause gout,” says Dr. Labos. “Also eating a lot of meat, and thereby a lot of protein, can potentially cause damage to your kidneys. If you are eating a lot of salted meat, that may affect your blood pressure.”

Concern #3: Cholesterol

I would certainly worry about cholesterol if I were tearing into a steak twice a day although, once again, bloggers are quick to point out that, actually, everything you know about cholesterol is wrong! It’s good for you!

“Cholesterol is most certainly not good for you,” says Dr. Labos. “There are over 25 randomized trials starting with the 4S study from the early 1990’s and, most recently, studies like the Jupiter study or the Odyssey Outcomes trial that show that lowering your cholesterol reduces cardiovascular risk. Maybe with an all-meat diet, your cholesterol won’t change too much, but that is different than saying that cholesterol has no effect on heart disease.”

But many carnivores are posting photos of their lab test results for cholesterol and vitamin levels showing they’re doing fine… so how do we respond to that? First of all, these are risks, not certainties. Secondly, Dr. Labos says, “most of these risks will manifest over years, which makes them even harder to study.”

Concern #4: Increased cancer risk

We also know that a high consumption of meat has been linked to an increase in the risk of developing colorectal cancer. “High meat consumption raises your lifetime risk of colon cancer from 5% to 6%,” Dr. Labos specifies. Not substantial, but these numbers are based on a diet high in meat, not one that is only meat, which might increase the risk some more.

Concern #5: Food is more than fuel

Finally, there’s what the carnivore diet will do to your mental health and social life.

Alan Levinovitz, associate professor of religion and author of the bookThe Gluten Lie, constrained himself to follow the carnivore diet for 13 days and, musing on his experience, reminds us all that there is more to food than fuel. “Reducing food to physiology,” he writes in Tonic ,“ is as shallow as reducing culture to biology. It’s hard to overstate the sociocultural importance of culinary traditions. Breaking bread. ‘Comfort food.’ Grandma’s recipe. Potlatchs. Wedding toasts. Birthday cake. Thanksgiving dinner. You don’t have to be a foodie for food to be meaningful—you just have to be a human being. And exponentially more than any other restrictive diet, carnivory isolates you from that meaning.”

Meaty testimonials

Long-term research on the carnivore diet is simply absent (and, no, that one-year study of two men in 1930 doesn’t count).

At the end of the day, we are mainly left with anecdotes.

Shawn Baker , one of the most commonly cited adopters of this diet, looks great for his age. But he’s just one person.

Mikhaila Peterson speaks of her meaty diet as the thing that probably got rid of her arthritis. Except look at Patrice Herbst and her piece, “I Had Horrible Arthritis. Then I Went Vegan.” And Juliea Baker who, like Mikhaila, suffered from juvenile rheumatoid arthritis until she corresponded with a doctor who told her to eliminate “all meat, eggs, dairy, wheat, soy, and corn” from her diet, and she claims her life was saved. Aftereliminatingmeat.

Whose story do you trust?

Whose anecdote is generalizable and whose is simply chance?

If you suspect you have a food trigger, I strongly recommend working with a registered dietitian to follow a proper elimination diet protocol, as unsupervised elimination diets can result in nutrient deficiencies.

As for the carnivore diet, I’m awaiting better evidence to add more meat on these testimonial bones.

Take-home message:

- The carnivore diet consists of only eating meat (and, for some, only beef)

- The health claims made by its fans are either unscientific or unproven, although you can lose weight on this diet

- There are potential risks to eating only meat, like vitamin deficiencies, kidney damage and increased cholesterol, but it’s difficult to put a number on these risks

@CrackedScience

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