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Why the carnivore diet is unhealthy and what to try instead

Article at a Glance
  • While it may be necessary for a tiny minority, the carnivore diet is unhealthy for almost everyone else and should be avoided.
  • The carnivore diet is too high in inflammatory amino acids that have been linked to cancer growth.
  • By creating a constant stream of protein waste, the carnivore diet burdens the liver, kidneys and colon.
  • The carnivore diet could increase the risk for urinary tract infection in some women.
  • The carnivore diet increases the risk for heart disease, especially in certain genotypes.
  • APOE4 carriers should avoid the carnivore diet entirely.
  • The protocols listed in The Plant Paradox could offer an alternative for people considering the carnivore diet.
  • One possible explanation for success on the carnivore diet could be undiagnosed sitosterolemia, a rare genetic condition in which people cannot clear plant sterol from their system, causing it to accumulate.
Genes Mentioned
Carnivore diet health risks

When it comes to food, no two people are alike. What works for one may not work well for the next person. For example, we’ve written previously about how certain genotypes are very poorly suited to the butter coffee “Bulletproof” style diets and how these people are likely to see very scary lipid numbers on a high fat diet. Others can eat a diet higher in saturated fats and do just fine.

The answer to almost all of the nutrition debates is genetics.

But there are exceptions. There are diets so fundamentally flawed that no one should be on them, almost ever. The carnivore diet is one of those diets.

Now, before I get into the meat of this post (no pun intended) I do want to offer one caveat. There are people out there who have severe health issues and find they do best on a carnivore diet. The Canadian intellectual Jordan Peterson and his daughter Mikhaila Peterson are two examples. It’s not for me to tell the Peterson’s how to eat. If they find their quality of life is enhanced eating nothing but read meat, then that’s exactly what they should do. In fact, I find their willingness to share their stories inspiring. However, I part company when the carnivore dieters step into the world of advocacy. Advocating for a carnivore diet, as Mikhaila Peterson is now doing with her website “Don’t Eat That,” is unfortunate. Unfortunate because, as I am about to explain, the carnivore diet is a really bad idea for most people.

What lab tests should carnivore dieters focus on?

This is a good one to get out of the way right off the bat as lab tests come up in all the podcast discussions. Many of the devoted carnivore diet followers claim their lab tests are “normal.” I would want to see the following labs from someone who has been on a carnivore diet for an extended period of time.

  • LDL-P – number one predictor of heart disease
  • APOB – protein that makes up LDL particles
  • sdLDL-C – small dense LDL cholesterol mass
  • LDL-C – cholesterol mass within LDL
  • C reactive protein – produced by liver when inflamed
  • Serum ammonia – toxic byproduct of protein metabolism disposed of via the urea cycle
  • Fasting glucose – level of blood sugar in the blood when not eating
  • Lp(a) – unique kind of lipoprotein that puts people at higher risk for heart disease
  • Homocysteine – common amino acid in blood associated with heart disease, can be elevated when eating meat

Most of these tests are markers for heart disease and inflammation in the body and they don’t show up on regular blood tests. If a carnivore diet is healthy, these tests would all come back in range. Now on to the reasons I don’t think the carnivore diet is a healthy option for most people.

Why the carnivore diet is unhealthy (really unhealthy)

Let’s list the ways a carnivore diet can make you unhealthy.

Increased cancer risk is the first one that comes to mind.

Carnivore diet turns on cancer pathways

Amino acids are the building blocks of proteins. Humans digest protein and use the different amino acids for all sorts of processes in the body, including building muscle and making neurotransmitters. But not all amino acids are created equal, some act as both good and bad guys at same time. Unfortunately, the carnivore diet offers a steady mega-dose of some of the “bad guy” amino acids which have been linked to increased risk for certain diseases such as cancer.

We’ve written previously about the different amino acid profiles of plant protein vs. animal protein in our Vegan protein powder post. Plant proteins contain different types of amino acids and in different amounts than animal protein. Plant proteins are often low in some of the muscle building amino acids like methionine, tryptophan, lycine and isoleucine. This is why it’s harder to be a Vegan bodybuilder, the amino acid profile of plants doesn’t stimulate the body’s growth pathways in the same way that animal proteins do.

This is both a good and a bad thing. It’s a bad thing if you want to get ripped, but the altered amino acid profile of plants is helpful in turning off some disease states in the body.

Researchers like Valter Longo at USC have published research showing how the amino acid composition of animal protein turns on cancer pathways in the body by increasing levels of a hormone known as insulin like growth factor one, or IGF-1. To quote from one of Dr, Longo’s research papers:

In humans, protein restriction (PR) has been associated with reduced cancer, diabetes, and overall mortality. Thus, interventions aimed at lowering the intake of proteins or specific amino acids can be beneficial and have the potential to be widely adopted and effective in optimizing healthspan.

To date, several studies have shown decreased age-related pathologies and lifespan extension through the modulation of protein intake. Low protein diets have been demonstrated to reduce spontaneous tumor formation, as well as in mimicking the effects of calorie restriction in improving renal function. In the past few decades it has also been demonstrated that protein restriction or restriction in tryptophan or methionine, can extend longevity.

The bottom line here is that consuming large daily doses of the pro-inflammatory amino acids found in animal proteins is not a great idea. If you trust in Dr. Longo’s work as I do then consuming animal protein exclusively is a very bad idea.

Carnivore diet is not ketogenic

I can hear some of you saying, wait John, forget all that research on amino acids by Dr. Longo, I prefer to get my nutrition science from Dr. Dom D’Agostino at the University of South Florida. First off, as a fellow member of the “last name with an apostrophe” club, I love Dr. D’Agostino. But kidding aside, he has done extensive research on the protective effect of ketone bodies against cancer and is a darling of the podcast circuit. Dr. D’AGostino is clearly a formidable researcher, as are early pioneers in ketone research like Dr. Veech.

However, regardless of what you may think about the health benefits of ketosis, the subject isn’t relevant to the carnivore diet. The carnivore diet includes too much protein to be a ketogenic diet. When the body takes in more protein than it needs, the excess is disposed of through the liver (which we will get to in a minute) but also by a process known as Gluconeogenesis, where protein is converted by the body into glucose. (R) The process of Gluconeogenesis is what prevents carnivore dieters from reaping the benefits of ketosis and instead eating what is probably the worst diet known to man – very high fat, very high protein.

Nutrition and autoimmune disease

In addition to his clear stance that a predominantly pescetarian diet is optimal for most people, Dr. Longo has also published research showing that reducing protein intake and cycling on and off a plant based “fasting mimicking diet” leads to the death of autoimmune cells.

The carnivore diet would be just the opposite of what Dr. Longo, one of the world’s leading authorities on longevity, would recommend for treating autoimmune conditions. Rather than flooding the body with protein, Dr. Longo is an advocate of using fasting plus a plant based diet to help stave off autoimmune conditions like Multiple Sclerosis, Crohn’s Disease and Colitis, and Rheumatoid Arthritis. (R)

Carnivore diet burdens the liver and kidneys

When we eat protein, the body breaks down the nitrogen molecules and turns them into ammonia, which is then processed by the liver into something called urea, which goes through the kidneys on its way out of the body as urine.

This process is known as the urea cycle. To break down the nitrogen in protein, the body uses a series of enzymes which are coded for specific genes. For example, the CPS1 gene makes an enzyme that represents the first step in the urea cycle. Kids that are born with reduced urea cycle function end up very sick with ammonia toxicity. (R)

This Harvard Health blog post does a nice job explaining how variants in urea cycle function may play an important role in how adults respond to high protein diets:

Urea cycle disorders are viewed as rare and primarily pediatric conditions, but there might be a whole range of unrecognized, genetically determined problems with protein metabolism experienced by adults. Some people may have mild mutations that compromise a gene’s function and cause slight symptoms. This may explain why one person eschews meat while another loves nothing more than a steak meal. Defects in protein metabolism may also explain why some people have bad reactions to high-protein diets like the Atkins diet.

Clearly, people with genetic variants in the urea cycle pathway (which are common, 33% of people have at least one copy of the risk allele for CPS1) will have major problems on the carnivore diet. Ammonia, a known neurotoxin, will pool in their body, leading to a range of different health problems over time. However, even people with a strong urea cycle may eventually become overloaded with ammonia after eating nothing but large portions of meat for months and years on end. Ammonia is a waste product. It’s something the body needs to clean up, the question becomes: how much ammonia can your body clear before your liver and kidneys are damaged? As with histamine, no two people will be exactly the same.

Carnivore diet and urinary tract infections

Researchers at Washington University in St. Louis have published some excellent research showing that E. Coli, a pathogenic strain of bacteria responsible for most urinary tract infections, grows best in acidic urine. Without an acidic environment, E. Coli can’t get the iron it needs to survive and thrive.

How does this impact on the carnivore dieters? The flood of meat will rapidly create an acidic environment in the body and urine. In women, this will create the perfect conditions for E. Coli to thrive. In men, the acidity of urine plays a role in prostate health and the likelihood of developing prostatitis. The Central European Journal of Urology published a study which showed that most cases of prostatitis in young men were actually fungal infections brought to the urogenital region by, you guessed it, E. Coli. One of the protocols the researchers used was potassium citrate because it alkalizes the urine.

The carnivore diet has the potential to create an acidic environment perfect for urinary tract infections and prostate inflammation in women and men respectively.

Carnivore diet and bone density

The acidity issue carries over into the osteoporosis and bone density conversation. This is a problem many women in the west have issues with. Sadly, Mikhaila Peterson, fresh off of a Joe Rogan appearance, dismisses the role of consuming animal protein in bone density loss in about 100 words.

To quote Mikhaila’s blog responding to this Good Housekeeping article which is critical of the carnivore diet:

This one is soooo bad. Healthy grains are good and eating only meat leads to bone loss and organ failure. Of which there are how many cases? Oh zero? Literally just lying. And it’s written by a registered dietician. Shameful.

This is exactly the problem with the diet debates! A diet works for one person, and then the advocacy begins with no recognition of bio-individuality or in this case, of the available data. Were Mikhaila to come out and say “the carnivore diet works for me and my father, but we recognize it is a tad extreme and please be careful if you decide to try it,” that’s one thing. But that’s never what happens. Instead we get attacks against dieticians making legitimate points.

On the one hand, some studies do show that a diet slightly higher in protein has been shown to be beneficial for bone density (and other health metrics) (R). But, and this is a big but, it is worth noting that all of the studies looking at protein (or specifically) meat intake in relation to bone density in humans, rely on recording food as part of a balanced diet, i.e., one with a good fruit, vegetable and other dietary intake. There are no studies looking at the effect of a meat only diet on bone health (or other health impacts), most likely because such a study wouldn’t pass ethical guidelines. In animal models where such studies are allowed there is a consistent trend for seeing reduced bone density (R).

There is likely a strong genetic component tied to the VDR genes. We have written previously about how variants in the VDR genes (which affect calcium uptake from the gut) play a role in bone loss associated with drinking coffee. Certain VDR genotypes are better served limiting caffeine intake as high caffeine consumption has shown to have bone leaching effects. Lower calcium uptake from the gut coupled with the diuretic effect of coffee, which causes greater excretion of minerals from the body, leads to loss of bone density. Coffee is also highly acidic and it’s the acid load that is blamed for osteoporosis in women on high animal protein diets. The theory is that the body leaches calcium from the bones to neutralize PH which has turned acidic by eating animal products. (R) (R)

Carnivore diet and gut health

The carnivore diet is objectively terrible for your colon and overall gut health. There are many sound reasons to eat fiber, with one of the most important being the impact fiber rich foods have on the microbiome. When we eat complex carbohydrates like yams, broccoli, rolled oats, apples, and other plant foods, the plant matter ferments in the colon, which is a good thing. It’s the fermentation process that generates short chain fatty acids like butyrate which we use for energy and which also line and protect the wall of the gut. By removing all fiber from the diet and eating only meat, you can almost guarantee that two things will happen:

  1. Your microbial diversity will suffer and;
  2. Some of that flesh will putrefy in the gut which can break down the gut wall and increase the risk for cancer of the colon in the future.

Don’t believe me?

Take a look at this meta-analysis of studies examining the link between colon cancer and red meat consumption. The evidence shows an increased risk for colon cancer and none of these studies look at a diet that is exclusively comprised of red meat. The carnivore diet is bad for your microbiome, increases the risk of intestinal permeability and of colon cancer specifically.

Still don’t believe me?

This NPR Article does a nice job summarizing the findings of a study that appeared in the Journal Nature which looked at the short term impact on the microbiome of a meat heavy diet vs. a diet that included much more plant fiber. The meat heavy diet was very similar to the carnivore diet and it altered the microbiome for the worse in just two days. In particular, bacterial species that feed on bile, called Bilophila, started to colonize the guts of the group on the carnivore diet. Bilophila bacteria, like Candida, aren’t necessarily “bad.” However, when they take over the gut as they are prone to do on extreme diets, that’s where problems can begin. Studies have linked Bilophila to colitis in mice. (R)

Carnivore diet and heart health

This is one that we get into in more detail in our custom nutrition plan product, and I won’t try to definitively cover saturated fat metabolism in one section of this blog post, but I will say this: saturated fat increases LDL-C, and LDL-C is one component of the LDL-P number, which is the biggest predictor of heart disease. In addition, for APOE4 carriers, it’s likely the carnivore diet would increase their risk for Alzheimer’s disease as APOE4 genotypes do a poor job with saturated fat in particular.

Now, to be fair, I am not necessarily demonizing saturated fat across the board. We have written previous about how the consensus has shifted on dietary cholesterol, which is now believed to be less of a problem than previously thought, but saturated fat and cholesterol are two different things. With a constant daily mega-dose of saturated fat, many people will significantly increase their risk for heart disease on a carnivore diet, with carriers of risk alleles for the SNPs I list below being at increased risk.

SNP IDGene(s) of interest within or near associated intervalMajor allele, Minor allele (Risk)
C, T
C, T
G, T
C, T
C, A
C, G
G, T
C, T
T, C
T, C

Alternatives to the carnivore diet

While it’s clear that I am no fan of the carnivore diet, I am also sympathetic to the fact that an increasing number of Americans are developing food sensitivities. I have written previous about my own issues with histamine intolerance. If you feel better on a carnivore diet, you’re not imagining it. You’ve cut something out of your diet that your body was reacting to, and the absence of that irritant has improved your health in the short term.

However, this doesn’t mean that a carnivore diet is the only way you can be healthy.

One of the striking admissions Mikhaila Peterson made in her Joe Rogan appearance was an unwillingness to try a basic elimination diet put together by a nutritionist because “it didn’t make any sense to her.” For example, she couldn’t see any reason why someone would avoid almonds, but not other nuts. But just because avoiding almonds doesn’t make sense to someone like Mikhaila Peterson doesn’t mean it wouldn’t be a good idea for you. One person may react to the histidine in almonds, another the glutamic acid, you never know. Some eat kale by the truckload, others can’t handle the high levels of oxalic acid. Elimination diets formulated by professionals are the best way to identify problem foods, and you may find there are lots of foods that cause issues.

But before “throwing in the towel,” and going on a carnivore diet, a more traditional elimination diet is worth a shot. By isolating foods that most commonly cause problems one by one, you can get to the bottom of your sensitivities without being forced to take the extreme measure of eating nothing but meat everyday.

Dr. Gundry, of Plant Paradox fame, created a rigorous elimination diet protocol aimed at first reshaping the microbiome and then eliminating all high lectin and otherwise toxic foods. I have spoken to more than a few friends who have seen great results on Dr. Gundry’s protocols, and even wrote a blog post defending lectin sensitivity and the Plant Paradox book.

If you want to explore Gundry’s protocols further, his approved shopping list and list of foods to be avoided can be found here.

If you’re suffering from multiple food sensitivities, it may also be worthwhile to give a fasting mimicking diet a try. Companies like Prolon have created kits that help people plan a fast according to the research of Dr. Valter Longo, a longevity researcher at the University of Southern California whose research on autoimmune disease I mentioned earlier in this post.

Have you tried the carnivore diet? We’d love to hear your experiences, especially if you tracked your labs, in the comments section.

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  1. Jerry German says:

    You make the point that there is almost no data on a carnivore diet, and then make all kinds of claims about the unhealthiness of the diet based on meat consumption levels in mixed diets. That’s not scientific. Plus, you don’t seem to have done any research on what constitutes a proper approach to a carnivore diet. Properly done, the diet contains about twice as many calories from fat as protein. The body is definitely in ketosis. If it wasn’t, there would be telltale evidence in floating stools. Properly done, the diet focuses on grass-fed, free-range meat which is high in omega 3s. It includes organ meats. It includes gelatin, which has no tryptophan and balances muscle meat in many ways. Making assumptions based on the health of mixed-diet individuals who eat higher or lower levels of lean muscle meat just brings nothing to the argument. Admittedly, many people who are trying the carnivore diet are doing it badly. I have been totally carnivore for 37 days. Before starting the diet I was waking to go bathroom 8 or more times per night. I am 68 years old and have been suffering from interstitial cystitis for 50 years and from BPH for about 10 years. I am now waking 2 or 3 times per night. I fall asleep more quickly and actually have dreams. I have more energy during the day and improved clarity of mind. My joint pains have subsided considerably.
    I am not promoting the diet. I think that would be premature and agree that a one-size-fits-all approach is not workable with most health issues. But I have a huge problem with your objections to the diet because you apparently view it as a daily feast on massive amounts of lean muscle meat. Certainly, there are people doing exactly that. But an intelligent approach is to look at the cultures that have been primarily meat eaters and to learn from them. I have been studying nutrition for a lot of years and the biggest problem I see is the sea of misinformation that discourages most people from taking an intelligent approach to trying new things. I have been vegetarian, high carb, paleo low carb, paleo medium carb, paleo low-fat, paleo high-fat. I have taken every stinking vitamin/herbal concoction on the planet and nothing has worked like this. I am currently taking no supplements other than fish oil and some occasional magnesium chloride (mostly topically). Thanks for reading my rant.

    • Jerry, thanks for the comment. I see your point, especially about the lack of “pure” data on an exclusively carnivore diet. Kind of a similar situation with the plant based crowd when they cite epidemiology that tracks lower consumption, but not zero consumption of animal protein, and then pass it off as evidence for a strict Vegan diet. I still think the carnivore diet is unhealthy for most people, with sitosterolemia as a possible exception, but I appreciate you reading and commenting.

      • Menko says:

        There is proper documentation of the health of people on a carnivore diet. The Masai traditionally lived off the meat and milk of their cattle and had extensive atherosclerosis, but no incidence of heart disease due to their active lifestyle. While I agree with him on your approach of the subject (you relied on omnivores to form a conclusion), I too would agree that it’s unhealthy. Balance is key.

    • Noah says:

      Hi Jerry,
      Do you know of any sources that outline in more detail how to do the carnivore diet ‘properly’? I have been trying the diet myself and noticing some major benefits, but also have been experiencing some difficulties getting enough fat relative to protein. Most sources I have found just say ‘just eat meat’, but as you say, just eating muscle meat can be very imbalanced

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