7 Reasons I Don’t Recommend the Carnivore Diet as a Dietitian

Article at a Glance

• Ultra low-carb carnivore diets can be harmful
• Many of the biggest advocates of carnivore diets, like Dr. Paul Saladino, have stopped the diet and started incorporating some plant foods
• There are no credible research studies supporting an all-meat diet
• Carnivore diets can increase cholesterol to unhealthy levels and damage the microbiome

Genes Mentioned

• CPS1
• LDLR
• VDR

There are universal, overarching principles of healthy eating that almost all of us can live by. Avoid refined grains and sugar. Don’t eat trans fats. Stick to a gluten-free diet if you are diagnosed with celiac disease or a wheat sensitivity.

And last, don’t overdo it with animal protein.

But what does it mean to “overdo it” with animal protein? Clearly, we all have different requirements, but a good rule of thumb is to eat no more animal protein than needed to maintain muscle mass.

Advocates of the carnivore diet, which is an all meat and eggs diet that excludes all plant foods, cast this logic aside and instead love to list the toxins found in plants. Oxalates! Phytic acid! Lectin! Glyphosate!

And yes, some of us are sensitive to certain species of plants, and when we are, we should avoid eating them. Dietitians often recommend excluding some plant foods when they place clients on Low FODMAP diets. However, as we will learn in this post, the idea that all plants are unhealthy is demonstrably false and meat does not come free of its own toxic burden, especially when eaten to excess.

The carnivore diet offers little consumption guidelines for participants other than favoring animal products in the diet. With no margins for the diet, it goes without saying that the diet likely is not as healthy as it is posed. 

Let’s list the reasons why.

#1. Carnivore diets increase LDL and heart disease risk

One of the unfortunate messages spread by many low carb communities is that LDL isn’t causal in heart disease. This advice flies directly in the face of the best research and position papers from organizations like the European Atherosclerosis Society, which takes the exact opposite position.

Although the role of sugar in contributing to heart disease has been downplayed for years, and dietary fat has gotten a bad rap, eating saturated fat raises LDL in all people, the only issue is by how much. In many people on an all meat, very high saturated fat diet, a carnivore protocol will raise LDL to unhealthy levels.

And despite what you may have heard at your recent low carb conference, elevated LDL (and really APOB) contributes to both cardiovascular and all-cause mortality risk.

Consider this massive study which appeared in JAMA: after reviewing 34 clinical trials looking at more than 270,000 patients, more aggressive lowering of LDL-C was found to reduce risk of all cause mortality (not just heart disease deaths) when compared to less aggressive treatment.

BUT the all-cause mortality risk reduction was only found when LDL-C started at >100 mg/dl. Greatest benefit was found for those who started at >160 mg/dl and dropped aggressively. In other words, people with what would be considered pretty “bad” lipid profiles by most people had the most to gain by lowering LDL-C.

Perhaps the goal of 50 mg/dl LDL-C is not necessary, but I don’t think the low carb crowd headed to bed each night with an LDL-P count of 2,000 should sleep all that soundly either.

#2. Carnivore diet may turn on cancer pathways

Scientists have studied the in vitro impact of various fruit compounds on liver cancer cells. Many of them significantly inhibit the growth of the cancer cells.

Amino acids are the building blocks of proteins. But not all amino acids are created equal. 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.

Researchers like Valter Longo at USC have published extensive 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 health span.

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, then consuming animal protein exclusively makes very little sense. But it is not just Dr. Longo who has published data on meat consumption, amino acid balance and cancer. Aaron, our team’s head of research and geneticist, dug up this study which links an excess of animal protein to cancer: Leucine (amino acid typically found in meats) induces resistant breast cancer. 7

No one is  that eating meat equals cancer all the time. More so,  eating nothing but meat for years can potentially increase the cancer risk for some people.

But even this study, which casts doubt on the link between eating red meat and colon cancer, offers as its explanation a diet that is abnormally high in meat and lacking in plant compounds as the reason for what it sees as an overstated link between colon cancer and red meat consumption.

To quote the study:

Experiments where protective dietary compounds were used to mitigate the extreme levels of meat and meat-derived compounds showed protection against colon cancer, with some essentially negating the impact of meat in the diet.

 Can you guess what those protective compounds are?  (Vitamin A, chlorophyll and resistant dietary starches).

Same result for this bladder cancer and meat study. These studies indicate that cancer risk may be mitigated by meat plus fiber intake. Ironically, carnivores eschew even leafy greens, which precludes the possibility of gaining the protective advantage of plant compounds described in several studies.

#3. Carnivore diets are not always ketogenic

Regardless of what you may think about the health benefits of ketosis, the subject isn’t always relevant to the carnivore diet.

The carnivore diet often 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 through a process known as Gluconeogenesis, where protein is converted by the body into glucose.8

The process of Gluconeogenesis is what prevents many carnivore dieters from reaping the benefits of ketosis.

#4. 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. Children born with reduced urea cycle function end up very sick with ammonia toxicity.9

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 [very low carb diets].

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 an inevitable waste product of protein metabolism. 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.

#5. 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 eaten on the carnivore diet 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.

#6. Carnivore diet and gut health

The carnivore diet could damage the colon and degrade gut health. In fact, changes to the microbiome eating nothing but meat could colonize the gut with bacteria that increase the risk for heart disease. Animal protein is high in L-Carnitine, a type of amino acid. The New England Journal of Medicine has published a study which demonstrates certain strains of bacteria turn carnitine, as well as choline in eggs, into TMAO, a compound that has been shown to damage the arteries. Not everyone who eats meat will have high TMAO levels, however, an unhealthy microbiome combined with a constant supply of red meat at every meal,could result in the perfect storm for TMAO to get out of hand.

There are many sound reasons to eat fiber, with one of the most important being the impact fiber rich foods can 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 lines and protects the gut wall while also providing the body energy. By removing all fiber from the diet and eating only meat, you increase the likelihood 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 the science?

The study above from Texas A&M,  was designed to push back on the link between red meat and colon cancer, but their reason for doing so was that plant foods consumed with meat are protective.

There is also a meta-analysis 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 composed of red meat. The carnivore diet is potentially bad for the microbiome, increases the risk of intestinal permeability, and may increase colon cancer risk.

The mechanism seems to be undigested meat, which then ferments in the colon, leading to increased ammonia production and strains of bacteria that produce histamine.13

This NPR Article does a nice job summarizing the findings of a study that appeared in the Journal Nature.  The study 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 following  carnivore diet protocol. 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. 14

See also: Can undigested protein contribute to leaky gut?

#7. Carnivore diet and gout

As  mentioned in a recent post from Gene Food  on lowering uric acid, many leading physicians now seem to believe that gout is a condition marked by an excess of sugar, alcohol, and most recently, meat in the diet. 

Vegans often have high uric acid, so this isn’t exclusively a carnivore issue. 15

However, beef, shellfish, and poultry are all high in purine, a crystal-like compound in food that creates uric acid when it’s broken down in the  body. A diet very high in purine can lead to gout and kidney stones as levels of uric acid accumulate to unhealthy levels. Further, elevated uric acid is also one of the primary causes of joint pain. The condition, known as “gouty arthritis,” is marked by the formation of crystal compounds in joints, commonly causing  pain in the big toes, feet and elbows.

Alternatives to the carnivore diet

 Food sensitivities are growing at a rapid rate in America, and dietary changes can be the key to feeling better. If you feel better on a carnivore diet, you’re probably not imagining it. You’ve cut something out of your diet your body didn’t like, 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. It also doesn’t mean the carnivore diet won’t take a year, two, or even ten to do some bad things to your health.

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 food sensitivities without being forced to take the extreme measure of eating nothing but meat everyday.

Traditional elimination diet

Many people arrive at the carnivore diet after experiencing years of digestive distress, or even suffering from a diagnosed condition like Crohn’s disease. They have an idea that food can be a trigger, but are often confused as to which foods are the culprit.

A traditional elimination diet, where common allergens like corn, wheat, soy, and dairy are strictly removed from the diet and then reintroduced one at a time, could be helpful. Dr. Will Cole offers a traditional elimination diet course at the Mind Body Green website. I’ve also benefited from the elimination diet outlined in the book Clean by Dr. Alejandro Junger.

Fasting mimicking diets

If you’re suffering from multiple food sensitivities, and are looking for a protocol backed by an abundance of clinical research, it may be worthwhile to explore the fasting mimicking diet. 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, cancer, and longevity is extensive and well respected.

Key takeaways

A plant forward diet is a healthy option for a lot of people, but it may not be sustainable for everyone. This does not mean turning to the other extreme is beneficial either.

However, this doesn’t mean that we can throw the baby out with the bath water.

Plant based science is imperfect but voluminous.

Carnivore literature is few and far between. 

The research challenging the role of red meat as a cancer causing agent does so because of evidence indicating that eating meat alongside chlorophyll rich plants has a protective effect.

Cut out or reduce gluten intake. Stop eating grains or focus 100% whole grain foods. No or limited sugar. Heck, remove lectins. Drill down on food sensitivities.

Just don’t go carnivore. Not unless you are 100% sure this is an intervention you need to maintain good health and have discussed it with a medical professional.