Does the Carnivore Diet Ruin Your Gut Microbiome?

You’ve heard the expression, “you are what you eat.” It’s been a guiding aphorism in the popular discourse on food's effect on the body - and a pretty good one at that. But researchers are increasingly concluding that we’re less what we eat, and more what the bacteria in our gut eat.

The microbiome - the community of organisms that live mainly in the lower bowel - has an outsized effect on our health, able to do things like lower cholesterol, reduce feelings of anxiety, and even reprogram our cells. 

Because it’s so essential, the question of how diet affects it naturally arises. There are growing noises that the carnivore diet could harm the human microbiome, but should we listen to them? Let’s take a look.

What is the carnivore diet?

The carnivore diet is predicated on the idea that humans thrive most when eating a diet entirely comprised of animal food. Those on the carnivore diet eat meat, milk, and eggs and eschew all other foods of plant origin, including beans, grains, fruits and vegetables. 

READ MORE: WHAT IS THE CARNIVORE DIET?

The carnivore diet is different from both the paleo and Atkins diets. The driving force behind the paleo diet is that people should eat foods that their paleolithic ancestors ate, including some green veggies and the occasional helping of nuts and seeds. The Atkins diet is similar, focusing on animal foods, but it allows people to derive fat calories from plants, such as oils. 

The carnivore diet has a similar driving force as the paleo diet in the sense that it tries to mimic the food eaten by ancestral communities. Followers of the former, however, are less accepting of the idea that early humans derived substantial calories from plants. Most energy, the thinking goes, came from meat and fish, so these should form the vast bulk of the diet. People, the reasoning goes, aren’t biologically adapted to consuming the majority of their calories in the form of starches so they should avoid them.

What is the gut microbiome?

The gut microbiome is the name that scientists give to the community of bacteria that live in the small intestine and colon. It comprises a vast number of different types of species of bacteria, each competing with the others to derive energy from indigestible elements of the food we eat. 

The microbiome appears to have extreme importance in the lives of most vertebrates: everything from people to lizards. Bacteria and their hosts live in a mutually beneficial relationship. Animal guts provide bacteria with food that they can eat, and in return, animals get beneficial fatty acids and comfortable stools.

Cows provide an excellent example of what's going on here. Cattle can’t digest the grass they eat directly. They haven't evolved the requisite mechanisms to do so themselves.

The cool thing, though, is that they don’t have to. Instead, they co-opt bacteria that live in their gut to do the job for them. These bacterial specialists break down the indigestible plant sugars in their fodder, churning out fatty acids that the cows can then absorb for energy. 

The colony of bacteria living in the stomach comes in a variety of flavors.  Researchers call these flavors an “enterotype.” Having a healthy enterotype means that a person has a community of bacteria living in their gut that affect their overall health positively. An unhealthy enterotype is the reverse - it negatively affects health. The accusation is that the carnivore diet leads to one of these harmful enterotypes, wrecking the health of the human host. But is it true?

Do you need a diverse gut microbiome if you don't eat plants? 

Different species of bacteria in the gut eat both plant and animal matter. If you preferentially eat one type of food more than another, the balance of species in the stomach will change. 

Carnivores, like lions, have dramatically different gut microbiomes than hippos. Lions need bacteria that breaks down indigestible elements in meat, while hippos need those that’ll help them break down grass and reeds. 

Evidence suggests that people who eat more plants, like vegans, have more diverse colonies of gut bacteria compared to their meat-eating counterparts. Those on the carnivore diet, like predatory animals, by contrast, don’t require the same range of gut bacteria to break down food residues. They no longer need all the specialists to attack starches and indigestible sugars in plant matter that regular people eat. The flesh of one animal is, at a chemical level, identical to that of another, so fewer species are required. 

While it might seem that having a diverse microbiome would be beneficial, there’s no reason ahead of time to assume that this is the case. Specialist bacteria that breakdown plant cells might have positive effects, but they could also be entirely negative. We just don’t know at this point.

Is it healthy in the long term?

Changing your gut microbiome is a significant undertaking that requires a wholesale change in the food you eat. Making changes around the edges of your diet is unlikely to impact the diversity of species in your gut substantially. Most colonies of bacteria can survive on meager amounts of the food that they prefer. 

Whether the enterotype that results from the carnivore diet is healthy or not isn’t known yet by science. The long-term studies haven’t yet been done. There is, however, enticing early evidence that suggests that a less diverse gut microbiome could be beneficial for health. 

Researchers at the Institue of Agrochemistry and Food Technology in Valencia, Spain, found evidence that the diversity of gut bacteria might negatively affect health. Their study reviewed numerous findings throughout the scientific literature that seem to indicate that gut microbiota changes correlate with mental health issues. The evidence is not conclusive, but cutting out plants could be a possible strategy for those who have mental health conditions. The researchers said that a greater understanding of the mechanisms of gut flora diversity was needed before conducting interventions in human subjects.

Wrapping up

Right now, we don’t know the long-term effects of adopting the carnivore diet on the human microbiome. There’s a conspicuous lack of research in the scientific literature. What we do know, however, is that many historical populations lived on something like the carnivore diet in the eons before the neolithic revolution. What’s more, we have shining examples today of people who are thriving on the carnivore diet without any of the issues that mainstream science might predict. 

There are hundreds of veteran carnivores like Shawn Baker, Amber O'Hearne, Jordan Peterson, and Mikayla Peterson who seem to be doing well but we need more research. When and where that research will come depends heavily on the carnivore diet gaining significant traction in the nutrition science community. At present, the mainstream view is that humanity would be best served eating something like the DASH or Meditteranean diet. While individual researchers are looking into the diet of groups like the Inuit and the Maasai who eat primarily animal products, it’s not the norm.

The connection between the carnivore diet and the microbiome appears strong. There’s compelling evidence that switching to an animal food-based diet swiftly alters the composition of bacteria living in the gut. Beyond that, however, there’s little research on its merits, other than the smattering of studies we discussed above. At the moment, the best “evidence” that we have for the effectiveness of the carnivore diet and its safety long-term are the self experimenters. So far, it seems like people like Amber O’Hearne, Jordan Peterson, and Mikayla Peterson are doing well. Whether they continue to do so will be of great interest to the community of people living on this diet.