How The Keto Diet Affects Your Gut Health

Switching to a keto diet — a diet that cuts carbohydrates almost entirely while prioritizing eating more fat — doesn't just affect what your body burns for fuel, it will impact your gut health as well. This doesn't mean a keto diet is bad, but if you're considering switching to one, you should understand how it may change your gut bacteria, which can change your digestion, metabolism, and even immune system.

A small study done on mice and people published in 2020 in the journal Cell, found that a keto diet may actually boost your immune system by helping your body fight inflammation, thanks to the drop in levels of a certain infection-fighting cell. However, even the study's authors were quick to note that the small sample size used for the study meant that more research was needed. And study reviewer Lona Sandon, Ph.D., RDN, LD, an assistant professor of clinical nutrition, told WebMD that there is more research that counters those findings and suggests "high fat/high protein diets are detrimental to the microbiome and increase inflammation."

In short, researchers know that a keto diet does impact the gut's microbiome, but they're not entirely sure how—or what the longterm impacts are.

"When you restrict the diversity within your diet, you are also restricting the diversity of your gut microbiome, which causes disease," Will Bulsiewicz, M.D., a board-certified physician in both internal medicine and gastroenterology, explained to Eating Well. Going on a keto diet typically means cutting out even the good, fiber-packed carbohydrates found in vegetables and fruit—and those are key to having a healthy, diverse gut microbiome. But if you can continue to keep fibrous fruits and vegetables in your diet—eating a plant-heavy version of keto, with lots of leafy greens and fat-friendly options like avocados—the fiber and diversity of plants in your diet may keep your gut bacteria flourishing.

The keto diet has been touted as a way to improve digestion and even decrease symptoms of irritable bowel syndrome (IBS), but at the same time, doctors like Bulsiewicz argue that a keto diet could just as easily be the cause of IBS (via Healthline and Eating Well). A person's gut microbiome is so highly individualized that it's nearly impossible to say what diet will work best for any one person, so in this case, if you are interested in trying the keto diet, pay close attention to how your gut and digestion are feeling. And it's always a good idea to have your healthcare provider weigh in, too.