A Common Yeast May Cause Trouble For Crohn’s Patients

Very high magnification micrograph of Crohn’s disease.
Very high magnification micrograph of Crohn’s disease.
Image: Wikimedia Commons

A fungal yeast found in cheese and other foods may wreak havoc in the guts of people with Crohn’s disease, according to new findings. In a study published Thursday, researchers have found evidence that Crohn’s patients are more likely to carry that yeast than people without the disease, and that this yeast is linked to the slow-healing gut wounds that patients tend to have. If valid, the findings could lead to new treatments and preventative measures for the chronic and painful condition.


Crohn’s is one of the most well-known versions of inflammatory bowel disease (IBD). There is no clear cause for IBD, but it’s suspected that genetics and a malfunctioning immune system play a large role. Patients experience a wide range of mostly gastrointestinal symptoms caused by chronic inflammation of the gut, which come and go as flare-ups of the disease. These include diarrhea, fever, intense cramps, and weight loss. Though there are medications that can manage symptoms, along with diets to help people avoid possible triggers of an episode, few sufferers experience sustained remission.

Researchers at the Cleveland Clinic and elsewhere have been studying Crohn’s for awhile now in hopes of finding something that could help explain how and why the gut becomes so damaged in these patients. Their new research, published in Science, points to one possible culprit: a fungus called Debaryomyces hansenii.

The scientists studied mice that were made to develop Crohn’s-like symptoms as well as biopsied samples of gut tissue from people diagnosed with Crohn’s. Across both groups, they found an abundance of D. hansenii around wounded or inflamed tissue, but not in samples taken from healthy people or in the uninflamed tissue of Crohn’s patients.

They found the fungi in all of the seven samples taken from a group of Crohn’s patients, for instance, but in only one of the 10 healthy controls used as comparison. They also found evidence that this yeast was directly connected to the slow healing of gut wounds in mice. And when they took samples of the fungi from a Crohn’s patient or diseased mice and gave it to a new group of healthy mice, the mice’s ability to heal gut wounds became worse. This effect was then reversed when mice were given antifungal treatment.

All the findings combined, the researchers say, fulfill Koch’s postulates, a criteria that scientists use for proving that a specific microbe is causing a specific set of symptoms. In other words, it suggests that D. hansenii isn’t just some harmless bystander found in the guts of these patients, but an active source of trouble. At this point, it’s not known how patients might be exposed to the fungi, or if foods rich in the yeast, like cheese, could be one source.


“We propose that D. hansenii inhibits repair of ulcers in the inner lining of the intestine in patients with Crohn’s disease,” study author Thaddeus Stappenbeck, chair of the Cleveland Clinic Lerner Research Institute’s Department of inflammation and Immunity, told Gizmodo in an email. “This feature is a hallmark of many Crohn’s patients with moderate to severe disease.”

Under their current theory, the fungal infection doesn’t cause Crohn’s disease itself, Stappenbeck added. Rather, it “perpetuates the disease that has already been initiated.”


The findings are still based on a small group of patients and animal research, so they shouldn’t be seen as definitive proof of the team’s theory. And even if they are right, Crohn’s and IBD in general will remain a complex illness with symptoms that can’t be explained entirely by a single microbe. In the mice they studied, for instance, the fungal overgrowth only happened after the mice were given antibiotics. Other research has pointed to antibiotics as a possible risk factor for Crohn’s, since they can disturb the delicate microscopic environment of our gut, called the gut microbiome.


If future research does continue to show a strong link between Crohn’s and D. hansenii, though, it could lead to important new treatments and strategies for managing the illness. “For patients with D. hansenii in their ulcers, we envision testing anti-fungal drugs,” Stappenbeck said. “We hope that this would also spur development of anti-fungals with fewer side effects.”

Another area of research could involve targeting how D. hansenii seems to cause gut inflammation in the body, through a protein called CC5 that’s produced by some immune cells. And since the yeast is commonly found in cheese and other processed food, it might be worthwhile for patients in general to avoid these foods, the researchers say. The team also plans to keep studying how the yeast interacts with the gut microbiome and immune systems of people with Crohn’s.


This article has been updated with comments from one of the study’s authors.

Born and raised in NYC, Ed covers public health, disease, and weird animal science for Gizmodo. He has previously reported for the Atlantic, Vice, Pacific Standard, and Undark Magazine.


Crohn’s is one of the most well-known versions of irritable bowel disease (IBD).

Common confusion - Crohn disease is a type of Inflammatory Bowel Disease (IBD). This is very different from the much more common Irritable Bowel Syndrome (IBS).