Why Do Mushrooms Make You Fart?

Pictured Recipe: Slow-Cooker Mushroom Soup with Sherry

You expect beans to do it. Maybe broccoli. Or, if you're lactose-intolerant, ice cream too. But mushrooms? For some people, they find the fungi gives them a serious case of flatulence.

What might be going on? And, do you have to totally avoid them now to stop the gas?

They're a FODMAP-containing food

Turns out, this is a legitimate side effect, as mushrooms are a FODMAP-containing food. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. "These are groups of foods that are easily fermented by bacteria naturally found in the large intestine. When foods are fermented in the gut, they can cause gas, bloating, abdominal pain and bowel changes, especially in people who are sensitive to these types of foods," explains Anna Binder-McAsey, RD, LD, owner of Rethink Nutrition in Manhattan, Kansas, who specializes in working with clients with gastrointestinal disorders.

FODMAPs are of particular concern if you have irritable bowel syndrome (IBS), which affects 1 in 7 adults, according to Monash University researchers. Avoiding or limiting certain FODMAP foods is one way to reduce GI symptoms.

That said, you don't have to have IBS to find that mushrooms make you fart. "Anyone can have a sensitivity or intolerance to almost any food, including mushrooms," says Binder-McAsey. But it's all individual. Even if you have IBS, mushrooms won't necessarily be on your avoid list because they can give some people discomfort while others can eat them free and clear. "Every human has a unique environment inside their gut that is shaped by the things they eat, their environment, stress, medications and a host of other things. The foods that work or don't work for someone's gut are unique to them," she says.

They may be high in mannitol

Guess what: Some of the more popular varieties of mushrooms have high levels of mannitol, which is a sugar alcohol from the polyol family that's found in many fruits and veggies, says Binder-McAsey. Who would have thought? Farting is a potential side effect, yes, but you may also notice diarrhea: "Mannitol, in particular, can pull water into the large intestine, causing looser stools," she says.

You're eating too many higher-FODMAP mushrooms

Pictured Recipe: Vegan Scallops

How mushrooms affect you can also depend on what type you're eating. Common varieties, like button, portobello, and shiitake, are on the list of higher-FODMAP foods that are more likely to trigger GI issues, explains Binder-McAsey. If you notice that you're farting a lot after mushroom eating, you have two options: Eat a smaller portion of mushrooms or switch to eating lower-FODMAP mushrooms, which include oyster mushrooms, she says. Canned mushrooms are also lower-FODMAP, according to testing from Monash University, making them a good substitute when cooking.

Maybe it's not actually mushrooms causing the flatulence?

Of course, there could be something else going on entirely. If you're clearing a room after a pizza topped with mushrooms, also consider that it could be something else in the pizza, like the cheese, that your GI system is having a tough time with. To find out if mushrooms are truly the culprit, Binder-McAsey recommends avoiding them completely for a few weeks. Then, slowly incorporate them back into your diet (try cooked first and then raw, as cooked may be gentler on digestion) and check in with yourself about how you're feeling.

Flatulence can also vary depending on what other foods you ate that day and how much, adds Binder-McAsey. For instance, a stir-fry with loads of mushrooms, broccoli and cabbage might trigger gas more than a sprinkling of a few sliced 'shrooms atop a salad.

The bottom line

Ultimately, mushrooms, like most higher-FODMAP foods, are healthy and keep your gut healthy too, says Binder-McAsey. Benefits of mushrooms may include lowering cholesterol, strengthening the immune system and fighting cancer and they provide important prebiotics that improve gut health, points out a research review in the International Journal of Molecular Sciences. (Prebiotics are the food for probiotics.) If you like mushrooms and you can eat them without problem, then you should include them in your diet. If they give you gas, then it may be worth it to figure out if there are ways you can comfortably eat them to snatch up their benefits—and feel good, too.