Abdominal pain, bloating, gas, and constipation are just a few of the sometimes debilitating symptoms that come along with irritable bowel syndrome (IBS). This gastrointestinal condition affects 10 to 15 percent of American adults and research suggests cases are on the rise.

One reason for the rapid increase in IBS: our modern diet, specifically an increase in consumption of high-fat foods, convenience items, and added sugar, says New York-based dietitian Emily Tills, R.D.N. “High-fat and sugar-laden products can alter the way we digest and process food, as fat slows down digestion while sugar can cause gastric dumping in those more sensitive to it,” she explains. “The increase in consumption of processed foods also has a negative effect on our digestion because they are essentially foreign substances.”

While these highly-processed foods can definitely contribute to symptoms of IBS, they’re not the only offenders. In fact, there are a number of whole, healthy foods that can actually spell trouble for those with irritable systems. Here, experts break down some healthy foods people with IBS might want to avoid—plus which can do their systems a solid.

• ABOUT OUR EXPERTS: Emily Tills, R.D.N., is a dietitian based in New York City. Jenna Volpe, R.D.N., L.D., C.L.T., is a functional dietitian. Johna Burdeos, R.D., is a registered dietitian. Andrea Kirkland, M.S., R.D., is a registered dietitian and the owner and founder of Culinary Med Ed.

Best: Chicken

Whether you prefer it baked, grilled, rotisserie style, or air-fried, chicken is an excellent source of lean protein that people with IBS can enjoy with ease, notes functional dietitian Jenna Volpe, R.D.N., L.D., C.L.T. Since it’s leaner than many other popular protein sources (looking at you, marbled steak), it’s kinder to sensitive digestive systems. “Chicken is also free of sucrose, a type of carbohydrate that some people are sensitive to,” she notes. “Unless someone has a specific food allergy or sensitivity to chicken, I’ve never seen somebody with IBS have a negative reaction to chicken that was prepared without too much grease or spice.” 

Read More: 15 Signs That Something Is Off With Your Gut

If you suffer from IBS-D, a specific type of IBS that is often accompanied by diarrhea, Volpe suggests opting for softer pulled chicken (like rotisserie) or chicken that’s slow-cooked on the stove, which may be less of a burden on your gut. 

Worst: Cruciferous veggies

Sad but true: A number of super-healthy foods that fall into a category known as the FODMAPS (which stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) are often the enemy of those with IBS. Why? These foods contain “short-chain carbohydrates that are poorly absorbed in the small intestine and prone to absorb water and ferment in the colon, causing symptoms like abdominal discomfort, bloating, and gas,” explains registered dietitian, Johna Burdeos, R.D. “Many nutrient-rich foods like fruits, vegetables, and dairy products contain FODMAPs.”

Some of the most well-known are broccoli and other cruciferous vegetables, like cauliflower and Brussels sprouts, which are high in concentrations of an indigestible sugar called raffinose, explains dietitian Andrea Kirkland, M.S., R.D., owner and founder of Culinary Med Ed. “Raffinose is made up of glucose, galactose, and fructose, and belongs to the oligosaccharide family,” she says. “Because raffinose is fermented by bacteria in the large intestine, it’s commonly a culprit of gas and bloating.”

If you have a sensitive system, stick to green veggie alternatives that don’t cause the same bloating like bell peppers, green beans, and zucchini.  

Best: Sweet potatoes

In addition to being low in FODMAPs, sweet potatoes are chock-full of nutrients like vitamins A and C. They are also rich in soluble fiber, which absorbs water and helps keep your digestive system flowing.  Research published in Scientific Reports has also shown that sweet potatoes can help promote the health of good gut bacteria, specifically Bifidobacterium and Lactobacillus species, in the gut. Certainly good news for those who need some digestive TLC!

Read More: The Best Supplements To Try If You’re Prone To Bloating

“Sweet potatoes are very versatile in that they can be incorporated into breakfasts, lunches, dinners, snacks, and even desserts,” says Volpe. “They can be roasted and added to fall salads, or mashed with some cinnamon and enjoyed with a drizzle of real maple syrup.”

Worst: Beans

Whether it’s pinto, black, white, or kidney, beans aren’t usually very well tolerated by most people with IBS when consumed in quantities greater than a few spoonfuls, according to Volpe. “Beans are very high in oligosaccharides (the ‘O’ in FODMAP), so they are likely to make people feel gassier and more bloated,” she says.

She recommends those with irritable bowel issues opt out of beans entirely. Try swapping them for rice and veggies to skip out on the unwanted aftermath of gas and bloating.

Best: Green beans

Although they’re called “beans,” green beans are not considered part of the same veggie subgroup as other beans, peas, and lentils, per the U.S. Department of Agriculture (USDA). What’s more: Unlike certain vegetables—like Brussels sprouts, broccoli, and cabbage—that worsen IBS symptoms thanks to gas- and bloat-inducing sulfur, green beans are naturally low in sucrose as well as sulfur. “Green beans are generally very well tolerated by most people with IBS, unless they have an allergy or sensitivity to green beans,” Volpe says. 

She recommends enjoying green beans canned, roasted, or freshly steamed with some olive oil, salt, and pepper. You can snack on them or prepare them as a side dish with an IBS-friendly protein like chicken. They also go well in recipes like Shepherd’s pie or as part of an IBS-friendly barbeque meal.

Worst: Cow’s milk

Even if you don’t consider yourself “lactose intolerant,” you probably want to avoid cow’s milk if you have IBS, notes Volpe. “Just eight ounces of cow’s milk contains around 12 grams of natural sugar, which is 100 percent from lactose, a.k.a. ‘milk sugar,’” she explains. Lactose falls into that FODMAP category, meaning it’s likely to spell trouble for sensitive stomachs.

Luckily, there’s no shortage of milk alternatives, such as almond, soy, or oat milk. It’s also easy to find lactose-free milk (which is simply milk with the lactose taken out of it), notes Volpe. Hemp is another milk alternative that’s not only high in protein but also in omega-3 fatty acids, which may offer benefits for the gut. 

Best: Fermented foods

Fermented foods like kimchi, sauerkraut, and kombucha, as well as cultured dairy products like yogurt and kefir, help keep gut biomes diverse and help improve digestion, according to Kirkland. And thanks to that fermentation process, these foods are easier for those with stomach issues to tolerate, even when they contain dairy or veggies that may otherwise stir up trouble.

To get the most live bacteria from probiotic foods and reap maximum benefits, “do not purchase yogurt with added sugar or artificial sweeteners, which are linked to poor gut health,” Kirkland says. “Also, heat can destroy the beneficial bugs in kimchi and sauerkraut, so buy them in glass jars instead of canned (which are heated during processing).” If you’re going to cook with fermented foods, add them as close to the end as possible to preserve those good gut bugs.

Worst: Onions

Onions contribute a ton of flavor to pretty much anything you add them to, yet this popular everyday aromatic contains an unfortunate amount of fructose, a monosaccharide that’s been documented to worsen the side effects of IBS. 

Because onions are difficult to digest (especially for those living with an intolerance to fructose who lack an important enzyme called aldolase B), it’s best to avoid them if you’re prone to IBS, advises Kirkland. Good aromatic substitutes for onions that won’t exacerbate IBS symptoms include celery, chives, carrots, and fennel.