About three quarters of people with IBS can soothe symptoms with a low-FODMAP diet. FODMAPs are fermentable oligo-, di-, monosaccharides and polyols—fancy names for carbs that some people have a hard time digesting. Not only do those undigested carbohydrates draw in excess fluid, but bacteria ferment them in the large intestine, causing gas, bloating, diarrhea, and more. Unfortunately, “there’s really no way to tell what foods have a high level of FODMAPs by looking at them or even by thinking really hard about it,” writes Meltzer Warren, who includes a list in her book. Disaccharides are easy enough to avoid by cutting out lactose (though low-lactose hard cheeses like cheddar and Parmesan should be fine). Oligosaccharides include onions, garlic, wheat, and black beans. Monosaccharides are a problem when a food has more fructose than glucose, like in apples, asparagus, honey, and high-fructose corn syrup. Polyps are sugar alcohols in artificial sweeteners, along with natural foods such as mushrooms, cauliflower, and blackberries.
If you have celiac disease, a gluten-free diet is a must. When those with the autoimmune disease eat gluten, a protein found in some grains (including these surprising gluten sources), their bodies attack themselves. Even if you don’t test positively to celiac disease, you might have gluten intolerance. Still, give it a gluten-free diet a test run before committing. One small study in the journal Gastroenterology found that only 8 percent of people with self-reported gluten intolerance felt a change after adjusting how much gluten they ate—though they all felt better after going low-FODMAP. Find out what conditions you could mistake for gluten intolerance.