Watermelon: The FODMAP That Often Worsens IBS

"Watermelon, watermelon, on the vine, on the vine, Sweet and red and juicy, Sweet and red and juicy, Please be mine, please be mine…" The popular preschool singalong aside, if you have irritable bowel syndrome (IBS), this juicy fruit may rev up symptoms like gas, pain, diarrhea or constipation.

What's the reason? Watermelon is high in FODMAPs, explains William J. Bulsiewicz, MD, a gastroenterologist in Mount Pleasant, S.C. and author of Fiber Fueled. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols — specific types of carbohydrates. More specifically, oligosaccharides include fructans and galacto-oligosaccharides (GOS), disaccharides contain lactose like that in milk and dairy products, monosaccharides contain fructose and polyols include sorbitol and mannitol, according to the International Foundation for Gastrointestinal Disorders.

These particular carbs can be poorly absorbed in the intestines, Dr. Bulsiewicz says. When this occurs, they feed bad bacteria in your gut and can cause the IBS symptoms that erode quality of life, like gas and abdominal pain. And, he says, watermelon is a triple threat because it is high in fructans, fructose and polyols, namely mannitol. "If you have a damaged gut, you may struggle in your ability to digest and process FODMAPs like watermelon and, as a result, you can have symptoms when your gut encounters an excessive load all at once," he says.

That's a hard fact to swallow since watermelon is not only delicious, but it's also loaded with vitamin C and lycopene and has one of the highest water contents of any food, according to the Academy of Nutrition and Dietetics. But do you have to avoid watermelon at all costs if you have IBS? Not necessarily.

"For each individual person, there is a threshold of how much you can eat," Dr. Bulsiewicz says. "Some people can eat a whole watermelon and feel fine, and some can't even eat a slice." It may take some trial and error to see where you fall, he suggests.

Read more: Side Effects of Eating Too Much Watermelon

It's also important to know that watermelon isn't the only fruit that is high in FODMAPs. Others include apples, pears, peaches, cherries and mangoes, according to Harvard Health Publishing. You may need to steer clear of them. Alternatives include blueberries, as well as boysenberries, cantaloupe, cranberries, grapes, oranges, lemons, limes, kiwi and strawberries, which are very low in FODMAPs, according to the Cleveland Clinic. As for bananas, the advice is mixed: when ripe, the fruit is high in FODMAPs, while unripe bananas fall into the low-FODMAP category, according to Monash University, developers of the low-FODMAP diet.

Unfortunately, many healthful vegetables are high in FODMAPs, too, namely broccoli, cauliflower, cabbage, asparagus and onions, the Cleveland Clinics notes. Better vegetables if you have IBS are eggplant, green beans, celery, carrots, spinach, sweet potato, yams, zucchini and squash.

If you have IBS, a low-FODMAP diet may make sense, Dr. Bulsiewicz says. This does not mean you can never eat foods that are high in FODMAPs. Rather, talk to your doctor or a registered dietician about how to safely try this diet. In general, you're likely to start off by eliminating all FODMAPs from your diet and then adding them back in slowly as you track your symptoms in a diary to see which foods are your greatest offenders, Dr. Bulsiewicz explains.

Read more: How the Low-FODMAP Diet for IBS Works, and How to Get Started

There is some evidence that a low-FODMAP diet can reduce IBS symptoms and even improve quality of life, which is known to be diminished in people with IBS. In an April 2016 study published in Gastroenterology, more than 50 percent of the people on the low-FODMAP diet showed major improvements in their abdominal pain, compared with 20 percent of those not following the diet.

There was also greater improvement of other IBS symptoms, like bloating, diarrhea and stool urgency, among those on the low-FODMAP eating plan. After four weeks, study participants with IBS who followed the low-FODMAP diet reported greater improvements in quality of life, anxiety and their ability to participate in daily activities compared with their counterparts who did not restrict FODMAPs.