A low-carb diet may help IBS as much as tricky elimination diets, and more than drugs

Dietary changes relieved abdominal pain and other symptoms of irritable bowel syndrome more effectively than medications, a new study shows.

Seven out of 10 study participants reported significant reductions in IBS symptoms after adopting either a type of elimination diet called the FODMAP diet or the simpler-to-follow, low-carb diet.

“Diet turned out to be more effective than medical treatment,” said dietician Sanna Nybacka, the study’s lead author and a postdoctoral researcher at the University of Gothenburg in Sweden. “It’s probably more cost effective to provide foods and guidance on how to eat to people than giving them a lot of very expensive medications.”

Moreover, the diet need not be complicated, according to the study published last month in The Lancet Gastroenterology and Hepatology. A low-carbohydrate diet provided nearly as much symptom relief as traditional IBS dietary advice, which limits a group of short-chain carbohydrates known as FODMAPs, found in many common foods including dairy, legumes, onions and garlic and grains.

An estimated 6% of Americans, the majority of them women, suffer from IBS. Symptoms include abdominal pain coupled with diarrhea or constipation or both and no visible signs of disease in the digestive tract. Chronic stress can trigger symptoms.

Researchers randomly divided 294 Swedish adults, mostly women, with moderate to severe IBS symptoms into three groups. One group received traditional IBS dietary advice — including eating regular meals, limiting consumption of coffee, alcohol and soda — along with free home-delivered groceries and recipes for a diet low in FODMAPs, an acronym for fermentable oligosaccharides, disaccharides, monosaccharides and polyols.

A second group received free home-delivered groceries and recipes for a diet low in carbohydrates. A third group received free optimized pharmaceutical treatment.

After four weeks, participants in both the diet groups reported significantly reduced symptoms — a 76% reduction with the low FODMAP diet and a 71% reduction with the low-carbohydrate diet. The medication group reported a 58% reduction in symptoms.

Two weeks after the study began, one participant, a woman in her 50s on the FODMAP diet, cried as she described the relief from abdominal pain she felt for the first time in her adult life, Nybacka told NPR.

Others in both dietary groups also said they felt better than they had for as long as they could remember, she said.

In addition to IBS symptom relief, participants in all three groups reported less anxiety and depression and an improved quality of life.

After six months, study participants had resumed some of their previous eating habits, but a majority continued to report fewer IBS symptoms.

Researchers were surprised that the low-carbohydrate diet worked as well as it did, Nybacka said. They added the diet to the study after patients who had tried it in an effort to lose weight or control diabetes told them it had reduced their IBS symptoms. A low-carbohydrate diet is easier to follow than a more complicated and restrictive FODMAP diet.

Dr. Lin Chang, a gastroenterologist and a professor of medicine at the University of California, Los Angeles, said the study supports the long-term benefits of diet in treating IBS. And the study informed her that a low-carb diet, high in protein and fat, could reduce IBS symptoms. “That was new,” she said.

But she believes the study might have biased diet over medicine. “It wasn’t completely a fair comparison,” said Chang, who wasn’t involved with the study.

Patients often need to be on medications for longer than four weeks, the length of the study, to see benefits, Chang said. In addition, American doctors prescribe IBS medications that are unavailable in Sweden, she said.

“Medications are still effective,” she said in a Zoom interview. “And I wouldn’t necessarily say that this study to me proved definitively that diet was better or more effective than medication.”

Nybacka agreed that a few additional weeks on some of the prescribed medications might have allowed them to reach their full potential. “But we cannot ignore the fact that the dietary treatment led to a twice as large symptom reduction in just four weeks,” she wrote in an email.

Chang also noted that behavioral therapies, such as cognitive-behavioral therapy, which the new research did not study, can reduce IBS symptoms. Some doctors are now prescribing apps that offer mind-body support.

Diets are not for everyone, Chang added. She would not put a patient with disordered eating on an elimination diet, for example.

Following these diets without free grocery and recipe deliveries could be challenging but Chang pointed to meal-services companies, including one in which she owns stock. ModifyHealth delivers prepared meals designed for people to comply with dietary restrictions. Unlike in the Swedish study, enrollees pay for the food.

Ronnie Cohen is a San Francisco Bay Area journalist focused on health and social justice issues.