SAN DIEGO – For patients with diarrhea-predominant irritable bowel syndrome, avoiding FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) improved abdominal pain and bloating significantly more than following standard advice to eat smaller meals and limit caffeine and alcohol, researchers reported.
“Both diets provided adequate relief to about 40%-50% of patients, but the low-FODMAP diet led to significantly greater improvements in abdominal symptoms,” Dr. Shanti L. Eswaran of the University of Michigan, Ann Arbor, said at the annual Digestive Disease Week. Results from the randomized, controlled trial, the first of its kind in the United States, “support a role for the low-FODMAP diet in the treatment of patients with diarrhea-predominant IBS,” she added.
FODMAPs are poorly absorbed or indigestible fermentable carbohydrates that can cause bloating, flatulence, and diarrhea when eaten in excess. Hence, the low-FODMAP diet involves avoiding or limiting foods high in fructose (such as honey and dried fruit), lactose (dairy), fructans (wheat, garlic, and onions), galactans (legumes), and polyols (apples and stone fruits). Several smaller studies have linked a low-FODMAP diet to improvements in IBS, “but the existing data are limited and inconsistent, and there is no randomized, controlled trial data from adults in the United States,” Dr. Eswaran said.
To fill that gap, she and her associates randomly assigned 92 adults meeting Rome III criteria for diarrhea-predominant IBS to follow either a low-FODMAP diet or a control diet that was based on recommendations from the National Institute for Health Care and Excellence (NICE, in the United Kingdom). The modified NICE diet included eating smaller, more frequent meals, limiting caffeine and alcohol, and avoiding foods that patients knew worsened their symptoms. Both groups of patients worked with a dietitian.
At baseline, all patients reported having regular bouts of at least moderate abdominal pain and stool consistency of 5 or higher (that is, looser) on the Bristol Stool Form Scale. In all, 52% of patients on the low-FODMAP diet and 41% of patients on the control diet reported adequate symptom relief during at least one of the last 2 weeks of the study – a statistically similar level of improvement, Dr. Eswaran said. “We were really underpowered for our primary endpoint,” she added. “We had calculated a 30% difference, and we did not get anywhere near that.” In fact, enrollment in the trial ended early because many patients were already putting themselves on the low-FODMAP diet, she added.
But despite its limited power, the study uncovered significant differences in abdominal symptoms with the two diets. More than half of patients on the low-FODMAP diet reported a clinically meaningful improvement in abdominal pain, compared with only 23% of patients on the control diet (P = .008). Likewise, 52% of patients reported clinically meaningful improvement in bloating, compared with about a quarter of patients on the control diet (P = .013). Low-FODMAP patients also were more likely to report improvements in stool consistency (42%, versus 28% for control patients; P = .18). However, there was no evidence that the low-FODMAP diet improved stool consistency or urgency, Dr. Eswaran said.
“Both diets were safe and well tolerated, although dropouts were more common with the low-FODMAP diet,” the researchers noted. Dietary analyses showed that at 4 weeks, the low-FODMAP group was consuming significantly less total carbohydrates, but similar quantities of total calories, protein, fat, dietary fiber, and alcohol as the control group. “The low-FODMAP diet is not designed to be long term, because it is fairly restrictive,” Dr. Eswaran commented. “I think it would be a good idea for the next set of studies to see how long patients can stay on it, and what factors are necessary for them to do so.”
Dr. Eswaran had no disclosures.