Allan S. Brett, MD and Douglas K. Rex, MD, reviewing
In a randomized trial, IBS symptoms improved with a diet low in these short-chain carbohydrates.
The idea that dietary constituents called FODMAPs (Fermentable, Oligo-, Di-, Monosaccharides, And Polyols) might be responsible for some cases of irritable bowel syndrome (IBS) is gaining traction. FODMAPs are poorly absorbed, short-chain carbohydrates that include fructose, lactose, fructans (found in wheat), galactans, and polyol sweeteners.
In this randomized, crossover trial from Australia, 30 patients who met IBS criteria and 8 healthy controls consumed either a low-FODMAP diet (prepared by the researchers) or a “typical Australian diet” for 3 weeks, followed by the opposite diet for another 3 weeks; the two diet periods were separated by a 3-week washout. Patients were blinded to diet constituents.
At baseline, the mean symptom score for IBS patients was 36 (on a 100-point scale); mean scores declined to 23 during the low-FODMAP period and increased to 45 during the typical-diet period — a highly significant difference (P<0.001). Regardless of IBS subtype, patients were more satisfied with stool consistency during the low FODMAP diet. In controls, symptom scores were low at baseline and did not change during either diet period.
Citations
Halmos EP et al. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology 2014 Jan; 146:67. (http://dx.doi.org/10.1053/j.gastro.2013.09.046)
Comment
This is the first randomized trial to provide high-quality evidence that FODMAPs contribute to irritable bowel symptoms. One potential confounding dietary constituent is gluten, because a low-FODMAP diet (which eliminates wheat, rye, and barley because of their fructan content) is also low in gluten; however, in a recent study by the same research group, FODMAPs — and not gluten — likely were responsible for gastrointestinal symptoms in nonceliac patients with perceived gluten sensitivity (NEJM JW Gen Med Sep 19 2013). Information on low-FODMAP diets is available from this research team's institution and from other sources (e.g., Stanford University). Clinicians should consider recommending a low-FODMAP diet to IBS patients with abdominal bloating, flatus, and diarrhea.