ABOVE: WIKIMEDIA, NATIONAL CANCER INSTITUTE

Going on a low-gluten diet moderately alters the composition of bacterial species in the human gut, according to the results of a randomized controlled trial published today (November 13) in Nature Communications. The results suggest that some of the positive effects associated with a low-gluten diet, such as reduced bloating after meals, may be the result of diet-induced changes in the intestinal microbiome.

To study the effect of a low-gluten diet, researchers in Denmark recruited 60 middle-aged, healthy adults. Participants followed a specialized diet for eight weeks—either low gluten (2 g per day) or high gluten (12 g per day). Then, after a six week break, they switched.

An analysis of the participants’ microbiome composition revealed that, of hundreds of bacterial species identified across the cohort, 14 consistently experienced changes in relative abundance in response to a low-gluten diet. For example, four species of Bifidobacterium, ubiquitous in mammals, regularly diminished, while one unidentified species in the Clostridiales order increased in abundance.

The researchers didn’t observe any differences in participants’ blood cell counts, nor in markers of intestinal permeability. However, a low-gluten diet did lead to improvements in self-reported bloating.

The authors note that, just like the general population tends to do, people following a low-gluten diet in the trial replaced cereal products with other sources of dietary fiber. So the results might not be attributable to gluten per se.

“The changes in colonic microbial composition and fermentation suggest that the effects of a low-gluten diet in healthy middle-aged adults may to some extent be driven by qualitative changes in dietary fibers upon reduction of gluten-rich food items rather than by the reduction of gluten intake itself,” the authors write.