Eating a low-gluten, high-fiber diet changes bacteria in the gut, decreases gastrointestinal discomfort such as bloating, and is linked to modest weight loss, according to new research.

The changes in intestinal comfort and body weight relate to changes in gut bacteria composition and function, researchers say.

An increasing number of people choose a low-gluten diet, even though they’re not allergic to it. The trend has sparked public debate about whether or not low-gluten diets are recommended for people without allergies. Now, researchers have looked into it.

“We demonstrate that, in comparison with a high-gluten diet, a low-gluten, fiber-rich diet induces changes in the structure and function of the complex intestinal ecosystem of bacteria, reduces hydrogen exhalation, and leads to improvements in self-reported bloating.

“Moreover, we observed a modest weight loss, likely due to increased body combustion triggered by the altered gut bacterial functions,” explains Oluf Pedersen, a professor in the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen, and the trial’s leading principal investigator.

Focus on fiber

The researchers conducted a randomized, controlled, cross-over trial involving 60 middle-aged healthy Danish adults with two eight-week interventions comparing a low-gluten diet (2g gluten per day) and a high-gluten diet (18g gluten per day), separated by a washout period of at least six weeks with habitual diet (12g gluten per day).

The two diets were balanced in the number of calories and nutrients including the same amount of dietary fibers. However, the composition of fibers differed markedly between the two diets.

Based on their observations of altered food fermentation patterns of the gut bacteria, the researchers conclude that the effects of low-gluten dieting in healthy people may not be primarily due to reduced intake of gluten itself but rather to a change in dietary fiber composition by reducing fibers from wheat and rye and replacing them with fibers from vegetables, brown rice, corn, oat, and quinoa.

A word of caution

A low-gluten diet has previously been proposed to diminish gastrointestinal symptoms in patients with inflammatory bowel diseases and irritable bowel syndrome, disorders which occur in up to 20 percent of the general Western population.

The present study suggests that even some healthy individuals may prefer a low-gluten diet to combat intestinal discomfort or excess body weight.

“More long-term studies are definitely needed before any public health advice can be given to the general population. Especially, because we find dietary fibers—not the absence of gluten alone—to be the primary cause of the changes in intestinal discomfort and body weight. By now we think that our study is a wake-up call to the food industry. Gluten-free may not necessarily be the healthy choice many people think it is. Most gluten-free food items available on the market today are massively deprived of dietary fibers and natural nutritional ingredients.

Therefore, there is an obvious need for availability of fiber-enriched, nutritionally high-quality gluten-free food items which are fresh or minimally processed to consumers who prefer a low-gluten diet. Such initiatives may turn out to be key for alleviating gastro-intestinal discomfort and in addition to help facilitating weight control in the general population via modification of the gut microbiota,” Pedersen says.

The governmental Danish Innovation Fund funded the research. Additional researchers are from the University of Copenhagen, the Technical University of Denmark, the University of Southern Denmark. and academic research teams in Belgium and China.

The study appears in Nature Communications.

Source: University of Copenhagen

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