Gluten-free diets have exploded in popularity in recent years, even for people who don’t have documented food allergies. The trend has made some folks, including scientists, wonder what the effects of gluten-free diets are on people who don’t necessarily need them. Researchers at the University of Copenhagen set out to learn more about it; they assessed the impact of a diet that is low in gluten and high in fiber on healthy Danish adults. Their findings, which showed that the diet had a positive effect, has been reported in Nature Communications. The study is outlined in the video.
The healthy changes that were observed in this study were likely due to shifts that occurred in the participants' gut microbes after the dietary change. The researchers saw that the different diets changed the composition and behavior of the gut microbiome (the microorganisms that live in the gastrointestinal tract) and probably led to the other changes seen in the participants. They experienced mild weight loss and a reduction in bloating and discomfort.
"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," noted the senior principal investigator of the study, Professor Oluf Pedersen of the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen.
In this study, 60 healthy people underwent two eight-week trials that compared low gluten consumption (of two grams per day) with a high-gluten diet (of 18 grams per day). A six-week washout period in which the participants ate their typical foods separated the two eight-week periods. While caloric intake, nutritional values, and amounts of dietary fiber were mostly the same, the fiber composition was very different in the two diets.
The researchers found that the gut bacteria were fermenting the two fibers in different ways. That led them to hypothesize that it’s not the amount of gluten itself that caused the changes in the study participants; it was the way gut microbes responded to the fiber. Instead of fiber from wheat or rye, the fiber in the low-gluten diet was coming from brown rice, vegetables, and quinoa.
It’s been shown that low-gluten diets can ease symptoms of gastrointestinal distress, and this work indicates why healthy people may feel better when they lower dietary gluten levels.
"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 gastrointestinal discomfort and in addition to helping facilitate weight control in the general population via modification of the gut microbiota", concluded Pedersen.