Little or no gluten: is it truly better for our microbiota?

Gluten-free diet was initially used by people intolerant to this protein, but it has now become increasingly attractive to healthy adults who are convinced of its benefits. What is the truth? Should we eat less gluten to be healthier? A Danish team investigated this issue…

 

Gluten is a major component in wheat, barley and rye, and consists of proteins that are mostly insoluble and difficult to digest. They then accumulate in the intestines where they can interact with the immune system, disrupt gut permeability and change the microbiota’s activity. Only a true gluten intolerance, called celiac disease, requires a permanent gluten-free diet.

Low-gluten vs. high-gluten diet

Given the popularity of gluten-free diet with the general population, researchers carried out a study in 60 healthy adults, comparing a low-gluten diet to a high-gluten diet (respectively 2 and 18 g per day). Both diets lasted eight weeks and were separated by a period of at least six weeks when participants resumed their regular diet (12 g of gluten per day). In both groups, dietary intake was the same (number of calories and nutrients, amount of fiber) and the only difference between the two diets was the nature of ingested fibers.

Benefits with unexpected causes

The results indicate that a gluten-free diet changed the composition of the gut microbiota (significant decrease in bifidobacteria), and that it mainly modulated its activity. The participants reported improved gastrointestinal comfort and less bloating, as well as a slight weight loss. A very small drop in inflammation was also observed, indicating an impact on the immune system. Are these results in favor of a low-gluten diet? Not so sure… These benefits seem to be related to the larger diversity of ingested fibers rather than to the decreased consumption of this protein. By excluding products containing gluten, people are forced to eat different sources of fiber such as vegetables, rice, corn or quinoa. According to researchers, the composition of these fibers, and not the lack of gluten, is the reason why there is a positive impact on the microbiota. The researchers indicated that there is no need to encourage people to follow a gluten-free diet, but they have everything to gain by diversifying their diet, as usually recommended by nutritionists…

 

Sources:

Lea B.S. Hansen et al. A low-gluten diet induces changes in the intestinal microbiome of healthy Danish adults. Nature communications (2018) 9:4630. DOI: 10.1038/s41467-018-07019-x www.nature.com/naturecommunications