Vegan diet may boost beneficial gut microbes

New research presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Barcelona, Spain (September 16–20) suggests that a 16-week vegan diet can boost the gut microbes that are related to improvements in body weight, body composition, and blood sugar control.

Gut microbiota play an important role in weight regulation, the development of metabolic syndrome, and type 2 diabetes. The aim of this study was to test the effect of a 16-week plant-based diet on gut microbiota composition, body weight, body composition, and insulin resistance in overweight adults with no history of diabetes.

The study included 147 participants (86% women and 14% men), half of who were randomized to follow a low-fat vegan diet while the other half made no changes to their diet for 16 weeks. At baseline and 16 weeks, gut microbiota composition was assessed. Dual energy X-ray absorptiometry was used to measure body composition, and a standard method called the PREDIM index was used to assess insulin sensitivity.

The researchers found that following the 16-week study, body weight was reduced significantly in the vegan group (treatment effect average -5.8 kg), particularly due to a reduction in fat mass (average -3.9 kg) and in visceral fat. Insulin sensitivity also increased significantly in the vegan group.

The relative abundance of Faecalibacterium prausnitzii increased in the vegan group (treatment effect +4.8%). Relative changes in F. prausnitzii were associated with decreases in body weight, fat mass, and visceral fat. The relative abundance of Bacteoides fragilis also increased in the vegan group (treatment effect +19.5%). Relative changes in B. fragilis were associated with decreases in body weight, fat mass, and visceral fat, and increases in insulin sensitivity.

The authors concluded that “a 16-week low-fat vegan dietary intervention induced changes in gut microbiota that were related to changes in weight, body composition, and insulin sensitivity in overweight adults.”

However, the authors acknowledge that further work is needed to separate out the effects of the vegan diet itself from that of the reduced calories. “The main shift in the gut microbiome composition was due to an increased relative content of short-chain fatty acid producing bacteria that feed on fiber,” said the researchers. “Therefore, high dietary fiber content seems to be essential for the changes observed in our study. We plan to compare the effects of a vegan and a standard portion-controlled diet on gut microbiome in people with type 2 diabetes, in order to separate out the positive effects of the reduced calories in the diet from those caused by the vegan composition of the diet.”

Press release