Plain language summary
The consumption of whole grains has been associated with a lower risk of developing obesity, type 2 diabetes, and heart disease. One theory behind this is that the high fibre content in whole grains can alter the gut microbiota, which has a critical role in the development of disease. This randomised control trial aimed to determine the effects of a diet high in fibre rich rye products compared to a refined wheat rich diet on gut microbiota and weight. The results showed that after 12 weeks there was a change in the composition of the gut microbiota of individuals eating a fibre rich diet. Agathobacter species were increased and Ruminococcus torques were decreased, which resulted in an increase in the production of a short chain fatty acid in the gut known as butyrate, which has been shown to have health benefits. In addition, individuals who were on the rye diet lost more body weight and fat than those on the refined wheat diet. It was concluded that a high fibre rye diet changed the gut microbiota composition and improved health outcomes especially those associated with metabolism. This study could be used by healthcare professionals to understand that eliminating refined wheat and substituting it with a high fibre alternative could be of benefit for weight loss and health.
Consumption of whole grain and cereal fiber have been inversely associated with body weight and obesity measures in observational studies but data from large, long-term randomized interventions are scarce. Among the cereals, rye has the highest fiber content and high rye consumption has been linked to increased production of gut fermentation products, as well as reduced risks of obesity and metabolic disease. The effects on body weight and metabolic risk factors may partly be mediated through gut microbiota and/or their fermentation products. We used data from a randomized controlled weight loss trial where participants were randomized to a hypocaloric diet rich in either high fiber rye foods or refined wheat foods for 12 weeks to investigate the effects of the intervention on gut microbiota composition and plasma short chain fatty acids, as well as the potential association with weight loss and metabolic risk markers. Rye, compared to wheat, induced some changes in gut microbiota composition, including increased abundance of the butyrate producing Agathobacter and reduced abundance of [Ruminococcus] torques group, which may be related to reductions in low grade inflammation caused by the intervention. Plasma butyrate increased in the rye group. In conclusion, intervention with high fiber rye foods induced some changes in gut microbiota composition and plasma short chain fatty acid concentration, which were associated with improvements in metabolic risk markers as a result of the intervention.