Whole grain wheat products, known for having beneficial health effects due to their higher nutritional quality, are a healthy choice compared with refined wheat.  More recently, there has been increased interest in investigating the link between whole grain wheat in the diet, gut microbiota, and health. Fermentable dietary fibers found in whole grains can be broken down by the gut microbiota, producing short-chain fatty acids that can reach the liver which, in turn, affect organ function and metabolism.

To investigate the effect of a whole grain wheat or refined wheat intervention on changes in fecal microbiota, Lydia Afman (Wageningen University, the Netherlands) and colleagues used data from a 12-week double-blind, randomized, controlled trial. A total of 37 women and men, 45-70 years of age, with a body mass index categorized as overweight or obese were included in the analysis. Feces were collected at baseline and upon completion of the 12-week intervention. On test days, liver fat accumulation and metabolic health parameters were measured.

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When the diet groups were compared, investigators found minor effects on the fecal microbiota composition after 12 weeks. The effects were primarily an increased abundance of certain fiber-degrading bacteria and a predicted pathway of fermentation to butyrate in the whole-grain wheat group.  Changes in abundances of some bacteria correlated with changes in liver fat and circulating concentrations of certain liver enzymes.

While whole-grain food-based dietary interventions suggested limited ability to alter gut microbiota, the response differs greatly between individuals. As such, it may be important for a priori characterization of responders and non-responders to specific dietary interventions. Nonetheless, the protective effects of whole grain wheat on metabolic organs such as the liver warrant further investigation. A corresponding editorial by Kia Nøhr Iversen and Rikard Landberg (Chalmers University of Technology) stresses the importance to work towards a better understanding of the interaction between diet and gut microbiota and possibly its predictive power of individual response to dietary interventions.

References

Trijp MPH, Schutte S, Esser D, Wopereis S, Hoevenaars FPM, Hooiveld GJEJ, Afman LA.  Minor Changes in the Composition and Function of the Gut Microbiota During a 12-Week Whole Grain Wheat or Refined Wheat Intervention Correlated with Liver Fat in Overweight and Obese Adults. The Journal of Nutrition, Volume 151, Issue 3, March 2021, Pages 491–502, https://doi.org/10.1093/jn/nxaa312.

Iversen KN, Landberg R.  Whole Grains, Gut Microbiota, and Health – Time to Get Personal? The Journal of Nutrition, Volume 151, Issue 3, March 2021, Pages 459–461, https://doi.org/10.1093/jn/nxaa412.

Images via canva.com.