Extensive research suggests that the consumption of whole wheat, rather than refined grain, should be regarded as a healthy choice due to positive metabolic outcomes in comparison. One of many proposed reasons why whole grains are more beneficial to human health is that their consumption results in a positive alteration of the gut microbiome, and this change is believed to be the mechanism of action for why whole grains appear to ameliorate nonalcoholic fatty liver disease, as evidenced by a recent clinical trial published in the Journal of Nutrition.
 
“The consumption of whole grains is associated with lower risk of diseases such as type 2 diabetes, cardiovascular diseases, obesity, and certain types of cancer in observational studies,” the authors of the study said. “In addition, consumption of whole grains rather than refined grain has been proposed to prevent nonalcoholic fatty liver disease (NAFLD). The presence of numerous bioactive compounds makes whole grains, including whole grain wheat germ in the wheat kernel, which are rich sources of dietary fiber, polyphenols, B-complex vitamins, betaine, choline, and minerals, have been removed.”
 
Additional health benefits have also been ascribed to fiber, the authors said. Fiber intake can affect the microbiota composition and functionality, such as an increase in Bifidobacterium and Lactobacillus, strains which are not fully-understood, however, it’s known that these microbes can produce short-chain fatty acids which can reach the liver, effecting the organ’s function and metabolism.
 
In the 12-week, double-blind, randomized, controlled, parallel trial, 37 men and women were administered a diet that was high in either whole grains or refined grains. The changes in microbiota composition were recorded via RNA gene sequencing following the intervention, with secondary outcomes including fecal microbiota composition, microbiota functionality, and stool consistency.
 
The authors of the study concluded that in middle-aged overweight and obese adults, the whole grain intervention increased the relative abundance of a number of bacteria from the Ruminococcaceae family, and increased predicted fermentation pathways compared to the refined wheat intervention, which could be involved in the changes in liver fat experienced by the whole grain group.
 
“In this study we found a positive correlation between a change in Ruminococcaceae_NK4A214 group and a change in liver fat in both intervention groups, although the RW intervention increased liver fat and decreased abundance of Ruminococcaceae-UCG-010, and Ruminococcaceae_UCG-005,” the authors wrote. Previous studies have associated liver fat with these two bacterial strains. Additionally, the whole grain group had increased concentrations of short-chain fatty acids in colonic content, based on flourishing of the strains which produce a handful of these short-chain fatty acids.
 
“In conclusion, we demonstrated that a 12-wk 98 gram/day whole grain wheat intervention increased relative abundances of a number of bacterial taxa that are involved in carbohydrate degradation and SCFA production and predicted fermentation pathways, whereas a refined wheat intervention decreased abundance of these bacteria or predicted fermentation capacity, pointing toward a less healthy gut microbiota phenotype. The difference in fiber intake during the WGW intervention compared with the RW intervention likely resulted in differences in predicted bacterial fermentation capacity. This may be one of the mechanisms underlying the significant increases of liver fat observed with RW intervention.”