Fatty liver disease: what are the benefits of whole-grain flour?

The main symptom of metabolic syndrome (sidenote: Metabolic syndrome Combination of several metabolic anomalies: high blood pressure, large waist circumference, increased blood triglyceride and glucose levels associated to a low blood level of “good” cholesterol. Alberti KG, Zimmet P, Shaw J. The metabolic syndrome--a new worldwide definition. Lancet. 2005 ; 366 (9491) : 1059-62. ) is the accumulation of fat (triglycerides) in the liver, which not only increases the risk of non-alcoholic fatty steatohepatitis (NASH), but may also alter the whole digestive system, thus leading to increased cardiometabolic risk factors (cardiovascular diseases and type 2 diabetes), including insulin resistance. Could replacing refined flour (white) with whole-grain flour (richer in fiber, minerals and vitamins) help limit these risks? Studies tend to confirm this hypothesis. However, underlying mechanisms remain poorly understood, thus illustrating the complexity of relations between the organs involved in the metabolism, especially gut, fatty tissue and liver.

Whole-grain vs. refined flour

To assess the benefits of whole-grain flour in the digestive system (including liver, fatty tissue and microbiota), Dutch researchers compared its effects to those of refined flour in 50 overweight adults whose total cholesterol levels were slightly elevated. 12 weeks later, the results showed that the wheat refining process does not impact lipid blood levels (lipemia) nor sugar blood levels (glycemia), nor subcutaneous or deep abdominal fat. However, hepatic triglycerides levels were increased by 50%, driving up the proportion of participants with NASH in the refined-flour group from 33% to 44%. On the contrary, this rate decreased from 35% to 25% in the whole-grain-flour group. Researchers also observed a decrease in bacterial diversity and change in composition of the gut microbiota in the refined-flour group, although these alterations were not predictive of changes observed in the liver.

A treatment for NASH?

According to the scientists, these results tend to show the benefits of whole-grain wheat products as a preventive and therapeutic avenue for fatty liver disease. Its protective effects against metabolic disorders could be due to the hepatic benefits of some chemical components naturally present in whole-grain wheat, or to the fermentation of fiber by gut flora bacteria. The authors concluded that, were this true, it would confirm the hypothesis that there is a bidirectional communication between liver and gut.