Need another reason to help convince overweight and obese patients to have a healthy diet? A small, randomized, controlled study concluded that eating insoluble dietary fiber found in cereal, fruits, and vegetables improved insulin sensitivity, Dr. Martin O. Weickert reported.
Eating a diet high in insoluble fiber might be a safe, effective, and low-cost way to reduce insulin resistance in patients at risk of developing type 2 diabetes, said Dr. Weickert and his associates (Diabetes Care 2006;29:775–80).
Eating cereal fiber has been associated with a reduced risk of developing cardiovascular disease and type 2 diabetes in epidemiologic studies, but the underlying mechanism was not clear, said Dr. Weickert of the German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany.
Seventeen overweight or obese women with normal glucose metabolism and no serious health problems agreed to eat macronutrient-matched portions of bread at meal times, supplemented by standardized liquid meals, for 3 days. The women were randomized to get oat fiber-enriched white bread or regular white bread, which served as the control. After a washout period of 7 days or more, the two groups crossed over to repeat the experiment using the other type of bread.
At the end of each 3-day period of bread eating, investigators measured whole-body insulin sensitivity and took blood samples. They conducted hydrogen breath tests to assess dietary adherence; previously they had shown that fiber consumption enhances colonic fermentation. The breath tests suggested that four women did not adhere to the study diet.
For the 17 women as a whole, 3 days of fiber-enriched bread significantly improved whole-body glucose disposal, equivalent to an 8% improvement in insulin sensitivity. Fasting insulin concentrations tended to be reduced after the days of fiber, an effect that might have been significant in a larger study, the investigators suggested.
A sub-analysis that excluded the four women who probably did not ingest the test meals found a highly significant improvement in whole-body glucose disposal after 3 days of fiber-fortified bread, equivalent to a 13% improvement in insulin sensitivity.