Effect of dietary fibers on glycemia and insulinemia and on gastrointestinal function in rats

Abstract

The effects of purified and semipurified dietary fiber supplements on glycemia and insulinemia were measured simultaneously with their effects on digestive tract function in the rat. An insoluble fiber (cellulose) and four soluble fibers (guar gum, carboxymethylcellulose, mustard mucilage, and oat beta-glucan) were added separately to a fiber-free solid diet and fed to Sprague-Dawley rats for 10 days. Guar gum and oat beta-glucan reduced the food intake, whereas cellulose increased it. Guar gum reduced weight gain. Cellulose increased the protein efficiency ratio. After a 13-h fast, glycemia and insulinemia were measured 45, 90, 210, and 360 min after the beginning of a voluntary short meal. Addition of fibers did not change the glycemic response, but soluble fibers significantly decreased insulinemia 45 min after the meal. All fibers significantly delayed gastric emptying, cellulose and mustard mucilage being the most effective. Dry matter contents of the small intestine were increased especially by guar gum and oat beta-glucan. All fibers seemed to slow down small intestinal transit and decreased intestinal absorption. In the present experimental situation, both gastric and intestinal components played a role in the hypoinsulinic effect of dietary fibers. The intestinal component appeared to be more determinant for all soluble fibers, except mustard mucilage where the gastric component was more important.