Improved carbohydrate tolerance in fibre-fed rats: studies of the chronic effect

The effect of chronic consumption of diets containing either different sources of dietary fibre (8% guar, 8% pectin, or 8% multifibre) or low carbohydrate upon carbohydrate tolerance was examined in rats. Weight gain was significantly lower throughout the entire 28-day study period with the guar group and after 20 days with the multifibre group. When tested with a liquid meal (1 g sucrose/kg body weight) after 14 days on the diets, only the guar rats had significantly lower fasting and postprandial plasma glucose concentrations. After 28 days, the improved carbohydrate tolerance persisted in the guar rats and started to appear in the multifibre rats. Pectin and low carbohydrate diets had no effect upon either weight gain or carbohydrate tolerance. Consuming the fibre diets did not affect jejunal sucrase activities. Jejunal glucose uptake activity was significantly diminished when measured in fasting guar rats while postprandially activities were similar to controls. Jejunal Na-K-ATPase activities in fasting and postprandial guar rats were not related to changes in glucose uptake. These studies confirm that only certain types of dietary fibre improve carbohydrate tolerance and suggest that reduced weight gain and altered intestinal glucose uptake are factors involved in the chronic fibre effect.