Effect of the glycemic index and content of indigestible carbohydrates of cereal-based breakfast meals on glucose tolerance at lunch in healthy subjects

Background: Diets with a low glycemic index (GI) have been shown to improve glucose tolerance in both healthy and diabetic subjects. Two potential mec hanisms are discussed in relation to long-term metabolic effects: a decreas ed demand for insulin in the postprandial phase and formation of short-chai n fatty acids from fermentation of indigestible carbohydrates in the colon. Objective: The objective was to study the effect of the GI and the indigest ible carbohydrate-resistant starch (RS) and dietary fiber (DF)-content of c ereal-based breakfasts on glucose tolerance at a second meal (lunch) in hea lthy subjects. Design: The effects of 7 test breakfasts with known GIs (GI: 52-99) and RS + DF contents (2-36 g) were evaluated. White-wheat bread was used as a refe rence breakfast (high Gi, low RS + DF content). Glucose and insulin respons es after the second meal were measured in healthy subjects. In addition, th e satiating capacity of 4 of the 7 test breakfasts was estimated before and during the second meal. Results: Two of the 4 low-GI breakfasts improved glucose tolerance at the s econd meal. Only these 2 breakfasts were capable of postponing the in-betwe en-meal fasting state. There was no measurable effect of fermentable carboh ydrates on glucose tolerance at the second meal. The highest satiety score was associated with the barley breakfast that had a low GI and a high RS DF content. Conclusions: Glucose tolerance can improve in a single day. Slow absorption and digestion of starch from the breakfast meal, but not the content of in digestible carbohydrates in the breakfast meal, improved glucose tolerance at the second meal (lunch).