Whole grains are associated with weight control and protection from obesity, metabolic syndrome and diabetes. Evidence suggests that that some of the health benefits of whole grains is on account of their high soluble dietary fibre content. However, there appears to be differences between various cereal grains with respect to their effects on postprandial insulin levels. Research has shown that rye bread made with whole grain flour, produces a lower insulin response that a similar quantity of bread made from whole grain wheat. However, there is no difference in the glucose response between the rye and wheat, suggesting that rye requires less insulin to dispose of the glucose produced from digestion. Because of this discrepancy, researchers1 have investigated the insulin response of rye and wheat cereals to determine if the dietary fibre content is responsible for the differences seen in insulin response.
Nineteen healthy 61 year old women with normal blood glucose tolerance were fed 50 grams of carbohydrate in the form of refined wheat bread (control), endosperm rye bread, traditional rye bread or high fibre rye bread. Measurements of plasma glucose, plasma insulin, glucose-dependent insulinotropic polypeptide (GIP), glucagons-like peptide 1 (GLP-1) and C-reactive protein (CRP) were measured at fasting and postprandially. The results showed that postprandial insulin, GIP and CRP responses to rye bread were significantly lower than to the control. However, no significant responses were seen in plasma insulin levels between the rye breads. These results suggest that it is not the fibre content of rye bread that is responsible for the difference in insulin response to wheat. This evidence was supported by analysis of the rye bread which showed differences in the structure of starch granules and slower starch hydrolysis (in vitro).
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