The effects of cereal source and processing on the metabolic responses to commercially available breakfast cereals and breads

Abstract

The effect of cereal source and processing on postprandial glycaemic and insulinaemic responses to test meals of commercially-available cereal products was investigated in two groups of six healthy, non-obese volunteers. The first study investigated the possible effect of different cereal sources used to make bread. Portions of a wholemeal wheat bread containing 50 g carbohydrate were compared with portions of bread containing either 20% oat flour or 50% rye, selected on the basis of similar processing and composition except for cereal source and containing an equivalent amount of carbohydrate. The second study investigated the effect of different processing on cereal starch from one source. Portions of three wheat-based breakfast cereals, processed by puffing, flaking or shredding and containing 50 g carbohydrate were compared. In the first study no significant differences were found in the postprandial incremental responses (0–180 min) between the breads for either glucose, insulin or the insulin-stimulating gastrointestinal hormone glucose-dependent insulinotropic polypeptide (GIP). In the second study, the incremental responses (0–180 min) for glucose and insulin were significantly lower following consumption of puffed wheat compared with shredded wheat. There were no significant differences in postprandial GIP responses between the three breakfast cereals. We conclude that substitution of starches from different cereal sources in commercially available bread is without effect on glucose tolerance and insulin secretion. Processing in wheat-starch breakfast cereals did influence glucose tolerance and insulin secretion, but the effect was small. It appears that the starch processing undergone in the production of commercially-available breads and breakfast cereals is severe enough to render the starch readily digestible, regardless of cereal source and processing used, thus minimising any differences in metabolic responses.