The addition of raspberries and blueberries to a starch-based food does not alter the glycaemic response

It is now known that health benefits associated with diets rich in fruit and vegetables may be partly derived from intake of polyphenols. Berry polyphenols may influence carbohydrate metabolism and absorption and hence postprandial glycaemia. To date, studies related to polyphenol effects on the glycaemic response have been completed only in liquids using either monosaccharides or disaccharides. It remains to be determined whether berries known to he rich in polyphenols can reduce the glycaemic response (GR) to a solid polysaccharide meal. The aim of the present study was to investigate whether berries alter postprandial hyperglycaemia and consequently the GR to a starchy food. Blood glucose was tested on seven occasions, on three occasions using a reference food and on four occasions using pancakes supplemented with either raspberries or blueberries or control pancakes containing similar amounts of fructose and glucose. Results showed that there were no differences in GR (blueberry 51.3 (SEM 5.7); raspberry 54.7 (SEM 5.6); blueberry control 43.9 (SEM 4.2); raspberry control 41.8 (SEM 6,4)), GR area under the curve or satiety index between any of the tests. The present study indicates that the ability of berries to reduce blood glucose from starch-based foods is unsubstantiated.