Effect of canning on the blood glucose response to beans in patients with type 2 diabetes

Cooked dried legumes have been shown to stimulate low blood glucose responses, and their consumption by individuals with diabetes has been encouraged. However, canned beans are more convenient to use than dried beans. Since the glycaemic effects of canned beans have not been determined, we fed 50 g carbohydrate portions of five varieties of beans, both cooked dried and canned, to groups of diabetic patients and calculated their glycaemic indices (GI). All canned and dried beans tested had significantly lower GIs than that of white bread, which was ascribed a GI of 100. The mean GI of the five types of canned beans, 71 +/- 4, was less than that of bread, 100 (P less than 0.001), and greater than that of the same five varieties of cooked dried beans, 47 +/- 5 (P less than 0.001). It is concluded that the glycaemic effect of dried legumes is increased by the canning process. Nevertheless, canned beans give lower blood glucose responses than bread and may be of use in low glycaemic index diets.