I have not looked at recent papers on glycaemic content of foods, but when the initial work was done, for some extraordinary reason they did not measure blood sugar for more than two hours. We know of course that some foods take much longer to be broken down to glucose molecules, as with some foods it happens farther along the gut. When the glucose release does happen, I would expect to see a rise in blood sugar in diabetics- it would just happen later. There may be new evidence that I have not seen, but I regard glycaemic indexing foods in the same light as food combining and blood type diets, I don't think there is any scientific evidence to support them and I would always rely on the carbohydrate content of food to determine whether or not I will eat it.