Traditionally unrefined grains (pasta, bread, barley, couscous) are the base of most Mediterranean diets. Leaving the grains whole lowers their glycemic index, so they are digested more slowly and produce gentler rises in glucose and insulin than refined versions; they also retain all their fiber, magnesium, vitamin E and other antioxidant phytochemicals. Diets rich in whole grains may protect against heart disease, diabetes and other chronic diseases.