Polyphenols and glucose homeostasis in humans.

T HE GLOBAL PANDEMIC OF TYPE 2 DIABETES mellitus places an incalculable burden on health care systems. In the United States alone, it is estimated that 52% of the population will have diabetes or prediabetes by 2020, conditions that already cost that country $194 billion a year in health care spending. Amelioration of type 2 diabetes mellitus risk usually targets lifestyle and diet, primarily with the aim of reducing obesity—the foremost risk factor in the development of insulin resistance and ultimately type 2 diabetes mellitus. However, particular dietary components, such as polyphenols, may assist in type 2 diabetesmellitus prevention in ways other than weight control. Dietary polyphenols are chemicals of plant origin that are abundant in fruit, vegetables, chocolate, and nuts, aswell as in beverages such as tea, coffee, wine, and soy milk. In tea leaves for example, polyphenols can account for up to 30% of their dry weight. As such, polyphenols are the most abundant antioxidants in the diet of human beings. Dietary polyphenol consumption is of interest because it is associated with lower rates of diabetes and cardiovascular disease. There are thousands of natural polyphenols in the plant kingdom (and in derived foods), all of which share the basic structure of an aromatic ring with attached hydroxyl groups. Variations in this structure led to individual classifications of polyphenols, with at least 10 separate classes identified, four of which are important in the diet of human beings: phenolic acids, flavonoids, stilbenes, and lignans. Historically, it has been difficult to determine polyphenol concentrations in food items, or to identify foods that contain specific polyphenols. However, a collaborative project between food and nutrition practitioners, food scientists, epidemiologists, and bioinformaticians has recently produced a database encompassing 500 different polyphenols known to be present in more than 400 food items. The amount and type of polyphenols consumed is largely dependent on the dietary patterns of individuals and populations. Nonetheless, it previously has been estimated that total polyphenol intake is ARTICLE INFORMATION