The caffeine in coffee may be the compound that makes coffee help prevent diabetes, researchers in Japan found. Fumihiko Horio of Nagoya University and colleagues fed either water or coffee to a group of laboratory mice. The mice that consumed coffee had lower levels of high-blood sugar and improved insulin sensitivity in the mice -- reducing the risk of diabetes.

Coffee also caused beneficial changes in the fatty liver and inflammatory adipocytokines related to a reduced diabetes risk, Horio said. Caffeine may be "one of the most effective anti-diabetic compounds in coffee," the scientists said in a statement. The study was published in the Journal of Agricultural and Food Chemistry.