Antioxidant Supplements Blunt Exercise-Induced Improvement of Insulin Sensitivity

Regular exercise increases insulin sensitivity and decreases risk for type 2 diabetes. One mechanism is known: Exercise stimulates glucose-transporter molecules to proliferate and move to the cell membrane, where they ferry glucose into the cell. Exercise also increases the formation of mitochondria, which give cells more energy but also create more harmful reactive oxygen species (ROS).

An international team randomized 39 young men (19 nonconditioned and 20 with prior physical conditioning) to exercise either with or without having ingested daily antioxidant supplements (1000-mg vitamin C and 400-IU vitamin E). In the groups that did not receive antioxidants, mean insulin sensitivity was higher after exercise among both nonconditioned and c…