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Joan Stephenson, PhD

JAMA. 2009;301(23):2432.

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

Antioxidant vitamins may mitigate some of the benefits of exercise, report scientists in Germany (Ristow et al. Proc Natl Acad Sci U S A. doi:10.1073/pnas.0903485106 [published online ahead of print May 11, 2009]).

Exercise improves sensitivity to insulin. But when muscle cells metabolize glucose, "free radicals"—reactive oxygen species (ROS), which can cause cell damage—are produced. However, the researchers reasoned, because reduced mitochondrial metabolism has been linked with type 2 diabetes, ROS generated by exercise also may have a health-promoting effect that antioxidants such as vitamin C or E might undermine.

The researchers compared insulin sensitivity and ROS levels in 40 men, half of whom were randomly assigned to receive vitamin C (1000 mg/d) and E (400 IU/d) supplements. After 4 weeks of exercise sessions, men who took the vitamins showed no change in ROS levels and no improvement in insulin sensitivity; ROS levels increased and . . . [Full Text of this Article]

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