It's not the first time studies have suggested that antioxidants can be a negative, Tiganis adds. Studies in worms have suggested that antioxidants can shorten lifespan, as have some epidemiological studies in humans. Other recent reports indicate that antioxidants may negate the longer-term benefits of exercise training by lowering the activity of certain genes involved in ROS defense.

Tiganis said it will ultimately be important to work out at what stage ROS go from being good to bad. He suspects it probably depends on the levels and/or the source of their generation. (ROS are generated both on the surfaces of cells and within cells by mitochondria, which convert nutrients such as glucose into energy, he explained.)

Although any health implications of the new findings would require further study, the findings lead Tiganis to suspect it is best not to take daily antioxidant vitamins, especially if you are otherwise healthy. "Do exercise," he says, as this is a natural source of ROS that may promote insulin action.

Source: Cell Press