Supplements of antioxidants such as vitamins C and E are thought by many to help fight the ageing process, but they may make things worse (Image: Image Source/Rex)

Free radicals aren’t always the bad guys. It even seems that popping antioxidants to mop them up might reduce some of the beneficial effects of exercise.

Free radicals have long been thought to contribute to the ageing process, which is one reason why people take antioxidant supplements such as vitamin C or E.

However, other studies have hinted that taking antioxidants may hasten death through an unknown mechanism. One possibility is that they interfere with the beneficial effects of exercise, as there are hints that free radicals might be used by the body to prevent cellular damage after exercise.


To investigate further, Michael Ristow at the University of Jena in Germany and his colleagues recruited 40 volunteers, and asked half of them to take 1000 milligrams of vitamin C and 400 international units of vitamin E per day – equivalent to amounts in some vitamin supplements. They were also asked to exercise for 85 minutes a day, five days a week, for four weeks.

Muscle biopsies showed a two-fold increase in a marker of free radicals called TBARS (thiobarbituric acid-reactive substances) in those volunteers who didn’t take antioxidants, but no increase in those who did take the supplements – suggesting that they were indeed mopping them up.

Lost benefits

Exercise is well known to have a beneficial effect on insulin resistance – a precursor condition to type 2 diabetes. However, when Ristow’s team measured the effects of exercise on insulin sensitivity, they found no increase in those volunteers taking antioxidants, but a significant increase in those who didn’t take the supplements.

“These data are fully in accord with recent work on the actions of reactive oxygen species in cells, although clearly at odds with the popular concept that dietary antioxidants are inevitably beneficial,” says Malcolm Jackson at the University of Liverpool, UK, who was not involved in the research.

In fact, in this case, “antioxidants are preventing the health effects of exercise,” adds Ristow, although he cautions that not all vitamin supplements contain such high doses of vitamin C and E.

These doses are also far higher than one would get from eating the recommended amount of fruit and vegetables, which do seem to have a positive effect on health – possibly because they contain other protective compounds. “Taking antioxidants cannot substitute for eating fruit and vegetables at all” says Ristow.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0903485106)