More Bad News For Antioxidant Vitamins

Taking antioxidant vitamins (such as vitamin C and vitamin E) has been promoted as beneficial in prevention of colds, heart attack, stroke and cancer. Unfortunately, it appears that none of these illnesses are prevented by taking vitamins. And worse yet, evidence has accumulated that antioxidant vitamins can be harmful.

The most recent study, published in the Proceedings of the National Academy of Sciences demonstrated that taking supplemental vitamin C and vitamin E eliminated one of the major benefits of exercise in healthy men. The study included 40 healthy German men, half were previously sedentary and half not. In each of these two groups, half were given vitamin C and E supplements and half placebo. All underwent measurement of insulin sensitivity (the body’s ability to respond to insulin and control blood sugar – known to predict development of diabetes) before and after exercise training.

Insulin sensitivity improved in the men who were given placebo tablets but did not in those given vitamin supplements. The authors conclude (and we agree) that taking vitamin C and vitamin E prevent this beneficial impact of exercise.

A recent review of 67 studies (involving over 230,000 participants) concluded that vitamin C (alone or in combination with other vitamins) did not lower mortality. The same review concluded that vitamin E supplementation (as well as supplementation with vitamin A and beta-carotene) may to increase mortality significantly.

The recent German study describing the negative impact of vitamins C and E on the benefit of exercise joins a list of prior trials suggesting that in some patients these vitamins can increase risk of stroke and heart attack.

We do not recommend routine supplementation with vitamins A, C, E or beta-carotene.

Comments / Posted by Scott W. Yates, MD, MBA, MS, FACP