Beware of antioxidant supplements, warns scientific review

Humans depend on oxygen to produce energy, but oxygen also has the potential to generate so-called oxygen radicals, which may cause oxidative stress and disease. Markers of oxidative stress have been correlated with cardiovascular disease, cancer, diabetes, and other conditions. Because of these associations, antioxidant supplements are taken by millions of people; however, none of the antioxidants tested in randomized clinical trials have demonstrated any benefit. On the contrary, some of them may cause harm.

This is because oxygen radicals not only trigger disease but also perform many important functions in the body, such as for immune defense and hormone synthesis. Thus anti-oxidants will interfere with both healthy and disease-triggering oxygen molecules.

"Oxidative stress could be important in some conditions and only in a small proportion of patients," said Prof. Ghezzi. "It can be targeted in a totally different manner, with drugs targeted only at those sources of oxygen molecules that are triggers of disease and leave the healthy ones alone," added Prof. Schmidt. The review is published the British Journal of Pharmacology.