Do antioxidant supplements have health benefits?

Systematic reviews and meta-analyses of these randomized trials have not demonstrated that beta-carotene, vitamin A, and vitamin E in the administered dosages lead to decreased mortality, and some analyses have suggested the possibility of increased mortality. As to vitamin C and selenium, the verdict is still out.

Randomized, placebo-controlled trials—which, when performed well, provide the strongest evidence—offer little support that taking vitamin C, vitamin E, beta-carotene, or other single antioxidants provides substantial protection against heart disease, cancer, or other chronic conditions. The results of the largest such trials have been mostly negative.