New research in mice that already had lung cancer suggests antioxidant supplements decrease the activity of a gene (p53) which destroys defective cells, including cancer cells. The supplements caused the number of tumors in the mice to triple, grow faster and become more aggressive. This has not been studied in humans, but it does raise a cautionary flag.
PositiveTip: Sticking with a healthy diet rich in antioxidant sources and skipping the supplements may be the best.