A new systematic review and pooled analysis of previously published randomized clinical trials in the Lancet provides strong evidence that antioxidant vitamin supplements are not effective in protecting against gastrointestinal cancer. Selenium may be associated with risk reduction. The investigators identified 14 randomized trials with a total of more than 170,000 participants. Overall results did not show any protective effect of supplementation with beta carotene, vitamins A, C, and E and selenium, alone or in combination compared with placebo on esophageal, gastric, colorectal, pancreatic and liver cancer incidences. There was some suggestion that some combinations of supplements might slightly increase gastrointestinal cancer risk, but this will require more study. In a previous study also published in the Lancet in 2002, antioxidant vitamin supplements did not produce significant reductions in 5-year risks of heart attack, stroke, cancer or other major outcomes in people at high risk of vascular disease.

Source: Lancet, October 2, 2004