Antioxidant vitamins and risk of lung cancer.

Tobacco use is the leading risk factor for lung cancer, yet in addition to smoking habit, diet may also play a role in the disease's appearance. While there are reports to indicate that antioxidant vitamins and carotenoids may decrease the risk of lung cancer, results to date have been somewhat ambiguous. This review aimed to describe the results yielded by different studies, which have addressed antioxidant vitamin intake and lung cancer, and to indicate the mechanisms whereby these nutrients might be exercising their activity. Antioxidant vitamins were observed to have no clear protective effect, though there was some evidence pointing to a protective role for vitamins C and E. Vitamin A, in contrast, evinced no clear effect. Insofar as provitamin A carotenoids were concerned, lutein/zeaxanthin, lycopene and alpha-carotene displayed a certain protective trend, yet beta-carotene exhibited no protective effect whatsoever; and indeed, there was speculation as to whether it might even be pernicious in smokers. Beta-criptoxanthin, on the other hand, showed a more consistent protective effect. The study highlighted the need to conduct further research on smokers and non-smokers alike, and in particular, to investigate the effect, if any, on lung cancer of carotenoids or vitamins when ingested in differing dosages.