We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.
Incidence of cancer and mortality following alpha-tocopherol and beta-carotene supplementation: a postintervention follow-up.
In the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, alpha-tocopherol supplementation decreased prostate cancer incidence, whereas beta-carotene increased the risk of lung cancer and total mortality. Postintervention follow-up provides information regarding duration of the intervention effects and may reveal potential late effects of these antioxidants.
                To analyze postintervention effects of alpha-tocopherol and beta-carotene on cancer incidence and total and cause-specific mortality.
                Postintervention follow-up assessment of cancer incidence and cause-specific mortality (6 years [May 1, 1993-April 30, 1999]) and total mortality (8 years [May 1, 1993-April 30, 2001]) of 25 563 men. In the ATBC Study, 29 133 male smokers aged 50 to 69 years received alpha-tocopherol (50 mg), beta-carotene (20 mg), both agents, or placebo daily for 5 to 8 years. End point information was obtained from the Finnish Cancer Registry and the Register of Causes of Death. Cancer cases were confirmed through medical record review.
                Site-specific cancer incidence and total and cause-specific mortality and calendar time-specific risk for lung cancer incidence and total mortality.
                Overall posttrial relative risk (RR) for lung cancer incidence (n = 1037) was 1.06 (95% confidence interval [CI], 0.94-1.20) among recipients of beta-carotene compared with nonrecipients. For prostate cancer incidence (n = 672), the RR was 0.88 (95% CI, 0.76-1.03) for participants receiving alpha-tocopherol compared with nonrecipients. No late preventive effects on other cancers were observed for either supplement. There were 7261 individuals who died by April 30, 2001, during the posttrial follow-up period; the RR was 1.01 (95% CI, 0.96-1.05) for alpha-tocopherol recipients vs nonrecipients and 1.07 (95% CI, 1.02-1.12) for beta-carotene recipients vs nonrecipients. Regarding duration of intervention effects and potential late effects, the excess risk for beta-carotene recipients was no longer evident 4 to 6 years after ending the intervention and was primarily due to cardiovascular diseases.
                The beneficial and adverse effects of supplemental alpha-tocopherol and beta-carotene disappeared during postintervention follow-up. The preventive effects of alpha-tocopherol on prostate cancer require confirmation in other trials. Smokers should avoid beta-carotene supplementation.