Don’t take antioxidant supplements to prevent cancer (beta-carotene, vitamin E, vitamin A)

This isn’t just ineffective — it’s actually harmful. A review of 78 randomized controlled trials involving nearly 300000 people found that those taking antioxidant supplements had a slightly higher overall mortality rate. Two large trials focused on smokers showed that beta-carotene raised the likelihood of developing lung cancer by 18% to 28% and increased death rates by 8% to 17%. Smokers and people exposed to asbestos should absolutely avoid these supplements.

Roughly 0.5 to 2 yuan per day. For smokers, the real cost is a higher risk of lung cancer.

Cochrane analyzed 78 randomized controlled trials with 296707 participants. Overall, those taking antioxidant supplements had a relative risk of death of 1.02 (a value of 1 means no difference; the 95% confidence interval was 0.98–1.05). When only higher-quality trials were considered, the relative risk rose to 1.04 (1.01–1.07). Specifically, beta-carotene raised the risk to 1.05 (1.01–1.09) and vitamin E to 1.03 (1.00–1.05). The ATBC trial followed 29133 male smokers who took 20 mg of beta-carotene daily; it found a 18% higher rate of lung cancer (range 3%–36%) and an 8% higher overall mortality rate (range 1%–16%). The CARET trial included 18314 smokers and asbestos-exposed individuals; it showed a 28% higher risk of lung cancer (relative risk 1.28, 1.04–1.57) and a 17% higher risk of all-cause death (relative risk 1.17, 1.03–1.33). The perception that these supplements are beneficial stems from the flawed logic that antioxidants prevent aging, which in turn prevents cancer — each step of this chain seems intuitive at first glance.

The US Preventive Services Task Force, the official US body that evaluates preventive measures, assigned a grade D to beta-carotene and vitamin E in 2022, meaning these supplements are not recommended. Smokers and asbestos-exposed individuals have already suffered harm from their use. Antioxidants naturally present in fruits and vegetables are not covered by this recommendation, so they can still be consumed as normal.

Bjelakovic G et al. (2012). Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. https://doi.org/10.1002/14651858.CD007176.pub2；The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group (1994). The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. NEJM. https://doi.org/10.1056/NEJM199404143301501；Omenn GS et al. (1996). Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. NEJM. https://doi.org/10.1056/NEJM199605023341802