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Life Guide U.S. essentials
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Don't take antioxidant supplements (beta-carotene, vitamin E, vitamin A) to prevent cancer

  • High value
  • Evidence A
  • Buys life
  • Free
  • Takes minutes
  • No willpower

In plain words

This one is worse than useless. When 78 trials with nearly 300,000 (30万) people are pooled, people who took antioxidant supplements had slightly higher death rates. In two large trials done specifically in smokers, beta-carotene raised the share who got lung cancer by 18% to 28% and raised deaths by 8% to 17%. Smokers and people who have been exposed to asbestos should especially not take it.

Cost

About 0.5 to 2 CNY a day. For smokers, the real cost is a rising lung cancer risk.

What you get

A Cochrane review pooled 78 randomized controlled trials with 296,707 people. Among people who took antioxidant supplements, total death RR 1.02 (RR is the risk ratio; 1 means the two sides are the same; 95% CI 0.98–1.05 is the plausible range). Looking only at trials with sounder designs that are less likely to go astray, RR 1.04 (1.01–1.07), slightly higher. Beta-carotene alone RR 1.05 (1.01–1.09), vitamin E alone RR 1.03 (1.00–1.05). The ATBC trial enrolled 29,133 male smokers who took 20 mg a day; the share who got lung cancer was 18% higher (3%–36%) and total death was 8% higher (1%–16%). The CARET trial enrolled 18,314 smokers or people exposed to asbestos. Their lung cancer risk was about 28% higher (RR 1.28, 1.04–1.57). Their risk of death was about 17% higher (all-cause death RR 1.17, 1.03–1.33). It looks like a good deal because in the chain of reasoning “antioxidant means anti-aging, and anti-aging means preventing cancer,” every step sounds like common sense

Notes

The USPSTF, the official U.S. body that grades preventive measures, in 2022 gave beta-carotene and vitamin E a grade of D, meaning it recommends against them. Smokers and people exposed to asbestos have already been harmed this way. Antioxidants that occur naturally in vegetables and fruit are not included; keep eating those

Evidence grade
A : Specific numbers from meta-analyses, large cohorts or randomized trials; for law and policy, the statute or official text.
Sources
  1. 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
  2. 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
  3. 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

Translated from the Chinese original. Original book, section 6, tip 4. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer