The claimEvidence A · guideline-tier
β-carotene supplements prevent cancer (even for smokers)
The evidence
CARET 1996 was halted early — β-carotene supplementation raised lung cancer in smokers. Antioxidant ≠ safe.
The mechanism, in brief
Walk into a dark cinema and it takes a while before you can see the seats. What gets you there is a switch that vitamin A flips in your retina.
Sources (2)
- National Institutes of Health, Office of Dietary Supplements. (2025). Vitamin A and Carotenoids — Fact Sheet for Health Professionals.
- Brown, M. J., Ferruzzi, M. G., Nguyen, M. L., Cooper, D. A., Eldridge, A. L., Schwartz, S. J., & White, W. S. (2004). Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. The American Journal of Clinical Nutrition, 80(2), 396-403. Dietary fat markedly raises absorption of fat-soluble carotenoids.