Supplement analysis backed by scientific evidence · PT

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Limited evidenceLongevity & antioxidants

Beta-Carotene

Beta-carotene supplements are one of the clearest cautionary tales in supplement science: two large RCTs found they increased lung cancer and mortality in smokers and asbestos-exposed workers. Get carotenoids from food; do not supplement isolated beta-carotene.

What the science says

  • Increases lung cancer risk in smokers Strong evidence

    The ATBC trial (29,133 male smokers, 20 mg/day beta-carotene, median 6.1 years) found an 18% increase in lung cancer incidence and 8% higher total mortality in the beta-carotene arms. CARET (18,314 smokers and asbestos-exposed workers, 30 mg beta-carotene plus 25,000 IU retinol) was stopped early for a 28% increase in lung cancer and 17% increase in death. This is a consistent, replicated harm signal.

  • Prevents cancer or cardiovascular disease in general populations Limited evidence

    Beyond the smoker trials, beta-carotene supplementation has repeatedly failed to reduce cancer or cardiovascular disease incidence in RCTs despite strong observational associations for carotenoid-rich diets. The dissociation between food carotenoids and isolated supplements is the whole lesson here.

  • Slows age-related macular degeneration progression (as part of AREDS) Moderate evidence

    The original AREDS formulation containing 15 mg beta-carotene reduced progression to advanced AMD by about 25% over 5 years, but beta-carotene was replaced by lutein and zeaxanthin in AREDS2 precisely because of the smoker cancer risk. Any AMD benefit is attributable to the combination, and the modern formulation omits beta-carotene.

  • Prevents sunburn or acts as an 'internal sunscreen' Limited evidence

    Trials show only marginal increases in minimal erythema dose after weeks to months of high-dose supplementation, far below what a topical SPF provides. Prolonged high intake mainly produces carotenodermia — harmless orange skin discolouration.

Dosage & safety

Studied doseNo RDA exists; beta-carotene is a provitamin A source, with roughly 12 mcg dietary beta-carotene equivalent to 1 mcg retinol. Trials showing harm used 20-30 mg/day. There is no dose of isolated supplemental beta-carotene with an established favourable risk-benefit profile in adults. Dietary carotenoids from carrots, sweet potato, and leafy greens carry none of this risk.
SafetyContraindicated in current and former smokers and anyone with significant asbestos exposure — supplemental doses of 20-30 mg/day increased lung cancer and all-cause mortality in two large RCTs. Carotenodermia (yellow-orange palms and skin) is common above ~30 mg/day and is cosmetic only. Unlike preformed vitamin A, beta-carotene from food does not cause hypervitaminosis A because conversion is regulated, and it is not teratogenic. Multivitamins and older AMD formulas may contain it — check labels if you smoke.

Scientific references

Where to buy

Swanson Vitamins, Beta Carotene, 10,000 IU (3,000 mcg RAE), 100 Softgels

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