Beta-carotene
Provitamin A carotenoid with EFSA claims, but supplements raised lung cancer in smokers (ATBC, CARET trials), shifting practice to dietary food-source.
Why
β-Carotene is the principal provitamin A carotenoid in orange and dark green vegetables, converted to vitamin A as needed by intestinal cells. EFSA has authorised health claims for β-carotene's role in normal skin and vision functions. The major caveat: two large RCTs (ATBC 1994 NEJM, CARET 1996 NEJM) found that high-dose β-carotene supplements increased lung cancer incidence in current and former smokers, defining the practical exclusion. AREDS2 replaced β-carotene with lutein/zeaxanthin partly for this reason.
How it works
Provitamin A, cleaved to retinal by intestinal β-carotene 15,15'-dioxygenase. Independent antioxidant effects. The smoker-cancer signal proposed mechanism: pro-oxidant activity in tobacco-smoke-exposed lung tissue.
Expected onset · Tissue levels over weeks; clinical relevance varies by indication
How to take
Dosage
RDI: 700–900 µg RAE/day (provided as β-carotene, ~4–5 mg/day if relying on it as vitamin A source). Avoid sustained supplement doses above 20 mg/day, particularly in any smoker.
Timing
With meals containing fat for absorption
On the label
Mixed carotenoids (β-carotene + α-carotene + lycopene + lutein + zeaxanthin) are more dietary-like than isolated β-carotene supplements. AREDS2 deliberately uses lutein/zeaxanthin instead of β-carotene.
Ideal for
Non-smokers with low dietary intake of orange and dark green vegetables; people relying on plant sources for vitamin A. Smokers should obtain β-carotene from food sources only, not supplements.
Safety
Evidence
EFSA-authorised claim for β-carotene as a vitamin A source. ATBC 1994 NEJM trial: β-carotene 20 mg/day increased lung cancer incidence by 18% in male smokers. CARET 1996 NEJM confirmed similar signal. These trials defined the practical exclusion of supplemental β-carotene in current and former smokers and led to its replacement with lutein/zeaxanthin in AREDS2.
- EFSA Reg 432/2012 authorised claims, β-carotene as vitamin A source (skin, vision, immune function)
- The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group, NEJM 1994, effect of vitamin E and beta carotene on the incidence of lung cancer (ATBC, n=29,133)
- Omenn et al., NEJM 1996, effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease (CARET, n=18,314)
Where to get it
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