Abstract
Studies employing time‐resolved techniques have shown that β‐carotene, astaxanthin, and lycopene behave quite distinctly with respect to radical quenching and stability, lycopene being the least stable. These results are compatible with the relative effects of the various carotenoids on ultraviolet (UV)‐mediated carcinogenesis in mice in which a statistically significant exacerbation by β‐carotene and astaxanthin, but not by lycopene, was observed. Interactions between these carotenoids and vitamin C and E radicals not only provide a chemical basis to explain the failure of β‐carotene to provide benefit in recent clinical trials but suggest that future carotenoid supplementation studies should proceed with caution until carotenoid interactions and radical repair mechanism(s) are elucidated.