Diet potentiates the UV-carcinogenic response to β-carotene

The role of beta -carotene as an anticancer agent has been questioned as a result of clinical trials in which the incidence of nonmelanoma skin cancer was unchanged in patients receiving a beta -carotene supplement and in beta -carotene-supplemented smokers who suffered a significant increase in lung cancer occurrence. In laboratory studies, beta -carotene-supplemented semidefined diets, in contrast to earlier studies employing commercial closed-formula diets, not only failed to provide a protective effect to ultraviolet (UV) carcinogenesis but resulted in significant exacerbation. A rationale for this distinct carcinogenic response to beta -carotene rests with the stability of the carotenoid radical cation, believed to be dependent on the presence of other antioxidants for rapid repair, and suggests that response to p-carotene depends on the presence and interaction with other dietary factors. Here, we report that diet potentiates beta -carotene mediated exacerbation of UV carcinogenesis. Although the dietary factor(s) responsible for this effect is unidentified these studies underscore the potential risk of beta -carotene supplementation in free-living populations where dietary status is widely varied.