Fourth International Conference on Prevention of Human Cancer:
Nutrition and Chemoprevention Controversies.
  June 3-6, 1992, Tucson, AZ, A16, 1992. (1992)

Retinoids or carotenoids: can I have another choice? (Meeting abstract)
Greenberg ER
Dartmouth Medical Sch. Hanover. NH

Both retinoids and carotenoids have been shown to decrease cancer  occurrence in selected animal models of carcinogenesis, but the retinoids appear to have more potent activity against a wider variety of tumors. Future use of retinoids for cancer prevention is likely to be limited, however, because of their toxic effects on bone and skin (among other organs). In contrast to retinoids, carotenoids seem to  be free of important toxicity, and this fact makes them much more  promising for use in the general adult population. The problem with carotenoids is that there is only circumstantial evidence for their  having a cancer-preventive effect in humans, since the data come  almost entirely from epidemiological studies of diet and serum. The lower risk of cancer observed in these studies among people who eat  more carotenoid-rich fruits and vegetables (and who consequently have  higher blood levels of carotenoids) could be due to substances other than carotenoids in these foods, or even to nondietary factors (such as not smoking)....  Pressed to choose between retinoids, with their clear toxicity and uncertain efficacy, and carotenoids, which thus far appear to be as ineffective as they are safe, a person might reasonably ask for a third option. For now, the most rational and prudent choice would be  to consume a diet high in fruits and vegetables and not to take either supplemental carotenoids or retinoids until there is better evidence of their efficacy and safety.

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