VITAMIN A SUPPLEMENT USE ASSOCIATED WITH BREAST CANCER PROTECTIVE BENEFIT

VITAMIN A SUPPLEMENT USE ASSOCIATED WITH BREAST CANCER PROTECTIVE BENEFIT in women with a low dietary intake of vitamin A, according to a study by David Hunter et al. recently published in The New England Journal of Medicine. The study found that supplement use significantly decreased the risk of breast cancer in women "with the lowest dietary intake of vitamin A." Women with a low dietary intake of vitamin A who took more than 10,000 IUs per day reduced their relative risk of breast cancer over the eight years of the prospective study by 47%, the authors found. The prospective study on the effects of vitamins A, C and E intake on breast cancer rates in 89,494 women, published in the July 22 issue of NEJM, was conducted as part of the Nurses' Health Study. In the study, large intakes of vitamins A, C or E did not appear to protect women from breast cancer but a low dietary intake of vitamin A appeared to increase the risk from the disease. The authors observed that while "only a small proportion" of the study participants took vitamin A supplements, "a large number of women took vitamin A as part of a multivitamin preparation." The study found "no consistent evidence of a protective effect of a long duration of use or a high dose of vitamin A supplements in the overall population." Hunter et al. suggested that the protective benefit of supplementation in the group of women receiving low amounts of vitamin A from foods "is consistent with a threshold effect, in which only women with a low intake of vitamin A are at increased risk." In contrast with the findings from vitamin C and E use, the study authors "observed a significant inverse association of vitamin A intake with the risk of this disease." However, they added, "our data suggest that vitamin A supplements are unlikely to influence the risk of breast cancer among women whose dietary intake of this vitamin is already adequate." Because of the potential side effects from high-dose preformed vitamin A supplements, including a potential teratogenic effect, the authors said it is "premature" to recommend vitamin A supplements to prevent breast cancer and called for further evaluation in randomized clinical trials. An analysis of the Nurses' Health Study data on the relationship of antioxidant vitamin intake to heart disease was published in NEJM in May. That study found that vitamin E supplementation was associated with a reduced risk of heart disease but did not find a cardioprotective benefit from vitamin C ("The Tan Sheet" May 24, p. 10).