Associations between breast cancer risk and the catalase genotype, fruit and vegetable consumption, and supplement use.
Observed weak or null associations between fruit and vegetable intake and breast cancer risk could be due to heterogeneity in endogenous antioxidant capabilities. The authors evaluated potential relations between a functional polymorphism in catalase, an antioxidant enzyme, and breast cancer risk, particularly in relation to fruit and vegetable intake and supplement use. Women (1,008 cases and 1,056 controls) in the Long Island Breast Cancer Study Project (1996-1997) were interviewed, completed a food frequency questionnaire, and provided blood for genotyping. The high-activity catalase CC genotype was associated with an overall 17% reduction in risk of breast cancer compared with having at least one variant T allele (odds ratio = 0.83, 95% confidence interval: 0.69, 1.00). Vegetable and, particularly, fruit consumption contributed to the decreased risk associated with the catalase CC genotype. Associations were more pronounced among women who did not use vitamin supplements, with a significant multiplicative interaction (p(interaction) = 0.02) for the CC genotype and high fruit intake (odds ratio = 0.59, 95% confidence interval: 0.38, 0.89), and there was no association among supplement users. These results indicate the importance of diet, rather than supplement use, in concert with endogenous antioxidant capabilities, in the reduction of breast cancer risk. CC genotypes were prevalent in approximately 64% of controls; thus, the preventive potential for fruit consumption has widespread implications.