2.31), 1.69 (95% CI, 1.07-2.67), 1.68 (95% CI, 1.052.70),and1.39(95%CI,0.80-2.42)(Pvaluefortrend,.37). Among the postmenopausal women who were currently receiving hormone therapy, the hazard ratios of breast cancer in the higher 4 quintiles of vitamin D intake compared with those in the lowest intake group were 1.19 (95% CI, 1.18-2.26), 1.83 (95% CI, 1.00-1.95), 1.59 (95% CI, 0.931.87),and0.73(95%CI,0.95-2.00)(Pvaluefortrend,.57). In postmenopausal women, body mass index (calculated as weight in kilograms divided by height in meters squared) tends to be positively associated with endogenous estrogenlevelsbecauseendogenousestrogensaremainlysynthesized in peripheral tissues such as adipose tissue. 2 We additionally evaluated the potential effect modification on the relation between vitamin D intake and the risk for developing postmenopausal breast cancer by body mass index categories (<25, 20 to <30, and ≥30). We again found no significant interaction (P value for interaction, .85). In conclusion, our data do not support the hypothesis that estrogensattenuatetheprotectiveeffectsofvitaminDonbreast cancer development among postmenopausal women.