Inconsistent results for the role of dairy food intake in relation to ovarian cancer risk may reflect the potential adverse effects of lactose, which has been hypothesized to increase gonadotropin levels, and the beneficial antiproliferative effects of calcium and vitamin D. Using data from the New England case-control study (1,909 cases and 1,989 controls), we examined dairy foods and nutrients in relation to risk of ovarian cancer overall, histological subtypes and rapidly fatal versus less aggressive disease. We used logistic regression and polytomous logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs). In models that were simultaneously adjusted for total (dietary plus supplements) calcium, total vitamin D and lactose, we observed a decreased overall risk of ovarian cancer with high intake of total calcium [Quartile 4 (Q4, >1,319 mg/day) vs. Quartile 1 (Q1, <655 mg/day), OR = 0.62, 95% CI = 0.49-0.79]; the inverse association was strongest for serous borderline and mucinous tumors. High intake of total vitamin D was not associated overall with ovarian cancer risk, but was inversely associated with risk of serous borderline (Q4, >559 IU/day vs. Q1, <164 IU/day, OR = 0.51, 95% CI = 0.34-0.76) and endometrioid tumors (Q4 vs. Q1, OR = 0.55, 95% CI = 0.39-0.80). We found no evidence that lactose intake influenced ovarian cancer risk or that risk varied by tumor aggressiveness in the analyses of intake of dairy foods and nutrients. The overall inverse association with high intake of calcium and the inverse associations of calcium and vitamin D with specific histological subtypes warrant further investigation.
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