Combined Mineral Intakes and Risk of Colorectal Cancer in Postmenopausal Women

Background: Despite considerable biological plausibility, other than for calcium, there are few reported epidemiologic studies on mineral intake-colorectal cancer associations, none of which investigated multiple minerals in aggregate. Methods: Accordingly, we incorporated 11 minerals into a mineral score and investigated its association with incident colorectal cancer in the Iowa Women's Health Study, a prospective cohort study of 55- to 69-year-old women who completed a food frequency questionnaire in 1986. In the analytic cohort (n = 35, 221), 1,731 incident colorectal cancer cases were identified via the State Health Registry of Iowa. Participants' calcium, magnesium, manganese, zinc, selenium, potassium, and iodine intakes were ranked 1 to 5, with higher ranks indicating higher, potentially anticarcinogenic, intakes, whereas for iron, copper, phosphorus, and sodium intakes, the rankings were reversed to account for their possible procarci-nogenic properties. The rankings were summed to create each woman's mineral score. The mineral score-incident colorectal cancer association was estimated using multivariable Cox proportional hazards regression. Results: There was decreasing risk with an increasing score (P-trend = 0.001). The hazard ratios and 95% confidence intervals (CI) for those in mineral score quintiles 2 to 5 relative to those in the lowest were 0.91 (CI, 0.88-1.08), 0.85 (CI, 0.75-0.95), 0.86 (CI, 0.75-0.97), and 0.75 (CI, 0.71-0.95), respectively. Conclusions: Our findings suggest that a predominance of putative anti-relative to pro-colorectal carcinogenic mineral intakes may be inversely associated with colorectal cancer risk. Impact: These results support further investigation of colorectal cancer etiology using composite mineral intake scores.