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 ( = 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 procarcinogenic 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 ( = 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.