Unpasteurized milk consumption and subsequent risk of cancer
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Concerns have been raised regarding the possible adverse health effects of consumption of unpasteurized milk and risk of cancer. We examined the association of self-reported intake of unpasteurized milk with subsequent risk of cancer in a large population-based cohort study. The Iowa Women’s Health Study is a prospective cohort study of 55–69 year old women at baseline in 1986. Of the 41,836 women in the cohort at baseline, 22,808 cancer-free women completed the fourth follow-up questionnaire in 1997. Risk ratios (RR) and 95% confidence intervals (CI) were calculated using Cox proportional hazards regression analysis. Reported intake of unpasteurized milk was high: 59.2% consumed only as a child, 2.5% consumed only as an adult, and 16.5% consumed as a child and an adult. A total of 2,379 cancers were identified in the cohort at risk. Overall, the age-adjusted risk of cancer was lower among women who reported consumption of unpasteurized milk only as a child (RR = 0.90, 95% CI: 0.82–0.99) or as a child and an adult (RR = 0.85; 95% CI: 0.75–0.97). Adjustment for confounding factors attenuated these associations (RR = 0.92, 95% CI: 0.83–1.02 for consumption only as a child, and RR = 0.91; 95% CI: 0.79–1.04 for consumption as a child and an adult). These data suggest that consumption of unpasteurized milk does not increase risk of cancer.