Zinc and heme iron intakes and risk of colorectal cancer: A population-based prospective cohort study in Japan

Background: Food sources and intakes of zinc and heme iron may differ between Western and Asian populations. However, all of the studies on the association between zinc and heme iron intakes and colorectal cancer have been conducted in Western populations. Objective: We investigated the association between zinc and heme iron intakes and colorectal cancer risk in a Japanese general population. Design: We conducted a large, population-based prospective study in 39,721 men and 45,376 women aged 45-74 y. Heme iron and zinc intakes were measured by using a validated food-frequency questionnaire in either 1995 or 1998. Results: During as many as 808,053 person-years of follow-up until the end of 2006, 1284 colorectal cancer cases were identified. In multivariate-adjusted models, zinc and heme iron intakes were not associated with colorectal cancer in either men or women. In comparison with the lowest quartile, the HRs (95% CIs) for developing colorectal cancer in the fourth quartile of zinc and heme iron intakes were 0.77 (0.58, 1.03; P-trend = 0.2) and 1.06 (0.79, 1.42; P-trend = 0.6), respectively, for men and 1.05 (0.77, 1.44; P-trend = 0.4) and 0.88 (0.61, 1.29; P-trend = 0.4), respectively, for women. Conclusion: Our results in a Japanese population with lower intakes and different major food sources of zinc and heme iron in comparison with those of Western populations suggest that zinc and heme iron intakes are not associated with colorectal cancer.