Heme and non-heme iron consumption and risk of gallstone disease in men.

BACKGROUND Excessive iron intake can promote biliary cholesterol crystal formation in experimental studies. The absorption of heme iron is more complete than that of non-heme iron in humans; however, the effect of long-term consumption of heme and non-heme iron on the risk of gallstones is unknown. OBJECTIVE The objective of the study was to examine long-term iron intake in relation to the occurrence of gallstone disease. DESIGN We prospectively studied intakes of heme and non-heme iron and the risk of gallstone disease in a cohort of 44 758 US men from 1986 to 2002. Iron consumption was assessed by using a validated semiquantitative food-frequency questionnaire. Newly diagnosed gallstone disease was ascertained biennially. RESULTS We documented 2468 incident cases of symptomatic gallstones during 597 699 person-years of follow-up. The age-adjusted relative risks (RRs) for men with intakes of heme iron and non-heme iron, when the highest and lowest quintiles were compared, were 1.21 (95% CI: 1.06, 1.37; P for trend = 0.0008) and 1.02 (95% CI: 0.90, 1.16; P for trend = 0.45), respectively. After adjustment for multiple potential confounding variables, when extreme quintiles were compared, the multivariate RR of heme iron intake was not significantly changed and remained significant with a dose-response relation (RR = 1.21; 95% CI: 1.03, 1.42; P for trend = 0.01), and that of non-heme iron intake was not significant (RR = 1.14; 95% CI: 0.99, 1.31; P for trend = 0.18). CONCLUSION Our findings suggest that a higher consumption of heme iron is associated with a greater risk of gallstone disease among men.