Background: We prospectively studied iron intake in relation to the incidence of coronary disease in a 4-year follow-up of 44,933 men (with no previous history of cardiovascular disease) aged 40 to 75 years in 1986 who completed a food frequency questionnaire at baseline.
Methods and results: We documented 844 incident cases of coronary disease (249 nonfatal myocardial infarctions, 137 coronary disease fatalities, and 458 bypass operations or angioplasties). After adjustment for established risk factors, there was no significant association between total iron intake and risk of coronary heart disease. Men in the highest quintile of total intake (median, 37 mg/d) had a relative risk (RR) of fatal coronary disease or nonfatal myocardial infarction of 0.73 (95% confidence intervals [CI], 0.51, 1.06) compared with men in the lowest quintile of intake (median, 11 mg/d). Dietary intake of heme iron--mainly from red meat--also was not significantly associated with risk of coronary heart disease. However, incidence of fatal coronary disease or nonfatal myocardial infarction was higher among men in the top quintile of heme iron intake compared with men in the lowest quintile (RR, 1.42; 95% CI, 1.02, 1.98). This association remained after adjustment for dietary cholesterol and fats. Heme iron but not total iron intake was positively correlated with serum ferritin among 123 members of the cohort who participated in a validation study.
Conclusions: These results do not support the hypothesis that dietary iron in general increases coronary risk in men; they are consistent, however, with an increased risk of myocardial infarction among men with higher intake of heme iron, which is itself positively associated with iron stores.