The study found that heme iron consumption increased the risk for coronary heart disease by 57 percent, while no association was found between nonheme iron, which is in plant and other non-meat sources, and coronary heart disease.
Along with first author Jacob Hunnicutt, a graduate student in the school's Department of Epidemiology and Biostatistics, the study's co-authors are Ka He and Pengcheng Xun, faculty members in the department.
Hunnicutt said the link between iron intake, body iron stores and coronary heart disease has been debated for decades by researchers, with epidemiological studies providing inconsistent findings.
The new IU research, a meta-analysis, examined 21 previously published studies and data involving 292,454 participants during an average 10.2 years of follow-up.
The body treats the two kinds of iron differently. It can better control absorption of iron from vegetable sources, including iron supplements, but not so with iron from meat sources.
"The observed positive association between heme iron and risk of CHD may be explained by the high bioavailability of heme iron and its role as the primary source of iron in iron-replete participants," the researchers wrote. "Heme iron is absorbed at a much greater rate in comparison to nonheme iron (37 percent vs. 5 percent). Once absorbed, it may contribute as a catalyst in the oxidation of LDLs, causing tissue-damaging inflammation, which is a potential risk factor for CHD."
The study has been published online in the Journal of Nutrition.