The study, carried out by the Indiana University School of Public Health – Bloomington, said it had found a "strong association" between heme iron, which is found only in meat, and coronary heart disease (CHD). It said heme iron increased the risk by 57% while non-heme iron, found in plant and non-meat sources, was not associated with the heart condition.
The study was published online ahead of print in the Journal of Nutrition. 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 had 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 new study is unique because it looks at the associations of total iron consumption as well as heme and non-heme iron intake in comparison to the risk of coronary heart disease. The only positive association involved the intake of heme iron.
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 in the journal article. "Heme iron is absorbed at a much greater rate in comparison to non-heme iron (37% vs. 5%). 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."
Iron stores in the body increase over time. The only way to reduce iron in the body is by bleeding, donating blood or menstruation. Some dietary choices, such as coffee and tea, can also inhibit iron absorption.