The observation that premenopausal women have a relatively low incidence of heart disease led in the nineteen eighties to the hypothesis that iron deficiency protects against heart diseases. These early observations were followed-up by conflicting epidemiological data. To confer causal relationships from epidemiological data is challenging as results can be influenced by residual confounding or reverse causation. For bias reduction, an alternative analysis strategy utilizing single-nucleotide polymorphisms (SNPs) as instrumental variables (Mendelian Randomization) has been developed. A recent study using 3 iron status associated SNPs suggested a protective effect of a higher iron status on the development of CAD.3 With a larger set of SNPs covering different components of iron metabolism, we aimed to provide a reliable answer to this lingering question.