Stored iron and vascular reactivity.

Zheng et al 1 report that volunteer blood donors with a high donation frequency have significantly greater flow-mediated dilation than low frequency donors. Iron status among the frequent donors approximated a state of iron depletion by assessment of conventional iron markers. The study provides important support for the “iron hypothesis,” which suggests a protective effect of iron depletion, ie, the absence of storage iron without anemia, against ischemic heart disease.2–4 The blood donor findings suggest a new direction for the study of endothelial iron status in vivo to complement a growing body of work on iron in cultured endothelial cells. In addition, the finding of lower serum nitrotyrosine in frequent donors is consistent with the hypothesis that myeloperoxidase, a powerful emerging cardiovascular risk factor,5–8 is modifiable by manipulation of iron status.