The challenge of defining the global burden of iron deficiency anaemia.

Competing Interests: We declare no competing interests. This work was supported by the Bill & Melinda Gates Foundation (INV-010744), Centers for Disease Control and Prevention, Eunice Kennedy Shriver National Institute of Child Health and Human Development, HarvestPlus, and the United States Agency for International Development. The findings and conclusions of this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.