Linking the bioavailability of iron compounds to the efficacy of iron-fortified foods.

The bioavailability (relative bioavailability value; RBV) of iron compounds relative to ferrous sulfate has proven useful in ranking the potential of iron compounds for food fortification. The efficacy of iron-fortified foods however depends on the absolute iron absorption from the fortified food and not on the RBV of the iron compound. Compounds of lower RBV can be used to design efficacious fortified foods by adding them at an appropriately higher level. Efficacy thus depends on the amount of iron added to the food vehicle as well as the daily consumption of the fortified food by the target population, the amount of iron lacking in the diet of the target population in relation to their needs, and the prevalence of widespread infections and other micronutrient deficiencies. The World Health Organization has recently published guidelines for food fortification, which include recommendations for iron fortification compounds and a method of how to define the iron fortification level. The same organization has also published guidelines on the iron status methods to be used to monitor interventions. Recent efficacy studies, which have to a large extent followed these guidelines, have shown good efficacy of iron-fortified salt, fish sauce, wheat flour, and rice in improving the iron status of target populations. However, although we now know how to design an efficacious iron-fortified food, efficacy cannot be ensured in populations with widespread infections and other micronutrient deficiencies. In such situations, other public health measures may be necessary before we can ensure an improvement in iron status.