Bioavailable nutrient density: a new concept applied in the interpretation of food iron absorption data.

The nutritive value of a diet for a certain nutrient must be based on its ability to meet certain requirements for certain target groups. The current low energy intake makes it sometimes difficult to cover the requirements of certain nutrients from the diet. Thus, an important measure of the nutritive value of a food or a meal will be obtained if the amount of a nutrient absorbed is related to the energy content of the meal studied (bioavailable nutrient density). The amount of iron absorbed from a meal depends not only on its contents of heme and nonheme iron and on various dietary factors affecting the bioavailability but also on the iron status of the subjects studied. The bioavailability of iron in a meal must therefore be given for a certain iron status. Thus the following definition of bioavailable nutrient density for iron is suggested: The amount of iron (milligrams) absorbed from a meal per unit energy (1000 kcal) by subjects who are borderline iron deficient, i.e., nonanemic subjects with depleted iron stores.