Bioavailability of Fortified Iron

A list of iron sources that are generally recognized as safe (GRAS) by the US Food and Drug Administration (FDA) is given in Table 3. However, as shown in Table 4, the bioavailability of different iron sources varies widely. Moreover, even within a given source of iron, such as the elemental iron powders commonly used to fortify various ready-to-eat breakfast cereals and other products, a significant disparity (5-148%) in relative bioavailability (compared to ferrous sulfate) can be observed. To some extent, these differing bio-availability estimates reflect the influence of the characteristics of the fortified product in terms of its contribution of various enhancers or inhibitors (Table 1) on iron bioavailability. In addition, other factors also can affect the bioavailability of elemental iron powders, such as the particle size of the fortificant

Table 3 Iron and zinc compounds listed as generally recognized as safe by the US Food and Drug Administration

Iron compounds

Zinc compounds

Elemental iron Ferrous ascorbate Ferrous carbonate Ferrous citrate Ferrous fumarate Ferrous gluconate Ferrous lactate Ferrous sulfate Ferric ammonium citrate Ferric chloride Ferric citrate Ferric pyrophosphate Ferric sulfate

Zinc sulfate Zinc chloride Zinc gluconate Zinc oxide Zinc stearate compound - a finer particle size is associated with greater iron bioavailability.

There is very limited information available concerning the bioavailability of calcium or other nutrients added as a fortificant to various products. One study in elderly women found that calcium citrate malate used to fortify orange juice had equivalent bioavailability to calcium from milk or calcium from a calcium carbonate supplement. In a study with adult subjects, the

Table 4 Average relative bioavailability in humans of various iron sources used as iron fortification compounds

Average relative

Iron compound



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