Bioavailable metals, definition

Elemental speciation studies show that human milk, especially colostrum and transitional milk, is very rich in HMW species associated with metals. Of course, many more studies are needed for a reliable speciation of such HMW compounds. In this sense, validation approaches, both for the reliable identification and exact determination of such species, should be urgently developed. In the same way as the elemental composition and/or distribution of human milk can be considered ideal for feeding the newborn, the composition of formula milks for newborns should ideally be as similar as possible to maternal milk at every lactating stage. However, essential element speciation in formula milks is far from that of human milk (the ideal composition). This could explain why the bioavailability of essential elements (including Cu, Fe, I, Mn, Se, and Zn) from formula milk is much lower than from human milk. Hence, artificial formulas are usually supplemented with such essential elements. More scientific knowledge is definitely necessary on the composition (speciation) of such elements and more attention must be paid to the chemical form in which they are added to formula milks. 

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