Effect of freezing on distribution of trace elements and minerals in human and cow's milk

Freezing is a common method for preserving human milk during storage and transport prior to its use for feeding to infants or for research purposes. Freezing milk samples may change the trace element and mineral distribution among their binding compounds, potentially affecting the bioavailability of these elements. In this study fresh human and cow's milk samples were fractionated and the distribution of these elements among fractions determined before and after freezing. Overall, very little effect of freezing was found on mineral distribution in human milk. Similarly, freezing did not have a strong effect on cow's milk; minor changes were observed for iron, copper, zinc and calcium in a few fractions. Thus, it is unlikely that freezing will affect the bioavability of iron, zinc, calcium and magnesium from human milk and cow's milk.