do they match infants dietary needs?
The protein content of human milk decreases rapidly during the first month of lactation26 and declines much more slowly thereafter. The decrease in total protein content is mainly due to a decrease in secretory immunglobulin A (sIgA) and lactoferrin. These two bioactive proteins, together with lysozyme, represent about 30% of the total protein in mature human milk. Therefore, the quantity of nitrogen in human milk changes dramatically, especially during the first days of life, from around 2–2.5 g/100 ml in colostrum to about 1.0–1.2 g/100 ml in mature milk. Nevertheless, the true protein content of human milk is often overestimated because of the high proportion of non-protein nitrogen (NPN) in human milk. Subtracting nonnutritional proteins and the NPNfraction (25%) from the total crude protein content (nitrogen 6.38), one arrives at a minimal protein content of 0.75 g/100 ml in human milk. Assuming an energy density of human milk of 67 kcal/100 ml, the protein energy ratio has been c
