Distribution of sialic acids in the milk of spanish mothers of full term infants during lactation

Abstract

The protective effect of human milk against infection is well known. Several non-immunologic components, including complex carbohydrates, have been described. The present study was undertaken to determine the sialic acid distribution in different milk fractions (complex carbohydrates). Milk samples from 12 Spanish women at three different lactational stages (colostrum, transitional milk and mature milk) were analyzed. Total and glycoprotein-bound, oligosaccharide-bound, casein-bound, and lipid-bound sialic acids were determined. Sialic acids from human milk are mainly bound to oligosaccharides and only a small amount is present bound to glycoproteins or in the free form. All the fractions analyzed showed a similar trend: sialic acids decrease rapidly along lactation. Casein-bound sialic acid does not follow this trend. We detected the presence of an O-acetylated species of N-acetylneuraminic acid. In human milk from Spanish women we observed slightly different values than those previously reported. This could be a result of population differences but nutritional or methodological aspects can not be discarded.