Variability of human milk neutral oligosaccharides in a diverse population

Background: A complex array of free oligosaccharides is a distinctive compo sitional feature of human milk. Although these oligosaccharides have been s tudied for several years, their variability and distribution have not been systematically studied, and their nutritional and functional roles have not been elucidated. This report describes a study in which a large number of human milk samples were analyzed for the presence;md content of nine neutra l oligosaccharides. The resultant data were used to probe for distribution trends by donor groups and stage of lactation. Methods: Milk samples from 435 women residing in 10 countries were analyzed using a simple preparation procedure, gel filtration, and high-performance anion-exchange chromatography. Results: All samples contained structures based on lacto-N-neotetraose and lacto-N-tetraose. This contrasts with the fucosyloligosaccharides tested, n one of which was detected in 100% of the samples. Unexpected distribution t rends were observed. For example, 100% of the samples from Mexico (n = 156) contained 2'-fucosyllactose, whereas only 46% of the samples from the Phil ippines (n = 22) contained this structure. Concentration ranges for the ana lyzed oligosaccharides revealed quantitative and qualitative distribution t rends. Conclusions: The oligosaccharide composition of human milk varied among sam ples. The geographical origin of the donors was one of the factors that acc ounted for this variability. This can be explained by genetically determine d traits that are not uniformly distributed. Results indicated that further systematic studies are needed to ascertain the effect of other factors, su ch as lactation stage or diet.