Brain ganglioside and glycoprotein sialic acid in breastfed compared with formula-fed infants

Background: The concentration of sialic acid in brain gangliosides and glycoproteins has been linked to learning ability in animal studies. Human milk is a rich source of sialic acid-containing oligosaccharides and is a potential source of exogenous sialic acid. Objective: The aim of the study was to compare the sialic acid concentration in the brain frontal cortex of breastfed and formula-fed infants. Design: Twenty-five samples of frontal cortex derived from infants who died of sudden infant death syndrome were analyzed. Twelve infants were breastfed, 10 infants were formula-fed, and I infant was mixed-fed; the feeding status of the remaining 2 infants was unknown. Ganglioside-bound and protein-bound sialic acid were determined by HPLC. Ganglioside ceramide fatty acids were also analyzed to determine the relation between sialic acid and long-chain polyunsaturated fatty acids. Results: After adjustment for sex with age at death as a covariate, ganglioside-bound and protein-bound sialic acid concentrations were 32% and 22% higher, respectively, in the frontal cortex gray matter of breastfed infants than in that of formula-fed infants (P < 0.01). Protein-bound sialic acid increased with age in both groups (P = 0.02). In breastfed but not in formula-fed infants, ganglioside-bound sialic acid correlated significantly with ganglioside ceramide docosahexaenoic acid and total n-3 fatty acids. Conclusions: Higher brain ganglioside and glycoprotein sialic acid concentrations in infants fed human milk suggests increased synaptogenesis and differences in neurodevelopment.