| Abstract
| - Sialic acid is found in especially high concentrations in brain gangliosides, and supplementary sialic acid is associated with increased learning behaviour in animals. It was hypothesised that breast fed infants may have higher concentrations of sialic acid in body fluids and tissues because human milk is a rich source of sialylated oligosaccharides, while formulas contain very little. The aim therefore was to compare the sialic acid content of saliva collected from full term infants who were either solely breast fed or formula fed until weaning at 3-5 months of age. Thirty three infants, 18 breast fed and 15 formula fed, were studied at a mean (SD) age of 5 (2) months. The breast fed infants, when compared with formula fed infants, were found to have almost two times more free sialic acid in saliva (mean (SE) 16.0 (2.7) v 8.2 (2.1) mg/l, p < 0.036) and nearly 50% more total sialic acid (47.3 (3.9)v 32.2 (4.4) mg/l, p<0.014). The findings provide a preliminary indication that an exogenous source of sialic acids derived from human milk may contribute to higher concentrations of sialic acid in body fluids. There are important implications for the formulation of human milk substitutes. Key messages. Sialic acid is found in especially high concentrations in the gangliosides of the cerebral cortex of the human brain Human milk contains significant amounts of sialic acid but infant formulas contain very little In rats, supplementary sialic acid has been shown to increase learning and the concentration of sialic acid in brain gangliosides In this study, breast fed infants, compared with formula fed infants, were found to have higher concentrations of sialic acid in saliva An exogenous source of sialic acids derived from human milk may contribute to higher concentrations of sialic acid in other body fluids, including brain gangliosides
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