THE ROLE OF SIALIC ACID IN INFANT NUTRITION AND BRAIN DEVELOPMENT

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Sub-optimal nutrition during critical periods of brain growth has persistent effects on the human brain. Premature infants are especially vulnerable because brain growth reaches its peak at 26 weeks gestation and remains high throughout the first year of life. Those fed human milk in the first month after birth have been shown to have a significant intellectual advantage compared with infants fed standard infant formulas. While the n-3 fatty acids such as DHA are thought to be important, other components of human milk may be of greater significance for brain growth. Our interest is in a sugar compound called sialic acid. It occurs in remarkably large amounts in human milk (up to 1g-L) but is present in only small quantities in infant formulas. Sialic acid is an important structural and functional component of brain cells. It is directly involved in nerve cell transmission, memory formation and cell-to-cell communication. During peak brain growth, young infants, especially pre-term ones, are unlikely to be able to synthesise sufficient sialic acid to meet their needs. At these times, they rely on human milk and infant formulas to supply the necessary building blocks. If their diet is a poor source of sialic acid, however, there may be lasting consequences for intellectual development. This research project addresses several questions. 1. Does oral sialic acid supplementation over the first few weeks of life increase both brain sialic acid levels as well as learning behaviour? 2. Is there any dose-response relationship - is more better? 3. Does supplementation influence the expression of genes encoding key enzymes in the brain? 4. Does dietary supplementation affect the activity of the liver enzyme involved in synthesis of sialic acid? If our findings can be extrapolated to human infants, they will have implications for the etiology of all types of cognitive and behavioural defects in children, including learning difficulties and attention deficit disorder.