Sialic acid is the generic name for a group of sugar molecules commonly present in animal tissues. Sialic acids are present in essentially all human tissues, with the highest levels being found in the brain, where they are typically located at the ends of the sugar chains of cell-surface glycoproteins and glycolipids. The most common sialic acid found on human cells is N-acetylneuraminic acid (Neu5Ac or NANA). Sugar precursors to NANA are glucosamine and fructose. Human breast milk is also rich in oligosaccharides containing Neu5Ac. Foods containing high amounts of sialic acid include eggs and the whey component of dairy 1.