N-acetylneuramin lactose sulfate: a newly identified nutrient in milk.

The identity of a sulfate ester in rat milk has been determined to be N-acetylneuramin lactose sulfate. This sulfate ester is present in rat mammary tissue and in human milk. The presence of this compound offers an explanation for the simultaneous delivery of sulfate and calcium via the milk, two essential nutrients in early life, without precipitation of calcium sulfate in the milk. N-acetylneuramin lactose sulfate is hydrolyzed in the gut of the neonate and absorbed as inorganic sulfate. This is the first report suggesting that this ester may be of nutritional importance.