Both Human And Non-Human Sialic Acids Can Be Found In Human Breast Milk

All mammals synthesize sialic acids as both N-glycolylneuraminic acid (Neu5Gc) and N-acetylneuraminic acid (Neu5Ac) except for humans, in whom Neu5Gc is not made because of a genetic mutation. Even so, recent work has shown that normal humans can both take up Neu5Gc from dietary sources, and spontaneously express antibodies against it. Small amounts of Neu5Gc have been detected in healthy human organs, but to our knowledge, never reported in human milk. We therefore used a sensitive fluorometric HPLC-based method to see if it could be detected in human milk samples. We found the mean Neu5Ac and Neu5Gc contents in our samples to be 649 mg/L milk, and 3.45 mg/L milk respectively. The Neu5Ac levels declined with lactation duration, but the Neu5Gc levels showed no correlation. Whether the Neu5Gc content of human breast-milk is related to maternal diet, and whether it is taken up by the infant, is yet to be determined.