Researchers in Zambia have reported that a substance in human breast milk seems to reduce the risk of mother-to-child HIV transmission.

The study found that women whose breast milk held higher than median-level concentrations of human milk oligosaccharides, a carbohydrate, were less than half as likely to transmit HIV to their babies as those with concentrations of the substance below the median.

"People talk about proteins and lipids that are important in human milk, but oligosaccharides are something people don't appreciate as much," said Lars Bode, the lead author of the study and an assistant professor of pediatrics at the University of California-San Diego.

The researchers collected breast milk samples from 81 HIV-positive women who transmitted the virus to their infants during breastfeeding, 86 HIV-positive women who did not transmit, and 36 uninfected women. The scientists analyzed the samples for human milk oligosaccharides in response to growing evidence that the substance contains immunologically active components that may reduce the risk of viral transmission.

In resource-poor countries, the risk of HIV transmission from breast milk is outweighed by its health benefits, so infected women are encouraged to breastfeed while taking antiretroviral drugs.

[PNU editor's note: The study, "Human Milk Oligosaccharide Concentration and Risk of Postnatal Transmission of HIV Through Breastfeeding," was published in the American Journal of Clinical Nutrition (2012;doi:10.3945.ajcn.112.039503).]