They Say: Breastmilk Fights Respiratory Viruses Better In Girls

Science gets particularly exciting when it turns up things no one was expecting. Researcher Fernando Polack, working in Buenos Aires investigating how much protection breastmilk provides for very-low-birthweight babies against the wicked metapneumovirus (no vaccine yet developed), was surprised to find stark gender differences in his results:

Girls who were not breastfed had a much higher risk of re-hospitalisation for respiratory illness than boys, but breastfed girls were almost never re-hospitalised. In boys, the difference between breastfed and not was insignificant. (The researchers hasten to point out that there are plenty of other benefits of breastfeeding that still hold true for boys.)

The fascinating part of this is that a gender difference may point to breastmilk’s protective properties working differently than previously supposed. Maybe it’s not just delivering mum’s immunities until the kid gets its own—why would there be a gender difference in that? Could breastmilk prompt anti-viral protection in the absence of exposure to viruses somehow, interacting directly with the baby’s developing immune system? (Of course, why would there be a gender difference in that either?) The report from Vanderbilt Medical Center speculates maybe, though they have no idea how.

Sounds to me for now like another thing to throw on the “we don’t know what breastmilk is well enough to replicate it” evidence pile.