Mothers Make Breast Milk Differently For Male And Female Babies: Research

LONDON – A mother’s milk may containdifferent levels of nutrients dependingon the sex of her baby to meet differentgrowth needs, according to a newstudy which suggests formula milkshould be gender-specific.Scientists believe that mothers makebreast milk differently for male andfemale babies, suggesting that baby formulashould be different for boys andgirls to match the differences seen inbreast milk.“We have good reason to be sceptical ofa one-size-fits-all formula,” saidProfessor Katie Hinde, an evolutionarybiologist at Harvard University.Speaking at the American Association forthe Advancement of Science meeting,Hinde described her work in rhesusmonkeys that showed mothersproduce milk with 35% more fatand protein for male babies, andeven richer milk when the malewas first-born. However, whenmothers fed female babies, theirmilk was less fatty and had morecalcium, probably to support thefaster growth of their skeletons.Mothers produced more milkoverall for females, and over the courseof their breast feeding, they received thesame amount of fat as the males. “Boysand girls have different developmentaltrajectories, so if they are not gettingwhat they need, their development willnot be optimal,” Hinde said. Previousresearch found that milk with higher concentrationsof cortisol made baby girlsmore irritable.Hinde measured levels of cortisol inbreast milk for 108 baby monkeys at onemonth old, and later when the animalswere three or four months old.She found some subtle but important differences.Female monkeys became morenervous when cortisol was high early on.Meanwhile, male monkeys behaved morenervously when cortisol rose over time.