Formula milk should be sex-specific, little boys need more fat

Formula milk should be sex-specific, with more fat given to baby boys, a recent study suggests.

Harvard University's Dr. Katie Hinde recommended the reformulation, comparing it to how deodorants for men and women are also tailored to each gender. She also suggests that formula milk may at times be better for babies than breast milk since every mother produces a different type of breast milk.

In her study, she noted the difference between the milk produced by nursing monkeys for males and females. Milk for males was richer in fat and protein, especially in the case of milk produced for firstborn males. On the other hand, milk produced for female offspring was less rich but much greater in terms of amount and contained more bone-building calcium.

Hinde also showed how male and female monkeys respond to the stress hormone cortisol in different ways. A study on human babies found that girls, but not boys, became more irritable if their mother's milk was high in cortisol. Rat studies suggest this has long term benefits, with the animals actually becoming better at coping with stressful situations than others.

The research also found that every mother has different amounts of vitamins, minerals, sugars, fats and other nutrients. In some mothers, quality of milk is classified as very low as it lacks the necessary nutrients a baby needs, in which case shifting to a formula may be best. The problem with this, however, is that some mothers feel guilty if they are unable to breastfeed, Hinde said.

"Public health should be aided if greater attention was paid to this," she said in a statement. "We have good reasons to be skeptical of a one-size-fits-all formula milk."