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The Sexism Lurking In Your Breastmilk

Photograph by Getty Images

There's a gender gap lurking in your milky boobs. And the advantage goes to the boys.

Psychologists Nancy Segal and Satoshi Kanazawaas analyzed data from a Longitudinal Study of Adolescent Health in the US. What they found was that the quality of a mother's breast milk changes depending on the sex of a child.

By comparing results of same-sex twins and opposite-sex twins, Segal and Kanazawaas concluded that a mother with different sex twins is not able to individually cater to each child while breastfeeding both children at the same time. Their analysis also suggests that mothers of boys produce heartier, more nutritional breast milk than those who have girls.

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In an article published on The New York Times website last week, Segal and Kanazawaas said that “Breast-fed same-sex twins were indeed either slightly taller or substantially taller than breastfed opposite-sex twins,” and that “Same-sex twins were, on average, nearly one inch taller than their opposite-sex counterparts. Similarly, same-sex twins were substantially heavier than the opposite-sex twins except during the first measurement period. The same-sex twins were, on average, 12 pounds heavier than the opposite-sex twins.”

Although latest theories may leave moms scratching their heads for a minute, it isn't the first time the debate over gender bias breast milk has come up. In 2014, Katie Hinde, an evolutionary biologist at Harvard University argued that "Mothers are producing different biological recipes for sons and daughters."

She went on to say, "It's not yet clear why human mothers produce such different milk for their babies. It could be adaptive in that it allows mothers to give more milk to daughters which is going to accelerate their development and allow them to begin reproducing at early ages."

Of course, this is all ignoring the fact that Hinde’s study was centered on the milk production of cows. Still, it was her belief that the stage is set for humans while a baby is still in utero. By having a better understanding of how a mother's milk catered to the individual sex of infants, she hoped to assist hospitals in finding better matches for donated breast milk.

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But the question remains: Is a mother's breast milk gender bias? According to Segal and Kanazawaas, it most certainly is. Their findings will be published in the April edition of The Journal of Experimental Child Psychology.

“To the best of our knowledge,” they argue, “ours is the first study to demonstrate that there are observable physical consequences of sex bias in human breast milk.”

While skeptics dispute the controversy surrounding their hypothesis, nursing mothers around the globe will unite in confusion and await confirmation. Until then, their infant boys and girls will have no other choice but to suck it up—as is.

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