Boys and girls get different types of breast milk when nursing, says study

Breast milk is endlessly fascinating. Aside from acting as a baby’s first vaccine, a baby can subsist on it alone without consuming anything else – yes, not even water – for the first six months of life. But its wonders don’t stop there. Take for instance, the concept of gender specific breast milk, which is discussed further in a study published in the American Journal of Physical Anthropology.

Gender specific breast milk is a response to gender and living conditions

According to the study, breast milk changes in composition depending upon the gender or the baby or the living conditions of their mum. 

Baby girls have been known to breastfeed longer and consume more milk. While boys tend to require more fat and protein in milk.

Researchers from the Michigan State University found that mums produce richer milk for sons when they are economically stable. But mums living in impoverished conditions tend to favour daughters more. When nursing baby girls, they tend to produce creamier milk.

‘Poor mothers will produce breast milk with higher fat concentration for daughters than sons,” reads the study.

What’s more, “poor mothers will breastfeed daughters more frequently than sons” while “economically sufficient mothers will breastfeed sons.”

Mums produced more energy-dense milk for boys, the study continues, if they are well off and better nourished.

Image source: File photo

Gender specific breast milk: How natural selection favours parental investment in boys or girls

Though the findings are fairly new, it further supports a 40-year-old theory, known as the Trivers-Willard Hypothesis, which explores the role of life circumstances in influencing parental investment.

For the study, researchers observed women from a poor community in rural Kenya and a well-off area in Massachusetts.

When times are tough, mums tend to invest more in daughters than in sons. When life is easy, they show more investment in their baby boys.

How so? From a socio-economical standpoint, investing in male offspring tends to be less of a priority in families who are in poverty. This is because their child is seen as having a disadvantage in life.

However, daughters are seen as “worth investing in” as they are likely to bear children if they survive until adulthood.

But the qualities of gender specific breast milk extend beyond the nutrition derived from breast milk.

According to Katie Hinde, a professor of evolutionary biology at Harvard University, milk composition could also influence the growth, development and behaviour of an infant. 

“Only half the story is what the mom’s producing,” she explains to the Scientific American. “The other [half] is how the infant uses the milk.”

Though these findings are quite fascinating, what matters is not the varying qualities of a mother’s breast milk. What’s important is the endless supply of love that goes into making sure a child grows up happy and healthy, regardless of their gender.

Sources: Scientific American, IFLScience.com, World Health Organisation

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