We often talk about the extraordinary ways that breast milk not only benefits your baby, but is also custom-made for the needs of your little love. But here’s one amazing thing about how breast milk supports your baby that you may not know: breast milk produced for boys is different than that made for girls. If your jaw just dropped, read on to find out about breast milk and your baby’s gender.
If you didn’t know any better, you may think your breast milk was a living, breathing, cognitive being. That’s because your breast milk has the incredible ability to change in nutrients, temperature and quantity to meet the needs of your baby. For example, the colostrum you produce in the first few days after birth is richest in protein and antibodies to help your baby survive outside the protective womb. As milk matures, it becomes more balanced with fat and sugary lactose to help your baby grow and develop. Your milk continues to evolve alongside your baby to meet her exact nutritional needs with every stage of development. Also, when your baby is hot or cold, your breast milk will cool her down or warm her up. And when your baby is sick, your breast milk will provide an extra dose of antibodies that you’ve made after being exposed to the same pathogens.
This tailor-made effect is nothing short of phenomenal, which is why it is even more astounding to learn that breast milk differs based on the gender of your baby. A recent study (National Longitudinal Study of Adolescent Health) based on same-sex vs. opposite-sex twins gathered that those who could receive breast milk specific to their gender – the same-sex twins – were better off based on height and weight at most points during childhood and adolescence. Those whose breast milk could not be customized because the babies were of opposite sexes were generally smaller as were non-breastfed twins. All of this data was collected based on self-reporting by the families participating in the study.
Other research published in the American Journal of Physical Anthropology recorded a notable different in the fat content of breast milk produced for boys vs. girls. Breast milk for baby boys contained 2.8% fat compared to 1.74% fat for baby girls. Girls tend to take in more milk and feed longer than boys. Examples among other mammals support these findings as well.
This recent research is based on previous studies that found cow mothers of female calves produce significantly more milk than mothers of male calves. This is in line with the human studies that indicate female babies drink more milk than males.
A study on rhesus monkeys showed that male babies received fattier milk with higher caloric value to fuel energy, strength and masculine behaviors, while milk for female babies was richer in calcium and helped them reach sexual maturity faster. These differences are likely critical to the survival of the primates because males must be dominant to find mates and females who can reproduce sooner (and therefore more throughout her lifetime) are more value to the species.
Breastfeeding is as old as time and yet there is still so much to discover. This new information linking breast milk and your baby’s gender is just another amazing piece of the evolutionary puzzle.
Sources: The New York Times, Mothering, IFL Science and Scientific American