Boys and Girls May Get Different Breast Milk

Mother's milk may be the first food, but it is not created equal. In humans and other mammals, researchers have found that milk composition changes depending on the infant's gender and on whether conditions are good or bad. Understanding those differences can give scientists insights into human evolution.

Researchers at Michigan State University and other institutions found that among 72 economically sufficient mothers in rural Kenya, women with sons generally gave richer milk (2.8 percent fat compared with 1.74 percent for daughters).* Poor women, however, favored daughters with creamier milk (2.6 versus 2.3 percent). These findings, published in the American Journal of Physical Anthropology in September,