Breast Feeding Fuels Big Brains

The study looked at the average pregnancy term, breast-feeding length and brain size of 128 species of mammals. They saw that between different species brain size at birth was determined by the length of pregnancy, while the brain growth after birth was determined by breast-feeding duration.

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The extreme length of pregnancy and breast-feeding in humans (nine months and three years, respectively) is required for the growth and development of our large brains, which can reach 79 cubic inches (1,300 cubic cm.) — the biggest in comparison to body size across mammals. For example, a species of similar size, the fallow deer, is pregnant for only seven months and suckles for up to six months, and has an average brain size of 13.5 cubic in. (220 cubic cm). The extended time that human mothers invest in breast-feeding their young enables their brains to grow.

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These results suggest that breast-feeding plays an important role in brain development in humans, and supports the importance of the World Health Organization'srecommendation that new mothers nurse for at least six months and continue as long as possible for up to two years, the researchers say, though they can't say if there are brain development differences between formula-fed and breast-fed babies from their study.

The study was published March 28 in the journal Proceedings of the National Academy of Sciences.

Women should breast-feed for at least six months and up to two years to encourage the growth of the infant's brain as much as possible.