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Cover Story

September 29, 2008
Volume 86, Number 39
pp. 13-17

Unraveling Breast Milk

Analytical scrutiny reveals how complex fluid nourishes infants and protects them from disease

Jyllian Kemsley

WHEN IT COMES to feeding infants, the mantra is "breast is best." A diet of breast milk for babies is correlated with benefits including less diarrhea as well as lower incidence of diabetes or asthma when compared to formula-fed babies. But precisely how breast milk confers those advantages is unclear. Scientists know the basic ingredients of breast milk but don't fully understand how exactly they work to provide optimum nutrition for infants and protect against disease.

Neil Michel/Axiom Photo
Milk UC Davis graduate student Richard Seipert pipettes a milk sample as Lebrilla (far right) and coworkers observe.

A better understanding of the components of human breast milk—especially its lipids and oligosaccharides—and their role in ensuring infant health could lead to improved foods and better ways to treat gastrointestinal diseases, not just for infants but perhaps also for adults. "The one thing that has evolved with humans, to nourish humans, is breast milk," says J. Bruce German, a food science professor at the University of California, Davis. "It is the ideal evolutionary model for what nourishment should be."

Human breast milk is made up of several solid components. The most abundant of those is lactose, a disaccharide that provides energy for the infant. After lactose comes lipids, which are tho