For decades, scientists and doctors have known that breast-feeding provides infants with numerous benefits that formula just can’t seem to duplicate.
Although babies fed on formula can thrive, there’s ample proof that breast milk can promote a baby’s nutrient absorption, protect against infectious diseases and aid development.
That common wisdom received a boost recently, when the American Academy of Pediatrics pronounced that almost all women should nurse their babies for at least a year–and they should keep it up just as long as the mother and child both want to.
Only recently, however, has science started to unravel which of the more than 100 components of breast milk offer those health benefits to infants. The picture is far from complete, but some answers are emerging.
The most widely accepted benefit from breast milk falls in the area of protecting babies against infections. Many believe that the substances responsible for this policing activity are antibodies mothers produce to mount their own defenses against infectious incursions. Breast milk may pass on these shields to breast-fed babies, guarding them against disease as well.
But this explanation would only account for breast milk’s protective benefits against diseases to which the mother has been exposed.
David Newburg, a biochemist at the Shriver Center for Mental Retardation in Waltham, Mass., has proposed that other entities in breast milk may be responsible for its protective effect. He suspects complex sugars in milk act as receptor-decoys against a number of pathogens, including those that cause diarrheal and ear infections.
Antibodies do the trick by binding directly to pathogens and disarming them. The complex sugars are even more clever. They pose as receptors on the surface of cells, where pathogens may try to bind to target host cells. The pathogens go for the sugar decoys instead, and the infant remains healthy.
Complex sugars differ from antibodies in another crucial fashion. Antibodies exist in breast milk only if the mother has been exposed to the pathogens, but these complex sugars float in every mother’s milk, Newburg said. In Western countries, where mothers may not be exposed to many diseases, these sugars could be providing the lion’s share of the benefits found in breast milk, Newburg said.
“There’s this whole array of complex sugars that we’re just finding out about now that seem to protect,” he said.
The complex sugar theory could have important implications for formula companies. Because formula gets heat-sterilized, any antibodies that would be added would destabilize. Complex sugars, however, might be easier to add–once scientists determine exactly which ones appear in breast milk. “If this is true, that would make it possible for them to improve formulas significantly,” Newburg said.
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In the meantime, formula companies are taking their own steps to bring their product closer to breast milk.
Almost a decade ago Abbott Laboratories’ Ross Products Division, the manufacturer of Similac, revised the approach to research. “Rather than focusing on breast milk, why not focus on the breast-fed infant?” asks William MacLean, vice president of pediatric nutrition and research and development.
Seven years and 42 studies of 2,400 infants later, Abbott released a new formula. Babies fed on this, they say, are physiologically speaking, almost identical to those who are breast-fed.
“The formula probably doesn’t look any different to the parent,” Abbott says, but they may notice the difference in their babies.
The new formula contains a mix of fat and calcium closer to the blend found in breast milk, which is thought to play a role in supporting the development of visual function in infants. In addition, the new formula has increased levels of nucleotides, small molecules found in all cells, approximating the levels of these substances in breast milk.
Finally and perhaps most important, the new formula appears to address a challenge that has faced pediatric nutritionists: how to deliver an iron-rich concoction that does not cause constipation. Studies found that more than 99 percent of infants fed the new formula passed stools similar in consistency to breast-fed babies, MacLean says.
That could be good news for mothers who work formula into their child’s feeding regimen. Despite physicians’ push for breast-feeding, many women continue to use formula because it’s more convenient. And while few would argue that in recent years, society has become more accepting of breast-feeding, not every woman has a job that allows her to disappear a few times a day to pump her milk.