WebMD Medical News
Laura J. Martin, MD
Dec. 22, 2010 -- Although women have been breastfeeding for generations and groups such as the American Academy of Pediatrics recommend exclusive breastfeeding for the first six months of a child’s life, researchers are finally beginning to get a better handle on exactly what makes breast milk unique and beneficial.
The new article appears in the December 23/30 issue of Nature.
“The diverse ingredients of an infant’s first meal have an impact on its development and no matter how much we tinker with the composition of formula milk, it will always lack many of the trace constituents of human milk,” concludes journalist Anna Petherick in a special article published in Nature with support from Nestle. “As research identifies these substances, it increasingly seems they serve a role beyond direct nutritional benefit.”
For example, the Promotion of Breastfeeding Intervention Trial (PROBIT) found that 6-year-olds whose moms breastfed had higher IQ scores than those whose moms were not encouraged to breastfeed. This may be related to specific genes in human milk but not cow's milk.
According to the article, breast milk for boys contains more fat and protein than the breast milk that girls get.
The sex differences in breast milk is “fascinating,” says Ginna Wall, coordinator of lactation services at University of Washington Medical Center in Seattle.
“We know that boys grow faster than girls, and perhaps this is due to the milk, or the milk may be responding to the commands of the child,” she says. “It could be triggered by prenatal chemistry or by the infant's sucking style, although in real time they sure don't look different when they're nursing.”
Barbara Holmes, a lactation specialist at New York University Langone Medical Center, agrees. “What it means is unknown,” she tells WebMD. “We don’t have clear evidence of why this might be or even if it is true.”
That said, preterm babies do get different milk than toddlers or bigger babies, she says.
“The body knows what milk to produce based on the way the baby sucks, so maybe boys suck differently than girls,” she says. “It would be great to do more long-term studies.”
Several studies have stated that infants who are breastfed get fewer infections, but new studies are showing that breast milk also affects gene expression in the stomach cells of infants.
“We know that there are benefits, but we haven’t been able to put our finger on it and say ‘this is it,’”says Sharon M. Donovan, PhD, RD, a professor of nutrition and pediatrics at the University of Illinois in Urbana-Champaign. Donavan’s research is cited in the new article.
“We have a lot of newer tools to answer some of the questions about how breastfed and formula-fed infants differ,” she says.
Her study looked at the colonization of bacteria in the infant’s gut and found that there are some differences seen in breastfed babies that may protect against diarrhea or food allergies.
What’s more, breast milk is rich in human milk oligosaccharides (HMOs), which help protect infants against infection.
“Some moms can have up to 200 different HMOs, and these are devoid in infant formulas, so the only way to get them is to add them,” she says. “We know that they are there, but we did not know about the content or diversity. The big question is whether there is a unique relationship between a mother’s HMOs and her infant.”
Adding HMOs to formula may not have the same benefit as those found naturally in a mother’s milk, she says. “We need to better understand the unique relationship between mother and her suckling infant.”
Going forward, “we can get formulas a lot more similar to breast milk,” she says. Donavan consults with various formula companies to help them optimize their products.
“Infant formulas are continually being improved, and are the best they can be,” she says. “We are trying to identify the uniqueness in breast milk and use the information to improve infant formulas because not everyone breastfeeds or is able to breastfeed.”
SOURCES:Sharon M. Donovan, PhD, RD, professor, nutrition and pediatrics, University of Illinois, Urbana-Champaign, Ill.Ginna Wall, coordinator, lactation services, University of Washington Medical Center, Seattle.Barbara Holmes, lactation specialist, New York University Langone Medical Center.Petherick A. Nature, Dec. 23, 2010; vol 468: pp S5-S7.Powe, C. American Journal of Human Biology, 2010; vol 22.
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