U. ILLINOIS (US)—While breast-fed and formula-fed babies both gain weight and seem to develop similarly, genetic tracking of an infant’s intestines offers new proof that the difference between the two are very real.

“For the first time, we can see that breast milk induces genetic pathways that are quite different from those in formula-fed infants,” says Sharon Donovan, professor of nutrition at the University of Illinois. Details of the study appear in the American Journal of Physiology.

“Although formula makers have tried to develop a product that’s as much like breast milk as possible, hundreds of genes were expressed differently in the breast-fed and formula-fed groups.”

“The intestinal tract of the newborn undergoes marked changes in response to feeding. And the response to human milk exceeds that of formula, suggesting that the bioactive components in breast milk are important in this response,” she notes.

“What we haven’t known is how breast milk protects the infant and particularly how it regulates the development of the intestine,” she says.

Understanding those differences, many of which were found in fundamental genes that regulate development of the intestine and provide immune defenses, should help formula makers develop a product that is more like the real thing, Donovan says.

In this small proof-of-concept study, Donovan used a new technique patented by Texas A&M colleague Robert Chapkin to examine intestinal gene expression in 22 healthy infants—12 breast-fed, 10 formula-fed.

The technique involved isolating intestinal cells shed in the infants’ stools, then comparing the expression of different genes between the two groups. Mothers in the study collected fecal samples from their babies at one, two, and three months of age.

Scientists were then able to isolate high-quality genetic material, focusing on the RNA to get a gene expression or signature.

Intestinal cells turn over completely every three days as billions of cells are made, perform their function, and are exfoliated. Examining the shed cells is a noninvasive way to examine intestinal health and see how nutrition affects intestinal development in infants.

“An infant’s gut has to adapt very quickly. A new baby is coming out of a sterile environment, having received all its nutrients intravenously through the placenta. At that point, babies obviously must begin eating, either mother’s milk or formula.

“They also start to become colonized with bacteria, so it’s very important that the gut learns what’s good and what’s bad. The baby’s body needs to be able to recognize a bad bacteria or a bad virus and fight it, but it also needs to recognize that even though a food protein is foreign, that protein is okay and the body doesn’t want to develop an immune response to it,” she explains.

If anything goes wrong at this stage, babies can develop food allergies, inflammatory bowel disease, and even asthma. “We’re very interested in frequent sampling at this early period of development,” she adds.

Scientists want to know how bacteria in the gut differs in formula- and breast-fed babies, and this technique should make that possible.

“Now we’ll be able to get a complete picture of what’s happening in an infant—from the composition of the diet to the microbes in the gut and the genes that are activated along the way.”

Researchers from Texas A&M University and Mead Johnson Nutrition contributed to the study. Mead Johnson also provided funding.

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