MONDAY, May 10, 2010 (HealthDay News) -- Babies who are fed directly from the breast in early infancy tend to consume less later in infancy than their bottle-fed counterparts, new research suggests.
This kind of self-regulation of food intake may help explain why past research has found that breast-feeding protects against obesity.
"Infant self-regulation can indeed be affected by how the milk is delivered to the baby," said the study's lead author, Dr. Ruowei Li, a medical epidemiologist at the U.S. Centers for Disease Control and Prevention. "The more infants were fed with a bottle, the more likely that they would empty a bottle in late infancy," Li added.
"Infancy is a crucial period that has an impact on self-regulation, and many other studies have shown that infant growth and rapid weight gain have an effect on obesity later," Li said. "Obesity prevention needs to start in infancy."
What this means for parents who feed their baby either expressed breast milk or formula with a bottle, Li explained, is that they need to pay special attention to their baby's feeding cues.
Results of the study were released online May 10 in advance of publication in the June print issue of the journal Pediatrics.
The study included data from 1,250 full-term infants who weighed more than 5 pounds at birth. Their mothers completed a monthly feeding questionnaire until the babies were 12 months old.
With 1-month-old babies, 52 percent of the mothers were breast-feeding exclusively, and 41 percent were formula-feeding. The remaining babies were fed expressed milk or some other type of milk, according to the study. When the babies were 6 months old, just 27 percent of the mothers were breast-feeding exclusively, and 66 percent were formula-feeding.
When the babies were between 6 and 12 months old, the researchers asked the mothers how often the babies emptied their cup or bottle.
The study authors found that among infants who were breast-fed exclusively in early infancy, 27 percent emptied their cup or bottle in late infancy, compared with 68 percent who were bottle-fed exclusively and 54 percent who were given both breast and bottle in early infancy.
Li said there may be several reasons for this. For starters, she said, breast-feeding is generally directed by the baby, but bottle-feeding is directed by the caregiver and could lead to overfeeding.
"Mothers or other caregivers may push the baby to empty the bottle, but if they're breast-feeding, there's no way to visualize how much the infant is consuming," Li said.
Another possibility is that a mother's milk changes from one feeding to the next, and even during a feeding, Li said. Depending on what the mother has eaten, the milk may taste differently. And, she said, the fat content is much higher near the end of a feeding, and that might send a signal to the baby that it's almost time to stop.
Another factor might be that an infant who's breast-feeding isn't getting milk the entire time, Li explained. The baby suckles for a few minutes before the mother starts releasing milk, but with a bottle, that non-nutritive suckling time doesn't happen.
Dr. Deborah Campbell, director of the neonatology division at the Children's Hospital at Montefiore in New York City, described the research as "another study that stresses the importance of breast-feeding."
And, "if you can't breast-feed, this study shows the importance of learning to recognize your infant's cues and to respect those cues," Campbell said. "When we're bottle-feeding we often override babies' ability to self-regulate their intake."
But when babies stop sucking, turn their head or thrust their tongue out, she said, then the baby has had enough to eat.
"Parents are often concerned that if a baby doesn't get a full feeding that the baby will wake up hungry soon after," Campbell pointed out. "And, that may happen. But you have to respect the cues your baby is giving you."
Li agreed. "Feeding directly from the breast should be your first choice, if possible," she said. "If it's not, be aware that you don't overfeed. Pay attention to the signs your baby gives you. Babies are born with the ability to self-regulate their milk intake."
Learn more about the benefits of breast-feeding from the U.S. National Women's Health Information Center.