November 13, 2013

Infant feeding behavior encompasses a wide array of actions including breastfeeding, bottle feeding and the introduction of solid foods. Alison Ventura, PhD, an assistant professor in the Nutrition Sciences Department is focusing her most recent research on bottle feeding behaviors.

“It kind of stems from my observation that, obviously, breastfeeding is best and what we want to promote to mothers. There’s a lot of great breast feeding promotion going on,” Ventura said. “But in reality, there is still a lot of bottle feeding that occurs.”

According to Ventura, more and more mothers are choosing to breastfeed their children, but these mothers also need to go back to work. Although they are feeding their children with breast milk, the infants are drinking a lot of this milk from the bottle.

Ventura has been working in a Women, Infants, and Children (WIC) Clinic to teach mothers how to bottle feed correctly in a way that is responsive to their infant’s needs.

The hypothesized problem with bottle feeding is that it’s too easy for the mom to take control of the feeding, said Ventura. During breast feeding, the mother has little inclination as to how much their infant is consuming. The mother is forced to respond to the infant’s cue and see when they come off of the breast, or fall asleep. With bottle feeding it’s easier to feed in response to how much is left in the bottle and not in response to what the infant needs. Ventura said this behavior is like the clean-your-plate behavior found in adult feeding. “So the idea is that we’re trying to teach mothers to feed in response to their infant and not in response to the bottle,” she said.

Ventura videotapes all of the feedings that her research group observes and then studies the reactions infants have to different feeding situations.

One of the ways to measure a baby’s reactions during feedings is through the Facial Action Coding system. “If I were to ask you if you’re happy right now, you could say yes but who knows what that means and who knows if your happy is the same as my happy,” Ventura said. “And it’s even more complicated when you work with non-verbal populations like infants because you can’t verbally ask them how they are feeling. So, we use a lot of behavioral methods.”  Ventura uses the observed facial cues from the infants to see how they predict the infants’ acceptance of the formula and level of satiation.

Some of Ventura’s previous research looked at the different types of formula and how that might be important to satiation levels.

According to Ventura, one of the key ways formulas differ is in the protein they contain. The protein in most formulas is intact, meaning the formula contains low levels of free amino acids (the building blocks of proteins). However, there are subsets of formulas for which the protein is either partially or extensively hydrolyzed (or broken down), meaning the formulas have high levels of free amino acids. This may be significant for infant feeding behaviors because evidence from animal models suggests that foods with high levels of free amino acids may lead to greater satiation than foods with low levels of free amino acids because the unbound amino acids are able to interact with amino acid receptors in the gut more quickly than protein-bound amino acids. These amino acid receptors are thought to be part of a satiation signaling system between the gut and the brain. Studies with adults also suggest that protein hydrolysates promote satiation better than intact proteins. Of additional interest for infant feeding, breast milk contains significantly greater amounts of free amino acids compared to formulas, which may be one of the key compositional differences that underlie the different intakes and growth trajectories of breast milk versus formula fed infants, Ventura said.

Ventura’s research has shown that when infants are given formulas high in free amino acids, they consume less formula compared to when given a standard formula that is low in free amino acids. Additionally, when infants feed on formulas high in free amino acids over a long period of time, they have rates of weight gain that are more similar to breastfed infants, whereas infants fed a standard formula show accelerated rates of weight gain.

 “Ideally we want to make formula-fed infants look a lot more like breastfed infants’ growth and health outcomes,” she said.

She continued, “Obviously breastfeeding promotion is the most important and we want all mothers to breastfeed but with more and more breastfeeding, you’re also going to get more and more bottle feeding of breast milk because it’s not realistic for every woman to stay at home and breastfeed their child for 12 months.”

“I’m really trying to learn what bottle feeding means for mothers and how whether you’re formula feeding or breast milk feeding, we can make it as healthy an experience as possible,” she concluded.