Humans have a very short window for learning about flavors and developing preferences – and it closes just a few months after birth, says flavor learning expert Dr. Julie Mennella.
This flavor-sensitive period may affect health outcomes later in life, including whether a child becomes overweight later in life, she said, making these early months an important time for research and possible interventions.
Speaking at a presentation at IFT in Las Vegas last week, Dr. Mennella, a professor at the Monell Chemical Senses Center in Philadelphia, presented new research that adds to a growing body of evidence suggesting preferences for flavors are developed as infants – as well as in utero.
“Flavors are transferred via the amniotic fluid and through breast milk,” she said. “There is good evidence that there is a sensitive period for flavor preference.”
That period finishes at when an infant is about three to four months old, she said, although there is variation among babies.
A preference for the flavors of foods that a mother eats during pregnancy and in the first months of breastfeeding may help the developing infant prepare for its initiation to the solid foods it is likely to encounter later in life, allowing it to acculturate to the predominant food culture. However, it also has implications for formula fed infants, who tend to grow faster than breast fed babies.
Different formula, different flavor preference
Presenting her latest research, published in the journal Clinical Nutrition, Mennella said: “We can’t consider formula fed infants as a homogeneous group when it comes to flavor learning studies or health outcomes.”
In the study, 46 two-week-old formula fed infants were fed either extensively hydrolyzed protein hydrolysate formula, which has pronounced savory, sour and bitter flavors, or cow’s milk formula for a period of one, three or eight months. At 8.5 months, all of the infants were given a savory broth. Mennella and her Monell colleague Sara Castor found that babies randomized to the hydrolysate formula for 3 or 8 months (but not one month) consumed more of the broth, and at a faster rate.
“This is really setting the stage for who we are and who we will become,” Mennella said, suggesting that babies exposed to savory flavors in formula or breast milk may develop a preference for savory compounds – such as those in broccoli, for example – that persists throughout childhood.
Differences in weight gain
The research also suggested that formula composition is important in determining risk of overweight.
“Several studies show that there is faster growth in formula fed babies than in breast fed babies, but we can’t lump formula fed babies together,” Mennella said.
“Those that were assigned to the cow milk formula showed higher rates of growth. Those who were randomized to the hydrolysate formula showed more normative growth. Babies satiated on lower volumes when fed hydrolysate formula.”
She added that more research needs to be done to determine why babies fed cow’s milk formula tend to overfeed.
“Sensitive period in flavor learning: Effects of duration of exposure to formula flavors on food likes during infancy”
Authors: Julie Mennella and Sara Castor