Babies remember (and prefer) smells, flavors from mom’s meals during pregnancy

Study shows picky eating might start before a child is even born

DURHAM, England — Parents everywhere struggle with getting their children to eat veggies, especially bitter greens like kale and broccoli. A new international study suggests that this challenge might be addressed long before a child takes their first bite of solid food. Researchers have discovered that babies can remember and prefer flavors they were exposed to while in the womb, opening new possibilities for developing healthy eating habits from the earliest stages of life.

This international collaboration, led by researchers from Durham University in the United Kingdom, along with scientists from Aston University and the University of Burgundy in France, provides longitudinal evidence of how flavor preferences develop before birth and continue into early infancy. The study, published in Appetite, builds on their 2022 findings that used 4D ultrasound scans to observe how fetuses reacted to different flavors in the womb.

“Our research showed that fetuses can not only sense and distinguish different flavors in the womb but also start learning and establish memory for certain flavors if exposed to them repeatedly,” says co-lead author Beyza Ustun-Elayan, Ph.D., from Durham University, in a statement. “This shows that the process of developing food preferences begins much earlier than we thought, right from the womb.”

During pregnancy, flavors from a mother’s diet make their way into the amniotic fluid surrounding the baby. Humans experience flavor through a combination of taste and smell, and fetuses encounter these sensations by inhaling and swallowing the amniotic fluid. By the last trimester of pregnancy, babies have developed sophisticated enough sensory systems to detect and respond to these flavor molecules.

“Fetuses not only detect minute amounts of all types of flavors the mothers ingest, but they overtly react to them and remember them while in the womb and then after birth for quite long times,” notes professor Benoist Schaal from the National Centre for Scientific Research in France. “In this way, mothers have an earlier than early teaching role, as the providers of the infant’s first odor or flavor memories.”

The research team recruited pregnant women at 32 weeks gestation, initially starting with 99 participants. Due to COVID-19 restrictions, the final study group included 32 healthy infants evenly split between males and females. These mother-infant pairs were divided into two groups: one group consumed kale capsules, while the other took carrot capsules.

To track the babies’ responses, researchers used sophisticated facial coding systems that analyzed specific expressions. They looked for two main types of responses: “cry-face gestalts,” which indicate displeasure (similar to when an adult might grimace at an unpleasant taste), and “laughter-face gestalts,” suggesting pleasure or acceptance (akin to a smile of enjoyment).

After their initial ultrasound scans, mothers took their assigned vegetable capsules several times a week for three consecutive weeks, consuming them between late morning and early afternoon. The consistency in timing helped control for any potential variations in how the flavors might be processed or transmitted to the amniotic fluid.

When the babies reached approximately three weeks of age, the research team conducted a novel olfactory test. They prepared wet cotton swabs dipped in either carrot powder, kale powder, or plain water as a control. Each swab was carefully held under the infants’ noses while their reactions were recorded on video. Importantly, the babies never actually tasted the substances, their responses were purely based on smell.

“Our analysis of the babies’ facial expressions suggests that they appear to react more favorably towards the smell of foods their mothers ate during the last months of pregnancy,” says professor co-lead author Nadja Reissland of Durham University’s Fetal and Neonatal Research Lab. “Potentially this means we could encourage babies to react more positively towards green vegetables, for example, by exposing them to these foods during pregnancy.”

The results revealed a fascinating pattern: babies showed fewer negative facial expressions and more positive ones when exposed to the smell of the vegetable their mother had consumed during pregnancy.

“These findings add to the weight of evidence that suggests that flavors of foods eaten by mothers during late pregnancy are learned by the fetus, preparing them for the flavors they are likely to experience in postnatal life,” says co-author professor Jackie Blissett from Aston University.

Understanding how food preferences develop could potentially prevent picky eating behaviors. Many children show strong aversions to bitter flavors, which is believed to be partly an innate survival mechanism evolved to protect against toxic plant compounds. However, these new findings suggest that early exposure through maternal diet might help override these natural aversions.

The research team emphasizes that this study represents a baseline understanding of prenatal flavor learning. Future research directions include longer follow-up studies to track how these early preferences influence eating behaviors throughout childhood. Additionally, researchers hope to explore how different cultural dietary practices might influence fetal receptivity to various flavors, as this initial study focused solely on children of white British mothers.

Scientists also plan to investigate how post-birth experiences, such as formula feeding with different taste profiles, might interact with prenatal flavor memories. Understanding these complex interactions could help develop more effective strategies for promoting healthy eating habits from the earliest possible stage of development.