Turns out kids aren’t the only ones who are picky about veggies. Fetuses between 32 and 36 weeks’ gestation may also appear to wince at kale and smile for carrots, according to a small study in the UK looking at how fetuses respond to flavors.
The peer-reviewed article, published in Psychological Science, examines fetal chemosensory reactivity and found that fetal facial movements could be detected within 30 minutes of the parent taking a single dose of 400 mg of powder. carrot or kale in a capsule, the equivalent of about 50g of raw vegetables. These facial movements together form expressions that resemble a “laughing face” or a “crying face.”
“We believe that this repeated exposure to flavors before birth could help establish food preferences after birth, which could be important when thinking about messaging around healthy eating and the possibility of avoiding foods. “food fussiness” during weaning,” lead researcher Beyza said. Ustun with Durham University’s Department of Psychology in a statement.
This is the first longitudinal study to suggest that fetuses can detect chemosensory information through food eaten by the parent, the authors said.
“The results of this study have important implications for our understanding of the development of human oral and nasal chemoreception, including the nature and timing of behavioral responses to prenatal flavor exposure, fetal memory engagement for flavors,” the researchers concluded in the paper.
“It could be argued that repeated prenatal flavor exposures may lead to preferences for certain flavor profiles…Future studies should be followed by postnatal behavioral analyzes to assess how prenatal flavor exposure may influence food preferences. short-term and long-term postnatal.
Previous studies have shown that most molecules can cross the placenta, and fetuses begin to sense their surroundings for the first time through amniotic fluid. Previous research has looked at flavor changes in amniotic fluid after ingesting different foods or measured reactions in babies after birth.
A previous study found that babies had fewer nose wrinkles, lowered eyebrows, and head-turning behaviors and expressions compared to carrot-flavored cereal if they had been exposed to the flavor during the third trimester of pregnancy, compared to those who were not exposed.
In the latest study, the researchers found that over a brief period, the flavors from the capsules were digested and absorbed into the bloodstream and then metabolized, reaching the fetal chemoreceptors in about half an hour.
Around 100 participants aged between 18 and 40 from the North East of England took part in the study from 32 to 36 weeks gestation. The researchers measured the outcome by capturing fetal facial movements frame by frame through real-time 4D ultrasound recordings.
Researchers found that fetuses exposed to kale flavor gave increasingly complex “weeping face” expressions as they matured, such as “lower lip depressor”, “lip stretch” and presser of lips. Those exposed to the carrot flavor generated more “laughing face” expressions, but the movements did not become more complex over time. The study only looked at the reactions of the fetuses and did not examine whether the reaction stems from actual pleasure or an aversion to the taste.
“This contrasting result may be explained by the anatomical substrate involved in generating the laughing face and crying face gestalts,” the authors explained, noting that the single movement of pulling the corner of the lips upward is sufficient. to make the “laughing face” but several different facial movements are needed to create the expression “crying”.
There are some limitations to the study, the authors noted. Information for the control group, which was not exposed to any flavorings, could not be collected at the same frequency as those taking the capsules. The facial responses of fetuses could also be influenced by the types of vegetables the parent normally consumes. Another variable that may have affected the results is genetic variations in bitter taste perception and sensitivity.
The researchers are now conducting a follow-up study with the same cohort after they were born to see if their acceptance of different foods was influenced by their pre-birth experiences.
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