The study proves that (and reveals how) the fetus reacts to the taste of food consumed by the mother

The study proves that (and reveals how) the fetus reacts to the taste of food consumed by the mother

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Some studies suggest that food preferences are established long before birth and are therefore largely influenced by the mother’s diet. To be sure, a team of psychologists from Durham University in the United Kingdom has, for the first time, investigated the reactions of fetuses to the various flavors that are presented to them. They were mainly interested in the facial expression.

Amniotic fluid is the first place where fetuses begin to perceive their surroundings. Their mother’s diet exposes them to a variety of tastes consisting of senses involving smell, taste and chemoesthesia (the ability to detect chemical irritants). Until now, the effects of prenatal aroma exposure on chemosensory development have only been measured after birth in infants. No one cared about what fruits might feel about different flavors.

The taste buds develop anatomically from the 8th week of pregnancy and can recognize tastes from the 14th week of pregnancy. In addition, fetal nostrils open to allow amniotic fluid access to olfactory sensory neurons that can detect odor molecules from 24 weeks of gestation. So while fetal chemosensors continue to develop anatomically and functionally after birth, they are mature enough to detect tastes, including tastes and smells, in the amniotic fluid during the last trimester of pregnancy, the researchers explain in Psychological science.

Facial expression examined by ultrasound

Several studies conducted on newborns support the idea of ​​stable, long-term preservation of fetal taste experiences, which may influence food preferences after birth. For example, infants a few hours old showed no aversion to the smell of garlic (compared to a control smell) if their mothers consumed it several times during the last month of pregnancy. Similar experiments were carried out with the smell of anise and the taste of carrots: infants whose mothers had recently consumed these foods showed less negative facial expressions.

In an unprecedented new experiment, a team of scientists wanted to investigate fetal responses to smells and tastes using ultrasound. First, they pinpointed the facial expressions that might convey feelings of pleasure and disgust by analyzing the different facial movements a human fetus can make—and examining which facial muscles were mobilized in each case. Usually, when the lower lip lowers towards the chin, it expresses negative emotions. They preserved 17 facial movements that could be attributed to fetal laughter and/or crying.

An example of a crying face expression from a fetus exposed to cabbage: (a) baseline, (b) crying face. FM11 = nasolabial fold; FM16 = lower lip pressor. © B. Ustun et al.

One hundred pregnant women aged 18 to 40 years based in North East England were recruited for this study. The researchers examined how fetuses between 32 and 36 weeks of gestational age responded to two contrasting flavors, namely cabbage and carrot (a control group was not exposed to either flavor). ” Kale was chosen because it gives babies more bitterness than other green vegetables like spinach, broccoli or asparagus. ”, the researchers note.

Based on experiments conducted on infants exposed to sweet and bitter flavors, the team hypothesized that there would be a significant difference in facial muscle movements between the different groups of fetuses tested here. They also expected facial expressions to become increasingly complex as fetuses developed.

The outline of a more frequent smile with a sweet carrot flavor

The taste stimulus was applied by ingesting a capsule containing carrot or cabbage powder – the capsule minimized taste decay until digestion. Participants refrained from consuming any food and/or beverage containing carrots and cabbage on the day of analysis and did not eat anything else for an hour before the experiment.

As expected, the 35 fetuses exposed to the carrot aroma showed more frequent lip stretching and laughing gestures, while the 34 fetuses exposed to the cabbage aroma showed more upper lip raising, lower lip lowering, lip stretching, lip compression, and crying gestures, compared to the carrot group and the control group (30 fruits) that were not exposed to any aroma.

facial movements fetus cabbage carrot
Relative frequency of fetal facial movements in the 32nd week of pregnancy, divided by exposure groups (cabbage, carrot, no flavor). © B. Ustun et al.

The team also found that the complexity of facial expressions increased from 32 to 36 weeks in the case of cabbage: expressions then more often consisted of four or more movements. On the other hand, no significant change was observed in the carrot and control groups.

[Ces résultats signifient] that even though the mother has not yet eaten, the fetus is already conscious or able to feel what her mother has eaten “, he said Guardian Dr. Benoist Schaal, researcher at the Center for Taste and Eating Habits at the University of Burgundy and co-author of the study. This study therefore has important implications for understanding the fetus’s ability to smell and discriminate between different flavors.

It could also be a useful support for guiding pregnant women to eat a varied and balanced diet so that they can pass on healthy eating habits to their future children. ” We know from other research that if the mother has a varied diet, consisting of vegetables, fruits, etc., babies are much less picky. “, emphasized Professor Nadja Reisslandová from the University of Durham, co-author of the research.

source: B. Ustun et al., Psychological Science

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