An unborn baby begins ingesting amniotic fluid at around 12 weeks and a powerful sense of smell starts developing by 28 weeks. Based on this prenatal development process, it is worth determining whether or not babies can learn about flavours and odours even before they are born.
Several studies have explored this possibility. Researchers J. A. Mennella, C. P. Jagnow, and G. K. Beauchamp hypothesised that pregnant women are able to shape the palate of their unborn children through their food choices. Accordingly, flavours from their diet are transmitted to amniotic fluid and swallowed by their fetuses.
To test the aforementioned hypothesis, the researchers recruited 46 pregnant women and grouped them in to three. The first group was asked to drink carrot juice during their pregnancy and stop after their babies are born. The second group was asked to drink water during pregnancy and begin drinking carrot juice after their babies are born. The third control group was asked to avoid carrot juice before and after their pregnancy.
The researchers tested flavour preferences of the infants more than five months after they were born. They gave the babies two kinds of cereals, their first experience with solid foods—plain and carrot-flavoured. Through video recordings that documented the feeding experience, results revealed that babies from the first group or more appropriately, the prenatally-exposed babies exhibited fewer negative expressions while eating the carrot-flavour cereal compared with the plain cereal.
Moreover, through a nine-point scale rating, those infants who were exposed to carrots prenatally were perceived by their mothers as enjoying the carrot-flavoured cereal more compared with the plain cereal.
The study has supported earlier animal studies and further established the fact that unborn babies acquire food and taste preferences through their intrauterine environment and prenatal exposures to flavourings initially ingested by their pregnant mothers and transmitted to the amniotic fluid.
Nonetheless, the aforementioned study has several implications. Mennella, Jagnow, and Beauchamp mentioned that the very early flavour experiences that transpire during prenatal development may provide the foundation for cultural and ethnic differences in cuisines.
But apart from sociocultural relevance, the study and other similar undertakings suggest a possible workaround for preventing diet-related illnesses in the future. Researchers Kimberly K. Tout and Lisa Wetzel-Effinger suggested that the concept of prenatal flavour learning could be used to motivate women to eat healthy food. This learned flavour preference persists in infancy and even into childhood and adulthood.
Because of the long-term effect of intrauterine environment and prenatal exposures, pregnant women and healthcare practitioners could take advantage of this developmental stage to promote healthy eating and future-proof children from obesity and diabetes. Simply put, the obesity pandemic and prevalence of diabetes can be controlled and prevented by starting from pregnant women.
Pregnant women can essentially shape the food preferences of their children. However, this prenatal flavour learning process can also have negative impacts. Researchers P. Abate et al demonstrated that rodents who were prenatally exposed to alcohol are more attracted to alcohol-tainted water after they were born. Furthermore, the newborn rodents were more attracted to the smell of alcohol than then smell of their own amniotic fluid.
While the study of Abate et al could not be replicated to human subjects for obvious ethical and practical reasons, their reviewed observational has suggested that babies born to women who drank moderate amounts of alcoholic beverages during pregnancy have more pleasurable reactions to the smell of alcohol. It is also worth mentioning that Abate et al has reviewed several epidemiological studies that linked prenatal or fetal alcohol exposure and alcoholism in later life. Take note that these studies had controlled for genetics and postnatal environmental factors.
Another animal study by S. A. Bayol, S. K. Farrington, and N. C. Stickland revealed that rats that were prenatally-exposed to high-fat and high-sugar diet are more at risk for obesity and diabetes due to an exacerbated taste preference of high-fat and high-sugar diet. The study of Z. Y. Ong and B. S. Muhlhausler further support this finding. To be specific, their research revealed that feeding pregnant rats junk foods had altered the reward system in the brain of their offspring. These prenatally-exposed rats need to eat more high-fat and high-sugar food to get a sense of “high” or “rush” and make eating pleasurable.
Prenatal flavour learning can essentially put unborn children at risk of developing bad habits and poor eating habits later in life. Nevertheless, this same phenomenon or prenatal development process can also be used to the full advantage of pregnant women and healthcare practitioners. As mentioned, by incorporating healthy eating habits during pregnancy, mothers and their healthcare partners can shape the taste and food preference of their children and in a wider perspective, the future or upcoming generation.
Further details of the study of Mennella, Jagnow, and Beauchamp are in the article “Prenatal and postnatal flavour learning by human infants” published in 2001 in the journal Pediatrics. More details of the study of Tout and Wetzel-Effinger are in the article “Flavour learning in utero and its implications for future obesity and diabetes” published in 2001 in the journal Diabetes and Pregnancy.
More details of the study of Abate et al are in the article “Fetal learning about ethanol and later ethanol responsiveness: Evidence against ‘safe’ amounts of prenatal exposure” published in 2008 in the journal Experimental Biology and Medicine.
Further details of the study of Bayol, Farrington, and Stickland are in the article “A maternal ‘junk food’ diet in pregnancy and lactation promotes an exacerbated taste for ‘junk food’ and a greater propensity for obesity in rat offspring” published in 2007 in the British Journal of Nutrition. More details of the study of Ong and Muhlhausler are in the article “Maternal ‘junk food’ feeding of rat dams alters food choices and development of the mesolimbic pathway in the offspring” published in 2001 in The FASEB Journal.