Patient Presentation
A 30-month-old female came to clinic for her health maintenance examination. She was growing well and her mother described her as “head strong.” She was a generally compliant and happy child, but her mother said, “When she doesn’t want to do something, she will whine, cry, scream or just sit there and stare at you.” The mother described that she most often had problems when there was a time constraint such as leaving home in the morning or regarding eating. “She just absolutely refuses any vegetables. She lives on carbohydrates and fruit,” her mother described. The food had to be prepared and presented the same way or the child would refuse the food, and sometimes the entire plate. “I’ve tried to give her other things, or mix them up in the food she likes but she refuses again. She likes to put her macaroni in tomato sauce, but when I put some vegetables in the sauce, she refused the entire plate.”
The pertinent physical exam showed a smiling toddler. Her growth parameters were 50-75% with normal vital signs.
Her examination was normal. She did show her “head strong” behavior when a book was moved by the physician and she screamed until it was replaced where she had put it in the room.
The diagnosis of a healthy toddler was made. Further questioning showed that her diet was not very atypical and she did eat more foods than her mother had originally stated. The physician discussed how it was important to keep offering foods even if they are rejected several times. “It takes at least 8-10 times before they will even try to eat it and then they may not still like it. Just keep offering it, and also show her that you are enjoying the food. That sets a great example for her of how to eat a healthy diet,” he stated. He also encouraged the mother to continue appropriate discipline and ignoring of her behaviors. After the visit, the medical student who had been present was asking about children’s eating habits. The physician noted that eating preferences start young and are very much influenced by experiences with what is offered and how the family reacts. Kids like sweet things and don’t like bitter things. It’s part of our biology. But we all learn to eat more than breast milk or formula over time.
There’s alot known about the genetics of bitter taste and this is part of the reason some people really don’t like those types of food even as an adult,” he noted.
Discussion
Taste or gustation is the sensation of taste and is a primary human sense. There are 5 basic tastes currently accepted including sweet, sour, bitter, salty and umami or savory. There is also some data for distinct tastes of fats (called oleogustus) or complex carbohydrates. Taste buds in the oral cavity are the primary chemoreceptors of whether or not to allow a substance into our bodies. Taste receptors are also found in the gastrointestinal tract and are involved in gut sensing.
Flavor and taste are not the same although in general everyday language people use them interchangeably. Flavor is “… the integrated sensation that arises from the combined inputs of taste, chemosensation and olfaction.” There are thousands to millions of combinations of these inputs which then allow humans to experience a wide array of flavors.
Chemesthesis is a group of sensations caused by chemical irritants. It includes the cooling sensation felt from menthol or the warming sensation from capsaicin. This occurs through the trigeminal nerve and is a separately neurological pathway than the chemoreceptors for taste. Metallic is also not a taste itself but an important quality which also has some genetic basis.
In fetuses and young children, “…flavors are transmitted from the maternal diet to amniotic fluid and breastmilk[. M]others who consume a variety of healthful foods throughout pregnancy and lactation provide infants with an opportunity to learn to like these flavors.” Taste and olfaction receptors are already working in the last trimester of pregnancy. Flavors of maternal foods are in the amniotic fluid and fetuses swallow up 1L of amniotic fluid a day providing the opportunity to experience these flavors. Newborn infants receiving breast milk similarly have the opportunity to experience a variety of flavors and tastes, transmitted from the maternal diet to the infant.
Learning Point
Taste preferences are influenced by different factors including genetics, culture, repeated exposures and role models such as parents and siblings, and taste preferences change over time. Sweet tastes are preferred by newborns and bitter taste is disliked by infants. In general humans “… are born with a biological predisposition to prefer sweet and to avoid bitter foods such as green leafy vegetables. It has been hypothesized that this predisposition evolved to attract children to energy-dense foods while discouraging the consumption of toxins.” Bitterness is considered affiliated with toxins. The presence of sugars can effectively mask bitterness (e.g. chocolate). Bitterness can be a desirable taste such as in beer, coffee and chocolate.
There are at least 25 known genes in the bitter taste receptor family. Sweet has at least 3 genes, and others have been identified for sour and salty foods. Although there are genetics at work, exposures both directly with the food and also within the socio-cultural context of family can and does expand the food choices accepted by children, teens and adults.
Changes in taste preferences occur over time. Repeated exposures are needed to increase the acceptance of a novel food (at least 8-10 or more). Even with acceptance and ingestion of the novel food, the infant or child may still not like it (e.g. demonstrates negative facial expression) and additional exposures are needed until the infant or child learns to like a novel food. Foods that share similar flavor characteristics to preferred or already accepted foods help to increase the novel food acceptance. This understanding may help parents to continue to offer novel foods to young and older children particularly fruits and vegetables.
Interestingly, for formula fed infants, families tend to use the same brand and therefore the variety of flavors experienced by the infant may be fewer. Infants do show flavor preferences for the formula they are fed which can be long lasting. Formala fed infants obviously can and do acquire taste and flavor preferences with repeated exposure to complimentary foods.
Taste sensitivity is the ability to perceive a taste and this also changes over time. One cohort study of 4-6 years olds (N=131) who were followed longitudinally for 3 years, found that for some basic taste sensitivities and preferences changed.
| Taste | Sensitivity | Preference | Preference Type |
|---|---|---|---|
| Sweet | Decreased* | Increased | Medium or high |
| Sour | Increased | Stable | Medium or high |
| Bitter | Stable | Stable | variable depending on individual |
| Salty | Increased* | Not evaluated | — |
| Umami | Increased | Not evaluated | — |
* Different from previous studies which are mainly cross-sectional studies
There are also changes in older children and adults where sweet preferences in general have an overall decline.
Questions for Further Discussion
1. What advice do you give for starting complimentary foods in infants?
2. Using the information above, what other parental advice would you give?
3. How do sensations in the gut affect food and taste preferences?
4. What parental advice do you give for discipline of young children? A review can be found here.
Related Cases
- Disease: Taste Preferences | Taste and Smell Disorders
- Symptom/Presentation: Health Maintenance and Disease Prevention
- Specialty: General Pediatrics | Gastroenterology | Otolaryngology | Nutrition / Dietetics
- Age: Toddler
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for this topic: Taste and Smell Disorders
To view current news articles on this topic check Google News.
To view images related to this topic check Google Images.
To view videos related to this topic check YouTube Videos.
Barlow LA. Progress and renewal in gustation: new insights into taste bud development. Dev Camb Engl. 2015;142(21):3620-3629. doi:10.1242/dev.120394
Forestell CA. Flavor Perception and Preference Development in Human Infants. Ann Nutr Metab. 2017;70 Suppl 3:17-25. doi:10.1159/000478759
Fry Vennerod FF, Nicklaus S, Lien N, Almli VL. The development of basic taste sensitivity and preferences in children. Appetite. 2018;127:130-137. doi:10.1016/j.appet.2018.04.027
Nolden AA, Feeney EL. Genetic Differences in Taste Receptors: Implications for the Food Industry. Annu Rev Food Sci Technol. January 2020. doi:10.1146/annurev-food-032519-051653
Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa
Pediatric Education 