Poor Taste Perception May be to Blame for Bad Eating Habits

As the global incidence of childhood obesity rises, researchers are examining whether differences in taste perception can influence eating behaviors. A recent study in Germany compared the taste sensitivity of obese and normal weight children and adolescents. Researchers found that obese youth identified taste qualities less precisely than their counterparts of normal weight (Arch Dis Child. 2012;97:1048-1052).

“Taste is a primary aspect by which children determine food acceptance,” the authors wrote. “It plays an essential role in eating behavior. In an evolutionary context, taste has an important function in the identification of valuable nutrition: Sweet tastes promise readily available calories, whereas bitter often indicates toxic substances.”

Sometime between early childhood and adolescence, taste sensitivity and quality undergo transformations. Newborns display a strong preference for sweets. During the second year of life, the nutritional shift from breast milk and formula to solid food coincides with a broadening of the taste spectrum, said Susanna Wiegand, MD, a co-author of the study and head of the pediatric obesity center at Charité Children’s Hospital-Universitätsmedizin Berlin. “There is clinical evidence that high sugar content at this period in life could cause the same fixation on sweet food and drinks for years, perhaps for the whole lifespan,” Dr. Wiegand said.

Study Details

In the cross-sectional study, Dr. Wiegand and her collaborators compared the gustatory sensitivity of 99 obese children (body mass index >97th percentile) with 94 normal weight children (BMI <90th percentile), aged 6 to 18 years. They analyzed the sensitivity of five taste qualities—sweet, sour, salty, umami and bitter—using impregnated ‘taste strips’ in different concentrations. A total score was determined for all taste qualities combined, as well as one for each separately. Additionally, the possible influence of sex, age and ethnicity on taste perception was analyzed. An intensity rating for sweet was performed on a five-point scale.

Compared with the control group, the obese children showed a significantly lower ability to identify the correct taste qualities regarding the total score (p<0.001). When analyzing individual taste qualities, the obese participants displayed a dramatically decreased detection rate for salty, umami and bitter.

In the sweetness intensity category, 93 obese and 75 normal weight children and adolescents rated sweet taste strips according to intensity. Participants from both test groups rated higher concentrations of sweet higher on the sweetness scale. However, when compared with the control group, the obese children rated all concentrations lower on the intensity scale and gave remarkably lower intensity ratings to three of the four concentrations.

Age and gender also had a major influence on taste perception. In the study, girls could identify taste qualities significantly better than boys, and advancing age was shown to affect taste sensitivity, with older children scoring higher than younger participants. There were no major differences in total score by ethnicity.

The researchers speculated that differences in taste sensitivity are multifactorial, and that genetic, hormonal and learning effects have an impact. Further, they say, polymorphisms of the genes coding for taste are believed to cause inter-individual differences in taste sensitivity.

There are ways clinicians can assess levels of taste sensitivity. “For example, some researchers would use liquids that are pipetted onto the tongue in various concentrations,” said Thomas Hummel, MD, a professor in the Smell and Taste Clinic at the University of Dresden Medical School in Dresden, Germany and one of the study co-authors. “We used filter paper strips that had been impregnated with the various tastants in four different concentrations each,” said Dr. Hummel. “Following placement on the tongue, participants indicated what taste quality they perceived. These answers produced a score that reflected taste sensitivity.”

The German researchers also established pediatric norms for umami—the fifth human taste, which is best represented by monosodium glutamate. “Those norms have not been previously available,” said Donald Leopold, MD, a professor of otolaryngology at the University of Vermont College of Medicine in Burlington. “They figured out a way. It’s a difficult stimulus to create.” Using the taste strips, the researchers found that obese children were less able than their non-obese counterparts to identify salt, umami and bitter tastes.

Other Factors

Whereas previous studies had evaluated participants’ reactions only to bitter taste, this research assessed all five taste modalities, said Jayant Pinto, MD, an associate professor of otolaryngology at the University of Chicago Pritzker School of Medicine. In addition, it is valuable that the researchers measured not only sensitivity, but also intensity, of response. “This does contribute to the field by sort of suggesting—not only for bitter tastes, but also for other tastes—that lower sensitivity to these tastes may be associated with obesity,” Dr. Pinto said.

What most people perceive as a problem with their taste buds often stems from a problem with their sense of smell, said Allen Seiden, MD, a professor of otolaryngology at University of Cincinnati and a rhinologist with a special interest in taste and smell disorders. “When people lose their smell, they notice that food doesn’t taste right. What they mean is, they’re not getting any flavor, but they interpret that as taste.”

A loss of smell, with its subsequent impact on flavor deficit, can lead someone to try to compensate by oversweetening or oversalting food. “The study suggests that a diminished sense of taste may be more common than we realize,” Dr. Seiden said. However, he added, “It is still not clear whether a diminished sense of taste preceded or followed the onset of obesity, which would require further study. How this would impact obesity is not clear, but the implication is that a diminished sense of taste might lead to greater ingestion.”

Aside from obesity, diminished sensitivity may reduce quality of life by interfering with the pleasure and social interaction that people derive from food, said Dr. Pinto. The inability to detect spoiled foods or liquids, particularly among older patients with taste disorders, is also a concern, so safety issues become paramount.

Cause and Treatment

When patients visit an otolaryngologist’s office complaining of taste loss, a scratch-and-sniff smell identification test is typically the first line of assessment, because a loss of smell is suspected as the culprit. If the test detects a diminished sense of smell, a nasal endoscopy and possibly a CT scan would identify or rule out a nasal blockage, said Dr. Leopold. In his clinic, he also tests tasting ability for four different tastants—salt, sweet, sour and bitter.

In general, treating taste and smell disorders is difficult, particularly without an underlying primary cause. Otolaryngologists can help if the problem is really olfaction, prompted by chronic sinus disease, allergic rhinitis or nasal inflammation. “That’s something ENTs are obviously good at,” Dr. Pinto said. “If you improve olfaction, you can improve taste.”

Diminished taste and smell has also been associated with neurodegenerative conditions, such as Alzheimer’s disease and Parkinson’s. Among patients with Sjögren’s syndrome, medication in the form of cholinergic agonists can help stimulate salivary flow, Dr. Pinto said. In these and other instances, he noted, there may be practical ways for patients to enhance the flavor of food by experimenting with a variety of spices, textures, colors and temperatures. All of these factors, Dr. Pinto noted, can play a role in taste perception and quality of life.

Socioeconomic factors also influence taste, the study’s authors acknowledged. Notably, 85 percent of the obese children in this study were from families in lower socioeconomic classes, and parents of obese children were more likely to be obese. “Care must be taken to avoid incorrectly interpreting this data. The authors are not saying that obesity results from a change in taste sensitivity,” said Edmund Pribitkin, MD, a professor and academic vice chairman in the department of otolaryngology-head and neck surgery at Thomas Jefferson University in Philadelphia. “Obese and non-obese children differ in their taste sensitivities, probably as a result of many different factors. An interesting extension of this study would be to examine how taste sensitivities change as subjects gain or lose weight.”

A “Dynamic” Process

The German study “confirms that taste is a dynamic process, which typically matures with age through adolescence and which is directly influenced by hormonal factors,” said Dr. Pribitkin. It’s “hard to separate hormonal and genetic factors, however. Are women better tasters because they are genetically female, because they have more estrogen or because women are often the cooks at home and develop these qualities more readily than men?”

For otolaryngologists, understanding more about what causes changes in taste sensitivity may help with the development of new therapeutic strategies for patients with loss of taste sensitivity, said Adrian Williamson, MD, an otolaryngologist at the Arkansas Otolaryngology Center in Little Rock. “Loss of taste is a difficult and frustrating problem for both the patient and the physician,” he added.

The German study illustrates a correlation between weight status and taste sensitivity; however, it does not explain what is at the root of diminished taste sensitivity—a clinically meaningful question, said Alison Ventura, PhD, an assistant professor in the department of nutrition sciences at the Drexel University College of Nursing and Health in Philadelphia.

“Are some people born with a poorer ability to detect tastes, which predisposes them to overeating and obesity? Or, do overeating and obesity lead to diminished taste sensitivity?” she asked. “A longitudinal study is needed to better understand how and why these diminished taste sensitivities develop, how they relate to the development of obesity and what implications they have for long-term health outcomes.”