A study in the November issue of Alcoholism: Clinical & Experimental Research examines associations between a newly discovered taste receptor gene (TAS2R38), perceived intensity of a bitter compound called 6-n-propylthiouracil (PROP), and perceived intensity of alcohol. Findings reveal that both bitter taste perception and genotype make overlapping and independent contributions to oral sensations from alcohol and alcohol intake.

"We do not all share the same oral sensory experiences from foods and beverages," said Valerie B. Duffy, a registered dietitian, associate professor in the School of Allied Health at the University of Connecticut, and first author of the study. "Some of the differences in oral sensation are under genetic control, and these differences can explain some of the variability in what we like and ultimately choose to eat and drink." She added that genetic variation in taste is a normal variation; it does not imply that some people are taste dysfunctional and others are not.

"It's about time that individual differences in taste perception have been considered in research since there are wide individual differences in the liking for the taste of alcohol," said Julie A. Mennella, a biopsychologist at Monell Chemical Senses Center. "Our sense of taste, along with the sense of smell, plays an important role in determining what foods and beverages we accept or reject. They are also our senses of pleasure."

Duffy explained that one measure for taste genetics is the bitterness of PROP. "Individuals who cannot taste the bitterness of PROP, or taste the bitterness of PROP as weak, are called nontasters. Those who taste the most bitterness are called supertasters. Previous research has found that PROP nontasters experience more positive, such as sweetness, and less negative, such as bitterness, irritation or astringency, sensations from alcoholic beverages and thus may be more likely to drink alcoholic beverages. Conversely, PROP supertasters have a sensory hindrance to consuming alcoholic beverages, because alcoholic beverages elicit more negative, such as bitterness or irritation, and less positive, such as sweetness, oral sensations."

Study participants (53 females, 31 males), primarily light and moderate drinkers, rated the bitterness of five PROP concentrations (0.032 - 3.2 mM). They were interviewed about how frequently during a year they consumed beer, wine, wine coolers, and liquor. Researchers also drew blood for genotyping from all participants in order to determine if the gene TAS2R38 “ which provides the blueprint for a protein that forms a receptor that allows individuals to taste bitter chemicals like PROP “ could predict PROP bitterness, alcohol sensations, and alcohol intake. Taste papillae on the anterior tongue (fungiform papillae) were also counted.

"There were two primary findings," said Duffy. "People who tasted the least bitterness from PROP or who were TAS2R38 nontasters consumed more alcohol than those who tasted the most bitterness from PROP or who were TAS2R38 tasters. For example, using PROP as a marker of taste genetics, those who tasted the least bitterness from PROP averaged consuming alcoholic beverages five to six times per week whereas those who tasted the most bitterness from PROP averaged consuming alcoholic beverages two to three times per week. This work suggests that genetics can influence our alcohol drinking behaviors, probably based on how pleasant or unpleasant we perceive the oral sensations from alcoholic beverages."

Duffy said that these findings, in conjunction with previous research, suggest that the intensity of PROP bitterness is a good marker for assessing genetic variation in taste on alcohol use. "TAS2R38 genotype and alcohol intake is probably mediated through the bitterness of PROP," she said. "In other words, the present study suggests another genetic mechanism that may mediate alcohol use based on oral sensory influences." However, she added, these results were found in light to moderate drinkers, and may not apply to individuals who abuse or are dependent on alcohol.

"The diet-health connection is not all bad for nontasters," added Duffy. "Other work from our laboratory and others' show that PROP nontasters experience less negative, as in bitterness, and possibly more positive, as in sweetness, oral sensations from vegetables, and like and consume more vegetables than do PROP supertasters, which may decrease their risk of chronic diseases associated with vegetable intake, such as some types of cancer."

"This is an exciting and important study involving genetic and taste influences on alcohol-taste sensation and intake in a group of light to moderate drinkers," said Mennella. "We now know that the earlier a young person drinks alcohol, the more likely he or she is to develop a clinically defined alcohol disorder at some point in life," said Mennella. "We also know that taste is usually the primary reason kids give for not using alcohol. Whether the genetic differences that underlie sensitivity to bitter tastes contribute to early experimentation with alcohol is an important area for future research."

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