The Super Tasters
A simple test may offer genetic clues about why some of us stay thin while others pack on the pounds.
When Beverly J. Tepper lectures, she often leaves her audience with their tongues hanging out. Literally. As part of a talk on taste sensitivity, she passes out little circles of filter paper embedded with what is, to some people, a bitter-tasting compound with the unappetizing name of 6-n-propylthiouracil. She can tell immediately who in the audience is genetically programmed to taste it.
"It is absolutely striking," she said. "You can see it on people's faces." Those who are sensitive to the compound usually grimace like a baby tasting its first Brussels sprout. The non-tasters look curiously around the room, wondering what the fuss is about because "it literally tastes like a piece of paper to them."
It's more than a party trick. This little test may provide genetic clues as to why some people like vegetables and others don't; why some can eschew high-fat foods and others can't and why some people stay thin while others (many others) gain weight.
Tepper, N'82, N'86, a food science professor at Rutgers University, has been studying taste sensitivity for almost two decades. As an academic who often works closely with the food industry, she is combining food sensory science with nutrition science and psychology to better understand the links between taste, diet and health.
Her interest in taste genetics began around 1994 when she was investigating why some people enjoy high-fat foods more than others do. She asked test subjects to rate foods with different levels of fat, and then tried to cross their reactions with different variables, such as their age, sex, attitudes toward nutrition, what they grew up eating and whether they could control their food urges. "But nothing was coming out of that [research] that was really very interesting," she said. "It's the kind of thing that food companies tear their hair out trying to understand: Is there something about people's backgrounds that push them in one direction or the other about what they prefer?"
Non-tasters and super-tasters
Then she learned about a colleague's study that found that people who were really sensitive to that bitter 6-n-propylthiouracil (or PROP, for the tongue-tied) also, for some reason, gave higher creaminess ratings to dairy products than those who could not taste PROP.
"Maybe that's the key," Tepper recalled in thinking about her own research. "Maybe the variability is genetic. It's biological. It's not just something out in the air."
Tepper has spent years studying a genetic trait that causes some people to taste bitterness while others taste none.
PROP was nothing new. PROP sensitivity had been known as a genetic trait since it was discovered in the 1930s. People with the TAS2R38 genotype have receptors on their tongues that recognize the acrid substance.
Based on the dairy study, Tepper thought that the PROP test could tell her more than how well people could tolerate bitterness. She started by dividing test subjects into PROP non-tasters, medium tasters and particularly sensitive "super-tasters." (Statistically, about 25 percent of Caucasians are non-tasters; 50 percent are medium tasters, and 25 percent are super-tasters.) She then gave them high- and low-fat versions of salad dressings to taste. As predicted, the non-tasters liked the high-fat dressings better.
Subsequent work by Tepper and others has pointed to a host of taste tendencies that separate tasters from non-tasters.
"We recognized that PROP tasters not only taste the bitterness of PROP and the bitterness of other compounds more, but they perceive sweetness more; they perceive the textural aspects of dairy products more; they perceive hotnessólike chili pepperómore," Tepper said. "It's a whole range of sensory characteristics that they seem to be more sensitive to." (continued)
Profile written by Julie Flaherty, Editor, Tufts Nutrition.
Homepage photo by Vito Aluia. Tepper photos by Thomas E. Franklin.
This story originally appeared in the Winter 2006 issue of Tufts Nutrition. It ran online on January 22, 2007.