In this weekly series, LiveScience examines the psychology and sociology of opposite human behavior and personality types.
During the gustatory celebrations this holiday season, not everyone enjoys the feast's foods in the same way. Although the roast turkey is generally a hit, side vegetables such as Brussels sprouts or broccoli can taste disgustingly bitter to a few folks in the room. Some diners enjoy these veggies just fine, yet do not share in the bliss others feel when pumpkin pie is served up for dessert.
Holiday (as well as everyday) food preferences, scientists have discovered, derive in large part from the anatomy of our tongues. About a quarter of the population, dubbed "supertasters," has many times more taste-sensitive structures on their tongues than average. Another quarter of people possess so few they qualify as "nontasters."
"People live in different worlds of taste intensity," said Linda Bartoshuk, a physiological psychologist at the University of Florida. "Supertasters live in a 'neon' taste world, while others live in a 'pastel' world."
For supertasters, this is both a blessing and a curse: Though bitters are bitterer, sweets are also sweeter. "Supertasters are more sensitive to the burn from ethanol, the sweetness of sugar, the burn of chili peppers and the astringency of red wine," said John E. Hayes, a professor of food science at Penn State.
These sensations matter because how foods taste to us influences our individual eating behaviors. Expressed in the parlance of childhood, we eat the yummy and avoid the yucky.
Yet supertasters can learn to overcome or compensate for their biologically built-in tendencies for picky eating. "Biology is not destiny — it predisposes you, but we're humans and we make choices," said Hayes. "Learning can override genetics." [How to Handle Kids' Picky Eating]
Historically, the term "supertaster" — coined by Bartoshuk in 1991 — referred to people who reported a powerful bitter taste when a chemical called propylthiouracil (PROP) was placed on their tongues.
Further research has shown that the PROP receptor is just one of at least 25 receptors for bitterness. To complicate matters, some people who have a heightened sensation of other flavors can lack the PROP receptor.
A better way to identify a supertaster, then, is to simply look inside his or her mouth. The tally of little mushroom-shaped projections on the tongue, called fungiform papillae, reveals a person's tasting prowess or deficit.
Nestled within the walls of these tiny bumps are our taste receptors, called taste buds, which register the five currently recognized tastes: bitterness, saltiness, sourness, sweetness and umami (savoriness). Touch receptors in the fungiform papillae also help us "feel" our food's texture and temperature. [Humans Have Sixth Taste for Fat]
The application of blue food coloring makes the papillae easier to count. In a 6-millimeter diameter circle, which is "about the size of a hole punch," Bartoshuk said, supertasters can have as many as 60 fungiform papillae packed into the small space; nontasters can have as few as five.
"If you look at a bunch of tongues, some are covered with fungiform papillae," said Bartoshuk. "Others are just polka-dotted and don't have that many."
Why the tasting extremes exist
Researchers still do not know which genes determine fungiform papillae number or why the counts vary so wildly. But evolution offers a possible explanation for the variance.
When our nomadic ancestors roamed into a new environment, they had to figure out which native plants there were safe to eat, Bartoshuk said. Many plants contain defensive toxins that taste bitter to the mammalian tongue. Those individuals with mutations that enabled heightened bitterness sensitivity — the first supertasters — stood a good chance of avoiding death by plant poisoning. In the process, they also alerted nontasters what vegetation to avoid.
The supertasters' ability came at a price, though. These early humans would have found less of the food palatable in a given area compared with dull-tongued nontasters.
"A supertaster is safer in a new environment, because they can pick up those bitters," said Bartoshuk, "but a nontaster eats better in a safe environment, because they like more foods."
Interestingly, women are more likely to be supertasters, at around 35 percent of the population compared with 15 percent of men. Perhaps that skewing emerged based on the protection of a fetus (from poisonous foods) during pregnancy, Bartoshuk noted.
A taste sensation
Arguments from evolution aside, many of us enjoy a touch of bitter in our gin and tonics, say, or acrid candies. "What matters is the concentration," Bartoshuk said. "We're herbivores. A little bitter green mixed with something — a lot of people like that. But no one likes a really intense bitter."
Indeed, a too-potent bitterness commonly turns supertasters off to substances including vegetables, grapefruit juice, alcohol and coffee. To cut java's bitterness, supertasters will often add lots of milk and sugar, while nontasters will take their coffee black. Supertasters tend to avoid spicy food, while nontasters hanker for hot pepper-infused dishes.
Not all supertasters are particularly picky eaters, however, indicating that eating behavior is not inextricably tied to taste-bud genetics.
Everything from dinner-table experiences growing up to the phenomenon of "acquired tastes" shows that taste sensation is malleable, researchers note. Research by Hayes showed that some adult coffee drinkers, despite having lots of bitterness receptors, had learned to like the stuff anyway.
One way for an extreme supertaster to get more veggies, for example, into his or her diet is to blend them with other acceptable foods. "If you don't like the taste of bitter vegetables, you don't have to eat plain steamed broccoli — you can puree it into something," suggested Hayes.
Another trick: salt, which blocks out the tongue's bitterness sensation. It's no surprise that a lot of people, especially supertasters, like salty snacks and add salt to their veggies.
In a last bit of advice, and in the holiday spirit, Hayes pointed out that Brussels sprouts and broccoli can be served candied and roasted — a preparation that might appeal to everyone seated at the table.
"Adding three Splenda on top of the green beans might not be a good idea," said Hayes. "But we know a spoonful of sugar helps the medicine go down."