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Recently, we brought you a whole cookbook of recipes featuring bitter flavors, from salad greens to grapefruit and beer. But it's a tough sell. The word bitter can make some of us wince. In conversation, it tends to suggest something unpleasant; there's the bitter pill to swallow or bittersweet memories. But if you're puzzled by bitter's bad rap, perhaps you're actually among those that likes the flavor. It may say something about your genes. NPR's Allison Aubrey reports.
ALLISON AUBREY, BYLINE: It's often said that opposites attract. And this may be true for Matthew Ferringer and Samantha Barney. Matthew, who has a hobby making beer, tends to like all things bitter, from hoppy, pale ale to Brussels sprouts and kale.
MATTHEW FERRINGER: Bitter's a key part of eating. So I think it's awesome, yes.
AUBREY: But Samantha, who he's out on a lunch date with, is not so sure.
SAMANTHA BARNEY: I've never been keen on bitter things.
AUBREY: So what might explain this difference? Well, scientists have been studying a particular taste receptor gene.
JOHN HAYES: What we're really looking at is that people differ across how intense bitterness might be to them.
AUBREY: That's John Hayes, a food scientist at Penn State. Several years back, he and researcher Valerie Duffy at the University of Connecticut decided to do an experiment. They already knew that certain people, about a quarter of the population, have a version of a taste receptor gene that makes them more sensitive to bitter.
VALERIE DUFFY: The idea of how bitter you taste something is how strongly that bitter in food binds with the receptor and sends that signal to the brain that yes, this is bitter.
AUBREY: Now, Duffy says she herself does not have a version of the gene that enables bitter compounds to bind tightly. So when she eats greens or Brussels sprouts, they don't taste bitter at all.
DUFFY: I taste Brussels sprouts as sweet.
AUBREY: And she really likes them. Now, compare this to people who have a version of the gene which makes them very sensitive to bitter. Their strong perception of bitterness overwhelms the natural sweetness in greens, and her hunch was that this may lead them to avoid greens. So she decided to test the theory.
DUFFY: So what we did was we recruited young adults. And we asked them to come into the lab, and we did a bunch of taste tests with them.
AUBREY: They sampled all kinds of vegetables to establish their sensitivity. They were tested for the gene, and they filled out questionnaires and kept journals to document what they were eating. What came out of the study was pretty striking, Duffy says. The tasters who had the version of the gene that makes them super sensitive to bitter ate far fewer vegetables of all kinds - more than 200 fewer servings over the course of a year.
Did that surprise you?
DUFFY: Yes. What we think is that if somebody finds some vegetables too bitter, they kind of generalize to all green vegetables that they don't like.
AUBREY: But Duffy is quick to point out that many other factors play into this. Take, for instance, the couple on the lunch date, Matthew and Samantha. Matthew says his affinity for bitter could be in his genes. Or maybe it's what he learned from his parents.
FERRINGER: I just know I was exposed to a lot of food growing up. And so I got an appreciation for all of it.
AUBREY: And researcher Valerie Duffy says definitely; what our parents teach us is influential. But there are other influences too.
BARNEY: Yeah, I don't know. I thought I heard that your taste buds change after a certain amount of years.
AUBREY: Samantha may be onto something. Duffy says there are changes over a lifetime. For instance, the perception of bitterness is boosted during the childbearing years. And then, by age 70, regardless of the gene you carry, the intensity of bitter tends to fade. Allison Aubrey, NPR News.
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