From Kale To Pale Ale, A Love Of Bitter May Be In Your Genes

From Kale To Pale Ale, A Love Of Bitter May Be In Your Genes

4:02pm Oct 07, 2014
The roots of your hankering for hoppy beers and cruciferous vegetables may be genetic.
The roots of your hankering for hoppy beers and cruciferous vegetables may be genetic.
iStockphoto

The word bitter can make some of us wince. In conversation, we talk of "a bitter pill to swallow" or "bittersweet" memories.

But if you're puzzled by the bad emotional rap on bitter — perhaps you even like the taste of bitter greens or bitter beer — it may say something about your genes.

Scientists have been studying a particular taste receptor gene to understand why some of us may be more predisposed to liking bitter foods and hoppy beers. And a new study sheds new light on the bitter gene connection.

"What we're really looking at is that people differ in how intense bitterness might be to them," says researcher John Hayes, a food scientist at Penn State.

Several years back, Hayes and researcher Valerie Duffy of the University of Connecticut set out to do an experiment.

They already knew that some people (about a quarter of the population) have a version of one taste receptor gene, known as TAS2R38, that makes them more sensitive to the perception of bitter.

"The idea of how bitter you taste something is [tied to] how strongly the bitter [compounds] in food bind with a receptor," explains Duffy. Then, the receptor sends a signal to the brain that says, "Oh, this is bitter."

Duffy says she herself must not have a version of the gene that enables bitter compounds to bind tightly. She describes herself as a "nontaster." So when she eat greens or Brussels sprouts, she experiences them as sweet.

"To me, they're naturally sweet," Duffy says. And she enjoys them.

Compare this with people who have a version of the receptor gene that makes them very sensitive to bitter. For these individuals, the strong perception of bitterness overwhelms the natural sweetness in greens.

Duffy's hunch was that this may lead them to avoid greens. So she decided to test the theory.

"We recruited young adults and asked them to come into the lab and did taste tests with them," Duffy explains.

They sampled asparagus, Brussels sprouts and kale, and Duffy's team assessed their sensitivities. The young adult volunteers were also tested for the gene, and they filled out questionnaires and kept food diaries to document what they were eating.

"We found that individuals who are least sensitive to these bitter compounds consumed significantly more vegetables" compared with those who are most sensitive, Duffy says.

In fact, over the course of a year, the difference was about 200 more servings of vegetables.

Duffy's study was not the first to find this association. Another study, conducted in 2007 at the Centre for Cancer Epidemiology and Prevention in Turin, Italy, with about 600 volunteers, pointed to the same link between the bitter gene and the consumption of vegetables.

Duffy says what surprised her about her findings is that the people who were sensitive to bitter ate fewer of all kinds of vegetables, not just bitter, cruciferous ones.

"What we think [is that] if somebody finds some vegetables too bitter, they sort of generalize to all green vegetables," Duffy explains.

The same study also found a connection with papillae, those little dots on your tongue that we've reported on in the past. People with more papillae reported eating more vegetables, compared with those with fewer papillae.

This suggests that there are multiple factors, both biological and environmental, influencing our food and beverage choices, including — as Duffy is quick to point out — how our parents raise us.

People can learn to like vegetables, Duffy says, even if they carry the version of the taste receptor gene that makes them more sensitive to bitter. A big piece of the puzzle is figuring out ways to make them taste good.

For instance, "roasting brings out the sweetness," she says. Adding salt is also an effective way to cut the intensity of bitter. A study she published previously demonstrates that it's possible to mask the bitterness in vegetables with salt and sweeteners to make them more palatable.

So, does an aversion to bitter tend to be lifelong? Not necessarily.

Duffy points to studies that suggest there are changes over a lifetime. For instance, she says, we know that during pregnancy, many women become more sensitive to bitter.

And then, in older age, as smell and taste perceptions begin to fade, the taste of bitter foods can seem much less intense.

Copyright 2015 NPR. To see more, visit http://www.npr.org/.

Transcript

AUDIE CORNISH, HOST:

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. Transcript provided by NPR, Copyright NPR.

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