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The Bitter Taste of Genetics

I think we have a taster! Maybe even a supertaster!”

That’s what the Denver Museum of Science and Nature’s curator of human health said, laughing, as I made a face. It was Thursday afternoon, and Nicole Garneau, the curator, and Patty Drever, a volunteer, had just swabbed my cheek and instructed me to lick a piece of bitter paper. Imagine black coffee grounds mixed with raw broccoli. To me, it tasted that bad.

They kindly offered me a breath mint to remove the bitter taste from my mouth. Then I was weighed, measured, and my tongue was stained blue. Visitors watched through the glass wall of the laboratory and on a live video feed while I stuck out my blue tongue for the camera, counting how many pink taste buds appeared. With that, I had participated in a research project on the genetics of taste at the museum’s Lab Central.

Lab Central is part of the museum’s ongoing exhibit on health and biology, Expedition Health. Its goal is to bring genetics research into the public arena with a community-run study that looks at how our genes affect our ability to taste bitterness, and how that influences our health.

“We ride the line between a lab and community outreach,” Garneau explains.

Most people who participate, reporters not included, are automatically enrolled in the study. After going through some light paperwork – a consent form, a few basic questions to identify smokers and ethnic ancestry – participants are instructed to put a nickel-sized piece of paper on their tongues. The paper contains a chemical compound known as PROP, which is responsible for the bitter taste associated with broccoli, brussel sprouts and cabbage.

Volunteers then count the number of taste buds by staining participants’ tongues blue. The dye highlights the taste buds, which don’t get absorbed. The more taste buds you have, the better you taste.

People fall into three categories: non-taster, taster or a supertaster. My reaction indicates that I’m a taster or supertaster.

And that makes sense. I require milk and sugar before considering a cup of coffee. I do eat vegetables, but only when they’re covered in dressing of some kind. I can’t stand cabbage, one of the bitter tastes that the PROP chemical emulates.

Most people are tasters, but as many as 25 percent of people of Caucasian descent are non-tasters, according Danielle Reed of the Monell Chemical Senses Center. Women are more likely to be supertasters than men. Pregnancy makes women more sensitive to taste. This sensitivity dulls with age. One of the purposes of this research is to better understand how these taste categories break down among gender and ethnicities.

So why look at taste? Everyone knows who in the family is the picky eater, who can’t stand broccoli, and who drinks their coffee black. What they don’t know is that the difference between those who find the paper bitter and those who don’t can be narrowed down to one gene: the Tas2r38 gene. My sensitivity to bitter taste is a result of three nucleotides (the A, T, C, and G that make up the DNA double helix). Volunteers with a different gene makeup might taste nothing.

Recoiling at the bitter taste may also have something to do with my genetic ancestry. By studying the genes of lab participants, scientists hope to learn if people from similar genetic ancestries are more likely to taste bitterness or not. Finally, the team at Lab Central wants to know if there is any relation between my bitter-sensitivity and my health.

What and how much we eat is in part determined by our sense of taste. If we can better understand our taste receptors, we can understand our dietary choices, a crucial element in the fight against obesity, says Tom Finger, co-director of the Rocky Mountain Taste and Smell Center.

“If we can understand what is driving food intake, then we can handle overconsumption,” Finger says.

The lab, which is staffed by 60 volunteers, has enrolled more than 1,000 subjects in the experiment over the past year – they’ll get 16 on a busy day. Volunteers have undergone intensive training by the National Institutes of Health, and do everything from extracting DNA from cheek swabs to maintaining biology research stations at the museum’s Biology Base Camp, where visitors don white lab coats, gloves, and goggles to perform experiments of their own.

One of the main mission’s of Lab Central is to get the public involved in science, Garneu says.

But the citizen scientist model means the research takes longer. In the cabinets sit boxes of cheek swab samples waiting for their DNA to be extracted and analyzed. They have no genotype data yet, because Lab Central is backlogged. And relying on trained volunteers rather than researchers to carry out a research project can cause problems, Reed says.

“Imagine having 60 people cooking in a kitchen,” Reed says.”It could work out just fine if everyone follows the rules. But if everyone doesn’t follow the rules, it could end up like an episode of ‘I Love Lucy.'”

While they haven’t started analyzing the genetic data, they are beginning to see some patterns, like this pattern among female smokers: “The more years they have been smoking, the less ability they have to taste the bitter compound,” Garneau says. “But which came first? Did they start smoking because it didn’t taste bad to them, or can they not taste as well because of the smoking?”

Taste research is often overlooked, Finger says. Far fewer studies have been published on taste than other senses.

“We rely much more on vision and hearing for our perceptual world, and it’s sad that taste becomes the poor stepchild of investigative research,” he says.”But that doesn’t mean it’s any less important.”

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