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The next time you crave a sweet treat, go ahead and buy a bag of jellybeans—guilt free. Your indulgence will be in the interest of science.

"Just be sure to get a good jellybean—not a cheap, generic one," said Thomas Finger, Ph.D., professor of cell and developmental biology at CU Anschutz.

Next, choose any color of jellybean. Plug your nose, and pop it in your mouth. After a few chews, notice what you sense.

Now, release your fingers from your nose.

"You'll experience an explosion of flavor," said Courtney Wilson, Ph.D. She explains that with a plugged nose, you probably could describe what you tasted as being sweet (or sour, if you chose a citrus-flavored jellybean). But it's only once you add in your sense of smell that you experience the jellybean's full flavor.

This "science" experiment is one Wilson and Finger conduct with students of all ages. They say the reaction is always the same.

"About half the people in the class say, 'Oh, wow!' when their sense of smell comes back online," said Wilson, assistant research professor of cell and developmental biology at CU Anschutz. "Most people have no idea how interconnected their sense of taste is with their sense of smell."

Finger and Wilson are working to help us understand the vital-yet-misunderstood sense that helped us evolve and thrive as humans. Here, they clear up some common misconceptions and share studies in their labs shining light on taste loss due to COVID-19—and the mysterious "undertaker" cells they discovered in the taste bud.

Why is taste important?

Wilson: Our system of taste evolved to warn us when something was potentially dangerous and help us seek out the foods we need to keep our bodies running. Taste is one of the senses we don't think about as much as vision or hearing. But it's innately important to our everyday life—for quality of life and function.

How do we experience taste?

Finger: Taste for people—and most mammals—is divisible into two broad categories: things that taste good and things that taste bad. We have only five basic tastes: sweet, bitter, salty, sour and umami (savory). Sweet and umami taste good. Salt tastes good as long as it's not too much. Bitter and sour tend to be tastes we find negative.

Wilson: Well, sour is complicated. We like margaritas and kimchi and lemonade.

Finger: Often, we add sugar to things that taste bitter, like chocolate. Chocolate that's 100% cacao tastes terrible. Sweet and umami can be added to negative tastes to modulate perception.

If we only have five tastes, how do we experience all the delicious flavors?

Finger: The way we use "taste" in a scientific sense is different from how we use the word conversationally. Say you eat chicken salad for lunch and remark, "That really tasted good." What you're saying is that you put food in your mouth, and your chemical senses—smell and taste—cooperated to give you a sensation we call flavor. In a scientific context, the word "taste" is about the sensations that come from our taste buds, which are limited to the five basic taste qualities.

So spicy things, such as hot wings, don't have a taste?

Wilson: Spicy is not something your taste buds sense. Your chemical senses also include touch. If you rubbed a hot pepper on your skin—or worse, got it in your eyeball—you'd feel the burn of a chemical called capsaicin. When you eat a spicy food, it's the heat-sensitive neurons in your tongue reacting to this chemical.

When we lose our sense of taste, does it have anything to do with our taste buds?

Wilson: Being sick can disrupt the ability to taste. We get a bad cold, and our noses get stuffed. Your taste buds are probably functioning just fine, in a scientific sense. When we chew food, air travels into the nose from the back of your throat, and you're smelling what you're eating. When our noses are plugged, air can't get into the nose so our perception of flavor goes down. But the sense of taste hasn't been tampered with. It's your sense of smell that diminished.

COVID-19 is known for impacting the sense of smell and taste. What do we know about this?

Finger: We recently looked . These people were never hospitalized, but they all reported taste problems a year after. We found that the long-term taste problems that existed mostly affected their ability to taste sweet, umami and bitter. But for most of the patients—about 90%—it was their sense of smell that was impacted. Taste was disrupted in a smaller group, but it wasn't because the taste buds were physically damaged. It's more likely that in COVID-related taste problems, the dysfunction is in how the taste cells communicate—their cellular signaling.

What do we know about the cells in taste buds?

Finger: We know from other studies that all the cells in taste buds are replaced at least once a month. The taste bud cells you're tasting with today are entirely different from the cells you tasted with two months ago. Yet "sweet" still tastes "sweet." In your other sensory organs, such as your eyes and ears, the sensory cells are fairly permanent. Your body doesn't replace the photoreceptors in your eyes or the hair cells in your ears. But for taste, they're turning over all the time, and then they're replaced. Some of the taste cells are really fast—like every two weeks—but other cells turnover much slower. For example, we know that the taste bud cells that detect a sour taste are slower than the sweet ones. But generally speaking, it takes a month to replace all the cells in the taste buds, including so-called type 1 cells like the ones Courtney is researching.

What are you learning about type 1 taste bud cells?

Wilson: Well, we know that taste buds are constantly renewing themselves. We also know that some cells must die to make room for the new ones. To understand what's happening, . What we discovered are some unusual cells that look unhealthy and show signs of programmed cell death (apoptosis). We affectionately call these cells "blebby."

The type 1 taste bud cells act like brain support cells called astrocytes (glial) cells. In the taste bud, they help by cleaning up the dying "blebby" cells. Interestingly, these type 1 cells don't seem to die in the same way as the other taste cells, suggesting type 1 cells might leave the taste bud differently or have other unknown roles that we don't understand yet. They do a lot of other jobs, such as clearing out neurotransmitter substances, but they're kind of janitors or undertakers of the taste bud. We plan to keep studying these cells to learn more.

Why is understanding the taste bud so important?

Wilson: Taste is an interesting system that we haven't put nearly as many resources toward as our other senses. And yet taste is vitally important for our quality of life and sense of the world.

Finger: Take people undergoing chemotherapies. They often lose their taste. It's a big problem, because they need nutrition. But how do you keep people eating when nothing tastes good?

Wilson: Your taste system is all connected to your swallowing mechanism. If food doesn't taste good, you won't want to swallow. It's an important sense, and this is illustrated in any organism based on how often a lack of a sense exists in its population. In humans, people with blindness or deafness live full, beautiful lives. People without a sense of taste are much less common. Maybe we're biased, but we think we should know as much as we can about our sense of taste and our taste buds.