The unexpected link between taste and smell (Transcript)

Body Stuff with Dr. Jen Gunter

Wednesday, May 11, 2022

Listen Along

My favorite smell is wet sagebrush.

Grilled cheese that is directly off of the skillet.

The smell of being in Japan.

Tomato plants. When you pinch off the suckers to help them grow better.

That humidity smell of like a mix of plants and water and rain and just warm weather.

When my family and I drive up the Northern California coast, we keep our windows rolled up. So when we arrive, we can get slammed with the smell of the sea and Cypress trees and grass and evergreen trees.

The scent of wool.

The smell of soil.

Vox Pop:
Goat manure!

A home remedy my grandmother used to make…

Juan Pablo:
I lived in the tiniest town called Puerto Williams and for Christmas Santa would arrive in a helicopter. This very strong smell of gasoline means that Santa is coming with gifts.

[00:01:00] Dr. Jen Gunter:
Smell reminds us of home, of nature, of childhood, of holidays. It’s wrapped up in so many of our memories. But when asked which of their five senses they’d be willing to lose, smell is the one most people choose. What’s everybody got against our sense of smell? Philosophers from Aristotle to Kant dismissed smell as an unrefined or even vulgar sense. A lot of people think of vision and hearing as much more powerful… more important to our lives — and our survival — than SMELL and the closely related sense…taste. But the COVID-19 pandemic got us paying more attention to these two senses and how they’re connected. At the beginning of the pandemic, before testing was readily available, I started each morning by smelling my coffee beans and making my kids do it as well. Looking for some kind of false reassurance that we didn’t have the virus. In fact, COVID-19 is the only major news story that I can remember about smell. So smell and taste, these overlooked senses… how do they actually work? How are they connected? And what do they do for us? I’m Dr. Jen Gunter. And from the TED Audio Collective, this is Body Stuff. We’re starting this season by exploring the power of smell and taste. If you want to play along, grab some jelly beans and maple syrup. We’re gonna take a sniff right after this.


[00:02:44] Dr. Jen Gunter:
The first time I really remember thinking about smell was at a National Institutes of Health conference years ago.

[00:02:53] Dr. Linda Bartoshuk:
Oh, I remember it. Of course.

Dr. Jen Gunter:
Yes. And so there was an evening program and I was like, really like the NIH does entertainment. What's up with that? And you were the entertainment. You gave us this fascinating talk and I have told so many people about that amazing evening. Dr. Linda Bartoshuk is a psychologist at the University of Florida, and she’s been researching these senses for more than five decades. She is literally the person who discovered supertasters…those are people who experience tastes more intensely than most of us. At that NIH conference, Dr. Bartoshuk got me thinking about how complicated and amazing these senses are. Let’s start with smell. It’s a powerful sense! One study found that we can even track a scent over space. The researchers dragged a piece of chocolate across a grassy field and then asked people to find its path with their nose. And they did!
You’ve heard of the cardiovascular system and the immune system. Well, you also have an OLFACTORY system. It detects and interprets smells.

[00:04:06] Dr. Linda Bartoshuk:
An awful lot of things in the world around us emit volatiles that is, they emit chemicals that evaporate into the air. Odors are all volatiles. You can perceive them because you sniff them in through the air.

[00:04:20] Dr. Jen Gunter:
There are many, many volatiles…Your olfactory system can’t detect every single kind of molecule out there. Instead, it’s tuned to functional groups on molecules. Imagine there are thousands and thousands of Legos. For ease of processing, your brain lumps all the red pieces together…and all the green pieces together. That’s what functional groups are like, categories of Legos… And your nose helps your brain sort through them.

[00:04:48] Dr. Linda Bartoshuk:
So here you have three or 400 different receptors tuned to those functional groups, spread all through your olfactory mucosa. You smell bacon. The classic molecules that make bacon odor, the functional groups that are the same on the receptors all gather together so all the receptors of one kind go up in one bunch of fibers, another group go up another. And those fibers that all come from one receptor type go to a glomerulus. A structure in the olfactory brain.

[00:05:20] Dr. Jen Gunter:
A glomerulus is a clump of nerve tissue. Different odor receptors transmit signals to different glomeruli. You can imagine it’s like these glomeruli light up when they get a signal. And the pattern of this lighting depends on the chemical makeup of the thing you’re smelling…The glomeruli then send that information to your brain’s cortex. From there, your brain creates a sensation, a perception of what you’ve smelled… and it can associate things with that sensation.

[00:05:50] Dr. Linda Bartoshuk:
The most important thing to know about olfaction is how affective – pleasurable, displeasurable, emotional it is. So you sniff bacon, you eat bacon, calories, protein, your brain loves it. So the brain attaches a positive hedonic label to that picture of bacon in your brain. Next time you smell it, you love it. What about if you get sick from it? It takes several trials to produce love, but it takes only one to produce hate in olfaction.

Dr. Jen Gunter:
Oh, I, I have a story with peach schnapps.

Dr. Linda Bartoshuk:
Oh! I would love to hear it.

Dr. Jen Gunter:
Well, let's just say I had no idea that, that peach schnapps was as alcoholic as it was, uh, at all. I didn't know and probably eight drinks later and being violently ill. I couldn't eat peaches for ages. Anything that just had a peachy smell at all, I felt unwell.

Dr. Linda Bartoshuk:
Well, that's a survival mechanism.

[00:06:53] Dr. Jen Gunter:
So associations with smell are learned. But TASTE is hard-wired. Taste comes from our tongue and mouth. Taste buds have receptor cells that send information to our brain. We also have taste receptors on the roof of our mouth and in our throat.

Dr. Linda Bartoshuk:
Taste responds to salt, to sugar, to some compounds that have a hydrogen ion so they are sour acids and bitters.

[00:07:22] Dr. Jen Gunter:
Sweet, salty, sour, bitter… our four hard-wired tastes…Some people add umami to that. And that ones’s actually a little controversial. What you really need to know is that smell deals with thousands of molecules but taste sorts through these four major categories.

[00:07:43] Dr. Linda Bartoshuk:
You're born loving, sweet, hating bitter, and your salt receptors are not mature at birth in humans, but in a couple of weeks, they mature and then you like dilute salt and you don't like it when it gets strong enough to sting your tongue. We are hardwired for a certain set of bitters to absolutely hate them. We've got 25 different bitter receptors. Why would you make a system like that? Well look at poisons. They don’t all taste alike. So what you've got to do is make a bunch of receptors, so you can respond to different things chemically that are poisons.

Dr. Jen Gunter:
So my, my distaste of grapefruit is my evolutionary adaptation to not liking poison?

[00:08:22] Dr. Linda Bartoshuk:
Yes, yes, yes. It's not too strong. In fact, every time I lecture on bitter, some student will raise his or her hand and say, well, wait a minute. I love bitter. And my reaction is. I'll take you to the lab and give you a bitter you won't like, it's a matter of concentration. When I first read these theories as a student, I went into the lab and made myself up some who whopping quinine. And I swallowed it. I will tell you I had to hold onto the table. It was so bad.

[00:08:51] Dr. Jen Gunter:
When one of my sons was little, he had an oral aversion, meaning he couldn’t put anything in his mouth to eat. Eventually I bypassed that by getting a thin wafer of milk chocolate into his mouth. Oh, as it dissolved I could tell he LOVED it. Soon enough, he was eating food. But Dr. Bartoshuk says it wasn’t the chocolate that did the trick, it was the sugar.

[00:09:21] Dr. Linda Bartoshuk:
Very clever and that's been shown in experiments. You used the sweet as an unconditioned source of pleasure to produce a conditioned source of pleasure to the chocolate.

[00:09:34] Dr. Jen Gunter:
And it worked because we’re all hard-wired to like sugar. For a long time, we thought taste and SMELL were completely separate. If you sniff it, it’s smell. If you put it in your mouth, it’s taste. But smell — olfaction — ALSO happens when you eat something.

[00:09:58] Dr. Linda Bartoshuk:
There's a path from the back of the mouth, up into the nose. Think about post-nasal drip. Where does that come from? Well, it comes from your nose down through what's called a retro nasal space into your mouth. Well, odors go from your mouth up into the nose that way. So when you say you sniff some chocolate pudding, you sniff sniff, sniff, that's chocolate. That’s smell. Now you put it in your mouth, you swish it around, you swallow it. And when you swallow those volatiles, the odors from the pudding are forced up the retro nasal space and into your nose from the back. This is very interesting because it's the same chocolate molecule that you sniffed. And, you know, it's chocolate, both by sniffing and having it in your mouth as flavor. But the information coming up, the olfactory nerve is processed in two different parts of the brain, depending on whether you sniffed it through your nose or came through retro nasal space.

[00:10:50] Dr. Jen Gunter:
The physical act of sniffing tells your brain you’re smelling something. The physical act of eating tells your brain you’re tasting something. And when volatile compounds travel from your mouth to your nose, something called retronasal olfaction happens…THAT is where FLAVOR comes from... You can test the power of retronasal olfaction with an at-home experiment... using any food you’ve got around. I used a bag of jelly beans!

[00:11:21] Dr. Linda Bartoshuk:
Hold your nose closed. Put the jelly bean in your mouth, chew and swallow it, keeping your nose closed, keeping your nose closed when you're ready, swallow it and open your nose.

Dr. Jen Gunter:

Dr. Linda Bartoshuk:
You couldn't perceive the flavor until you opened your nose

Dr. Jen Gunter:
Yeah. And it took a second or two as well.

Dr. Linda Bartoshuk:
And then it hits. And the reason why is because air currents from your mouth to your nose, through the retro nasal space are stopped when you hold your nose, they can't move. When you open your nose, the air currents can move. And as soon as you swallow, the air is going to take the volatile up into your nose. And you're going to perceive the flavor.

[00:12:00] Dr. Jen Gunter:
My favorite flavor…orange creamsicle. So, Dr. Bartoshuk says FLAVOR doesn’t come from your taste buds.

Dr. Linda Bartoshuk:
I say to you, ok I'm going to give you a dish of ice cream. Taste it. What's the flavor? Are you going to tell me it's sweet? No. You're going to say it's chocolate or it's vanilla or it's butterscotch.

[00:12:20] Dr. Jen Gunter:
Flavor comes from volatiles, and the pathway they take to the brain means they are interpreted as flavor and not smell…Okay, that’s smell, taste and flavor. Smell and taste have a SHARED connection in our brain. If there’s trouble with one, it could affect the other.

[00:12:42] Dr. Linda Bartoshuk:
Let me give you a thought experiment. I'm going to give you some maple syrup and I want you to try it.

Dr. Jen Gunter:
I've actually got some maple syrup right here.

Dr. Linda Bartoshuk:
Okay. Try it and tell me what you sense. What do you experience?

Dr. Jen Gunter:
Sweet, for sure. Uh, and because I'm Canadian, it makes me think of Canada.

[00:13:03] Dr. Linda Bartoshuk:
And it's maple. Maple flavor, right?

Dr. Jen Gunter:

[00:13:06] Dr. Linda Bartoshuk:
Now I want you to do the following thought experiment. I'm going to take your ability to taste sweet, completely away from you. I use an Indian herb named Gymnema Sylvestre, and I make it into a candy. And I'm going to give you the candy and you let the candy dissolve so it even gets the sweet receptors in your throat as you begin to swallow the dissolving candy. Okay. So sweet is now totally gone. And I'm going to ask you to try the maple syrup again and tell me what you perceive. Now what do you imagine you would perceive?

Dr. Jen Gunter:
Wow. Uh, I guess I imagined that I would, I would still perceive maple.

Dr. Linda Bartoshuk:
Everybody gives the same answer, including my colleagues in chemical senses, which is why I set this up. As a matter of fact, the truth is the maple completely disappeared. Wow.

[00:14:00] Dr. Linda Bartoshuk:
Now, remember the maples coming from your nose. When I give you this candy I'm not doing anything to your nose. And here you are, you put the maple syrup in your mouth and retro nasal olfaction is taking the flavor molecules for maple right up there, but you don't perceive them. Why not? The sniff is what cues, the brain that you're smelling. And it knows to send the olfactory input to the smell area and taste is the cue that tells the brain, the odors coming from your mouth and should be processed as a flavor.

[00:14:36] Dr. Jen Gunter:
This blew my mind when I first heard it… When you don’t have the input from the taste buds, your brain doesn’t know you’re eating so it can’t process the retronasal olfaction... you won’t experience flavor. These senses are tied together in such intricate, extraordinary, and surprising ways. That is also why it can be hard to figure out why someone loses their sense of smell or taste. You have to think about the whole unit. Where is the problem? For example it could be in the nose, with nasal polyps. Or scarring from an injury in the mouth. There could be damage to the nerves, or the part of the brain that interprets smell and taste signals. With COVID-19, some early research shows that the virus might damage cells that support olfactory neurons… which could affect how messages about smell are sent or received. COVID also affects the brain, so it could be that the virus does some damage to the brain’s olfactory center. It’s so early that we just don’t know what we don’t know. Reports of loss of taste from COVID, raise questions too…is it because of the loss of smell and retronasal olfaction? Or is it caused by something else?

[00:16:00] Dr. Linda Bartoshuk:
COVID clearly affects olfaction. The effects on taste are less obvious the data are sufficient to make me think.There could be some direct effects on taste, and they occur like all viral damage to taste. For example, you get an ear infection, you get a really bad cold, the viruses from your nose and mouth go through your Eustachian tube into your middle ear. Viruses have access to your taste nerve, and they attack it. And we know that people who have repeated ear infections lose taste. They lose taste on the front of the tongue, which is an area innervated by that chorda tympani nerve. We can measure that very well. And we have. COVID’s a virus. Why couldn't it go through the Eustachian tube and attack taste in the middle ear? I think it would.

[00:16:43] Dr. Jen Gunter:
Dr. Bartoshuk told me about something that really blew me away. When we lose taste, we sometimes experience more PAIN.

[00:16:52] Dr. Linda Bartoshuk:
It's as if the taste input normally inhibits touch sensations, including pain in the brain. You damage taste, it's dis-inhibited and suddenly you not only feel more intense touch sensations, you feel more intense pain. And we actually did some measures in cancer survivors, and we found a connection between the most intense pain people reported and whether or not they had taste damage.

[00:17:22] Dr. Jen Gunter:
If you’re going to do a procedure on an infant, you might give them sugar to suck on because of this connection between taste and pain. Losing your sense of smell can have big consequences too — like missing warning signs about fires and rotten food, losing your appetite or adding extra salt, sugar, and fat to food because it seems flavorless. It can also be associated with depression. Smell and taste are so important, but I barely learned about them in medical school. I asked Dr. Bartoshuk why.

[00:17:56] Dr. Linda Bartoshuk:
I heard a talk by Margaret Mead at Yale many, many years ago. And she talked about why there was no nutrition institute at NIH and she thought it was because it was related to food and women's work and stuff, and it wasn't seen to have the same status. And the other thing is, the kind of puritanical nature of the society. We live in. Food we think of as joy, pleasure, enjoyment. It's not a fit topic for science. We're going to enjoy life? Worry about food and why we like it. Figure it out, understand it, work out the brain mechanisms. My God. That's important.

[00:18:36] Dr. Jen Gunter:
Culture informs so much of what we care about…and what we study! And it turns out, culture – language, in particular – also affects how we smell.


[00:18:57] Dr. Jen Gunter:
When we have to describe how something looks, we can usually do it pretty easily… This flower is pale pink, with five rounded petals and a little clump of yellow pollen in the middle. But if you asked me to tell you how it smells…I’d say…it smells like a flower. Kind of sweet…nice, you know, like a flower! This is common for English speakers. We say coffee smells like coffee. A banana smells like a banana. We just don’t have the words for describing smells…WHY??? Asifa Majid is a psychologist who researches how language affects the way we think and how we perceive the world.

Do you have a favorite word for describing a smell?

Dr. Asifa Majid:
I think it has to be petrichor, which is a made up word made up by some scientists to describe the smell of freshly fallen rain.

Dr. Jen Gunter:
I love that smell.

Dr. Majid says for a long time smell researchers assumed that our language for SMELL was universally limited. She started doing experiments across cultures to test what language could, and couldn’t, express. Then, one day, a colleague came back from the Malay peninsula with an amazing story about a nomadic hunter-gatherer community, the Jahai. He told her…the Jahai have a rich olfactory language. They have all these words to describe and categorize smells.

[00:20:35] Dr. Asifa Majid:
Well, I was like, that's impossible that that can't happen. Didn't really believe him at first. And when he was trying to explain. What these categories might be. I couldn't really imagine what they were.

[00:20:51] Dr. Jen Gunter:
I had a hard time imagining it too. But it helped to make a visual comparison. If I see a tomato, I can categorize it as “red.” I can look at the sky and call it “light blue.” Imagine doing that for smells. Imagine being able to say the smell of coffee or a banana belongs to a specific, descriptive category? As if there were red smells or blue smells. Dr. Majid was so curious, she started spending time with the Jahai.

[00:21:23] Dr. Asifa Majid:
ltpɨt smells for example, are really fragrant smells. Flowers, soap, a species of bear cat that smells like popcorn. And that's different from cηәs smells, which are also pleasant, fragrance, sorts of smells, but maybe more edibly delicious sorts of fragrant smells so cooked onion, for example, be cŋəs. haʔɛ̃t smells are rather unpleasant, but it's the smell of tiger, tree sap., That's different from plʔɛŋ sort of smells that are kind of bloody sorts of smells. Each of them are picking out different qualities of smell in the same way that color words, like red picks out a certain quality of color or green picks up a certain quality of color.

Dr. Jen Gunter:
So, how would they describe smells they've never encountered before? Would they be able to describe it in a richer way than I would be able to describe it?

Dr. Asifa Majid:
We took a set of odors that they wouldn't have experienced before. So monomolecular odorants that we sampled from chemical space. We gave them to the Jahai and we gave them to a similar group of Dutch speakers. I was living in the Netherlands when I was doing this research and we found the Jahai used their existing categories to name these novel odors.

[00:22:50] Dr. Jen Gunter:
Having many words for smell affects how well the Jahai can learn and name smells. Language helps us think through and process the world around us…A bigger smell vocabulary can expand our perception. The Jahai also communicate about smell with each other in ways we don’t; in fact it’s a big part of their culture.

Dr. Asifa Majid:
A brother and sister shouldn't sit too close together because their scents will mix and that's a kind of incest. For some types of meat, you shouldn't cook them on the same fire. So the Jahai will build two separate fires and cook the meat separately. They also believe that some smells make you sick and other smells can ward off sickness. So people often wear fragrant, roots around their neck or a belt or behind their ears to ward off sickness. So you see people with these like huge, you know, ginger roots tied around their neck that look awful, but smell really nice.

Dr. Jen Gunter:
But WHY do the Jahai have this smell language? Is it because they’re hunter-gatherers living in a rainforest? Do they just have a richer world of smell than I do?

[00:24:05] Dr. Asifa Majid:
In tropical rainforests, you have just much more biodiversity. So more things that are emitting smells, more volatiles in the air. And I guess maybe another thing to say just about the tropical rain forest is, is, is extremely dense vegetation. So your line of sight isn't very far, and so then sounds and smells become particularly informative about what's happening around you. But then, you know, you think, okay, that, that gives a kind of plausible scenario for developing a smell vocabulary, but then we find smell vocabularies in other environments that are quite different.

Dr. Jen Gunter:
Like, I grew up in Winnipeg…in Canada…where it can reach minus 40 degrees. Everything is frozen and almost smell-less for months at a time. So I wondered how the language of smell might have evolved for those like Inuit who live in very cold climates.

[00:25:01] Dr. Asifa Majid:
There are these like moments where smell kind of punctuates everything like the emergence of spring, but also in their food practices. So they, they're also a community that ferment food. So they have different stages of kind of rotting or fermenting foods that they also seem to recognize with distinct words.

[00:25:22] Dr. Jen Gunter:
So there are sophisticated smell languages in all kinds of different communities and even in languages spoken by big populations like Thai and Cantonese. It turns out that Indo-European languages all share a similarity: they have limited smell language. Indo-European languages range from Iceland to Sri Lanka, and include English, Spanish, Hindi, Greek, and Ukrainian. These languages all have a common ancestor. And we’re not sure why their smell vocabulary is so poor. But even without the words, smell still shapes our lives and social worlds…we’re just not as conscious of it.

[00:26:04] Dr. Asifa Majid:
We know from experiments in the west that we're very sensitive to social smell, so we can recognize if somebody is related to us based on their bodily smell. So grandparents can recognize their grandchildren by smell.

Dr. Jen Gunter:
Really? I didn't, I didn't know that.

Dr. Asifa Majid:
Yeah, we can also recognize somebody’s emotion from their sweat so we can recognize if someone's scared from the sweat that they emit.

Dr. Jen Gunter:
Do we still think that pheromones are something that humans can detect or do we believe that that's something that we've evolved out of?

[00:26:43] Dr. Asifa Majid:
This is one of those things where everybody gets very excited. I would say, the data today don't support something like that in humans. But that doesn't mean that there aren't certain smells that have some sort of biological significance for people. So newborn infants are very sensitive to the smell of breast milk and will orient to breast milk as soon as they're born.

Dr. Jen Gunter:
Wow. I, you know what? I never thought about that, but of course it makes sense because infant vision isn’t developed at all.

[00:27:16] Dr. Asifa Majid:
Infants do have preferences for certain odors and don't like other smells. But it's kind of more complicated because it turns out that their infant maternal diet is a really important factor in what infants like. So in one experiment, researchers gave mums a diet in which they included anise seed or in which they included garlic. And then they measured their newborns' reactions to these odors. And they found that infants liked the smells that their mothers had included in their diet when there were fetuses. We often think of infant studies as showing us what the human preference is without culture, but what these studies with odors show us is that there's already a chemical environment that's different for mothers in different cultures or even different social classes. And that's affecting what the young children are orienting towards.

[00:28:18] Dr. Jen Gunter:
Growing up, my mom cooked the worst of British food, and the only spices I experienced growing up were salt and pepper. I’ve really tried to expand my taste… and it’s worked pretty well. Just the other day I made an amazing chicken and sweet potato curry. By playing around with different combinations of cumin, turmeric, coriander, garam masala, and sometimes some chili powder, I’ve come up with something that I would have never been exposed to and now I don’t know how I could live without. It is so fragrant, and the way the smells fill the house…I absolutely adore it.

We really can learn to like new smells, especially when they’re associated with a delicious flavor.

And we can get better at describing smells, too… Dr. Majid says wine experts get around the limits of the English language by using metaphors.

[00:29:15] Dr. Asifa Majid:
One common one is to make an analogy to body. So wine has legs and body, and is full bodied, for example. So there's a metaphor of the body, metaphors that are related to speed and cars. And some wine experts have also kind of come up with a specific vocabulary. So Robert Parker for example, has his own dictionary of, of wine expressions, things like austere or backward.

[00:29:44] Dr. Jen Gunter:
You can pick up a wine dictionary and start using the words you find in there! But Dr. Majid says you can practice beyond wine. Smell things in your life and try to describe them to someone else. Make smell a shared pleasure. Or displeasure…

Dr. Jen Gunter:
So I once had a wine that was pretty awful, I think. And I thought that it had notes of cat urine in it. And someone said that's actually a term used to describe wine. I was horrified because I do not believe there's a worse smell on the planet than cat urine.

Dr. Asifa Majid:
I was just going to say that is in fact a dedicated term that wine experts use for wine.

Dr. Jen Gunter:
Okay. Walk me through that. That is like the worst smell.

Dr. Asifa Majid:
I know I can't walk you through it. I can't justify it. And I can't explain it.

Dr. Jen Gunter:
'Cause I’m like there is, I'm never cleaning out the litter box thinking, oh, I should go have a glass of Chardonnay.

Dr. Asifa Majid:
Mm Hmm. That puts me in the mood.

Dr. Jen Gunter:
Yeah. I might like the slug back a glass of Chardonnay, so I can go deal with the cat urine.

It’s not just that we can get better at describing smells. We can get better at identifying them too. I asked Dr. Bartoshuk how…

[00:31:00] Dr. Linda Bartoshuk:
Because we know that the pleasure of olfaction is associative, that is it's learned. Make your olfactory world more pleasurable.I mean, sniffing, when you're happy, sniff things while you're got sweet in your mouth. I tell people to sniff things while they're having sex, but that probably would take on a different connotation but, I once asked an exam question to the kids. I said, I've taught you about condition preferences. You now work for a company that makes odorants and you've created a new odorant. And you want your boss, the president of the company to market your odorant. What are you going to do to make him like it? And these kids were unbelievable. Put it in the air conditioning, give it to his mistress as a perfume. You know, I mean, they were just phenomenal and they were right. I mean, that's what you do.

[00:31:50] Dr. Jen Gunter:
Smell and taste are powerful. They warn us of danger, tie us to memory and emotion, give us information about the people around us — and tell us about our world, before we’re even born.

So next time you pour yourself a glass of full-bodied, austere Cabernet with notes of cherry. Or delight in the bright strawberry flavor of your favorite ice cream…marvel at all the work these senses are doing! All to tell you about your world and to help you enjoy it.

Next time, on Body Stuff…

Hall: Every heartbeat that we beat, every flutter of our eyelashes, is all driven by metabolism and energy.

Dr. Jen Gunter:
Everything you’ve probably heard about your metabolism is wrong. And we’re gonna wipe the slate clean…

Body Stuff is brought to you by the TED Audio Collective. It’s hosted and developed by me, Dr. Jen Gunter. The show is produced by TED with Transmitter Media. Our team includes Mitchell Johnson, Poncie Rutsch (rutch), Gretta Cohn, Michelle Quint, Banban Cheng, Sammy Case and Roxanne Hai Lash. Phoebe Wang is our sound designer and mix engineer. This episode was written and produced by Camille Petersen and edited by Sara Nics.
Fact checking by the TED fact checking team.

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Dr. Linda Bartoshuk:
I would recommend that you just put the tip on the tongue first and if it's intensely bitter, don't put the whole thing

Dr. Jen Gunter:
Okay. All right. For science.

Dr. Linda Bartoshuk:
For science. Is it getting nasty?

Dr. Jen Gunter:
It nasty, but it's not awful.Yeah, It tastes a bit like grapefruit to me.

Dr. Linda Bartoshuk:
Okay. I would call you a medium taster. A supertaster would have whipped that thing out of her mouth and probably insisted on taking off her earphones and going off, getting water or whatever complaining the whole time.