Kaitlin Luna: Welcome to Speaking of Psychology, a bi-weekly podcast from the American Psychological Association. I'm your host Kaitlin Luna. Why do some people scarf down anchovies by the pound while others recoil at the thought of a tuna fish sandwich? Why do the textures of certain foods like mushrooms turn people off? Not only is taste a biologically complex experience, it is quite psychological. Our guest for this episode is psychologist Dr. Linda Bartoshuk, an international leader in taste research who is the Bushnell professor of food science and human nutrition at the University of Florida and director for the psychophysical research at the University Center for smell and taste. She is known for her discovery of supertasters; people who have more taste buds than the average person, her work on enhancing the flavor of tomatoes and for discovering a condition known as burning mouth syndrome. Dr. Bartoshuk is joining us via Skype from the University of Florida. Welcome.
Linda Bartoshuk: Hi.
Kaitlin Luna: So, it may be surprising to people that taste is as psychological as it is biological. Can you explain how taste is studied from a psychological perspective?
Linda Bartoshuk: Well taste is both biology and experience, and it's psychological because of the learning that we do. We learn to like things. Some of our liking or disliking is built into the brain, but most of it is learned.
Kaitlin Luna: Does that explain why some people like very polarizing foods like Vegemite, durians, those really stinky cheeses is that genetic, cultural or is it based on personal preference?
Linda Bartoshuk: A lot of that is early experience. They learn to like it very early and their culture promotes it, they learned it from their parents. And what we learned to like when we experience it very early in life sticks with us.
Kaitlin Luna: And so, what if you hated say broccoli growing up but now all of a sudden as an adult you can't get enough. Are there changes in the taste psychology over time?
Linda Bartoshuk: The changes over time, some of its biological, again their changes with aging. But most of it is just the experience you accumulate, and probably you didn't switch from just liking broccoli to liking it a lot, it was probably gradual. And it probably happened because you paired broccoli with a lot of things you did like, and so you learned it almost accidentally as you were eating things you liked a lot
Kaitlin Luna: And so, what causes certain food textures to bother people? You know for example you know I like bananas but sometimes the texture is, it just makes me want a gag.
Linda Bartoshuk: You know, texture is interesting. In fact if you lecture students and you mention texture and you say there are textures some people don't like you can actually watch people's faces get red in the audience it's embarrassing, it's emotional and we don't understand that very well. For example, you know the little curly thing next to an egg yolk? I can't stand that. If I get that with my egg, I don't want to eat the rest of it, and I don't generally admit that because people think it's a little weird. Texture aversions are considered rather strange, we don't talk about them much.
Kaitlin Luna: But they are quite common though you said right?
Linda Bartoshuk: They're very common. And why is really a puzzle because they don't really have nutritional consequences, so something else is going on and that is something that hasn't been studied much. It, I'd really like to know more about it myself.
Kaitlin Luna: Many of us probably have that person in our lives who only likes, or maybe we are that person who only likes brown food or white food so that's pasta, potatoes, chicken or whatever so what causes people be picky eaters?
Linda Bartoshuk: Well picky eaters is really a loaded subject, especially with parents. Occasionally, I have a parent or grandparent bringing a child to me because they're upset because the kid is a picky eater and they think the kid must be a supertaster and that explains it. So, they come to me in the hopes that I can verify that there's something going on. The truth is, we're all picky eaters to start with. We learn to accept things, but if you look at the way we acquire preferences from the time we're babies, for example vegetables are really really slow to develop a preference for and what are the reason is you don't get much immediate reward from a vegetable. Things that have fat in them you get an immediate calorie load, things that are sweet or salty, you've got hardwired liking built into your brain, but vegetables don't buy you much. So, we really are acquiring our liking for foods one food at a time except for sweet and salty, which we like as soon as we can perceive them. And that liking, that learning liking just takes time.
Now why do some people develop such dislikes? That's actually a wonderful question, and part of it can do with gastrointestinal illness. For example, if a small child tends to get nauseated frequently and throw-up, anything that you eat when you're experiencing nausea is likely to be learned as disgusting very very quickly, it's one-trial learning. So sometimes people have aversions to a lot of foods because they got sick a lot as a baby. When you don't have that kind of history or can't remember it, sometimes it can be very puzzling to explain. But I'll tell you one thing don't do, if you got a picky kid don't bug them about it. Don't insist they eat things they don't like and don't make a big fuss about it because you're gonna create a problem that you're then really gonna require professional help to solve.
Kaitlin Luna: So if you do want to get a picky eater to eat more vegetables or fruits let's say but might be difficult, is there a way you can try to, instead of forcing them to eat something like that you know find a way to show them how good it can taste or hide vegetables or fruit in other foods, is that possible?
Linda Bartoshuk: You know one of the best ways to get a kid to try something new to eat is to have another kid at the table eat it. Now when that's not practical there is another solution. For example, you want a kid to eat broccoli, serve it with something good on it, like sprinkle a little sugar on it, put something bad on it, add butter to it add cheese. The beauty is that our learning theorist experts tell us that the kid will acquire a preference for the flavor of the broccoli because it's paired with something that's really highly liked. Later on, when you take that highly liked substance away the flavor preferences remain. So you can actually condition a preference to something like the flavor of broccoli by adding sugar to it and later when you take the sugar away, you still have the broccoli preference.
Kaitlin Luna: That must be an interesting taste have some sugar on your broccoli, right?
Linda Bartoshuk: Well you know dietitians tend to be very bothered by the instructions like this, but sugar is not the evil that we tend to make it out to be, we evolved with sugar. Frankly artificial sweeteners worry me a lot more.
Kaitlin Luna: Why, how come, why do you think they're so much worse than regular sugar?
Linda Bartoshuk: Well first of all they have a lot of toxicities associated with them. It concerns me that we tend not to pay attention to some of the literature about this. For example, cyclamate was taken off the American market because it was found to be carcinogenic. Well it turns out that probably wasn't correct, but saccharin is known to be mildly carcinogenic and there it stays. Because at the time, people tried to get it off the diet it was about the only artificial sweetener out there and people who thought they needed artificial sweeteners really raised a row about it.
Kaitlin Luna: So, it's probably almost better if you can, I mean less you're diabetic or some other physical need, to have regular sugar on your food?
Linda Bartoshuk: Just don't have a lot of it. Be careful about the quantities you eat, but a certain amount of sugar is really not a bad thing. You're right, if you're a diabetic then you have to worry about it. This is one of the reasons that I'm interested, very much interested in research that might lead us to a sweetener that really is safe. I'm happy to tell you we're doing that right now.
We're working on volatiles. Now, a volatile, for people who aren't trained in chemistry it's a compound that can be in gaseous form. Like you sniff something, a flower, the compounds that you're smelling are volatiles they're there in gaseous form. The compounds that we sniff when we smell a fruit and are so pleasant those are volatiles. Now those compounds, when you bite into that fruit, those compounds actually go in your mouth and they rise at the back of your mouth through a space up to the back of your nose. Think about post-nasal drip, that space that the post-nasal drip comes through is what volatiles rise through. And so, a volatile can, you can bite in and the odorant, a volatile, can rise at the back of your mouth and go into your nose from the rear. Now when your brain detects a volatile coming in that path, it sends it to a part of the brain that also handles taste and the two interact there. And there are some volatiles that actually intensify the taste message.
Kaitlin Luna: That's fascinating, and you, you raised a lot of really interesting points that I want to address in a couple different questions here, but just to wrap up the section about picky eaters. You know why are some people more adventurous than others on the on the flip side of being a picky eater?
Linda Bartoshuk: Well first of all being adventurous is a more general characteristic of personality, and I honestly don't know what makes us more adventurous. But if you want to become more adventurous in food, you have to go out and try new foods. This is something that I run into when I see a patient who's got taste damage and they can't taste things as well as they used to. I urge them to go out and try a lot of new things. And part of that is in the hope that they're going to find a few sensory inputs that are still going to be really good, but there's a hidden purpose to that, the hidden purpose is, the more things you try the more things you give your brain an opportunity to learn to like. You eat something and the sensory signature of that, actually the retro nasal olfaction that message I was telling you that comes up the rear of the mouth, that is the signature of the food the flavor of it. Your brain records that and if that flavor is coming into the brain at the same time calories are coming in through your stomach, your brain is going to tell you to like that flavor. So, the more different things you eat, the more unusual flavors you are pairing with calories and your brain is going to make you like them.
Kaitlin Luna: That's fascinating so there are ways to you know enhance what you like to eat just to give it a shot and try it and see if see if you can like it again, okay that's really interesting.
Linda Bartoshuk: The more you explore the food world, the more things you're gonna learn to like. Now you have to be careful because if you start out really disliking a lot of things you can then expose yourself to things you don't like. And sometimes it'll backfire and you'll get to like it even less, so it's better to start off neutral and pair something with calories or a good taste like sweet or salty and your brain will make you like it.
Kaitlin Luna: And you see we've talked about smell a little bit, so can you talk about how integral smell is the full sensory experience of food? So, you know anyone who's ever had a cold, which is probably everyone who's listening, can attest to how bland and basically terrible food tastes when they're sick.
Linda Bartoshuk: Well that's actually a myth. The notion that you can't perceive the flavor of food when you've got a cold, there are some people that do lose the ability to smell, because the area that odorants have to go through to get to receptors gets swollen from a cold and the odors just don't get through the area. But that's not true for most people, for example I don't lose a sense of smell at all when I get a cold, and I think most people don't. But unfortunately, there is a fairly rare condition where the virus itself can damage the olfactory system and those people do lose smell with a cold, but it outlasts the cold.
Kaitlin Luna: Okay, but just smell in general how is it, how integral is it to enjoying and tasting your food?
Linda Bartoshuk: It's extremely important. And let me first distinguish between taste and smell, because I think it's easier to understand all this if you really get that distinction. Taste is what's coming from your tongue; sweet, salty, sour, bitter, umami, if you buy the advertising stuff coming from places like Ajinomoto which I do not, but the four basic tastes sweet, salty, sour, bitter are coming from your tongue. Now, when you sniff with your nose, you're bringing volatiles, odorants in through your nose they have to go through a very small opening, and that opening is what gets swollen during a cold for some people. But once the volatile goes through that and hits the receptors and sends a message to the brain, and that is smell that's what we sniff from the outside world.
But the nose has a second job, and that second job is you put food in your mouth, you bite into it, you chew it, you swallow it and swallowing forces those volatiles up that passage at the back of the mouth that I mentioned. Now, that input is going up and it's hitting it going through the same small opening going to the receptors so you've got a molecule that you could sniff and it comes into your nose one way and that same molecule can go through a different pathway if you get it from your mouth but the brain pays attention to the difference and it sends the input to different places in the brain. So, when you sniff, the input goes to one area and we call it smell, you put food in your mouth chew it swallow it and that odorous input goes to another part of the brain and actually that input is what produces flavor. And flavor is going to the same part of the brain as taste and they can interact that was what I was mentioning earlier.
Now here's the key thing, we are hard-wired our brains are wired to make us like sweet, sour, well not sour so much for most people, but sweet, salty and to dislike bitter that's hardwired. But liking smells is entirely learned in humans, at least that's what we think so far. If there are any smells that we are born loving, we haven't identified them yet.
So, let's put this together for food. You've got taste, which is giving you hardwired to affect, plus or minus, and you've got smell which is giving you learned affect and that depends very much and almost entirely in fact on your experience. Put it together and you've got food, it's complicated.
Kaitlin Luna: Yes, it's very complex. And also smell and taste is known to evoke powerful memories, so you can explain how that works as well?
Linda Bartoshuk: Yeah not taste, it's smell that produces those memories. We call it the Proust effect because Proust wrote about his madeleine's with tea in his, I think aunt's kitchen, and they brought back all these evocative memories. So yes, we associate emotion with smell very very powerfully. And in fact, it may be the most important phenomenon and maybe with the exception of being able to identify food by smell but having affective reactions to it controls a huge amount of our food behavior.
Kaitlin Luna: And going back to speaking about food itself, you know why do some foods like say fish sauce or anchovies like I mentioned on their own most people don't like or many people don't like, but if they're added to something they suddenly become delicious. So, like in Vietnamese food a fish sauce really enhances the flavors or anchovies in a Caesar dressing can really make it taste really good can you explain how that works?
Linda Bartoshuk: Yeah, a lot of it is simple concentration, that is when you taste pure fish sauce you're really getting a full dose. When you add it to food it's both diluted by the food and it's diluted by the other sensory experience. That is when you put a whole bunch of tastes and smells together, they suppress each other, and what you end up with is an experience that is certainly not the linear sum of all the things that went into it. For example, imagine when you make a beautiful Chinese sauce to have on dumplings yet soy sauce maybe you add, if you really love salt, salt, sugar, a little vinegar you put all that together and if you added those tastes and smells linearly it would knock the top of your head off, so they suppress each other. So, what happens when you eat food is it's all kept within a reasonable intensity demand domain.
Kaitlin Luna: So, it's really those chemicals reacting together and working together that make them taste really good once they're all mixed?
Linda Bartoshuk: Absolutely, and also you learn the mixture sensation. That is one of the beautiful things our brains do is to record information about what we've eaten before, and those are saved almost as like templates in the brain. So, for example look at bacon. You eat bacon it's got protein in it it's got fat in it those are two things that your brain perceives as really good so it's gonna make you love the flavor that comes with bacon. Now that flavor is actually a composite, it's a lot of salt, it's a variety I mean dozens of different volatiles make up the smell and the flavor of bacon. You put those altogether and they produce a template, a certain sensory signature that's stored in your brain, and the next time you eat bacon you're gonna recognize it very quickly.
Kaitlin Luna: Yea and people go wild for bacon these days it seems like.
Linda Bartoshuk: Well look what it's got in it, fat, protein, what's not to like?
Kaitlin Luna: Exactly, and a little sugar maybe from pancakes or something, maple syrup, dangerous combination. And why do some people, can they, why can some people tolerate super spicy foods like they can add the hottest hot sauce to their chili and love it or eat these ghost peppers and all sorts of things like that, but while other people can't even stand a hint of heat, that's like some of my family members are like that, no heat at all on their food. Why is that, why can some people eat really hot food and others can't?
Linda Bartoshuk: Some of its genetic. For example, taste buds in your tongue are surrounded by a basket of pain fibers so the more taste buds you've got, the more pain your tongue is capable of perceiving. Now the number of taste buds you're born with is under genetic control at least in part, there may be several factors. So, if you're born with a lot of taste buds we call those people supertasters, you're also born with a very large number of pain fibers and so you're gonna feel the burn of a pepper about 3 times as much.
And I was I love watching the Food Channel and you watched these pepper eating contests, the person who can eat that really powerful peppers, there are two factors. One of them is they're probably not a supertaster so they don't have the biology to perceive the pain as intense, but in addition capsaicin is the compound that makes all chili peppers burn. And capsaicin desensitizes pain receptors. So if you habitually eat chili pepper your desensitizing the pain receptors on your tongue. If you'd like to prove that to yourself go for a vacation, go for two weeks or so without eating any chili peppers then come back and eat the amount you're used to eating, it will burn.
Kaitlin Luna: And that relates to your taste buds regenerating over time, correct?
Linda Bartoshuk: No, there's no, regeneration is a natural part of the taste system and all of our taste buds die off and regenerate, they don't even have a very long taste life. And burn doesn't actually damage anything, I mean it produces a powerful sensation of burn but for the most part things like capsaicin and chili peppers do not actually produce any damage.
Kaitlin Luna: But you said you just become desensitized to them over time?
Linda Bartoshuk: Yeah you don't feel the burn, and that is really fun. For example, suppose you go to a restaurant and you order a hot dish and it's too hot for you. Fill your mouth with it, really let the burn hit a maximum and then sit and chat for a few minutes, you can drink ice water to keep the burn down while you're doing that. And the burn will naturally fade away in 10-15 minutes at the end of that fade, put the hot food back in your mouth and it won't burn as much. You can desensitize your pain receptors on your tongue that fast.
Kaitlin Luna: Wow that is fascinating, I thought it would be like a gradual process, but it can be in just look over the course of one meal.
Linda Bartoshuk: Nope it can happen in, in really in minutes.
Kaitlin Luna: And speaking of those supertasters you just mentioned, so those are people with more taste buds. And while this sounds like a blessing in some ways, you also found that that may not be the case, so can you explain why?
Linda Bartoshuk: Well it's in terms of eating food, there's one thing about being a supertaster that really is wonderful. We discovered this fairly recently. That is, the pleasure you get from your favorite foods is more intense if you're a supertaster. Now we don't know why that is. This is why I think there's more to being a supertaster than just taste buds, because pleasure is happening in the brain. So, something in the brain is different with supertasters and they're getting more pleasure from their favorite foods.
Now that isn't the blessing you might think because the supertasters don't have quite as many favorite foods. There are also a lot of things they don't like to eat, they tend to be picky eaters because they're very sensitive to bitter, for example, and they don't like certain texture. Now that's a case of where texture, there is a certain amount of biology in it, and texture is more intense to supertasters so they can be put off by it.
Kaitlin Luna: Yeah and so for those supertasters they may not be likely to eat, you said bitter things, so maybe that's you know they're not eating some of those cruciferous vegetables like Brussels sprouts and those things?
Linda Bartoshuk: That can be very good for you by the way. So that's the second piece of this. Your diet has, it involves risk factors for diseases and one of the reasons we're very interested in the fact that there are supertasters is that their diets are affected, they don't choose to eat the same foods. And because of that it changes their risk factors.
So, for example, colon cancer. One of the risk factors is fiber in your diet, well supertasters don't like eating highly textured foods as much as others, they eat fewer of them and so they actually are at a slightly higher biological risk for colon cancer. Now that's a small difference but it's big enough that you can actually see it. We did a study for example looking at colon polyps. Colon polyps are risk factors for colon cancer, and they're produced in people who don't consume enough fiber. And if you look in fact at supertasters and people who are not supertasters, they have different number of colon polyps, the supertasters have more.
You switch to something else like head and neck cancer, now the risk factors are consumption of alcohol and smoking. And supertasters don't drink as much alcohol, they don't like it because it burns their tongues and doesn't taste very good, and they also don't like to smoke for a reason, sensory reasons as well. So, the supertaster is at an advantage when you look at head and neck cancer.
Kaitlin Luna: And is there a genetic component to being a supertaster?
Linda Bartoshuk: There is. We don't know how big it is, nobody's done a family study on it yet, but it certainly is genetic. For example, if you look at the tongue of identical twins, they're gonna look very very similar.
And by the way you can look at the tongue and see whether somebody's a supertaster. And your listeners can do this by going to the supermarket and buying blue food coloring. Bring it home, swab it on your tongue with a q-tip and swallow a couple times to move the dye around look at your tongue, best to do it in a magnifying mirror with a flashlight. And what you'll see are pink circles against a blue background. Those pink circles are fungiform papillae, they're structures that hold taste buds, and you'll see that some people have a huge number of them. Their tongues look like they're absolutely tiled with these pink circles. And then there are others like me, I'm not a supertaster, and for me those pink circles are like polka dots, there's a lot of space between them. So, you can see by looking at the tongue whether you're really an extreme supertaster or not. You have, you can't really see it most people are in the middle, but you can see it with the extremes.
Kaitlin Luna: That sounds like a fun experiment to do at home.
Linda Bartoshuk: Oh, it's wonderful, kids love this by the way for science projects.
Kaitlin Luna: Yeah that's a great idea, and how would being a supertaster relate to weight? I mean you talked about and possibly obesity or being overweight, you talked about it maybe being a risk factor for not consuming enough fiber, but could it also relate to someone maybe being more overweight or obese because they might not be eating some of these healthier foods that aren't as tasty?
Linda Bartoshuk: Wouldn't you think so? We thought so early on, but in fact obesity is not really connected with super tasting. If you look at weight differences you can find some groups of people where there might be a slight weight difference and when there is, usually the supertasters are thinner, but it's not a very big effect.
Kaitlin Luna: Okay that's interesting. I want to also touch on a point you mentioned a little while ago, when you were talking about getting food poisoning or sick on some food maybe as a baby, but you know this happens, can happen throughout your life. So say you've got food poisoning from some food and you feel like you can never eat it again, is there any way to overcome that, without making yourself sick?
Linda Bartoshuk: It's hard. It's one trial learning. But consider for example a cancer patient who's going to get radiation therapy or chemotherapy and some of these therapies make you nauseated. So that nausea is going to condition onto foods and make a lot of foods become disgusting. So, picture the cancer patient surviving cancer, going home hoping to eat his or her favorite meal, biting into it and finding it disgusting. This is rough. And one of my tasks in the clinical world is to talk to patients like this and explain that in fact this is the biology of food aversions.
The way to get over such an aversion, it's a conditioning effect, so you try to extinguish it. That is, try to eat the food that you've had trouble with when you're really feeling good and if you're lucky and you repeat this a few times you may be able to extinguish the aversion. But I have to tell you it's rugged. I developed an aversion to maraschino cherries sitting eating them in the back of the car driving to California on a vacation, I was reading comic books and I was carsick. That aversion is so powerful that I cannot eat those things today. If I get one on a plate and I hope nobody's looking and I just shove it off the edge, I don't even want to see it.
Kaitlin Luna: Yea so it's so tied into you, and like we were talking before about you know the smell and the whole experience is tied into your memories, and if that nausea memory is so strong it's very difficult to overcome that.
Linda Bartoshuk: Very, very difficult.
Kaitlin Luna: Does the same principle, does that seem a principle apply to say if you're trying to get yourself to like some food that you want to like but struggle with? Whether that be you know mushrooms, Brussels sprouts that sort of thing, can you apply that same technique?
Linda Bartoshuk: It's easier to learn to like a food than it is to get over an aversion. That is if you're completely neutral to something, as I said before your best bet, first of all simple exposure will help. That is just eat it a few times, don't eat a lot of it but just to eat it, you'll probably find yourself coming to like it. But if you want to speed that up like with a kid who's finicky, put something good on it. It's like we said with the broccoli, sprinkle a little sugar on, put some cheese on it it'll help.
Kaitlin Luna: And speaking of disgusts we but kind of touched on that as well, are there any foods that disgust nearly everybody? I mean I know that we've talked before about some of these foods that are cultural something people had growing up like Vegemite or durians but is there anything that's universally panned?
Linda Bartoshuk: You know the person to ask about that is Paul Rozin, he's the disgust expert. And I think he has found that there are disgusting, foods that are disgusting to a lot of people and they often have an animal origin like feces or a decaying body, something like this. So there are certain things that we do as culturally tend to be really disgusted by. But then again disgust is also learned by these conditioned aversions. It's very easy to develop a disgust for something if you've eaten it and gotten sick.
I did this to myself on purpose once. I was coming down with the flu and I was nauseated. I drove home and I always go by Kentucky Fried Chicken, so I stopped off and bought my favorite all dark meat extra crispy and ate it while I was nauseated. Now I knew what I was doing, but I still developed the aversion and it was very powerful. For a while I found myself not even driving by Kentucky Fried Chicken, and even now if I want extra crispy all dark meat I buy it at Popeyes I don't go to Kentucky Fried Chicken.
So, these aversions are powerful and they take over, and it's important to have some compassion for people who've experienced these. And this is one of the things I feel about people who have real food dislikes. It's not something to make fun of, it's something that produces real distress. And I really don't believe in giving kids a hard time if they don't want to eat something they find disgusting.
Kaitlin Luna: Yeah you do raise a good point I mean you said some people you know are picky eaters for whatever reason it might be stressful for them to go into a situation like a party or a restaurant where they struggle to find something they like and don't want to also be singled out in the crowd for getting something quote-unquote boring. So yeah that's a good point though to be sensitive to that and try not to push people because if you said it does have a stress component to it.
Linda Bartoshuk: By the way a food anthropologist told me a wonderful excuse to make if you don't want to eat something. Suggest you have an allergy to it or that that particular food is something that makes you sick. Mostly that's a social explanation that works for people. And I actually have seen some children who turned out to be extreme supertasters and I took pictures of their tongues and gave them copies to take back to show their friends and told them that they've now heard from an expert that it's not healthy to eat foods you don't like.
Kaitlin Luna: That's a great idea, makes the kids feel a little better I love that.
Linda Bartoshuk: I'm not sure their parents agreed, but I think it's important.
Kaitlin Luna: So speaking of children. Children seem to be more sensitive to food than adults, is that true and does taste change over a lifespan?
Linda Bartoshuk: That's a wonderful question. The truth is we are all born neophobic. That means we're worried about anything new. And that's a very important survival characteristic, you want to watch out for something you don't know anything about, you don't want to eat it unless you've learned it safe. Well in our culture we learn it is safe because our parents tell it. You know even animals do that, for example a rat pup will sniff its mother's mouth to tell what she's been eating, and that rat pup is very likely to go off and eat the food that has the same smell. So, we socially teach people how to eat things that are safe and culturally we even label our food to make it safe. That's what spices do for us. For example, typically if you want to eat a food that reminds you of your homeland, if you're an immigrant for example, you use the spices from home. And you put those even on a novel food and you can make that novel food seem like it belongs more to that culturally safe food you grew up with.
Kaitlin Luna: That's a great idea I hadn't, I never thought about it that way because it is a learned behavior. I was also reading somewhere as I was researching this that babies in the womb might like, so for example if the mother ate garlic, the baby can tolerate garlic in breast milk after they're born because they were able to taste it in the amniotic fluid.
Linda Bartoshuk : You're talking about Julie Mennella's work, that is brilliant research. Yes, Julie has shown that both volatiles that a baby can detect in amniotic fluid as well as in mother's milk will carry valence. That is, if you get mom to eat something special like carrots when she's pregnant you may find that your newborn baby is more interested in eating carrots than if they never had the exposure. So amniotic fluid and mother's milk are ways to get an organism to like foods, both other mammals and humans.
Kaitlin Luna: Yeah that's really interesting I'm actually pregnant right now, and I've been eating a lot of carrots and garlic so hopefully that bodes well for an adventurous eater in the future. We'll see I guess I can I can keep you updated on that. Is there any, does specific gender have a better palate? I've heard anecdotally o that women have a better palate so they're better at tasting wine and all the different notes you can get off a glass of wine, is that true?
Linda Bartoshuk: There's some truth to that. First of all, women have a more sensitive sense of taste. Which is pretty fascinating and if you consider the fact that what women eat affects a fetus, there's real biological wisdom to that. But more, remember that women, especially in our culture and actually in most cultures, have more experience in the kitchen. So, they've learned more about smells in particular. So, having a woman be say a better wine taster probably has something to do with the fact she's learned to identify so many odors because she's had more exposure to them.
Now anybody can get that exposure, and this is what wine tasting is all about. If you learn to become a better wine taster, the way you learn that is you learn to recognize specific volatiles that are associated with the things that are likely to be found in wine.
Kaitlin Luna: Yeah, the interesting part of that, I have a friend who's into wine, and he does some, you know, wine tastings for friends, and there's this wheel they talk about all the different tastes. And some of them can be amazing like a fresh strawberry some of them can be downright disgusting like cat urine, that was on the wheel, or a rubber you know that kind of thing that things you can taste in wine. And I was just have, what I've gotten through you know osmosis through the years it's just that if you are into wine tasting you want to sniff things like tobacco, leather, chalk all these things so you can identify those flavors when you're, when you're sniffing the wine when you're tasting it.
Linda Bartoshuk: That's right, and that wine aroma wheel is Ann Noble's. She's an expert in both the chemistry and psychophysics of wine. She's retired now, she's out in California, and she's the one that put real science into a lot of that.
Kaitlin Luna: And it's very fascinating, like I said I had no idea, I was thinking you see these charts that say you can taste chalk or smoke and wine. I'm like how do, I guess we all know the smell of chalk from growing up or whatnot. But of all the things like yeah you have to kind of re-sniff that to be able to identify that in a glass of wine, but I didn't realize if you're training yourself in that, in that area that you should be to be smelling a lot of different things.
Linda Bartoshuk: That is correct.
Kaitlin Luna: And you, I want to talk about some of your research you've done. You've been involved in work to enhance the flavor of tomatoes, so why tomatoes?
Linda Bartoshuk: Well we started with tomatoes because my colleague Harry Klee is one of the world's experts on tomato volatiles. And we began with the tomato because we wanted to make it more palatable. Now, I don't know if you've eaten supermarket tomatoes recently, but they leave a lot to be desired. Most people have our memory of a tomato that was really wonderful and a lot better than what you can usually buy in the supermarket. Well part of the reason for that is that we have raised tomatoes to ship, and if you want to breed tomatoes to have good shipping characteristics, you're not paying much attention to their flavor.
So, Harry wanted to make tomatoes more palatable and also tomatoes are healthy. So, if we make them more palatable can we improve the diet by getting people to eat more of something like a tomato that's a healthy thing to eat? Well it turns out it's not a very difficult problem. You really want to know what it is in the tomato that makes it liked, well you do the chemistry on the tomatoes and we actually grew at the University of Florida, because we are a farm the Agricultural College, so we have farmland. We grew our own tomatoes and we grew heirloom tomatoes.
Now heirloom tomatoes, people think heirlooms are better tomatoes, they're not. Heirloom means they're genetically diverse, it refers to tomatoes that came before we started breeding them for shipping. Anyway, we grew heirloom tomatoes because they're genetically diverse. We did the chemistry on them and we did the psychophysics. We measured both what they tasted and smelled like and we measured how much people liked them.
Turns out you put all that together and you put it into a regression model, which we were helped with by our colleague Howard Moskowitz, and this regression model actually will give you the formula for the great tomato. Now, we could have created the best tomato in the world but actually that's really really hard to do because it requires a lot of chemistry. Anyway, what we did do is determine which constituents in the tomato contributed what to palatability so that we could create tomatoes that were better. And actually Harry Klee did create such a tomato, it's called a garden gem and if you want to get seeds and grow that tomato, send him an email message and send a donation to his lab and I'll bet he'll give you some of his rare tomato seeds.
Anyway, why did we start with tomatoes, because they were there, and it was easy. But we've now done the same work with strawberries, and oranges, and peaches and blueberries and we know a very very great deal about which constituents in fruit make them liked better. And we also know which volatiles in the fruit contribute to sweet.
Kaitlin Luna: So, it has more to do with transporting food than it is the food itself. So, you know I definitely have tasted some very disappointing tomatoes at the grocery store or when I have grown some outside, they're incredibly delicious. So, it's fascinating it's really based on consumer needs in the grocery store.
Linda Bartoshuk: It's, you know, the sad part about it is we've got the science to make almost anything we grow better. What you need to do is understand the economics. And you have to understand what the farmer is paid for and what he's going to grow. And unfortunately, a lot of farmers are paid for fruit or vegetables by weight, and we don't insist that they become, that they'd be very palatable. If we insist on that, the breeders and the growers can produce it, we just have to insist on it.
Kaitlin Luna: And those may be the ones you, and they might be a little more ripe, so you might have to eat them more quickly if you get them from the grocery store, that might come into play a little bit correct?
Linda Bartoshuk: Yeah, yep that's called post-harvest. That is, how you treat something is going to affect its flavor as well as the genetics of the plant, so you have to pay attention to all of it.
Kaitlin Luna: Have you ever heard about how a juice tastes better on airplanes or people tend to order more V8 when they're on an airplane than they would on the ground?
Linda Bartoshuk: I‘ve heard that, and I know of absolutely no good science that supports it. There are some papers on that, but they aren't very impressive, maybe I haven't read them all. But this notion is, I know every so often it pops up online, and it is not something that is generally understood and believed in by experts.
Kaitlin Luna: So, it is maybe more of a placebo effect?
Linda Bartoshuk: I'm not sure what it is, I shouldn't say absolutely it can't happen. There are the same kinds of stories come from submarines, the same things come from our astronauts. Do things taste different to them when they're in outer space? Unfortunately, we have not done a lot of research on that, but in fact there's not a lot of really solid evidence for it. However, if anybody's got some evidence, I'm happy to look.
Kaitlin Luna: You know that would open up some new areas of research too like you said if we're going to space, under underground that sort of thing. Maybe it's also people are just ordering um Bloody Mary's or something on the, or they wish they had a Bloody Mary on the plane.
Linda Bartoshuk: Well I think that most of the people who are getting tomato juice on the plane, I mean they're probably getting alcohol in it, that probably has a little bit to do with their judgment.
Kaitlin Luna: Yeah that could be true too it would taste better. For those experiments you're talking about with strawberries and oranges, is that because maybe the strawberries are picked too soon? Because I thought of, like you know, an orange or a strawberry I typically thought you know if you get them at the right time of year at the grocery store they're pretty good, but is the same concern there with you know we're focusing on asking farmers to give it to us by weight and we're worried about shipping we're not concerned about the taste?
Linda Bartoshuk: There's a lot of interest in making good things, making strawberries good, and wow we know a lot about that now. Because we know which volatiles in the strawberries make them sweeter, and in fact this, there are about thirty some volatiles in a tomato that all add a little bit of sweetness to it. Because those volatiles, when we bite into the strawberry, travel the message, travels to the same part of the brain that codes for the sweetness of sugar. And those volatiles enhance the sweetness message in the brain. Now once you've identified those volatiles you can take them out of the strawberry and put them in pure sugar and it'll get sweeter.
So, this is one of the things I'm very excited about right now, because it looks like about the safest way to make a so called artificial sweet that could possibly exist. We use volatiles that we've already been eating ever since humans were humans and they're going to, if you pick the right volatiles, they're going to produce sweetness in the brain. Now first of all you can certainly breed for those volatiles in the strawberry and you're gonna produce strawberries that do not need any sugar. I have tasted some of these strawberries and I'm telling you when they're widely available people are really going to like them. But at the same time, we can put these volatiles in anything that we want to be sweeter and we can make it sweeter safely, for let's say diabetics.
But there's something else about it that I'm very excited about. I spent a lot of my career studying people who have taste damage, and one of the things about using volatiles to affect a taste message in the brain is those volatiles bypass damaged nerves. That is if your taste nerve is damaged you can't perceive more sweet from sugar because you don't have the nerve to carry the message. But if you consume sugar that has some of these volatiles in that enhance sweet, those are kind of the volatiles that the message is going to bypass the damaged nerve and increase the sweet message in the brain. And I'm happy to say that the early tests with patients supports this, it looks like it's going to work.
Kaitlin Luna: Would those enhancements be considered genetically modified?
Linda Bartoshuk: No, no, nobody does that today, well not nobody, but the fact is there's so much prejudice against genetic modified. And I have to tell you I am, I'm not a supporter of that prejudice. If we want to feed the world, we want to use the best science we've got. And if we can genetically modify something to make it put up say a vitamin in rice that's going to save children in the third world from going blind, I say all for it. And I know of no evidence that genetically modified organisms are in any way dangerous. I think that's a type of prejudice that's gotten into the world. I don't know how it got there and I'm sorry it's there because I think it's doing a lot of harm.
Kaitlin Luna: Yeah I've definitely, I mean there's a lot of arguments against it, but I've heard more than one person say your side of it, typically someone who's a researcher in the science field, saying like if we can feed people out there who otherwise wouldn't be able to get the nutrition they need, then we need to think about that.
Linda Bartoshuk: We sure do.
Kaitlin Luna: And also, I wanted to touch on your burning mouth syndrome. So, we've, I'm sure most people who are listening have all burned their mouths on food and know how annoying it is, your tongue goes numb and nothing really tastes great for a couple days, but for some people that doesn't go away. And so, your lab uncovered the reasons why people suffer from this. So, can you explain what the causes of burning mouth syndrome are and how many people might have it and how it can be treated?
Linda Bartoshuk: Burning mouth syndrome actually has nothing to do with damage in the mouth. Burning mouth syndrome occurs in the brain. It's what we call a sensory phantom. You can make a phantom in any sensory nerve in the body. Have you ever heard of a phantom limb? There is this is feeling in the arm that is there after it's been amputated? Well you can have a phantom smell, a phantom taste and a phantom pain in your tongue. So how does it happen? We think what causes it is, believe it or not, damage to the taste nerve, the seventh cranial nerve. That nerve normally has two jobs, it both brings taste information to the brain, but it also terminates oral pain, maybe even pain on other parts of the body.
Now think about why that might be a good idea, imagine an animal in the wild fighting to survive with its teeth. It's gonna get bitten on some occasions and another animal might bite it, it might bite its own tongue. And if tongue pain stops it from eating, the animal is gonna die. So, a survival characteristic would be to somehow stop the pain of any kind of oral damage. Well if the animal takes a bite of food and the food input, the sensory input, inhibits the pain it's gonna eat and survive. It looks like that mechanism connected the taste system to pain. So, what happens is, if you damage taste, you lose the ability of taste to inhibit pain, and essentially pain turns on in the brain. It's like you flipped a switch and you can't reach it to turn it off.
Now how can you get rid of the phantom? And by the way let me tell you how we discovered that the phantom was in the brain. If you had a burnt mouth it would be easy to treat it, all you'd have to do is anesthetize the area of the burn and the pain will go away. When we anesthetize the tongues of people with burning mouth syndrome, the burn gets worse. Why does it get worse? Because the pain, the burn is only occurring in people with damage to taste, and when we anesthetize their tongues, we take out whatever taste was left, and we make the effects of the damage worse. So, the pain phantom in the brain gets worse. Now that goes away when the anesthetic wears off fortunately, but you don't have just burn phantoms in the mouth, you can have taste phantoms and you can have touch phantoms. For example, you could wake up one morning with a bitter taste in your mouth that never went away. Believe me you would not be happy.
Kaitlin Luna: And so, can it be treated?
Linda Bartoshuk: Yes, it can. And I can tell you one of the reasons that I got so interested in this was my father had lung cancer when I was in college, and his most distressing symptom was a metallic taste in his mouth that wouldn't go away, and we didn't know what to do for him at that time. But one of the reasons I got interested in phantoms was to try to figure out how to help patients. It turns out we can use a medication that intensifies inhibitory neurotransmitters in the brain, it's called a GABA agonist. And a GABA agonist will restore some of that inhibition from taste that was lost from damage, and it will reduce that burn phantom in about 60, 70 percent of patients. And I can't take the credit for that, that was discovered by Dr. Miriam Grushka, who is an oral pathology expert.
Kaitlin Luna: Yes, it sounds like a really troubling situation that can happen but it's nice to know there's at least a solution for people. Like I said and not just for burning mouth but having a metallic taste, and that's from, that really can inhibit the quality of your life if you have a bad taste in your mouth all the time.
Linda Bartoshuk: It is, it is awful it's one of it's one of the reasons why that's the specialty area that I work on in taste pathology. Because it probably produces more distress for patients than any other taste problem.
Kaitlin Luna: Yeah because the quality of, you know the quality of life, the enjoyment of food, it's just everything, I mean you're living with that every second of every day of just like having a disturbing taste in your mouth.
Well thank you so much for joining us Dr. Bartoshuk, this has been a really fascinating conversation and I'm probably gonna head out to the grocery store and get some of that blue dye and test out that experiment you mentioned earlier today, it sounds like a lot of fun. Do you do that at parties?
Linda Bartoshuk: You know the truth is I actually have done it at lectures. I take paper with me that is bitter to supertasters and pick the people in the audience who think the paper is just awful and put blue food coloring on and let everybody look at their tongue.
Kaitlin Luna: That's a lot of fun that's a really great idea a good thing to do with kids, so thanks again so much for your time it's been a real pleasure speaking with you.
Linda Bartoshuk: I'm delighted and thank you for being so well prepared I really enjoyed this.
Kaitlin Luna: Before we go, just a reminder that we want to hear from you. You can email your comments and ideas to kluna@apa.org, that's kluna@apa.org. Also please consider giving us a rating in iTunes, we'd really appreciate it. Speaking of Psychology is part of the APA podcast network, which includes other great podcasts such as APA Journals Dialogue about new psychological research and Progress Notes about the practice of psychology. You can find all of our podcasts on iTunes, Stitcher or wherever you get your podcasts. You can also go to our website SpeakingofPsychology.org to listen to more episodes. I'm Kaitlin Luna at the American Psychological Association.
Linda Bartoshuk, PhD, an APA fellow, is the Bushnell professor of food science and human nutrition at the University of Florida and director for psychophysical research at the university’s Center for Smell and Taste. Bartoshuk studies sensory perception of foods such as taste, olfaction and irritation/pain. She is known for her discovery of supertasters, people who have more taste buds than the average person, her work on enhancing the flavor of tomatoes and for discovering a condition known as burning mouth syndrome. Bartoshuk and her students developed new measurement techniques for quantifying sensations as well as the pleasure/displeasure these sensations evoke. Most recently, Bartoshuk has collaborated with horticulturists to connect sensory variation in fruit with variation in fruit palatability. She is frequently interviewed by national and international media including The Atlantic, BBC News, The Wall Street Journal, NPR and Popular Science. 
