TASTE BUDDIES: No Sugarcoating How Sweet Affects The Brain : Short Wave Our ancestors evolved the ability to taste the sweet goodness of foods like pastries and creamy chocolates. They were enticed to consume quick calories that might only be available sporadically. What does that mean today for our brains and bodies in a world where sugar is much more abundant? Host Aaron Scott talks to taste and smell researcher Paule Joseph about the sticky science of sugar and how we can have too much of a good thing.

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TASTE BUDDIES: No Sugarcoating How Sweet Affects The Brain

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EMILY KWONG, BYLINE: You're listening to SHORT WAVE from NPR.

AARON SCOTT, HOST:

All right, Short Flavors. It is time for another episode of our TASTE BUDDIES series - sweet. I was super excited about this episode, especially after finishing the sour episode that so curdled my stomach, until producer Berly McCoy told me I would once again be eating sour foods, which made me a bit confused and a little bit queasy.

PAULE JOSEPH: Well, you have vinegar.

SCOTT: Yeah.

JOSEPH: Maybe you should try a little bit of that.

SCOTT: OK. Oh. Oh, it's so sweet. Holy moly. It's like somebody dumped a cup of sugar into this vinegar. It's incredible. So I think that means the berries are working.

JOSEPH: They're working.

SCOTT: That's from the taste test I did with taste and smell researcher Paule Joseph, and the berries we're talking about are the reason that vinegar actually tasted sweet.

JOSEPH: These miracle berries are what we call as taste modifiers. In the presence of a low pH, they actually make it taste sweet.

SCOTT: These mostly tasteless berries come from a plant that grows in West Africa, sometimes called miracle fruit. You can order the berries online in a tablet form.

JOSEPH: So we took the miracle berries, right? So these coated our tongue. And the miraculin, which is the protein that this berry has, binds to these human sweet taste receptors. And when we eat things that are sour, they actually taste sweet because it activates the sweetness receptors.

SCOTT: The sweet-activating power of the miraculin protein only works when the pH is low enough - so when I ate acidic foods. Otherwise, our sweet taste buds work pretty much like normal. Sugar tasted the same.

Yeah, no difference.

JOSEPH: No difference here.

SCOTT: Dark chocolate tasted a little bit sweeter.

JOSEPH: Just a little bit.

SCOTT: But lemon?

Three, two, one.

JOSEPH: One. Wow. It tastes like lemonade.

SCOTT: It really does. That is like a sweet...

JOSEPH: Wow.

SCOTT: ...Lemonade. That is extraordinary.

JOSEPH: That is incredible.

SCOTT: With all the recent warnings about curbing our sugar intake, miracle berries may sound like the perfect solution. But it turns out, making a sugar substitute is pretty sticky.

(SOUNDBITE OF MUSIC)

SCOTT: So today on the show, we investigate our ability to taste sweet things and what an excess of sugar in our modern diet means for our bodies and our brains. I'm Aaron Scott, and you're listening to SHORT WAVE, the daily science podcast from NPR.

(SOUNDBITE OF MUSIC)

SCOTT: So, Paule, we're talking about our sweet taste receptors. And I like to imagine that we are going on a "Magic School Bus" tour. Can you take us through what happens when a sugar molecule sticks to one of our sweet taste receptors?

JOSEPH: So in the tongue, we have lots of taste buds. So the things - those little bumps that you see on your tongue and then the receptors are within those taste buds. So for example, you'll get sugar. They get together with their taste receptors, and then they activate a cascade down within the cells that allows us to then send a signal into the brain that tells us, OK. This is sweet.

SCOTT: OK. And so we evolved then to taste sugar because it signals that food has calories, which, of course, our bodies need to survive. But now we are swimming in a sea of processed sugar, so I would love to focus on how consuming too much sugar affects our brains.

JOSEPH: So sugar can actually lead to this inflammatory process that affects the neurons in our brain. And that may affect the communication between those specific neurons in different areas of the brain. There's been quite a bit of work that shown how sugar in excess can disrupt memory formation. Sugar also affects mood, and we know that the ability to process emotion is often compromised when we have elevated blood glucose. And this has been shown in brain imaging studies where we look at the brain, and we're able to see what areas of the brain are activated. So these two things are very important, especially if we think about the link between sugar and depression.

SCOTT: And you're one of many scientists who are involved in this big study that is exploring a lot of these links, particularly on the brains of the younger sweet tooths amongst us. Would you introduce us to the ABCD study or the Adolescent Brain Cognitive Development study?

JOSEPH: Yeah. So the ABCD study is the largest long-term study on brain development and child health that is being done in the United States. So one of the things that we have been doing is leveraging this data to really try to understand how high sugar and high fat affects the brain of these children and how it impacts motivation and decision-making. Kids that are consuming high sugar and high fat tend to actually make more risk to be able to select these types of foods.

SCOTT: Like, they want this sugar so bad they're willing to risk stealing from the cookie jar.

JOSEPH: Yes. So that's one of the latest analysis that we have done. And currently, it's under review for publication.

SCOTT: And I think one of the other studies you've worked on shows that children who experience a lot of stress in their early years tend to overconsume sugar, right?

JOSEPH: Yes. So that's another analysis that we have done recently. We look at early-life stressors - for example, abuse. You can think of a number of early-life stress events that a kid can have. And then we wanted to really understand, again, how this might impact how they consume high sugar and high fat and their motivation behind it. One of the things that I will say that I think is particularly important is to really consider how early-life stress might be shaping the brain of these children and then affecting, subsequently, motivation for what they eat.

SCOTT: And, I mean, given all of this, there is just a race to create a replacement substance that will still tickle our taste buds but not hurt our health the way that sugar does. And yet no one's really found a perfect substitute. So do you have a sense of why it's so hard to create an alternative?

JOSEPH: These sugar substitutes tend to taste a little bit bitter. They're not quite sweet. It's like their taste is a little bit off. So I think it's the fact that we haven't really hit, like, something that really tastes like sugar. And I think this is where the miraculin and the miracle berries kind of come into play. But again, you need to have it activated on a lower pH environment. So what does that mean in terms of formulation? How do we actually formulate something that actually works and that allows us to really substitute? And there's been a - like, recent paper that kind of looked at, you know, the mixture in beverages. If we have the miraculin and then we also have, for example, like, a bitter substance - a liquid that also has a little bit of sour in it, you know, can that help still activate the sweetness but without getting the calories?

SCOTT: So there's some promise there, but also a lot of things still to be worked out. Do you think that humanity is capable of moving away from sugar overconsumption?

JOSEPH: I mean, we need sugar. We need the calories, right? So we cannot go totally away from not having sugars. I mean, sugars are naturally available in fruits, right? But the issue is the overabundance of these added sugars. We would need to have quite a bit of policies to really reduce the amount of sugar that is added on foods. And there's some of those already in play, at least in Europe.

SCOTT: And so it's not something we can expect individuals to completely handle on their own. It's going to take a much larger, systemic effort.

JOSEPH: I think so. I think that if we really want to make systemic change, we really need to have systemic policies that can help us regulate the food industry.

(SOUNDBITE OF MUSIC)

JOSEPH: Even pharmaceutical companies - you know, there's a lot of added sugars in some of medications. And you can think of the long-term effects, especially if we look at kids that have chronic conditions. You know, we giving them medications that are coated with sugar and artificial sweeteners to be able - for them to taste better so they can actually make that medicine go down, which is one of the things that they did in West Africa with the miracle berry years back. Like, they used to give it to kids to suck on it, so they can actually consume their medicine.

SCOTT: Oh, wow. So a spoonful of miracle berry makes the medicine go down in West Africa.

JOSEPH: Totally.

(SOUNDBITE OF MUSIC)

SCOTT: Paule, it has been a joy to talk with you. Thank you so much for sharing your time.

JOSEPH: No, thank you.

SCOTT: This episode was produced by Berly McCoy, edited by Gabriel Spitzer and fact-checked by Rachel Carlson. The audio engineer was Josh Newell. I'm Aaron Scott. Thanks for listening to SHORT WAVE from NPR.

(SOUNDBITE OF MUSIC)

SCOTT: Before we go, dear listener, we want to include you in an upcoming episode. Can you remember a moment when you realized how math impacts the real world, or maybe a favorite problem that math's power can be harnessed to solve? Well, if you've got a story, we want to hear it. So record yourself in a voice memo that's less than 20 seconds long, and send it to us at shortwave@npr.org. Make sure to include your name and your location, and your voice could appear in an upcoming episode. We can't wait to hear from you.

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