The Sweetest Thing

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1:25Latif Nasser:Wait, you're listening. Okay. All right. Okay. All right. You're listening to Radiolab. Radiolab. From WNYC. See? Yeah.

1:42All right.

1:43Latif Nasser:So, Latif. Yeah. What are we doing today? We're going to go on a hunt. All right. That actually starts in my car. All right. I was with my two kids. I think at that point my kids were six and three, maybe. and the U2 song, The Sweetest Thing, comes on. Do you know that song? Of course.

2:08Yeah, of course.

2:09Latif Nasser:It's a bop. Yeah, it's my favorite of their songs. And my kids, who have never heard the song before, they're listening to the song, and they ask, what is the sweetest thing? Did you try love? Were you like, love? Yeah, no, my kids, they don't care about that. They were just like, no, no, no, but what really is the sweetest thing? So just what's the sweetest thing I can get in my mouth? Yeah, they're kids. They love sugar. Yeah, of course. Right now they're obsessed with gummy bears. And they just wanted to know, is there some other thing out there we've never had before that's even sweeter? So I figured, like, I'm a journalist.

2:44I can answer this.

2:46Latif Nasser:Well, Latif, bless your amazing children who I adore. Do you care about this question? Yeah. Yes. Why? Because, okay, because it sounds like a dumb, simple question. Or not a dumb question, but it seems like it has an answer. And then you're like, son. I kind of expected it would be that way too. But then this question turned out to be so much more. More than just a hunt for like a substance, it became like this thing where I was trying to get to the edge of human experience. And sweetness as one of those experiences. It's this basic familiar thing that we all know. It's like almost mundane. But I kept finding that, wait a second, like, no, no, no, no.

3:31The edge is even further to these levels of sweetness that I didn't even know existed in the first place.

3:40And there's some mind hacks and brain lasers and space raspberries. There's a lot of fun stuff along the way.

3:46Latif Nasser:All right. All right. Let's go. Okay. All right. So the very first thing that I found right off the bat, I found all these scientists. Check, check, check. Okay. Hey, okay. Hello. Who are out there trying to answer rigorously, scientifically, this exact kid question. My name is Eric Walters. Can I call you Eric? Please do. You don't have to doctor me. Like Eric here, a biochemist who used to work at NutraSuite where he developed artificial sweeteners. I spent a lot of my career working on sweeteners, studying sweeteners, and ultimately writing a book about sweeteners. And what scientists like Eric in the food industry do is they find or even make new sweet molecules.

4:30Yeah, yeah. Tweaking the structure in small ways and seeing, does it get better or worse? And then they literally rank them in terms of sweetness. Yeah. And they keep like a list of the sweetest things on Earth.

4:42Latif Nasser:Oh! And I want to walk you up my top five of the list using table sugar as our baseline here. Because that's the most common sugar that we use every day. Okay, great. So, number five. Honey. You know honey. Heard of it. Honey is about 1.5 times sweeter than sugar. Which, what does that mean? It's just, it's just, what does that mean? So, typically, in the food industry, people do this with trained taste panels. These specialized taste testers who are really good at noticing differences in sweetness. I haven't done it in years, but I used to be very good at it. And here's what they generally do.

5:19They take a little sugar. One gram of sugar. Like a pinch. Dissolve it in water. Call it a cup of water. Taste it. Sip and spit. Then they mix the same amount of the thing they're testing, let's say in this case honey, with the same amount of water. And again. Sip and spit. To see which is sweeter. Yeah. Now, to be able to say how much sweeter this thing is than sugar, what you do is you just add water. Until it's the same? Until it's the same. So, like with honey, you would theoretically need to add 1.5 times as much water for them to taste the same. Then you can say it's 1.5 times as sweet. Yep.

5:58There you go.

6:00Latif Nasser:Okay, that's a good way to, like, come up with a scale. Yeah. Okay. Okay, so that was honey. Honey was number five on the list. Now, one level sweeter, number four. Aspartame. Aspartame, which is used to sweeten equal. Sure. Okay. It's about 200 times as sweet as sugar. So it takes 200 times more water. Wow. With aspartame to taste the same as a cup of sugar water. That's wild. Yeah. Next, number three. This one actually comes from nature. Ooh. This is a katemfe fruit, which is a little red berry that grows in West African tropical rainforests. And it is 2 ,000 times sweeter than sugar. Orders of magnitude.

6:47Yeah. But then, number two, adventame. How sweet? Just take a guess.

6:55Latif Nasser:5 ,000. Adventame is 20 ,000 times sweeter than sugar. Oh my gosh. That means just a pinch of adventame could sweeten 500 gallons of water. That's like a jacuzzi of sugar water. That's freaky. Yeah. Okay, number one. The number one sweetest thing, according to these expert sweetness sippers, sitting around in their food labs, is... Lugdenum. Yeah. I don't even know how to pronounce it. Lugdenum? I always say lugdename, but I... Lugdename. Okay. This is 300 ,000 times sweeter than sugar. Oh. Yeah, that's what we said. Oh, my God. Yeah, that's insane. Okay, so what is this? This is a swimming pool.

7:46This is almost a full swimming pool. Wow. What was the mood and the reaction at NutraSweet to this news? I was jealous. Yeah. Wish I'd thought of that. because in his line of work, they're always trying to push this limit a little bit further.

8:02Latif Nasser:Right. I discovered a sweetener that was 28 ,000 times as sweet as sugar. Interesting. So I didn't win. I didn't win the prize on that one. But the prize goes to this like Frankenstein of a molecule called lugdinum. Okay, sit down. The Y is mad. You want a very little amount of this one, okay? You ready? So I set up a little tasting for my kids. Yeah, that's a good amount. 502 much. I couldn't actually get my hands on any Lugdename because it turns out it's not FDA approved for human consumption. Because apparently if you try it, there's a chance it turns your blood the color of chocolate. What?

8:47But. Why don't you guys drink some water? I did give them some Adventame, number two on our list. Okay, ready guys? Okay, and...

9:03Oh, okay. What do you think?

9:08Latif Nasser:Ugly. Ugly? You spat it out all over the floor? Okay, Huck is now scraping his tongue with his fingers. What are you doing? No, don't spit on the couch. That's gross, man. That's gross. That's gross. So the thing that scientists say is 20 ,000 times sweeter than sugar does not actually taste sweet? Yeah, I got it. Now, isn't that remarkably dumb? According to psychologist Linda Bartoszek, this whole ranked list is ridiculous. Like, this is the dumbest way to measure this. Have you ever heard anybody say that saccharin is 100 times as sweet as sugar? Yes. Have you ever tasted saccharin and sugar at the same time?

9:51Latif Nasser:No. Well, I assure you, you will not think the saccharin is 100 times as sweet as sugar, for God's sake. Well, these sweeteners, they do have some off flavors. Eric says that the problem with coming up with a perfect sweetener is that there's only one sweetness receptor. But on the other hand... Humans have, I don't know, 20 or 30 different bitter taste receptors. So it's like a minefield that you have to kind of tiptoe through to get to the promised land of the sweet receptor. Yes, yes. So it's really hard to develop a compound that triggers the sweet receptor, but doesn't trigger any of the bitter receptors as well, which is why you get those off tastes from so many sweeteners.

10:36Right. But the food chemists, when they're ranking sweeteners, they are just looking at one very specific thing.

10:42Latif Nasser:And that's a value that we refer to as potency. They just want the thing you can use the smallest amount of to turn on that sweetness receptor. The weakest thing you can just taste is sweet. Got it. Okay. And that kind of measurement is very, very helpful if you are a soda company or making chewing gum or something and you have a giant vat of something. And you want to put in the least amount of a thing to make the most money. Put in the least amount of that thing, right? Right, right. But that's not what my kids are asking. That's not what I'm looking for. We're looking for a whole other thing.

11:17Latif Nasser:And that's intensity of sweetness. How sweet does it actually taste to you? Yeah, I think that's right. Because we're talking about sweetness and sweetness as a perception. This is Paul Breslin. Professor in the Department of Nutritional Sciences at Rutgers University. And he says, you know, with things like Adventame, right? You might think that if you just kept adding more and more of it to the water, it would keep getting sweeter and sweeter and sweeter until it went to the moon. But it wouldn't. You'll eventually reach a point where the sweetness intensity sort of reaches a plateau. The amount of sweetness that you perceive sort of levels off.

11:57The thing is that our sweetness receptor, it's not just like a regular light switch you turn on or off. It's more like a dimmer switch.

12:05Latif Nasser:Okay, sure. So we can get brighter and brighter. And these sweeteners, they can only get a certain amount of bright. So what we really want to know is what thing will turn that dimmer switch up the highest? To the brightest bulb. To what'll get you the brightest bulb. Okay. And according to Eric, by that measure? Maybe sugar is the sweetest thing there is. No. Because it can get you to a higher perceived intensity of sweetness. He's never heard of or tasted anything sweeter than sugar. Wait, so is that the answer? The sweetest thing is sugar? Which feels like an extremely anticlimactic answer, right?

12:47Latif Nasser:That's just why, I mean, we're just back where we started. We are. We are back where we started. But, like, for a kind of profound reason, actually. Sugar plays a critical role in survival. Glucose is the best fuel the brain can use. From the very beginning, Linda says, The first thing when a baby is born, you want the baby to do is nurse. And the baby has reflexes that help it begin to nurse. But the sweet taste of mother's milk. The sugar in the mother's milk. Is what keeps it nursing. So sweet taste is an incredibly important cue. Our brains basically evolved this particular sensation, the reward of sweetness, as a way to get us to want sugar.

13:32Yeah.

13:33Latif Nasser:The receptors have evolved specifically to respond to sugar. Like, it's the thing the light switch was made for. In fact, there have been theorists in the past who've thought that sweet might be the beginning of our understanding of pleasure. Ooh, that's interesting. And so I started to see sugar and sweetness as almost the same thing. Like, sweetness doesn't describe sugar. It is sugar. Yeah. Which is cool and which is revelatory of our basic human nature. But also, like, I don't know. I still was craving more. Like, there's a limit here. I just want to go beyond it. And lucky for me, I ended up stumbling into a whole world of things that could take us beyond that limit.

14:28Latif Nasser:Really? And I'm going to take you into uncharted sweetness territory. And that's after the break.

15:06Latif Nasser:We'll see you next time. in a good way. What's in your wallet? Terms apply. See CapitalOne.com slash Bank Capital One N-A member FDIC. Radiolab is supported by the Allen Institute. What could science achieve if we understood the rules of evolution? What if we could accelerate that process to find solutions faster? AI Biodesign is an ambitious partnership to do just that. They're pairing laboratory research with powerful AI models to continuously learn and test at a massive scale, leveraging big data to create open access tools and accelerate discovery. See how at alleninstitute.org. This is Ira Glass.

15:45Latif Nasser:On This American Life, one thing we like is a good mystery. Sometimes about really big things, things you hear in the news. But most times, the little mysteries are the best. Our lost and found is currently filled with pants. I don't know, I've never seen this happen. I've got skirts, I've got shorts. Wait, this is true? This is true. Mysteries of every size each week. This American Life, wherever you get your podcasts.

16:15Latif Nasser:This is Radiolab. I'm Lulu. I'm here with Latif Nasser. Yeah. Latif is on a quest to discover the sweetest thing in the world, on the planet, the sweetest thing on Earth. And where we left off, you were at a potential answer that the sweetest thing is sugar. Yeah, except maybe not. Okay, so, Lulu, what is sweeter, a strawberry or a blueberry? I think a strawberry. So a blueberry has technically more sugar. Really? That's right. The blueberry has twice as much sugar in it. According to Linda Bartoszik, there are fruit that can make their sugar sweeter. What? Now, why do fruits care? Because animals that eat the fruits spread their seeds.

17:02Latif Nasser:So the fruit would really like that sugar to be sweeter. And maybe the fruit doesn't know how to add more sugar to it. I'm talking about the fruit's got consciousness. Of course, it doesn't. Evolution is doing this. But what has happened through evolution is that some fruit are now using volatiles, which make the smell of the fruit, to increase the sweetness. Volatiles are just little molecules that float around in the air. They make things smell. Now, there are two ways you can perceive volatiles. You probably only know about one of them, and that's you sniff them. But what happens when you put food in your mouth that is giving off odors?

17:43Latif Nasser:You chew it, you're releasing the odors in your mouth, and when you swallow, those odors are pumped through a hole in the back, and they go into your nose and can intensify the sweet signal in the brain. So the strawberry tastes sweeter than the blueberry because it puts out all of these non-sugar smell molecules that send smell signals to your brain, which overlap with the taste signals and give them a little boost. And according to Paul Breslin, As an ape, our species, our natural proclivity is to mostly want to eat fruit. Thanks to our long evolutionary history with fruit. A lot of animals can make their own vitamin C.