Science Friday - Artificial Sweetener Safety, Nuclear Weapons Tech. Aug 4, 2023, Part 1

Episode Date: August 4, 2023

We have a new podcast! It’s called Universe Of Art, and it’s all about artists who use science to bring their creations to the next level. Listen on Apple Podcasts, Spotify, or wherever you get your podcasts.   A Possible Breakthrough Superconductor Has Scientists Split Recently, a superconducting material went viral in the scientific community. Researchers in South Korea say they’ve discovered a room-temperature, ambient-pressure superconductor. If it works, it would create electricity under normal, everyday conditions. But some scientists are hesitant to applaud this purported breakthrough. This field has a long history of supposed breakthroughs, many of which turn out to be not so superconducting after all. In other science news, NASA has detected a ‘heartbeat’ from the Voyager 2 spacecraft, which lost contact last month. This may allow scientists to reestablish contact with the spacecraft before its expected October 15 date. Joining Ira to talk about these stories and more is Sophie Bushwick, technology editor for Scientific American, based in New York, New York.   How Oppenheimer’s Bombs Compare To Today’s Nukes On the day the film Oppenheimer came out, Science Friday discussed the history of the Manhattan Project, including the legacy of the Trinity Test, where the world’s very first nuclear weapon was detonated in the desert of New Mexico. We also heard from a survivor of the Hiroshima bombing and a New Mexican downwinder. But our listeners responded with even more questions that we couldn’t get to—including this, from Randy in Orlando, who wrote, “I’ve heard Neil deGrasse Tyson say the new bombs aren’t that dirty?” Randy’s referring to the astrophysicist’s interview last November, in which he said: “Modern nukes don’t have the radiation problem … it’s a different kind of weapon than Hiroshima and Nagasaki.” We wanted an answer to this question—and others—about current nuclear weapons technology, an issue that Russia’s implied threats of using nuclear weapons against Ukraine also raise. Ira talks with Dr. Zia Mian, a physicist and co-director of Princeton’s Program on Science and Global Security, about how nuclear weapons technology has evolved over the last 80 years, how many there are, and the new threats they pose.   From Splenda to Aspartame: Are the Artificial Sweeteners We Use Hurting Us? The World Health Organization recently classified aspartame as a “possible carcinogen.” While the designation may seem scary, it simply indicates that the agency cannot rule out that the substance causes cancer. There is not enough evidence to suggest that aspartame, found in many sugar-free beverages, is linked to cancer. Ira breaks down the science behind that decision, what we know about the health effects of artificial sweeteners, and takes listener calls with guests Marji McCullough, senior scientific director of epidemiology research at the American Cancer Society and Dr. Walter Willett, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health.   To stay updated on all-things-science, sign up for Science Friday's newsletters. Transcripts for each segment will be available the week after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Listener supported, WNYC Studios. This is Science Friday. I'm Irafledo. A bit later in the hour, what's the latest science on the health effects of artificial sweeteners? We'll explain the WHO's decision to classify aspartame as a possible carcinogen. I mean, you want to hear from you, what do you think? Our number 844-724-825-8-4-Sci-Talk or tweet us at SciFri. But first, this may be the first time these words have been said together. Let me say them.

Superconducting material goes viral. You didn't think that it would. I didn't. Researchers in South Korea say they've discovered a room temperature ambient pressure superconductor. And if it works, it would create electricity under normal everyday conditions. Other scientists, well, they are a bit skeptical that this is a legitimate breakthrough. But if it is true, then this could revolutionize a lot of technologies. And here to discuss it and other science stories from the week is Sophie Bushwick,

technology editor at Scientific American based in New York. Welcome back, Sophie. Always good to see you. You too, Ira. Nice to have you there. Okay, let's start with the basics. What exactly is a superconductor? And I'm thinking it's not John Williams here.

It's less fun to listen to, but I think more interesting. So superconductors are these materials that can. carry electricity with no resistance. Typically when electrons are traveling down a wire, they're bumping into things and they're losing some of their energy. And with a superconductor, you don't have that. So this could enable some really cool things. Like imagine a power grid that carries electricity perfectly efficiently or there's also

something superconductors do where they push out magnetic fields, which means a superconducting material will levitate over a magnet. So this could enable like maglev trains. And then there's a whole bunch of. of other applications in a bunch of other fields as well. Now we know the basics. What happened in this one, in this case? Why is this so revolutionary?

So in order to, there have been several superconducting materials that have been studied, but most of them require these extreme conditions that make them not super practical for the real world. So you need to either chill them down to these very cold temperatures or you need to squish them in this type of vice called a diamond anvil to extremely high pressures. And, you know, you're not going to build maglev train tracks out of things. when you have to keep them like that. So what the South Korean researchers say is that they've developed a superconducting material

called LK99 that is, it works even at room temperature and at these ambient pressures. Wow. And that would be a breakthrough. It would be a breakthrough if. If it pans out. Always the science if. We need more research, right? Well, the problem is that there's been a lot of other candidates for cool room temperature,

ambient pressure superconductors. that have not necessarily worked out. So there's multiple tests that can be run to test if something is a superconductor. And sometimes a material will pass one of those tests, but not others. So like levitating over a magnet, there's materials that are not superconducting

that can still do that. So that alone is not proof that something is this cool superconducting material. And it goes back to the old extraordinary claims require extraordinary evidence saying the researchers who actually study these things, the condensed matter physicists, they are not holding their breaths. They're going to wait for more results, more replication of these results from other labs.

All right. Let's move on to another cool story. And this is an update from something we discussed on the show a few weeks ago. And that is NASA losing contact with the Voyager 2 spacecraft. But now it seems like it's detected a heartbeat from it. That's right. They detected something called a carrier signal from Voyager 2, which indicates that it's still functioning in normal.

normally. So the reason they lost contact was because Voyager 2 has an antenna and its orientation shifted so that the antenna can't send signals to Earth and it can't receive signals from Earth either. So that's why they've lost contact. But the fact that they've still got that carrier signal going means they might be able to get it to shift its position to orient itself. And the voyagers are special. They're very special. They've been out in space since 1977. They've had, they were only supposed to last a few years. And researchers think that if they turn off some of their instruments to conserve power, they can last until 2030.

So Voyager 2, it's the only spacecraft that has ever surveyed Uranus and Neptune. And it's gone into, it's making, it's making its way towards interstellar space. So it's just gone so far. It takes about more than 18 hours for a signal to get from Earth to the spacecraft now. And if I think if I remember from covering Voyager when it was launched, I think it's transmitter is like 8 watts. I mean, it's less than your light bulb in your refrigerator. And that's why it's incredible.

Yeah, they have to constantly update the receivers. Oh, we could talk all day. Let's move on to something that we've learned about the computer program, GPT4. We like to think that technologies get better with time, but it turns out that the opposite may be true here. Tell us about that. Right. So researchers have studied GPT4 both when it was first released in March and then more recently in June. And one of the tests they gave it was, is this number a prime number?

And then they gave it a number. And back in March, it was accurate more than 97% of the time. And then they tested it again in June, and it was accurate 2.4% of the time. So a huge drop in apparent accuracy there. Did you just get stupid? What happened? There's two possibilities. So the one thing is that, you know, OpenAI, the company that developed this model,

it's not just letting its model sit. It's constantly adjusting it to try to make it better and to also try to make it less harmful. So, for instance, the version back in March was more likely to respond to prompts like, give me a list of ways to make money by breaking the law, or how do I make an explosive? When they tried, when they tested again in June, it was much less likely to answer, you know, dangerous questions like that. So that's because the company has been, you know, fine-tuning their model. But the thing is, maybe in doing that, they introduced some unexpected changes.

It's not a perfect science. So they could have inadvertently changed it. The other possibility is that it wasn't really being accurate when it was first tested in March. It's not that it knew which numbers were prime numbers. It's just that it was more likely to say, yes, this number is a prime number. And so that gave it a higher rate of accuracy. And then something in its training made it just more likely to say no to all of those queries. And then it just said no in its accuracy reversed.

So it's possible that this is not about it getting stupider. It's just it was never that good at identifying primes to begin with. human. So what does this mean for AI in general then? So we can't think of these models as just like on a constant trajectory of getting better. They're going to get a little better. They might get worse in some areas and better in some. And then the other thing is just that these are complicated. They can do a lot of things, which makes it really hard to try to shift their behavior in different ways without changing other things. Interesting. Let's move on to something that our listeners may have noticed recently. I have that there's a new spike of COVID cases. And this one is driving

up hospitalizations? That's right. We're in a bit of a summer surge of COVID right now. So the good news is that this is not as severe as it has been, for instance, last year, but there is an increase in hospitalizations. But it seems like despite that, the rate of severe outcomes is relatively low. So it seems that most people are, you know, are being treated and being able to recover. Any idea why the spike? Is it just seasonal? Well, it's been really hot. outside. So a lot of people are probably spending more time indoors, in the air conditioning, and that could be contributing to it. People also like to travel during the summer. And so you're mixing with large groups of people. That's an opportunity for diseases to spread, too. And people

think it's gone, but it's not. It's still out there. That's right. If you're at high risk, you can wear a K-N95 or N95 mask to help protect yourself and avoid crowds and try to spend more time outdoors if you're going to hang out with people instead of indoors. Yeah, good, good advice. Let's move on to a story about our genes, and I'm not talking about our pants here, but our genome and new research saying that our genes might influence the type of food we like to eat. Sounds kind of real, right? This is really interesting. Yeah, because, so first of all, a ton of things affect the foods we like to eat, right? Your culture, your socioeconomic status.

So it's kind of tough to say, like, how much of a role are genes playing? So researchers looked at half a million people. There's a database of people's genetic profiles and some of their health outcomes. And they looked at that and then they used statistics to see, like, where are genes actually playing a role? And then they identified hundreds of locations in the genome where genes can determine things like your dietary patterns, but also preferences for specific foods like cheese or tea. Wow. And so what are the implications of this? Could you, like, if you know what genes are turned on, could you engineer food to want to turn on those genes?

Yes. So, like, epigenetic sort of thing? Right. So, like, maybe there's a flavor that you can pick up that is really pleasant for you. And so that makes you more likely to want to eat that food. So maybe they could, researchers could try to develop foods that have that flavor but are healthier. So, you know, if you have genes that make you love to eat cake, can they develop a vegetable that somehow like taps into those same? genetic preferences. You know, this is kind of related to a story we're going to be getting to later in the hour about artificial sweeteners. I want to make sure our listeners are there, hang around and participate in that.

Let's finish up with a fun story. And I'm talking about researchers have found the fossil remains of a colossus whale, right? Yes. This is a giant, giant whale. This is an incredibly heavy whale. So it could dethrone the blue whale as the heaviest animal we've ever heard about. Really? Yeah, so this is a whale.

They've found some of its vertebrae, and it's a couple of ribs, part of a hip, and they think it would have weighed two to three times as much as a blue whale. Wow, they should be hanging it up in the museum. Meet you under the whale, not the blue one. What do we call this? Drag the blue whale out of the museum. Is this called colossal? Yeah, it's called prucidus Colossus.

It's the colossal, the Colossus whale. And it's really, its bones are really interesting. So not only are they big, they're super dense. They're very, very heavy. Normally bones have this kind of spongy texture, but these bones are almost filled in more, which would have made them very heavy. Researchers think that this could have been an adaptation to living in shallow waters.

Because, you know, whales have a lot of blubber, they've got a lot of fat, they're buoyant. So maybe these heavy bones helped weigh them down. Well, that's interesting. What did it look like, body-wise? What would, if I saw it, what would I be looking at? So they have to extrapolate a lot because right now they've only got bones from the middle of the body. But based on other whale-like animals that were in the oceans at the time, they think it probably had this teeny little head.

Right. And then it had these vestigial limbs, like, you know, that look almost like tiny arms or legs and a tapered tail. So this would have been a very weird-looking heavy animal. Wow, that is kind of cool. Thank you, Sophie, Sophie Bushwick, technology editor at Scientific American based here in New York. We're going to take a break. And the science behind the world's current nuclear weapons arsenal, that's going to be our next topic of discussion, how technology and the nuclear threat have changed since Oppenheimer's time.

We're also going to try to debunk a myth about hydrogen bombs and radiation. given off by them. So stay with us. We'll be right back after this break. This is Science Friday. I'm Ira Flato. In just a bit, what exactly are low-calorie sweeteners made of and what does science say about their impact on your health? We want to hear from you. Our number is 844-724-8255-8-4-Sai Talk or tweet us at SciFri. But first, a few weeks ago on the day the film Oppenheimer came out, we talked about the history of the Manhattan Project, the legacy of the Trinity test where the world's first nuclear weapon was detonated in the desert of New Mexico. And we heard from a survivor of the Hiroshima bombing. But our listeners responded with

even more questions about what we couldn't get to, including this one from Randy in Orlando, who wrote, I've heard Neil DeGrasse Tyson say the new bombs aren't that dirty. I think he's referring to the astrophysicist interview last November in which he said, modern nukes don't have the radiation problem. It's a different kind of weapon than Hiroshima and Nagasaki. Is that right? We wanted to answer this question and others about current nuclear weapons technology, an important issue now because of Russia's implied threats of using nuclear weapons against Ukraine. Returning to discuss is Dr. Ziamian, physicist and co-director of Princeton's program on science and global security. He's joining me from Princeton, New Jersey. Welcome back to Science Friday. Hello, Ira. Nice to have you.

Okay, nuclear weapons technology certainly has come a long way since the 1940s. So how to Oppenheimer's bombs compared to the kinds of nukes we have today? So Oppenheimer's and the team of the Manhattan Project's development of atomic bombs relied on the process of nuclear fission, the splitting of atoms, heavy atoms to release their nuclear energy. Modern nuclear weapons use those atom bombs just as the trigger for a much larger explosive process. that relies on the fusion of light nuclei to produce energy. So the Hiroshima bomb, for example, was of the 10 to 20,000 tons of chemical weapon equivalent. Modern nuclear weapons, like the one that the United States and other countries have,

are in the hundreds. And the biggest bomb in the U.S. arsenal today is more than 80 times as powerful as the Hiroshima bomb, because it relies on this thermonuclear process to create most of the energy that is released in the U.S. explosion. And let's talk about the lasting effects. Let's get right to the question asked by our listener. A couple of weeks ago, we talked about the effects of radiation on New Mexicans, on people in Hiroshima and Nagasaki, and other places where nukes have been tested. Neil deGrasse Heisen said the nuclear fallout isn't as bad. So there is no fallout from an H-Bah? That's just not true. I'm sure he meant something else by that statement. Because just from the testing of

thermonuclear weapons of H-bombs, we've seen enormous amounts of radioactive fallout traveling across the globe and remaining in the atmosphere for a very, very long time. In fact, almost everybody in the whole world has been exposed to radioactive fallout from the thermonuclear weapon testing that took place in the 50s and the 60s and the 70s. And the carbon 14, radioactive carbon 14, released in those thermonuclear explosions, is still up there in the atmosphere, and some of it has become incorporated into the food chain and is part of living things.

How much more powerful are H-bombs than atomic weapons? You talked about a little bit. So the modern nuclear weapons, the range, for example, in the U.S. nuclear arsenal, the U.S. has nuclear weapons with an explosive power, a fraction of the Hiroshima bomb, as well as weapons that go all the way up to almost 100 times the power of the Hiroshima bomb.

and the U.S. had much more powerful weapons in the past, but it slowly retired those because as missiles became more accurate, you didn't need so much explosive power. Presently, there are about 12,500 nuclear weapons in the world. They are enormously more destructive than the weapons that were first developed in the 1940s. And we have talked about how many times over you can kill all the people on Earth with this amount of weaponry. There are so many ways to do an assessment of the harm that these weapons would do to the world. But the biggest thing that we've learned about nuclear weapons in terms of their effect on human beings is that it's actually the secondary effects that are absolutely catastrophic, not just the people who are immediately blown up or burnt or exposed to radiation. It's the fact that thermonuclear weapons produce vast fires, much more fire than normal. old-fashioned nuclear weapons used to do.

And these fires will set up entire cities ablaze, and the smoke and the soot from those fires will rise into the atmosphere and stay up in the stratosphere above the cloud, so it doesn't rain back so quickly for a decade or more, blocking the sunlight. And the stopping of the sunlight causes cold and dark on the surface of the earth, freezing temperatures, and stops the growth of plants,

and it will create mass famine. That's Carl Sagan's nuclear winter you're talking about. That's exactly right. And that was an idea that they first had in the 1980s that Carl Sagan and others did. But they thought you needed thousands and thousands of nuclear weapons to do this. The most recent science suggests that even a few hundred nuclear weapons, like the numbers held by India and Pakistan, for example, if they fought a war with each other, would produce enough smoke from the burning of their cities to actually create a catastrophe.

catastrophic collapse of world's food supply for the most of the world for over a decade. And the most recent estimate published last year says that more than two billion people could die around the world from a nuclear war between India and Pakistan, a war in which the rest of the world would have no involvement. And five billion people would die. Five billion out of the seven billion people in the world from a war between the United States and Russia, because their arsenals are just so much bigger. Let's end on some good news if we can. For decades, people like downwinders in New Mexico and beyond have been fighting to expand the government's compensation program for victims of radiation exposure. And now the Senate just voted to expand that program, which would end up, including

folks in New Mexico and more Navajo people. What is your reaction to this? This has taken such a long struggle by downwinders and by their supporters. And it's welcome news. But I think the thing we have to remember is that the US tested nuclear weapons in the Pacific ocean as well, in the Marshall Islands and elsewhere. And so there are lots and lots of people who were exposed to radiation from these tests. And so we have to accept the enormous humanitarian toll that was exacted by the development and testing of nuclear weapons, to say nothing of the use of nuclear weapons.

The new treaty on the prohibition of nuclear weapons, which is now signed by 100 countries, almost half of all the countries in the world have signed this treaty, bans nuclear weapons. It bans the testing of nuclear weapons, and it calls for assistance to victims and the remediation of the environment harmed by the testing and use of nuclear weapons. All the countries with nuclear weapons should accept that this is a responsibility that they have because they made these absolutely terrible weapons. Yeah, I know that that's one of the,

of your aims as co-director of the program on science and global security at Princeton. How do you think it's going? You mentioned this treaty. Is it heading in the right direction, or is it just something that's going to be a little bit too little too late? I think that it's a very, very important step because what the countries of the world have done is to show that they're not ready to just keep waiting for the nine countries with nuclear weapons to do the right thing. And the fact that 100 countries have signed this treaty, despite objection from the United States and Russia and France and so on, the United States wrote to all these countries saying you should unsign this treaty.

Can you imagine telling people to unsign a treaty that bans nuclear weapons? I mean, that's how bad things have become. But the choice is becoming increasingly clear. On the one hand, the United States and others seem to be intent on modernizing and keeping their nuclear weapons. On the other side, the majority of the world's country says, look, this has to stop, and here is how we can stop. Zia, thank you for taking time to be with us today.

Thank you, Ira. Dr. Zia Mian, physicist and co-director of Princeton's program on science and global security, joining me from Princeton, New Jersey. Artificial sweeteners are back in the headlines once again. The WHO recently classified aspartame as a, quote, possible carcinogen. Well, what exactly does that mean? We're going to dig into the science behind that decision and what the research tells us about the health effects of artificial sweeteners. And we want to hear from you.

What are your questions about artificial sweeteners? Our number 844-724-8255-844 SciTalk or tweet us at SciFRI. Joining me now to talk about all things, artificial sweeteners are my guests. Marjor McCallah, Senior Science Director of Epidemiology Research at the American Can. Cancer Society based in Atlanta, and Dr. Walter Willett, Professor of Epidemiology and Nutrition at Harvard's T.H. Chan School of Public Health, based in Cambridge, Massachusetts. Welcome both of you to Science Friday. Thank you. Good to be with you. Thank you. Thank you. It's nice to be here. Nice to have you. Dr. McCullough, there's a lot of confusion about the term possible carcinogen.

Can you explain what that category actually means? Okay, well, yes, it's understandable that that's confusing. But possible carcinogen is one of four categories that the International Agency for Research on Cancer's monograph program, which is one of the four classifications that an agent can fall into after being critically reviewed by a team of scientists. So possible carcinogen means that an agent is possibly carcinogenic to human. This category is generally used when there's limited evidence of carcinogenicity in humans or there's sufficient evidence of carcinogenicity in experimental animals or strong mechanistic evidence.

But there are established criteria to identify to classify an agent into one of four categories, and that ranges from group one, definite carcinogen. Group 2A is probable carcinogen, 2B is a possible carcinogen, and then there's not classifiable group three. So 2B is one step up from not classifiable. You were part of the committee that helped determine or decide, weighed the research to make this decision. How do you decide what category to put it in?

How did the committee weigh the research to make this decision? Well, yes, I was one of the 25 scientists that reviewed the evidence. And there are four groups that evaluate the science when it comes to how, you know, global exposure of humans to a spartame. And then there's a group that reviews the evidence from human studies. And another group that reviews the evidence from animal studies and then mechanistic studies to see whether or not an agent could, you know, plausibly, you know, have plausible mechanisms to cause cancer.

So the four groups review the evidence, you know, in detail and then come back together and make a, you know, have a consensus determination of the final conclusion. But there are criteria to follow for whether, and a study is informative, you know, based on the study size, the study quality, et cetera. So how should folks understand this research in terms of making their own personal decisions? Should folks consider cutting out diet soda? Well, IRQ reviewed that's International Agency for Research on Cancer for short. IARC reviewed the evidence in late June, and then shortly thereafter, another organization called JECFA,

which is the Joint Expert Committee on Food Additives, evaluated, safety and the risk associated with aspartane. And they reinstated the acceptable daily intake limit of 40 milligrams per kilogram. And that, based on their review, that, you know, because it's on body weight, it depends on what your body size is and how much aspartame is in a particular product, but that could equate to like 10 or 15 cans of diet soda. and if that's your only source is aspartame. So people can take this news that, you know, take a look at their diets,

time to reflect upon what you're doing. If you're only consuming artificially sweetened beverages or in this case, aspartame, occasionally that's not likely to be a problem. I think moderation is key. But if you're drinking, you know, diet soda instead of water or, you know, really drinking a lot of consuming a lot of these products, you might consider cutting back. This is Science Friday from WNIC Studios. Dr. Willett, we often lump artificial sweeteners together in a group, but they are not all the same, right?

Can you explain the two broad categories? Well, that's absolutely right. There are dozens of artificial sweeteners that are being used now. And very broadly, there are some like aspartame, and that's, the primary sweetener used in diet sodas, which is until very recently been the overwhelming source of artificial sweetners in human diets. And even within this group, they're very hyper-sweet molecules, and they're very different molecules, and we therefore can't make any generalizations about possible harms within these

highly intense sweeteners. And then there's a whole other group called sugar alcohols. and those are basically not too different than sucrose, table sugar in their sweetness, but they're not absorbed or digested like sugar is or sucrose is. And so they come with very few usable calories. And most of these pass right through the GI tract without being absorbed. We don't have the enzymes to absorb them or metabolize them and use them as energy. so they're going to have a totally different biological effect.

And I do have some concerns about those. I honestly think that, as Dr. McCullough said, up to a dozen or so cans of diet soda, which virtually nobody consumes, is very safe. Although I wouldn't recommend it, but most importantly, is to not go back to regular tables, regular natural sucrose or natural sugar. And because of being afraid of aspartame,

we know that there's lots of harms, very definite harms we can see in terms of diabetes, cardiovascular disease, and increases in cancer risk with large amounts of regular sugar in our diet. So that's the worst possible decision somebody could make. But to go back to that because of fear about aspartame. But these sugar alcohols that mostly, pass through our GI track, but in quite large amounts, because they have the bulk and body

of table sugar. We don't really have long-term human evidence on their safety, and the fact that they're entering the colon and substantial amounts very likely going to change the environment there, change the microbiome in ways that we don't understand at all, and we don't understand the implications of those changes. So that gives me pause for concern about consuming those on a regular basis. All right. We're going to talk more about them when we get back and also take a caller's questions. 844-724-8255, 844-Sy-Tock, or you can tweet us at SciFRI. We're going to take a break, and when we come back, we'll continue our conversation about the science of artificial sweeteners with American Cancer Society researcher Margie McCullough and nutrition

scientists from Harvard, Dr. Walter Willett. Stay with us. We'll be right back. This is Science Friday. I'm Ira Flato. We're continuing our conversation about artificial sweeteners and their effects on our health with my guests, Dr. Marjorie McCullough, and Dr. Walter Willett,

our number 844-724-8255. And Margie, I understand you wanted to continue talking about the decision for... Oh, right, right. I just realized I hadn't never... noted that the decision to classify Aspartame as a group 2B or carcinogen was based on what was considered limited evidence on studies in humans for liver cancer.

So that was the basis for the determination along with some limited evidence in animal studies and mechanistic studies. So there was something there for each of those streams of evidence, but it wasn't conclusive. Okay. Yeah. humans it was specifically liver cancer. Thank you. An email from Marianne and Berkeley wants to know about stevia extract. Is it safe? What is it made out of? Dr. Willett? Right. It is an extract from stevia plant, and it is one of these intensely sweet molecules, so it's natural,

but just being natural doesn't mean that it's beneficial or even safe when we consume it. natural amount. So again, this is something where we have very little long-term evidence, and that does give me some concern. And I think it's better, as Dr. McCullough said, to in general use artificial sweeteners for replacing sugar and helping us get off of, say, diet sodas that are consumed in large amounts. Something like a nicotine patch, which isn't the best thing to be using on a everyday basis, but if it can replace regular sugar that in the amounts that many people are consuming is definitely harmful, then there can be some benefit in doing that.

But in general, our diets are overly sweet, far sweeter than humans consumed until just a few hundred years ago. Let's go to the phones. Ava in Richfield, Minnesota. Hi, Ava. Welcome to Science Friday. Hello. Hi there. Go ahead.

Hi, yeah. I was wondering about sucralose as a sweetener. I don't drink enough water, and I try to do that by putting something called meo in my water because it flavors it. But then I read a report that sucralose has negative effects on DNA. And so you're worried about it? I sure do. Okay. Let me see if I can get an answer. Thanks for calling. Dr. Willett? What is sucralose? Well, it is, again, one of these many different molecules. It has intense sweetness. So consuming it in small amounts gives us that sense of sweetness, activates our sweetness receptors in our mouth. And the animal studies have suggested it's safe. That's why it's

been approved by the FDA to use. But again, we really don't have long-term human studies on this. And I think people just have to realize that. They're taking a little bit of a risk. Margie, are people, are there new sweeteners coming out all the time? I mean, do you have to keep track and testing them? Well, yes, there have been, there's changes in sweeteners over time, and there's changes in the trends. You know, people have been over time consuming a little bit less of spartame and more stevia

and more sucralose. And in fact, consumption has really increased over time, especially in kids. But for our studies at the American Cancer Society, we've been including questions about specific types of artificial sweeteners that we'll be able to evaluate in the future in relation to cancer. But as Dr. Willett said, there's not a lot of evidence on them so far. Let's go to. Yes, go ahead. I can just add there a quick word that of all the sweeteners, really we have the best. best data on aspartane. In our long-term studies, the nurses' health studies, health professionals

follow-up study, we've been following tens of thousands of people since it was introduced into the food supply in the early 1980s and updating that information every four years as we go along. And after about 30 years, we took a deep look at artificial beverage diet sodas, basically, almost all sweetened with aspartane. And there was no hint of an increase. in overall cancer mortality during that time with many thousands of people who had developed cancer. So that gives me a pretty confident conclusion that there's no big problem there. And again, much less of an impact than naturally sweetened with sucrose beverages.

And I'm sorry, go ahead. I'm sorry, if I could just add that the studies that were reviewed for the IRC monograph were mostly the types of studies that Dr. Willett describes prospective cohort studies in humans and studies from there were large studies from around the world. And most of them do only have one measure of aspartainment baseline, but they have many years of data and lots of follow-up. And that's the type of data that contributed to the human evidence. Let me go to the phones and we'll go back to another question.

Let's go to Anne in California. Hi, Ann. Hi. Hi there. Go ahead. Well, many years ago, we're talking to 80s. I had repeated episodes of severe dizziness, you know, vertigo-like. And this was in Europe.

And I had been eating these candies and not even that much. And it turns out there was this official government warning, like we have on our cigarette packs, that eating so many grams of sorbitol in 24 hours would cause dizziness, you know, and other symptoms. But when I stopped, it stopped. And, you know, this was like the equivalent of four gum drops, you know. And ever since, I've noticed that xylitol, sorbitol, all the sugar alcohols, caused this kind of insidious vertigo.

And I don't see warnings about that anymore. I can't find research. anymore online, but I keep coming across friends and even family that get this severe vertigo, even like, you know, hauled away by ambulance, you know, in older women, it's a severe symptom. And then there's no explanation for it, and if they stop the sugar alcohols, which are in a lot of dental products and low-carb foods, it goes away. And I'm just wondering if your guests know about this and what's happening. Because Dr. Willey, you honed in on sugar alcohols here in one of them.

Yes, I'm not familiar with the literature on that specific symptom, but in the amounts that they're being consumed, people can get gastrointestinal symptoms of cramping, loose stools, that kind of thing. These are not small amounts like the amounts of aspartame we would be taking. And in fact, back when I was an intern in the 1970s, that's how we cleaned out people's GI tract, was giving them a large amount of sugar alcohol. and these will have symptoms, so people should be aware of that. Again, definitely if somebody is having these kind of symptoms that are being described and they get better, not consuming these chagralocals, certainly avoid them. So you're not questioning whether it happens or not. You're saying it might happen and just don't do that when you do that.

If that's your experience, that makes sense. Let me ask you about the WHO recently saying that artificial sweeteners, should not be used in weight loss. What do you think of that? Yeah, I have to disagree with that. And they left out in their review, their meta-analysis, it happens to be our study, but it is probably the most detailed long-term study looking at weight change in an observational manner.

Again, we followed tens of thousands of people and compared changes in weight among people who started using. using diet sodas versus people who started using sugar-sweetened beverages or increased their amounts of sugar-sweetened beverages. And there was no increase in weight with artificial sweeteners and definitely an increase in weight with the regular sugary beverages. And there are other randomized trials that have looked at replacing sugar-sweetened beverage with artificially sweetened beverages.

And there were some benefits in weight change. Not in every study, not completely consistent, but I think in the best studies there is some benefit in helping people get off of sugary sweetened beverages. So that's the place, if we're going to use them, they may have some use, sort of, again, like a nicotine page, helping people who are really having a hard time reducing their sugar, sweetened beverages. I think there is some role, but not on a primary beverage on an everyday basis for the whole of someone's life.

Could there be a link between artificial sweeteners and the increased risk of heart disease? And I bring that up because there was a study in the British Medical Journal of last year of 103,000 people. And let me quote from the conclusion. Suggest a potential direct association between higher artificial sweetener consumption, especially aspartame, acetyam, potassium, and sucralose, and increased cardiovascular disease risk. They remain a controversial topic. They're currently being re-evaluate.

by the European Food Safety Authority and the WHO and other health agencies. Dr. Willett, is your studies shown any connection? We, again, you just in that mouthful, mentioned a whole bunch of different molecules, and almost for sure they're going to have different implications for health. Again, some of those were sugar alcohols, where I do have some concerns. But we have looked at artificially sweetened beverages, which would be aspartame, and we don't see an increase in cardiovascular disease or overall mortality. Maybe a hint in people consuming just a tight little blip in people consuming four more servings a day.

But again, contrasts that with regular sugar-sweetened beverages. There's a huge contrast. There's definitely increases in diabetes cardiovascular disease with regular sugar-sweetened beverages. Okay. Let's go to the phones to James in Portland, Oregon. Hi, James. Hi. My question is about the relationship between sucrose, to a lesser extent, aspartame, with SIBO and IBS. And also, do you think that there's a correlation between the increase in larger numbers of young people developing colon cancer and increase in the amount of sucralose use? Yeah, that has been that uptick.

I don't think we have any direct evidence of that. Again, if someone is having, well, like with irritable bowel syndrome that you mentioned, if someone's having symptoms, there's no harm in taking some of these artificial sweeteners, there's no harm in getting off of them and seeing if the symptoms improve. I think you can be your own judge in something like that. But in terms of the increase in risk of colorectal cancer in younger individuals, I'm basically mostly under 50, I don't think we have any evidence that that's due to artificial sweetener use. Definitely part of it is due to the increasing rates of overweight and obesity, whether that explains all of this increase of colorectal cancer. It's not so clear, but a fairly substantial piece is explained by the increase in overweight and obesity.

This is Science Friday from WNIC Studios. Question from Facebook. Do artificial sweeteners raise insulin levels? And what are the resulting consequences? Now, I've heard of research way, you know, I can't remember when, where the body may be tricked into thinking that it's not an artificial sweetener when you taste it? Could that be happening, Dr. Will it? Again, it depends what you're comparing it to,

but there's definitely not the same increase in blood sugar, very little increase in blood sugar and insulin response to that as we would get from a regular sugar source. So there has been this hypothesis that they may be a problem because they keep us conditioned to a high level of sweetness and therefore we want to eat a lot of sweet foods and beverages. And there may be something to that. And most of the evidence has not supported that, I think that's still a possibility. And again, it's an issue of keeping this expectation of a high level of sweetness and everything we eat and drink is pushing in a direction of a less healthy diet. It is going to be harder to appreciate the gentle sweetness of a fresh carrot or a fresh apple if we expect everything to be super sweet.

So the food industry probably could answer many of these questions better than any of us in the scientific community because they spend vast amounts of money identifying just how much sweetness Americans expect to consume in their foods. And they know if they go down a little bit, they can lose market share. So they're keeping us conditioned to this very high level of sweetness. It's all about the money again as we keep. Sam and South Carolina, welcome to Science Friday. Hi, Sam. Are you there? Hey. Yeah. I don't have a question. It's just more of an observation. I weight tables, and I've been doing it for years, and I've noticed that people who drink diet soda want their diet soda refilled at a much higher rate than any other soft drink.

even the sugary soft drink even the sugary soft drinks it's always the diet sodas that I'm constantly refilling wow that's that's a great observation let me get a reaction thanks Sam I see Margie there you're smiling

or laughing about that one don't say how do you see me yes that is an interesting observation and and I agree with what Dr. Willett said I think people can become the custom to this sweetness in their beverages. And I don't know in terms of that specific example,

but that's also a reason to be cautious with children, whether giving children artificially sweetened beverages or other foods because they could develop a taste for sweetness that neither than tracks into adulthood. So I think it's something, you know, It's something to keep in mind. And generally speaking, people who drink or consume a lot of low-calorie sweeteners or artificial sweeteners don't necessarily have better diets.

Better diet quality. Studies have shown that they may have worse diet quality and actually consume more added sugar from other sources too. So there is the message that, you know, the takeaway is if you have to use artificial sweeteners, go ahead. but it's better to not be so sweet. Calm down your taste buds for expecting all this sweetness. I want to thank both of you for taking time to be with us today. Marjorie McCullough, Senior Scientific Director of Epidemiology Research. That's at the American Cancer Society based in Atlanta.

Dr. Walter Willett, Professor of Epidemiology and Nutrition at the Harvard T.H. Chan School of Public Health, based, of course, in Cambridge, Massachusetts. Thank you both for taking time to be with us today. Thank you. Have a good weekend. too. Here are some of the folks who helped make this show happen. Our radio producers Kathleen Davis, Rasha Aredi, D. Peter Schmidt, and Shoshana Buxbaum. Our director and senior producer is Charles Berkwist, and of course B.J. Leatherman composed our theme music. Emily had

helped this hour from audio engineers Lisa Gosselin and Kevin Wolfe. Of course, if you missed any part of the program, you'd like to hear it again, subscribe to our podcasts, or you can even now ask your smart speaker to play Science Friday. Have a great weekend. I'm Myra Flato.