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Last year, I was deeply in my Diet Coke era, like drinking multiple cans every single day. And then around July, I suddenly started seeing this headline everywhere.
— The World Health Organization has classified the artificial sweetener aspartame as, quote, "possibly carcinogenic to humans." — As a possible cause of cancer. But the agency warns more research is needed. — Aspartame is a synthetic chemical made in a lab, and it mimics the taste of sugar. So it's in thousands of low-calorie products. Stuff like… — Breakfast cereal. — Mints. — Chewing gum. — Intuable vitamins. — But also diet sodas, like my diet Coke.
Now, aspartame is not like cigarettes, which are clearly linked to cancer. Instead, the WHO said that aspartame is in the category of things that are possibly connected to cancer. Other things in this category include pickled vegetables, carpentry, and exposure while working as a dry cleaner. But I still had some questions here. Like, I was wondering, essentially, should I take all my beloved Diet Coke and...
pour it down the sink or, you know, cut back. The WHO's cancer research group said it was categorizing the artificial sweetener as a possible carcinogen, but the agency's food safety group said the evidence wasn't convincing. I was still a little dubious. So I turned to our health and science reporter, Karen Lintman. She is a doctor and a trained epidemiologist, so she's kind of my go-to for what's going on in the world of health.
The good news is she has been digging into this exact question. But the bad news, unfortunately, is that she is just as lost as I am. A lot of people have looked at this and a lot of people have published a lot of science about this. But, I mean, the punchline is not aspartame causes cancer, for sure. It's not aspartame is totally safe. It is we don't know. Aspartame is one of the most studied food additives out there.
And yet we don't have great answers. Which kind of begs the question, why? Karen says one reason is just that studying food and food additives is hard to do. But there's also another reason for the muddy scientific water here. The reality is that there are so many industry conflicts in the science that is out there. Basically, the beverage industry and the sweetener industry are
They funded a big chunk of the research that we have on aspartame, which confuses the picture. And this is not unusual. This story is bigger than just aspartame because there is lots and lots of industry-funded science for all sorts of foods. This is a real study in how conflicts of interest make their way into society.
safety agencies and why that makes it so hard to really trust in the safety of a lot of the products that we use on a daily basis. I'm Bird Pinkerton, and this week on Unexplainable, the story of aspartame and cancer research, but also a bigger story about nutrition research and why it can be so hard to get good information about our food.
Aspartame was first discovered in the 1960s, but it really hit the shelves in the 1980s when there was an explosion of all kinds of sugar-free, sugar substitute products onto the market.
It wasn't supposed to start a revolution, but it did. You know, there's this great interest in controlling weight, and here's a synthetic chemical that you can include in things that people love to consume. It made the things it's in taste better than anyone ever imagined. People really go for it. NutraSweet. Why so many things taste so good?
Kind of from the beginning, some people were concerned, and especially a neurologist named John Olney, who actually fought the FDA's approval of aspartame. Basically, the company making aspartame had done safety studies on rats, but John Olney thought that their rat studies around aspartame and cancer were
actually showed that aspartame might lead to brain tumors. And he said that more research should be done. This kind of led to a years-long back and forth. A scientific panel reviewed all the evidence, and they also called for more research. But in 1981, the FDA ultimately decided, no, aspartame was safe. But John Olney...
He kind of decides to keep monitoring the situation. And in the 90s, he starts looking at some brain cancer data and notices some real changes in brain cancer trends. And those changes really coincide with aspartame use and aspartame approval. Now, you have to be careful when you look at data like this and see bumps in disease numbers. It's not always just that
More cancers are happening. Sometimes it's that we're getting better at finding those cancers. So John Olney digs into the data, and he finds that, yes, some of that increase might be due to better cancer detection, but not all of it. And he thinks that aspartame might explain the rest, in part because of his concerns about the safety studies, and also because he sees there was a sharp increase in cancer after aspartame was introduced in the U.S.,
But now, this is where you start to get a sense of how convoluted and messy conversations around this research can get. Because there was pushback on Olney's findings here. Days after he published, NutraSweet put out a report critiquing his work. And it wasn't just NutraSweet, the aspartame company. There were also some other scientists that critiqued it as well. So when you read that, you're maybe like, hmm, that doesn't seem great.
But then if you dig into some of the scientists who are making these critiques and you look into their backgrounds, one of them has received funding for his research from the company that owned NutraSweet. Which leaves me sort of trying to figure out, like, whose take should I believe here?
And maybe you think, ah, the answer is just do some more research. And people did. Some Italian researchers decided to run their own rat tests with lots and lots of rats. An unusually large number of rats.
These researchers take all these rats and they give some of them no aspartame, some of them a little, some of them a lot, like much larger doses than a human would usually consume relative to their body weight. And they do find some concerning things that...
The rats that consumed aspartame had higher levels of a range of tumors and a range of organs, including breasts and the nervous system and their kidneys. And that even low doses of aspartame produced these results.
The research took several years, so this came out in the 2000s. And of course it generated a lot of controversy and a lot of pushback from the beverage industry. So instead of clearing things up, you get more confusion, essentially.
Some scientists thought the studies were good quality, worthwhile, but others critiqued how the Italian scientists did the research. There were some concerns about how the rats were treated, and some scientists suggested that the tumors might have been misdiagnosed. It does seem that the take of a lot of scientists on whether these are ultimately good studies or bad studies is
seems to track with whether those scientists are funded or not by the beverage industry. Over the next few decades, more studies were done. Studies looking at humans, a mouse study, research going back over the rat studies, research going back over health records. Some of this research was funded by industry, some of it was not.
And the conclusions kind of ping-pong back and forth. So you get, like, aspartame is not linked to cancer. Well, I don't know. It might be. No, never mind. It's not. And on and on and on. And again, as she sort of read through the studies, Karen saw this pattern. The scientists that are funded by the beverage industry generally find reassuring things. The scientists that are not funded by the beverage industry find less reassuring things.
This isn't a totally uniform trend. Like, there are studies done by independent scientists that find reassuring things about aspartame. But if you're someone like me trying to figure out what to do...
you end up with a confusion of conclusions. And it doesn't make sense to just dismiss every study funded by industry, right? Like, I reached out to the American Beverage Association. They suggested I speak with Danielle Wyckoff, who's a scientist who's evaluated aspartame research for them. And as she told me, it's important to go through the actual studies and carefully evaluate the science in them to see what's good science and what is less useful.
which is hard to do if you're just sort of a normal person like me, chugging Diet Coke like it's my job. But to paraphrase Danielle, that is why we have regulatory agencies, right, to sort through the science for us. And in 2013, a European food safety agency says, we're going to look at all of this. We are going to evaluate all the science that's out there, grade it all, and come up with some kind of
result of what we think all of this says on the whole. Their meta-analysis did find that aspartame is safe, as have many regulatory agencies. Except Karen, my colleague, spoke to a researcher named Eric Millstone. He's been studying food additives and food safety since 1974, continues to do so even in retirement. And when he analyzed that 2013 meta-analysis on aspartame, he
He found some flaws with how the researchers judge study quality, these flaws that could have skewed the results. So that makes me hesitant to just accept this ruling. And then if you fast forward to the sort of latest chapter of this story, the announcements from the WHO that came out last year, there are also issues.
There were two different groups of experts involved in these announcements. One group, which said aspartame might possibly be carcinogenic. And then a second group, which said, keep calm, carry on consuming aspartame, it's fine. But then The Guardian reported that a bunch of members of that second group, the keep calm, carry on group, they have current or former ties to the beverage industry. Which is a long way of saying that, again, there is more doubt here.
So scientists like Millstone and others who are urging caution at this point, they're not saying that there is a big study out there that definitively proves a strong link between aspartame and certain kinds of cancers. They're not saying there's a smoking gun that we are not seeing because it's being hidden due to some nefarious plot by the beverage industry. What they are saying is that the science that is out there is being discredited by
by people who look legitimate but actually have a conflict of interest. If I'm being honest, it's really frustrating for someone like me. Like, I do not enjoy feeling like a conspiracy theorist trying to follow the money and question everything. I just want to sip my little beverages in peace. As I heard this story about aspartame, I started to wonder, one, how common is this kind of industry funding in nutrition research? And two,
How does it shape what we know about our food? So I called the woman who wrote the book about industry funding and nutrition science. Or the books, technically. I've written 12 books and edited three others. Most of them, but not all, deal with industry funding of research because it's an enormous topic. That's after the break.
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Hey, unexplainable listeners. Sue Bird here. And I'm Megan Rapinoe. Women's sports are reaching new heights these days, and there's so much to talk about and so much to explain. You mean, like, why do female athletes make less money on average than male athletes?
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Marion Nessel has been writing about food and politics for decades. She's an emeritus professor of nutrition, food studies, and public health at NYU. I retired in 2017, but I'm still kind of hanging around there. I called her because I've been trying to figure out how much of our understanding of food is influenced by industry-funded studies.
And that is something that she spends a lot of time thinking about. She told me about her blog, foodpolitics.com, where she posts a lot about industry-funded studies. I mean, I'm really just sort of boringly consistent about this. And they're hilarious because I can look at the title of a study and guess who funded it. A study about the health benefits of fungus-based meat. It has funding from a fungus-based meat organization called
A study about the health problems with plant-based meat? It has funding from meat interests. A study suggesting that cheese could prevent dementia has funding from a dairy interest.
In fact, Marion says that there are a lot of studies about the brain-boosting benefits of various foods. And they're really silly. I mean, really? If you eat cherries, if you eat mangoes, if you eat avocados, if you eat any of these things, you're going to be smarter? I mean, come on. So Marion has lots of anecdotal examples that show that industry money can shape science.
But I wanted to know what we actually know about the bigger picture here, right? The numbers and the data, right?
So I asked Marion if we know exactly how much nutrition research is industry funded and if we know what effect that has. We don't. There have been very, very few studies of that. It's kind of another place where we don't have perfect answers. I read one meta-analysis on nutrition research that showed a pretty clear connection between industry funding and pro-industry conclusions.
but also some meta-analyses that found much weaker links. There is clear research out there, though, on stuff like pharmaceuticals and tobacco. And that research does show that industry funding can lead to pro-industry conclusions. So I asked Marion, why do we allow industries to research themselves? Like, why do we let them study their own efficacy to begin with? Why do we allow it? Why wouldn't we allow it? This is America!
We also allow it because there are examples of really useful research coming from industry, right? Like there's been a ton of industry-funded science into taste and smell, for example. So a lot of what we know about those things is thanks to food manufacturers and agricultural researchers. So the solution here is not to just categorically dismiss every industry-funded study. Marion does have a lot of advice for how to evaluate food-related research, though.
The first question is, does it make sense? Does it make sense that if you eat this product, it will have this absolutely incredible outcome? If it seems too good to be true, be skeptical. Marion also does always check to see if the authors are connected to or funded by industry,
And then she digs into the research itself. When you do a research study, there's the issue of design, how you frame the research question that you're studying, how you go about studying it, your methods, the kind of results you get, and how you interpret the results. Marion says one part of that process to pay particular attention to is how the research question is framed. Is it something like, is this food a source of antioxidants?
Because she says that's not a useful question. A better question is, are antioxidants actually healthy for you? That's a much harder question.
more complex question to answer. Now you're into the whole problem of nutrition research in general, which is people eat a lot of different foods and individuals differ and diets differ from day to day and they differ from individual to individual. You cannot overestimate the difficulty of doing nutrition research. It's really hard to do.
The other place in which the bias shows up is in the interpretation of results. I see studies all the time that are industry funded and that come out with null results. In other words, there's no difference between people eating that particular food and people not eating that. And then the study is interpreted as this could make people healthier.
Or this isn't any worse than anything else, therefore it's good. These are all very useful tools to have in your analytical toolkit. But as we saw in the example of aspartame, things do get complicated quickly, right? Like regulating bodies and experts can look at all the research, evaluate it carefully, pay close attention to the research methodology. And at the end of the day, they still won't have perfect answers.
So I wasn't too surprised when I asked Marion, basically, what should I do about my aspartame consumption? And her answer was, well, it depends on your philosophy about this. You know, if you believe in the precautionary principle, you don't touch the stuff. I don't personally think that it's very harmful. People aren't dropping dead eating it.
You know, but is it good for you? No, it's probably not. Is it bad for you? I don't know. I don't know how bad. And so, you know, and the committees that have grappled with this have a tough time grappling with it. My colleague Karen said basically the same thing, except she was even less definitive than Marion about giving aspartame up. She says that as I think about whether or not to sip my Diet Coke,
I also need to think about the trade-offs I'm making. What are the alternatives to this product for me personally, not just on a population level? But if I don't consume this, what am I going to do instead? Because you'd be switching to drinking an enormous amount of sugar, which we know is bad for you in a whole range of ways. Ultimately, I need to accept that everything in life is about weighing risks, making choices, etc.,
But that, again, is why this is all so infuriating. We deserve transparency and we deserve to not have the people who have a financial interest in our consumption of stuff guide what information we have access to about the safety of that stuff, right? And what bothers me about this story is that even if you wanted to know what we know about aspartame, it would be really hard to find out. That's not okay.
So where did I land on all this? I decided to quit Diet Coke. I haven't had one for several months now because it just felt like the right thing to do for me. But if you're trying to figure out if you should kick the can yourself, I can't tell you that. You're going to have to do your own research.
This episode was produced by me, Bird Pinkerton. It was edited by Jorge Just and Brian Resnick. Noam Hassenfeld composed the music. Christian Ayala did the mix and sound design. Meredith Hodnot runs this show. Melissa Hirsch did our fact-checking. Special shout-out to her for this one. And Manning Nguyen is a flock of geese honking in flight. Thanks also to Lisa Biro for sending me her work.
For anyone who does want to keep digging into nutrition science and keep looking for answers, do not despair. There are lots of great places out there to help you navigate all this science and help you figure out what's worth reading. I asked Marion where to go. Well, I'm laughing because my answer to that question is always me, of course. So check out her many books, but also her blog, foodpolitics.com.
If you want to read more about aspartame specifically, Karen Landman has an amazing piece on our website. And also one of our wonderful listeners, Natasha Allen, is a librarian, and she reached out to tell us that we should be shouting out library guides more. So in this specific case, she suggests Carol Shannon's Library Guide for Nutritional Sciences. We will link to all of these things in the transcript of our episode if you're looking for them.
This podcast and all of Vox is free in part because of guests from our readers and listeners. You can go to vox.com slash give to give today. And if you would, and if you could, it would be so much appreciated because it really helps the show. Also helps the show to leave us a review. Or if you want to just write us an email with your thoughts or questions, we are at unexplainable at vox.com. I love hearing from you all.
Unexplainable is part of the Vox Media Podcast Network. And unless there is some horrifying global apocalypse, we will be back next week.
