PBS News Hour - Full Show - The ‘Health Nerd’ on what we get wrong about science

Episode Date: December 16, 2025

Epidemiologist Gideon Meyerowitz-Katz, who writes the “Health Nerd” blog, talks with Geoff Bennett about bad scientific data, misconceptions around what we eat, and RFK’s “Make America Healthy Again” crusade. PBS News is supported by - https://www.pbs.org/newshour/about/funders. Hosted on Acast. See acast.com/privacy

Hey everybody, it's Jeff Bennett. Welcome to another episode of Settlein. My guest is Gideon Myerwood's Katz, an epidemiologist, data analyst, and one of the most trusted explainers of public health and risk in the digital age. Known for his clear-eyed analysis and knack for cutting through misinformation, Gideon's work has helped millions make sense of everything from COVID data to chronic disease, health policy, and the way numbers shape our lives. His writing and research have become essential reading for anybody trying to navigate health,

behavior and public communication. So we'll talk about how he approaches data what the pandemic taught us and didn't and why clarity and transparency matter now more than ever. So settle in and enjoy our conversation with Gideon Meyerwitz-Cats. So Gideon, thanks for speaking with me. It's my pleasure. You are an epidemiologist by training. You've also become one of the most trusted voices online explaining health and science to the public. What drew you to this line of work? Honestly, it was a bit of a, I stumbled into it. I finished an undergraduate degree in psychology a long time ago, and I was looking at my career options as someone who didn't want to become a psychologist,

which I realized too late. And I saw that the University, Sydney University here in Australia, was offering a degree in a Masters of Public Health. And I had just finished reading a book by a doctor called Ben Goldacre called Bad Farmer, where he talked a lot about epidemiology. And I thought, you know what? Why not? I'll go into some debt and do some more study.

And, yeah, more than a decade or about 14 years on, it's turned out pretty well. What do epidemiologists actually do? Yeah, well, it's a great question. Epidemiology is the study of human disease. So I work at the University of Wollongong in here in Australia, and I mostly study diabetes at the moment, chronic diseases, diabetes, cardiovascular disease, metabolic dysfunction. I worked a lot on COVID during the pandemic, as most epidemiologists did. And epidemiologists run sort of the gamut of most medical research that you can think of.

So at the moment, in my day-to-day job, I am looking into diabetes statistics, better ways to monitor diabetes, using large data sets to identify people who probably have diabetes but are undiagnosed, some work with AI models. And then I'm also running a group of randomized clinical trials looking at ways to improve the diabetes situation. You write under the moniker health nerd, right? So when did you first realize that there was this need for clear-eyed, myth-busting communication? Also, a very sort of stumbling into things story. I was writing, I kept seeing headlines that were a bit ridiculous online, and I was writing long, angry posts on Facebook a decade ago. And my friends were like, you should start a blog. This is pretty good writing.

So then I did. And I think it's pretty obvious. became more and more obvious to me that there was a huge amount of health misinformation and even really simple, basic mistakes in the media and in reporting when I finished my master's. Well, what's a good example of that? One of my first sort of semi-viral pieces was on the contraceptive pill and depression. And there was a big study that came out in 2016 looking at whether the pill is associated with depression. And most of the media headlines were really misrepresenting this connection as being

proven as showing 100% that the pill definitely causes depression. But in reality, if you look at the research, firstly, the link was much weaker than you might expect based on sort of the press release and the headlines. And also, it was a very modest increase. I think this is nearly a decade ago I was writing about it, but I think the absolute increase in depression rates for people who took the pill compared to people who didn't was on the order of about one in a thousand people.

And so it just was very frustrating to see that people were being put off an effective and useful medication based on sort of really bad misrepresentations of what the science was actually saying. And these days, I mean, I've written so many blogs and so many pieces over the last decade. I could shower you with examples. Well, we talk so often these days about misinformation, medical misinformation. This strikes me as a pretty good example of a subtler form of what you might call misunderstanding.

Yes, yeah. I think what really drew me at first was mostly, as you say, misunderstandings. It was misrepresentations. There was real research. It was good research, but it didn't say what the headlines and what a lot of the media stories said. And I mean, one thing I used to do back in the day when I had fewer sources to identify stories, I used to just go through the Daily Mail, just go down their health stories to find media misrepresentations. It was a very convenient way to identify problematic stories.

But I think over the years, I've looked into a lot. my focus has broadened substantially because in some cases it's very it's true that there are sort of scientific studies that get misrepresented in the media and often it's not even the fault of journalists often you see university press releases can be terrible they can really misrepresent things but then there is also out there quite a lot of bad research and there's very little protection for your average person who's trying to understand the world if the research itself is bad or misrepresents its findings. And then, I mean, something that I've been doing for the last five years or so since the pandemic came about is also looking at unreliable research. And

unreliable is a term we use to describe research that's either has mistakes in it or or is potentially some form of misconduct. So sometimes people fake studies as well. Wow. How would anyone, how would a layperson know that research or data is bad or unreliable? Or could they? Would you have to be an epidemiologist like yourself?

At the moment, what I think is that it is very difficult for a lay person to really know if the scientific research itself is accurate or good quality. it takes quite a lot of time and effort. You know, I teach courses to master's level students now and also to doctors on how to identify good research, bad research, how to sort of review studies in a systematic way. And it often takes people weeks, these very intelligent, very well-qualified people,

it still takes them weeks to understand what we're talking about. So I think for the average person to find a scientific scientist, study, easier than ever to find the study these days, but to understand the study to interrogate the potential biases, potential issues with the study is very hard. And then when we're talking about sort of unreliable research and research that potentially in some cases was never conducted at all, so fake studies, even experienced researchers, people who peer review studies on a regular basis tend to find that really hard to do. I think it used to be the case. that the best people to trust were the government, the health authorities.

But unfortunately, in the United States, at least, that seems to be less and less true. Yeah, I want to talk more about that in a bit. What's a common belief or a common practice that is actually undergirded by bad research, bad data? There are innumerable myths that I could talk about. One of my favorite myths, for example, which I'm writing about soon, is the idea that sugar, makes children hyperactive. It's an absolutely wonderful myth because every parent believes it,

but we have known since the 90s that if you give children sugar or if you give them artificially sweetened candy or if you give them nothing at all, it makes no difference to their levels of hyperactivity. Really? Yeah. Every parent I know is surprised when they hear that.

It's fairly extensively proven and there's actually a wonderful study from, I think it was 1994. Did the sugar lobby pay for that data that says that's... No, these are all independently funded, I think. I would have to look that up. But this wonderful study in 1994, they gave... They randomized mothers to be told that their children had either gotten sugar,

candy or artificially sweetened candy. But in fact, the researchers gave all of the... children in the study artificially Sweden candy. So it was Aspartame, which is, I think it's used in Diet Coke's artificial sweetener. And the mothers who were told that their children were given sugar thought that their children were much more hyperactive than the mothers who were told their children were given artificial sweeteners, even though none of the children got sugar. So we know in that case that the reason why people think that their children are hyperactive after they get sugar is because they expect it to be true. And so

they, when they see hyperactivity, they ascribe it to the sugar, even though it probably isn't caused by the sugar. Well, tell me more about something you said about the fraudulent scientific papers. What's behind that trend? What's driving that? I think that fraud in science is largely driven by the same mechanisms that we see for all of the major. issues in publication. So there's a big problem in science, which is that there are too many people, there's too many scientists, and there are too many papers. And we've known this for a long time. There is a drive. If you want to get promoted, if you want to get a tenured professorship in the United States, you have to publish lots and lots of papers. You really, we're talking about

30, 40 papers a year often. And you have to publish papers in big journals. You have to get a lot of this academic prestige, sort of the building blocks of your career. And the problem is that that drives people to publish papers, even if those papers aren't very good. And again, we've known this for a long time, depending on your estimates, somewhere between 50 and 60% around that of papers that are published are very low quality. And so if you are in an environment where you are pushed,

to not just to get your career advance, but also just to keep your job, to publish lots and lots of papers. That pressure leads some people to fabricate datasets or to plagiarize or to do all sorts of things. And I think it's a particularly big problem these days in some low-income countries where there is a huge drive to publish,

but there's no funding at all to do research. And it's also combined with the fact that It is very uncommon for frauds to get caught in science. I would say the vast majority of fraud is not caught. I mean, so we know from surveys of scientists of people working in academia that anywhere between sort of 3% and 10% of scientists will admit to what they personally believe to be misconduct of some kind. And if that is true, the number of scientific papers that has played,

plagiarism or data irregularities or even is outright just fabricated must be much higher than the number of fake papers that we catch. Gideon, I will tell you, you know, coming out of the pandemic here in the States, one of the most popular sayings among public health officials was trust the science, trust the science. You even hear people say that now in this RFK Jr. era. And I hear you say, you can't really trust the science, not all of it. Yeah, I've never been a fan of the phrase trust the science personally. I think it the problem is we're talking about something that's very complicated and usually public officials like simple messages. You don't want to have a 20-minute conversation whenever you are communicating with the public. And so trust the science,

it's a beautiful catchphrase, speaks to a lot of people, but personally it's not how I think about it. How do you think about it? So the problem is that the science is sort of a very one. question. I think there's a reasonable, you can reasonably say trust the experts because the people who tend to know the most about a topic are generally the best people to go to when you have questions about that topic. You know, if you want to know about the prevalence that the number of people who currently have cancer, then going to the top cancer epidemiologists in the United States is a great way to understand that. But I don't think saying trust the science exactly, it makes that much sense.

We were talking earlier about the study in which the kids were given sugar, or at least their parents were told that they were given sugar. It reminds me of this debate in this country about ultra-processed foods, with some studies calling them toxic, others urging moderation. How should we make sense of that debate? I grew up in the 80s and 90s where that's pretty much all we ate was ultra-processed foods. And in many ways, I remember thinking that McDonald's was healthy, because that's just kind of what people thought.

And it was a big deal if he went to McDonald's after school or whatever. And now it's like, you know, people frown on fast food, ultra-processed foods. How should we think about that debate from an epidemiological or even like a health standpoint? So I think it's such a, the ultra-processed food space is such a fascinating one because ultra-processed food is a really vague definition. The term ultra-processed food doesn't mean. that much. So you just mentioned McDonald's. If you go to McDonald's and you order the beef paddy with if you order a Big Mac without the bun, that is minimally processed because the

beef patty is entirely made from ground beef. The lettuce is fresh lettuce. And even the sources, they produce their own sources. And you could argue maybe it's it's sort of the you should get it without the Big Mac sauce as well. But I would argue that a big Mac, generally speaking, would be processed, not ultra-processed. Okay. So, and then if you go to a supermarket and you look on the shelf, you see the Dorito corn chips, right, Doritos, and then you look next to it and there's a home brand, we call them in Australia, like a generic brand of corn chips.

and the generic brand is usually minimally processed. And the Doritos are ultra-processed. And the reason for that tends to be because Doritos adds flavorings to their corn chips. But those two packets of corn chips are both almost exactly the same for you in terms of health. And so it's really difficult, I think, to distinguish between a an ultra-processed and a processed and a minimally processed food for your average consumer. And processing itself, most of what we measure when we talk about ultra-processed food is not the processing steps.

It's not the number of steps it takes to go from field to plate. Instead, we measure sort of these vague concepts of how many ingredients a food has, how many things that you don't keep in your kitchen. But that's not what processing is, you know. I mean, creamed corn has more processing steps than just a can of corn kernels. But they're both considered to be minimally processed foods, usually under the UPF guidance. The way I really think about all of this is that if you go back, I also grew up in the 80s and 90s. If you go back to that time and what my mom used to call junk food, if you avoid junk food, you're probably going to be doing better in terms of your

health. Well, that's no fun. Yeah, and what we call ultra-processed foods today are mostly what my mom would refer to as junk food in the 90s. Is the debate overblown then? Absolutely. I think it's personally, I find it to be ridiculous, because I don't think that the definition of ultra-processed, what does ultra even mean? I mean, you've got the Nova Scale. So all of this is based on something called the Nova Scale, which was developed by a Brazilian scientist in the, I think his first paper on it was in 2011. It might have been a little bit earlier. And he spent a lot of time, he spent a number of years sort of refining this scale. But it's ultimately still this sort of subjective judgment. The way that you define what an ultra-processed food is, is you put the

various food categories up in front of scientists and they talk about it and they figure out what they think an ultra-processed food should be in these terms. And in different studies, you often find that they've categorized foods into different categories. So honey is a perfect example. People cannot decide whether honey is unprocessed, whether it's minimally processed, or whether it's processed. Because all of those, you could apply all those categories to honey, which is processed.

The vast majority of honey you buy goes to a centralized factory. It gets put in a giant vat. and then it gets sort of and homogenized and they take all of the bits of the bees out because when you extract honey you usually get some little, you know, bee legs and stuff. And so it is processed to some extent and no one can decide whether, what category of food it should be. And so, and I think the term ultra processed, it implies that there's something intrinsically different about foods, but really it's a spectrum where at one end you have picking an apple off a tree, And at the other end, you have freeze-dried apple chips.

And in between that, there's a whole range of ways that you could process that apple. We are speaking to you in Australia right now, just pulling back the curtain a little bit. I just finished co-anchoring the news hour, came upstairs to this office and given the time zone situation, it's what, a little after 7 p.m. Eastern here. I say all that to say that you were in Australia. And I want to ask you about, you know, from your vantage point there, how is the international public health community absorbing, thinking about what's happening here in the U.S., with all of the changes to public health put in place by the Trump administration, RFK Jr, and his Make America Healthy Again approach? I think the international response that I've seen has been, well, firstly, there's a great deal of sadness because everyone I know has had colleagues. who have been made redundant, lost their positions, lost their funding, some amazing

researchers with decades of experience who have sort of just been left or thrown away by the United States and some of them are moving overseas. I think most researchers were aware of the tropes broadly that are being adopted by the United States. government now, but we know that there's a great deal of evidence that most of the claims made by the Maha movement are not true. So I think a lot of people are looking on in horror as major public health programs are sort of just thrown away. And also a great deal of confusion, because one of the things that the United States has been for 50 years at least is bipartisan when it comes to the health of the nation

and the health of the world, really. And now it seems to be more about sort of strong partisan drive to overthrow the previous public health establishment even when the scientific evidence sort of proves that what's being said isn't true. Seed oils as one example, vaccines as the other example, I believe the FDA commissioner recently said that they were planning on no longer recommending multi-dose shots.

Yeah, and vaccine skepticism exists in all parts of the world. What do you think is specific about the U.S. version of this phenomenon? I think the biggest thing is that it has become a partisan political issue, to be honest. In Australia, vaccine skepticism, it is to some extent part of it. So you have a very small difference between the people who vote for our major left-wing and major right-wing party in terms of whether they trust vaccines. And the pandemic did influence that. And there's been a bit of a rise in vaccine skepticism. But broadly speaking, if you talk to the main politicians from the two major parties in Australia, they are on 100% on the same page when it comes to vaccines.

And you have to go really out onto the fringes to find anyone who says anything negative. about vaccines. Whereas in the United States, to me at least, as an international observer, it appears that what's happened is the Republican Party has made its official position anti-vaccine rhetoric, and that has then filtered into the general population, and it's become a very common belief. Even though we should say President Trump got a COVID vaccine and a flu shot at his last physical. so that's worth that's worth noting you know yeah there's always a there's an interesting divide

between the people who push vaccine skepticism in in terms of what they say and what they do i mean one example is that all of rfk junior's children i believe were vaccinated as children the uh the u.s is standing as a global leader in public health once that's lost or if that's lost can that be regained or once we lose it that's that's that's that's It's it. One issue is that I think it's possible that you could regain some level of leadership. But the challenge from my perspective, I mean, I'm not the best person to talk to when it comes to world politics. I'm much more about scientific evidence. But the issue is that people can no longer rely on the US in the same way that we once did.

because for 50 years there was a very solid continuous support that stopped and now it's clear that that could happen again i think so if if the u.s was going to step back try to step back into that role firstly when it comes to funding other countries are sort of replacing not all of the u.s funding but a reasonable chunk but yeah i think you know i've got colleagues who run a conference every year, and they've been running this conference on, it's on diabetes epidemiology. They've been running it since the 80s using CDC funding, and the CDC funding disappeared when President Trump took office. And if the CDC, if in three years time, the president changes, the CDC starts offering that funding again, or even longer, I don't know if my

colleagues would necessarily take it because they're going to replace that funding that we've already discussed ways of replacing the funding. And they would certainly treat it differently. They wouldn't treat it as something that they were going to count on. Yeah. When we talk about the health secretary, RFK Jr., Robert F. Kennedy Jr., what do you make of his personal crusade to reveal to unearth the cause of autism? So when we talk about autism, what we're discussing isn't necessarily. the sole cause of autism what what certainly what rfk junior when he speaks he's mostly discussing the increase in the rates of autism so if you look at the number of

people who are autistic if you look at the earliest studies of that they were conducted in the 60s in the United States and also in the UK and they estimated that around 1 in 2,000 children had autism. Somewhere around 5 and 10,000 kids, give or take. If you look at the most recent estimates, the number is now closer to 1 in 30. So somewhere it's just under 3% of children would be diagnosed as autistic today.

So that's about a 60 times increase between the 60s and 2025. But if you look at the history of autism, it quickly becomes clear the main thing that's happened there. So in the 60s, when we talk about autism, it was a term used to describe severely disabled or children with very significant developmental delay who were mostly nonverbal, who required a great deal of assistance in their lives. So it was a very specific disease. And then as the decades went on, when we talk about autism spectrum disorder, it is very, very broad compared to the 1960s definition of autism. It includes children who are fully verbal, who are succeeding at school, who are very able to take care of themselves. And these are all things that in the 60s would be considered.

to be exclusions. So if you could do any of that, you wouldn't be diagnosed as autistic. And so we know that a large portion of this increase that RFK Jr. and co are attempting to explain is simply because we've changed the definition of what autism is. And I mean, the other big thing that's changed,

I know, again, we're referencing the 90s, growing up in the 90s and the 80s, it was very hard to be diagnosed with autism. And that's because there were very few providers who recognized the term, who were experienced and trained in recognizing autism. And I remember when I was a kid, you know, you had to go to a special psychiatrist who had months long wait to see, to even get assessed for autism. These days, you can be assessed online and it takes maybe two appointments to get a diagnosis if you believe that you have autism. It's very quick. And so the expansion of the diagnostic criteria and the substantial expansion in sort of the ability

to get diagnosed explains the majority of the increase in autism. And there are studies looking at this. So there was one study in California that found that just replacing the term mental retardation, which fell out of favor in the 80s with autism, which became. the new diagnosis explained 25% of the increase in rates of autism in California, which is, you know, 25% just for that one term being removed. And there was a study in Denmark that found the overwhelming majority of the increase in autism is explained in that country by the change in diagnosis and the improved access to diagnosis. So where did this vaccine

autism myth begin, this idea that vaccines or thermosol, the preservative that was used in some vaccines, that that's the thing that causes autism. So the origins of this belief about vaccines and autism are mostly traced back to one study from the 90s. And it was a study that has since been retracted by The Lancet, the journal it was published in, where they looked at a very small number of autistic children, and they found some inflammation markers in their gut that they associated with a previous vaccination, specifically the combined measles, mumps, and rebella shot. And I won't go into the details of why that study was retracted, but suffice to say that it is a completely and thoroughly discredited study. Which is extraordinary, because this goes back

to your other point about bad research, the fact that this was in the Lancet, which is a well-regarded, credible publication, is, I didn't know that. Yeah, well, the problem is, so the Lancet, as you say, it's one of the biggest medical journals in the world. It's, I think, been going since the early 1800s. But the thing is, within science, the entire system operates on trust. So the editors of journals assume that everything submitted to them is trustworthy and that there are, that when you ask people to disclose their competing interests, that they do it,

that they don't, that they have ethics approval to do everything they do, et cetera, et cetera. So they, they, they, they, it's all about trust. And unfortunately, it allows people who may not be trustworthy, a lot of scope to sort of break the system. Wow. There's so much misinformation about autism, it strikes me, really plays on parental fear. I mean, we saw that recently with this idea that Tylenol causes autism or that Tylenol can create problems in the pregnancy. Yeah, I mean, this is again, it's, to me it seems like the administration, the Department of Health and Human Services announced in February that they were going to fix autism.

And so they had to find a reason. They had to find something that they could pin the increase on. but wasn't just we've increased the diagnostic criteria because you can't fix that. That's just something that's happened. And I was not entirely surprised to see that Tylenol, acedaminophen, was picked as one of the things that they are arguing causes autism. I mean, the evidence for Tylenol,

there's been some concern about the use of Tylenol in pregnancy for a while, mostly because it is the only medication that pregnant women are advised to take. So there's been a lot of research into that just to make sure, you know, this is the drug we're recommending, is this actually safe? And generally speaking, yes, we found that it is safe. But there has been some concern because there's been a series of studies that have found a fairly weak and inconsistent association between Tylenol use and developmental disorders. So not just autism, some of the papers have found an association with ADHD,

some of the papers have found an association with other developmental disorders as well. And if you look at the data, all of the data together, and particularly some of the more recent high-quality studies, like the one that was done in Sweden, where they correct for genetic factors, what you find is that this link is very unconvincing. And most likely there is no connection between taking Thailand, and pregnancy and any developmental disorder.

However, if you sort of cherry-pick the data and you really, really want to prove a specific conclusion, you could come, it's not impossible to argue that there's some association there and that potentially that association might be causal. There are some people who argue that Tylenol could cause autism. I think personally, and I think this is the position of every medical association, in the world, that the link is very unlikely to be causal, that almost certainly, or Tylenol does not cause autism, probably doesn't cause ADHD or any other issues. But the evidence is not like 100% certain.

Unlike when it comes to vaccines, we are as close to 100% certain as it is possible in the scientific world that vaccines do not cause autism. But I would say Tylenol, it's more like 99% certain that it doesn't cause autism. You've built a career correcting bad science, oftentimes in real time, sometimes at a personal cost. What keeps you doing this work? Mostly, I'm a bit of a pedant. I really hate it seeing when people get things wrong. And particularly when it's something that really touches on my areas of expertise.

And I feel like these are things that have direct impact onto people's lives. So, I mean, in the fraud space, one of the studies, or unreliable science, I should say, one of the studies that I worked on was a study that appeared in a review that I was reading to inform my wife's pregnancy treatment. While she was pregnant, I was looking into supplements, and I found a study that was highly suspicious for various things. And, you know, I think... pointing out where people are getting science wrong can directly impact people's lives,

people's health. It's something that I can do and I've gotten pretty good at, so I guess that's why I keep doing it. I love that you describe yourself as a pedant. We need more of those in public health and epidemiology for sure. What gives you hope in a moment like this that we can ultimately restore the public trust in good science and good data? Well, I think what gives me hope, at least, is that in most countries in the world, the public still does sort of trust science and trust data. So I think, at least I hope, that you can only deny truth for so long. And eventually, people understand sort of reality. I mean, it happened in communist Russia under the USSR with the trofim lysenko who's very famous

Soviet scientists who denied the theory of evolution and instead had his own theory which was based on a different scientist at the time and he caused millions of people to starve to death but eventually you know that was recognized and they stopped doing it so my hope is that it doesn't that the US comes back to sort of a sane place in terms of public health before too many people are hurt. Gideon Meyerwood's cats, thanks for speaking with me. I appreciate it. My pleasure. Thank you.