The Most Cited Nutritionist in the World
Today we speak to Dr. Walter Willett from Harvard T.H. Chan’s School of Public Health. Walter is the most cited nutritionist in the world. Our conversation goes over some of nutrition science’s greatest successes: the banning of trans fats. We also talk about what the biggest problem in our diet today is, what nutrition science has gotten wrong, why there seems to be so much conflicting information about what to eat, and more.
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Juna: So I feel like sometimes on the show we harp a lot on the problems with nutrition research and how it's led us astray many times.
Eddie: Definitely covered that a time or two.
Juna: Well, today I thought we should actually spend some time in talking about what nutrition research has actually gotten right in the past couple decades.
Eddie: And to do so, I think, why don't we find the most quoted nutrition scientists on the planet? Oh, so, you know, do you remember when we had Ben Bergeron? He actually came in this year? Okay, so I learned the phrase that day. Yeah. That you were fangirling all over the place. So you've taught me so much I'm going to take on. I think this works. Can I be a fanboy? Yeah. Okay. All right. Then I am a fanboy for Professor Walter Willis. I've known Walter for 20 years professionally. He is always such a gentleman or amazingly generous with his time. And unbelievably productive. Yeah. Published. I think it's over 2000 articles. You know, I have not read that many articles in my entire life, and that's how many I know.
Juna: And for those of you that have been listening since day one, Walter is actually in one of our first ever episodes. And the episode sounded so different then, and we would have like 2 or 3 guests per episode, and it was just like a very different format. But I remember like, it was at Eddie's conference and Eddie introduced me, and then I think I like, pulled him into like some back room somewhere to try to record it. It was a quiet back room and I was like, Can you answer this question? I think I asked my question at potatoes. I was like, yeah, sure, about white potatoes. Yeah, yeah. Anyways, yeah. So this is a throwback to one of our first ever episodes, but now we kind of had a longer, discussion with Walter, which I'm really, really excited about, and something that I think you and Walter do a really good job of is reminding you I like.
Eddie: To be included with him. So I come on.
Juna: Walter and Eddie Phillips do a great job of reminding you that the world, in fact, does not revolve around her and her healthy choices. It doesn't, I know, shocking, but apparently your food choices also impact the world around you and the climate, which I think you guys are very good about reminding me of because I always forget that. So I am very glad to have both of you here to remind me.
Eddie: And another thing is that, you know how we try not to say this food is bad and this food is good.
Juna: Yeah.
Eddie: Walter just comes straight out and it says.
Juna: This food is bad.
Eddie: And we're going to be covering that in.
Juna: Depth. So on today's episode, find out what is the one truly bad food and what is a food that Walter wants to add to that list of truly bad foods? How can you think about the climate and your health and your food choices? And what are the things nutrition research has gotten right over the past 50 years, and the things that they have gotten wrong? I'm Juniata.
Eddie: And I'm Doctor Eddie Phillips, associate professor at Harvard Medical School.
Juna: And you're listening to food. We need to talk, the most cited health podcast in the world.
Eddie: Wait, wait, where'd you get that statistic?
Juna: Don't worry about it. Before we start, we just want to take a moment to shout out one of our favorite reviews of the week, guys, because we are so close, so close to 2000 reviews and we need your help to get over the finish line. It would be so awesome to have over 2000 guys. So if you haven't already, please go rate us five stars, leave a nice review, say nice things. The nicer you are to me, the more likely you are to get picked, because I'm the one that picks the reviews and just getting so say nice things about 82. He's nice. Anyways, Eddie, do you want to do the honors of reading this review?
Eddie: Yes. And this is from pre pre 633. Oh God knows what that's for. But here we go. As an endocrinologist obesity and metabolic diseases are my specialty. I spend a lot of time teaching patients about food and exercise. And I have found this podcast to be a great supplement, a supplement. Get it? To what I talk to my patients about. I have shared it with my entire team at work and they are now hooked as well. I appreciate the evidence based medicine and perspectives from experts around the world, and these are all findings that I hear about at the national endocrine conferences as well. I love the non-judgmental approach to discussing these modern day issues, and I hope Doctor Eddie and Yoona keep up the great work. Yeah, yeah, thank you so much.
Juna: That is so nice. I also heard, not to take away from people. Thank you so much. People. Yes, exactly. But I also heard that, my friend went to her doctor's office, and they had our book in the waiting room, and they.
Eddie: Tell everyone.
Juna: About, there's a book. There's a book called food. We Need to talk. And and she said that he said he loved our podcast, and he had bought books for all the people that worked in his office. And it was just it just warms my heart that I. So whenever all the doctors that listen shout out, thank you so much for sharing and leaving us a review and spreading the message. And we really, really appreciate it because as always, we would not be here without you guys. And with that, let's get straight to the episode. Welcome to another episode. Today we are joined by Professor Walter Willett. Or I know if you prefer, Doctor Walter Willett, both professor and doctor. And I saw on your website you are the most cited nutritionist in the world, which is really, really cool. And so our first question was that we know you've been working in the nutrition field for decades, and I was wondering if you could briefly discuss what the problems are in nutrition research, or why you think it's so difficult to run nutrition studies that give us, conclusions that we can go on?
Walter: Well, titration studies are challenging for multiple reasons. First of all, diet is almost infinitely complicated. We can look at it from different perspectives. We can look at nutrients. We can look at foods. We can look at phytochemicals. And these come in all different combinations. Moreover, the diseases, the outcomes that we're looking at occur over many years. For example, for heart disease, we need to be on a bad diet probably at least 30 or 40 years before the event. And for some cancers like breast cancer. What was really important, it seems, for diet, is what was happening when we were a child or a young adult, and many other conditions developed either long ago or cumulatively over many years. So you put the complexity of time together with the complexity of diet. And that makes it a little bit challenging to study.
Eddie: And Walter, of could you share just to give the listeners some context, you mentioned that it could take 30 or 40 years to set yourself up for a heart attack, but the data that you're looking at has been following people, many, many of them, for that length of time and further. So can you just give us a sense of the scope of the the data that's available?
Walter: Yes. Ideally we would start actually probably from before conception even then, during.
Juna: oh my goodness or.
Walter: Mother's pregnancy with us and follow people for that whole time. And we are actually piecemeal. So life cycle parts together. In some of our studies, we ask the mothers of our participants what they ate during the pregnancy with our participant. But our long term studies themselves have been going on for over 40 years now, so we are starting to get to realistic timelines for many outcomes.
Juna: So as a consumer, or just like a person in the general population, I feel like it seems as though nutrition advice is always flip flopping back and forth. But I wonder if you, as an insider in conducting nutrition research, what is your impression of dietary recommendations? Because I remember when we actually looked at them, it actually seemed like most of them had not really changed since the 1950s. But for some reason, the public perception is that they're always changing.
Walter: There is some disconnection between the public perception and what the evidence really shows. And part of this is the problem with media and it's gotten. Worse with time that the newspapers and radio and television and now internet and other novel sources of information are all struggling to get attention. They tend to highlight the newest finding, even if, though it may be the least reliable or the most exotic unexpected finding. And again, that's likely to be the least reliable information. So the public, I think, certainly has a good right to be confused. If I were if I didn't know what was really going on in the literature, I'd be confused too, just looking at the headlines or the latest stat reports. That's not to say that things haven't changed over time in terms of our understanding of diet and dietary recommendations. In fact, when I started work in this area back in the 1970s, I realized that the public was being told, eat this or don't eat that. And when I scratched down below the surface to look at the evidence, there was almost none. It was just slices. And so I realized we really did need to have a source of information that would be based on large numbers of people followed for many years. And so that's the reason we set up the long term studies that we're still conducting today. We picked health professionals for our studies because we knew that they could provide good information, and also be more likely to be committed to a long term follow up. And that's turned out to be true in the Nurses Health Study. Still, about 90% are participating over almost up to 50 years now.
Juna: Wow. And for our listeners, for those of you who don't know, the Nurses Health Study is a study that is cited all the time. Like every time I see a paper published about nutrition, there is some sort of data coming from the Nurses Health study. It's like a really massive study that doctor will it was a part of. And can you just tell us over the past 50 or 60 years what is some dietary recommendations that have stayed the same and very consistent? And what is an example of something that we've changed our opinion on.
Walter: In terms of consistency? Probably the desirability of consuming an abundance of fruits and vegetables. I think that really hasn't changed much over time. But if we go back to when I was getting started back in the 1970s, people were saying and the American Heart Association was saying we should load up on margarine, stay away from, butter, stay away from other kinds of animal fats. Now, that was half right. It's good to keep butter and animal fats low, but margarine turns out not to have been a good solution because it was very loaded with trans fat at that time. And that was an issue that was really sort of behind the curtains that even most nutritionists were not very familiar with trans fat. And as it turned out, after 15 years of follow up or so, we found that people who ate more trans fat were getting more heart attacks. And it was actually worse than saturated fat on a gram for gram basis. The good news is our studies were replicated. Other people did short term studies looking at the effects of trans fats and blood cholesterol fractions and putting it all together. There was a consensus that trans fats were in fact really bad, and they are now banned in the United States as of 2018, it took quite a while, but that is a major reversal.
Juna: Goodness.
Eddie: I want to drill down on that a little bit. Walter, one of our mantras on this podcast is that we're trying not to demonize foods as or categorize them as like, this is a good food and is a bad food. So I'll use another category. Trans fats are not good from what you're saying, right? For sure.
Walter: Yeah, there's nothing good about them. I you know, I don't have trouble saying this is a good food or a bad food, but it's it's relative. It's all relative to something else.
Eddie: Can you take us through the anatomy of a, what has become a national ban? Where did it start? I know that for there to be a sort of a ban on it, then that has to come from the government. But take us through the anatomy of what grassroots level this was recognized. And how does one and I'm also looking towards the future. If we could ban trans fats because they are not good or they're bad food, what could we do with with other things that we have the evidence to know are not good for.
Walter: Us, right? It is, I think, worth going through that because there are some lessons that we could apply to other aspects of diet. Perhaps, the first level is really getting, strong scientific evidence and that we really have to start that way. And again, back in the 1970s, trans fats were thought to be good, or at least not a problem because they weren't saturated fats. The idea was that saturated fats were the main cause of heart disease, and they play a role. Again, it's not all or nothing, but they are part of a bigger picture of things that help reduce heart disease risk and things that add to risk. And we did, first publish our paper. And actually, I think it was 1993 for the Nurses Health study, showing quite a strong relationship, but. Trans fats and heart disease risk. That was one study. And appropriately, we don't take major action just on the basis of one study. Replication is an important part of a scientific process. Also, it's good to have other kinds of information. And there, other colleagues, particularly in Europe, we're doing randomized controlled feeding studies. These are studies of a few dozen people where they're given a fixed diet for a few weeks, and then the changes in blood cholesterol or blood pressure or other risk factors are examined. And those studies also show that trans fats were uniquely bad. They raised LDL, the bad cholesterol, just like saturated fat, but they also depressed HDL cholesterol and raised triglycerides. That's we call it dyslipidemia. Now, a saturated fats did not have that bad effects of trans fats were behaving unlike anything else we had seen in a diet. Actually, these original studies were disputed. The American Heart Association was objecting to reductions in trans fat even at that time. But after enough time, there are long term cohort studies where replicated. These control feeding studies looking at effects on blood lipid fractions were replicated. And after about 6 or 8 years, I think it's fair to say there was strong scientific consensus that trans fats were not good, as you might say. And, but that wasn't enough. And there was huge, as you can imagine, industry pushback. Because if you looked at a grocery store, virtually everything on the shelves that was in a package said, and ingredients partially hydrogenated, vegetable fats, partially hydrogenated was there in virtually everything that was touched by the manufacturing process. And some of the industry said, we just can't do anything about it. And interestingly, all the major margarine brands and margarine was the main source, along with Chris. Well, at that point in time, all those companies were owned by tobacco companies at that time. So you just can't imagine their CEO getting out of bed in the morning and say, what can I do that would make Americans more healthier? That that just wasn't happening. But fortunately, in Europe, some of the manufacturers I have to give credit to Unilever, who was a big producer of trans fats. They looked at the evidence and say this, this has to go. And one of my colleagues said in, in Europe, they hired food technology people and engineers in the United States, they hired PR people and lawyers to deal with the problem. But so Unilever, it did actually produce trans free margarine when the American manufacturers were saying it can't be done. That was really important because the American manufacturers can no longer say it's impossible. So it took, quite a bit of effort. About ten years we worked, actually, with the center for science in the Public Interest and advocacy group that complimented our efforts because they knew about writing petitions to the Food and Drug Administration. That wasn't that's not where we were experienced. And, we provided the scientific evidence. And they had a petition that, sat there at the FDA for about ten years and nothing was happening, despite all the evidence by that time. And finally, someone from our school, actually, John Graham was appointed, to have a senior position in the Office of Management and Budget and the federal government. And he looked at the evidence and wrote a very strong letter to the FDA saying, you need to put this on the label. That's what the petition was, or make a good case. Why not? And so finally, and there were delays, motivated by the industry. Put it off a few more years, but I think it was finally about 2005, trans fat was required to be on the food label. So that was a big step forward. Actually, a lot of the trans fat was removed back by 2008, but that still didn't deal with foods that had no label. And in restaurants and schools and institutions, trans fat was still very high and in many products, and we were tracking the trans fat content, McDonald's and Burger King French fries, which are big source 30% of the fat in French fries was from trans fat. And then it really became a grassroots effort. And I think that's interesting. And actually, the same pattern happened with cigaret smoking and banning in restaurants that it was really small towns here, Brookline and Massachusetts, some small towns in California, banned trans fat in their town. So quite a big step was that Mayor Bloomberg and New York City banned trans fat in restaurants. And then the food industry said, you know, we give up. We can't have a patchwork distribution system. One area, one town gets trans free oils and other gets high trans fat oils. So they said, okay, well, we'll take it out by 2018. When the FDA finally banned trans fats, it was pretty much gone. It was actually pretty much gone by 2012, in fact. So it was really after the fact that the FDA did ban transfer. It was still important that they did it. We can sort of take it off the table literally and not have to worry about it, because there's plenty of other problems out there in the food system.
Eddie: So what's next? Where are you focusing your energy? I may not be a single answer, right?
Walter: There's no single answer. There are many things that need to be increased in our food supply and make it more affordable, more available, more delicious and aspirational. Fruits and vegetables and whole grains. That whole part of a diet. But there's other really bad actors out there still. Probably number one is sugar sweetened beverages. Oh, there is no nutritional benefit, only harm. And we see harms for weight gain, for diabetes, cardiovascular disease, total mortality. You can just go down the list but they're still promoted everywhere. If you had to pick one component of our food system that is driving in a major way, the obesity epidemic, it would be sugar sweetened beverages.
Eddie: So Mayor Bloomberg went after that market as well. Wasn't there a the soda tax at some point?
Walter: He tried, but right wing court overturned that. So, his efforts to limit sugar sweetened beverages. And it wasn't that people couldn't have them, it was just that there would be some limit on serving size. Actually, and if you really wanted some more, you had to walk back, 15ft or so to get, you know, 22nd refill. But he also would like to or wanted to remove sugar sweetened beverages from the Snap program. And that is a really important program that provides a safety net for people with low income. And you have to be really low to qualify for Snap. But still, there are tens of millions of people in this country that depend on Snap, but with no restriction. Except you can't use it for dog food and pre-heated food. But, sugar sweetened beverages are still the single biggest product purchased with snap benefits. Basically, we're paying to consume sugar sweetened beverages, and then we're paying again to treat the consequences of sugar sweetened beverages. So it's a it's a double hit. Wow. And it just doesn't make sense.
Eddie: We're going to be right back with Professor Walter Willett. And we're back with Professor Walter Willett from Harvard T.H. Chan School of Public Health.
Juna: So I think a lot of what you're seeing is also alluding to this point of the food industry not really having yet people's health at all on their mind when they are creating the foods that we eat today. And at least from what I've read, it seems like ultra processed food is one of the biggest problems in the American diet, which, and sugar sweetened beverages along with that and like trans fats, came into the American diet when ultra processed foods were rising in consumption. Right. And so I'm constantly reminded that, like, no matter what health claims all these foods make on their packaging, which a lot of them do make health claims even though they are ultra processed foods. It just seems like if it has any sort of health claim or if it's in a package, it doesn't. It's not good for you. And they didn't have your health in mind when they were creating it.
Walter: The food industry is not monolithic, and I think we have to look for the good players there and support what they're doing, actually. And trans fat, or the fact that Unilever was concerned and spent a lot of effort and money to remove trans fat. I think they do have more of a health interest, in part because they are a food company. They they're going to be in that business or hope to be in that business for a long time. And much of the US history is just traded around like baseball cards. And there's not a long term perspective on is it operating as a company in the long term. And I think many of the American companies are aiming for their quarterly bottom line. And that's unfortunate because for health we are really talking about timelines of decades. Also, I'm a little bit try to avoid the ultra processed label as well, because there are some foods that are classified as ultra processed, but are actually some of the better foods that we eat, like whole grain bread. Some of the alternatives that are not ultra processed, like so-called artisanal bread. When I've looked at them, they're made out of refined starch and huge amounts of sodium. They're actually much worse than the ones that I called ultra processed. So labels are always a little bit dangerous. And also, some of the alternatives to red meat are almost certainly much healthier than red meat itself, and, very importantly, can have a much lower environmental impact. Not all of it necessarily, I think. But I think we need to look, more deeply. Labels are always a little bit dangerous.
Eddie: But the new sort of faux meats you're saying are more processed than a piece of steak.
Walter: Oh, absolutely. They're defined as ultra processed. I think especially for climate change, the urgency of shifting away from red meat is so great that we can't expect that everybody's going to eat the perfect diet that we'd like them to. Many people find that difficult, and we need to give them as many options as we can. It's sort of like a nicotine patch that, sure, we wish that everybody just went cold turkey. But for a lot of people, that's really hard. And a nicotine patch is not a perfect solution. But if it can get people off of smoking tobacco, that's a huge step forward and hopefully a stepping stone to ultimately be off of tobacco.
Juna: So can we talk about climate change, actually? Because I know that's something that, you've done a lot of research in. What are the biggest culprits of our food that contribute to climate change? I'm sure you're going to say red meat, but maybe we can talk about, like, what kinds of meat within that, I guess. And then what do you think is the biggest thing that people can do to reduce their footprint?
Walter: Yes. We have spent quite a bit of time over the recent years looking at the effects of different dietary patterns on greenhouse gas emissions and thereby climate change. And there are huge differences among different foods in terms of how much greenhouse gas they emit and the production of that food. And as you implied, red meat, basically, especially for beef and lamb comes out right at the top. And the differences are huge that per serving, there's about 160 times more greenhouse gas emissions from a serving of red meat compared to a serving of beans. There's been some discussion debate about grass fed beef versus feedlot fed beef, although at this time somewhere close to 95% of beef in the United States is coming from feedlot beef. So that grass fed sector is pretty small. And it's a bit unclear if there's really a major difference in terms of greenhouse gas emissions.
Juna: Do you think that the diet that is best for the climate is also the diet that's best for human health, or if there's conflict there, how do you think people should reconcile the two?
Walter: Well, fortunately there's not huge conflicts there. Again, it's mostly animal sourced foods that are responsible for greenhouse gas emissions. Though there are some animal source foods. That are much lower. For example, some forms of seafood. Mussels have quite low greenhouse gas emissions. Other bivalves too, and some kind of small fish, but in general, especially red meat and dairy. Keeping those low, we don't have to totally eliminate them. In our last commission, we saw that we could sustainably consume about one serving of red meat per week. Which is like the traditional Mediterranean diet and, traditional diets from many parts of the world where red meat is not a daily food, but something that's, occasional or for special events. There's one inconsistency, though, with it. Basically, sugar and starch have very low greenhouse gas footprints, and therefore you can have a good environmental picture in general compared to most other foods, but a very unhealthy impact from eating them, especially in terms of refined grains and sugars. And those are, of course, are the base of most highly processed foods, because those ingredients are so cheap and you can jazz them up with coloring and flavoring and packaging and marketing and make a huge product like the standard soda. I calculated a couple of years ago, has about $0.02 per bottle or can have ingredients in it. So oh my gosh, that margin is huge there. And of course lots of people are feeding on that all the way from, the original producer, and then up the food chain to the retailer and in a supermarket. So there is a discrepancy. There's not a perfect correlation. But in general, having a healthy plant based diet will have both major environmental advantages as well as health advantages.
Eddie: And, just to close out this wonderful conversation, maybe just share. What do you think is the biggest misconception about good nutrition to leave our listeners with? Like what? What advice might you give to, folks that are interested enough to listen to food? We need to talk.
Walter: Okay. That's a good word. And, of course, for a long time, it was that all fat is bad. And that drove people toward eating these diets that were high in carbohydrate and, unfortunately, mostly unhealthy carbohydrates, refined starch and sugar. I think we've turned that ship for the most part. But there are important distinctions among the types of fat and saturated fats do have positive health benefits. And there there has been some confusion about omega six fatty acids. There's a popular myth out there that they're toxic. And, in reality, they are very healthy. In fact, we see them strongly related to lower risks of cardiovascular disease. Diabetes, total mortality and omega three fatty acids are also beneficial to us. So the best is to have adequate or good amounts of both of those. And the ratio. There's a lot of people saying much about the ratio of N6 two and three fatty acids. That's pretty irrelevant because you could have actually low levels, inadequate levels of both of them and still have a good ratio. But we do want to ensure that a diet has adequate amounts of both omega six and omega three. Having said that, in our country, there's probably more people that are short in the omega three fatty acids than the omega six fatty acids.
Juna: Can you give us some examples of foods with omega six? I'm sure people know omega three just kind of like fish is what comes to mind. But for omega six, one of the main food sources.
Walter: In terms of added fats, olive oil, which is my go to oil, has some modest amounts of both omega six and omega three. And if you have it as a substantial amount of your diet, you're going to get quite a bit. Many nuts have a good amount of omega sixes in that as well. So we can get omega six is from many different sources.
Juna: Okay, great. Thank you so much, Walter, for coming out.
Eddie: Thank you so much. I think we got you out on time and. Well.
Walter: My pleasure. And, thanks again for carrying the torch of good nutrition.
Eddie: Thank you. Regards to Gail. I will talk soon. Okay. You have a great day.
Juna: Bye bye. Bye. Bye bye. Thank you so much to Professor Walter Willett for joining us on today's podcast. We will link to all 2000 papers. Oh, no, I'm just kidding, guys. Academic profile has academic profile where you can find all 20 papers. If you want weekly episodes of the show, you can go to food. We need to talk.com/membership or click the link in our show notes. If you want to see Eddie and my new dog, head on over to our Instagram at A Food We Need to Talk because I posted the cutest video of the two of them meeting for the first time.
Eddie: Go viral with little Pooh Bear.
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Juna: We were created by Carey Goldberg, George Hicks, Eddie Phillips and me.
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