Are Red Meat Warnings Based on Flawed Science? Dr. David Klurfeld on Nutrition Myths and Industry Bias

Dr. Gabrielle Lyon: 00:00

You've probably heard the claim that eating red meat causes cancer. That message went global. Hardly any understood where it came from or the science behind the claim. Dr DavidKlurfeld spent decades at the USDA. He's not a fringe voice. He helped write the US Dietary Guidelines. This episode may change how you think about Red Meat Science and who is shaping your health. Are you concerned that a lot of what we've been told about red meat has been built on shaky science? You should be keep watching to find out what red meat really means for your health.

Dr. Gabrielle Lyon: 00:41

Dr David Klurfeld, welcome to the show. Thank you. I cannot tell you how long I have been reading what you have been researching and publishing. You've just been a tremendous force, and it is not always easy to be a fantastic scientist and to question and push for transparency, but you have done that. You are up there better than anybody that I think is out there. So just welcome to the show.

Dr. David Klurfeld: 01:17

Thanks. I could roll up my sleeves and show you some of the bruises, but I'm not sure your fans

Dr. Gabrielle Lyon: 01:23

want to see Yeah, well, we are going to talk about the bruises, and I to give people context about you and your work. You have been in academics for years. You recently retired, so congratulations. You were an adjunct professor in the Indiana University School of Public Health. You also retired as national program leader for human nutrition in the USDA Agricultural Research Service, and that was at the end of 2020, prior to that, you, I mean, you have a long list of accolades, Professor and Chairman of the Department of Nutrition and Food Science at Wayne University in Detroit, Michigan, for 12 years. And then, of course, before that, you were faculty at the Worcester Institute and at the University of Pennsylvania School of Medicine for 15 years. Yeah, seems like you just haven't been doing much for all that time. Really extraordinary. But it goes beyond that. You've published more than 200 peer reviewed articles, book chapters, associate editor of the American Journal of Clinical for clinical nutrition for 12 years, and you're currently the Associate Editor of the Journal of Nutrition, right? Distinguished Fellow. And that is ASN. Again, this goes on and on, but one of the reasons why I really wanted you to come here is you have been very outspoken in terms of your work and your research, really pushing for transparency and reproducibility, and especially when it comes to nutritional sciences and red meat. Also, you haven't done a ton of podcasts or speaking publicly, so we're going to share it here. Tell me about a little bit of your journey as to how you just became interested in all of these things regarding nutrition.

Dr. David Klurfeld: 03:18

Well, I have no formal training in nutrition. My undergraduate degree is in agriculture, and as an undergraduate student, I need to tell your short story. I got interested in nutrition and health, and I bought a paperback book in the college bookstore called the poisons in your food, and it's still on my bookshelf at home, but I reread it about 10 or 15 years ago, and it's garbage. It's really scaremongering. But I worked in my last summer in college. I worked in a pathology lab at a hospital in New York City, and I got really interested in pathology, and I applied to graduate programs in pathology, and was accepted at the Medical College of Virginia, and ended up getting a Master's and PhD in human pathology. As a postdoctoral fellow, I went to work with David kruchevsky, who's very famous nutritional biochemist, and always described himself as a biochemist, not as a nutritionist, but he was one of the most prominent nutritionists in the world, and wrote the first book on cholesterol, and was probably the funniest guy in the nutrition business. So I actually ended up working with him for 15 years, and Dave was a very honest guy and put his own work in perspective. And he always said, Never change what you do based on one study. And he also was very much a fan of Craig. Editing the right people, not sticking to the elite group of people who seem to hold sway in various scientific fields over time. You know, he used to say that people change their mind after they die, and that's a problem in science. You know, one of the real problems that has bothered me for decades is the concept of allegiance bias. If you tell me the name of an author of a nutrition paper and just read me the title, I can tell you what the conclusions are just from knowing that person's name. Wow, yes. And when Dave and I used to do animal studies, things didn't always come out crystal clear and reproducible from study to study, but in the human nutrition business, that seems to be the standard for getting people repeatedly showing the same thing over and over. It's just never that clear cut.

Dr. Gabrielle Lyon: 06:07

Was it always that way? Seems, you know, again, I obviously have not been in the field in the way that you have been, but it seems as if things have become a bit more heated, a lot more divisive, and there's a landscape that I've never seen before, and it's really scholars disrespecting scholars outwardly and vocally and really even to the extent of attempting To ruin people's careers because it didn't align with their views.

Dr. David Klurfeld: 06:43

Absolutely, I don't think that's new. I think it was hidden behind the curtain in the past. Again, I had the advantage. Dave krichevsky was 30 years older than me and was quite prominent when I joined his lab in the 1970s but he had been invited all over the world, and he was an iconoclast, and would speak out for moderation and variety no matter who he was talking to. And I think those are two of the recommendations you can still take to the bank today. And you know, when the world was saying low fat, Dave was saying, wait a minute, it's not that simple. Wow. And wow. You know, a lot of recommendations are still stuck in the low fat rut decades later, even though science has progressed way beyond that.

Dr. Gabrielle Lyon: 07:38

Yeah, even now, saturated fat recommendation at 10% Yeah, or less, which potentially, I think, weaponizes food in 2015 you were part of. And I this is a very important conversation. 2015 you were part of 22 scientists that got together with the task of evaluating, from what I understand, the Carson that the cancer causing properties of red meat. And there was an official press release that concluded, which I'm going to read. And it was after thoroughly reviewing the scientific literature, a working group of 22 experts from 10 different countries convened by the IARC program, classified the consumption of red meat as a probable carcinogenic to humans, group two, a based on limited evidence that the consumption of red meat causes cancer in Humans and strong mechanistic evidence supporting a carcinogenic effect. Okay, it just gets better. There's one more section here. Processed meat was classified as carcinogenic to humans, group one based on sufficient evidence in humans that consumption of processed meat causes colorectal cancer. And I have a quote from you that says this was the most frustrating professional experience of my life,

Dr. David Klurfeld: 09:08

and it still is. 10 years later, it hasn't gotten any less annoying to me.

Dr. Gabrielle Lyon: 09:14

Please share with me the background of this group and the IARC what what its role is, and really the impact that it's had.

Dr. David Klurfeld: 09:26

So the IARC, International Association of Research on Cancer is part of the World Health Organization. They're funded primarily by the US and Japan National Cancer Institutes of those two countries, with small contributions from others. Their whole purpose in life is to evaluate the potential cancer causing effects of chemicals in the environment, but they've spread out to other things, like foods such as coffee and. Uh, red meat and working the night shift. You know, there are things like ultraviolet light exposure where we know is a risk factor for skin cancer. There's pretty solid evidence cigarette smoking. There's no argument that, at least for primary smoking, there's no argument that it causes lung cancer and probably cancer in other organs. The group, working group that I was on was, as you said, 22 scientists. They're all self nominated. We had to apply to be on that, and I had published a number of studies on couple on meat, but several more on the effects of dietary fat, in particular on rodent models of breast and colon cancer. And when I was doing those studies, the dominant thinking was that it was all fat, causing the increased risk that it was nothing else. I think that was a gross over simplification, simplification that even I bought into at the time for a variety of reasons. But coming back to the IARC, once we were all accepted, we worked with a group of staff members there in Geneva, sorry, in Lyon, France, who is in Geneva, where they prepared documents for us to work on and edit and evaluate all the literature that they found for us. This was not a systematic review of the literature, which, even 10 years ago, was the standard approach in medicine. There was no meta analysis of the epidemiology, and the epidemiology is what ended up determining the decisions that were made.

Dr. Gabrielle Lyon: 12:05

And can you explain a little bit about epidemiology for the listener who is thinking, Okay, well, that sounds okay, sure,

Dr. David Klurfeld: 12:15

epidemiology is the scientific term for observational studies. And the problem with observational studies is when you observe people's behavior, it might be a snapshot in time of how someone's diet is that day that they're filling out the questionnaire, and then you make believe that the diet has been the same for 20 or 30 years of follow up. And there are different kinds of questionnaires where you can ask people to estimate how much red meat they ate, or how often they ate red meat, you get a different answer when you ask, how many times a month Did you eat red meat versus how many ounces a month Do you ate? And so combining those kinds of questionnaires, you're asking differently, you're getting different answers. They're not actually justifiably combinable. So it sounds to get the same answers, low quality, like low quality evidence, precisely. And in fact, the working group, there was a there were four subcommittees. I was on the animal subcommittee, and we decided that the animal subcu animal experiments did not contribute to making a decision about red meat, because some saw an increase, some saw no change, and some saw a decrease. So the net result was zip. Nothing happened, so they relied on mechanistic studies and epidemiology studies. But the mechanistic studies were highly problematic. They claimed that this is what linked the behavior of eating to the end result of colon cancer. But the mechanistic studies simply say what's possible, because none of those mechanisms were shown to occur in people eating meat,

Dr. Gabrielle Lyon: 14:36

because I'm looking at this IARC monograph hazard classification. This is published on the World Health Organization. And if someone who was not a scientist like yourself would go to this, this has group one, and it basically says, smoking, radiation, consumption of alcoholic beverages are sufficient evidence for cancer. Concern humans. And then right underneath that is emissions from high temperature frying, DDT, the chemical compound, and then consumption of red meat. And this is published. And then, funny enough, even underneath that the next group is occupational exposure, so engine exhaust and lead red meat trumped that. That's really concerning,

Dr. David Klurfeld: 15:30

of course. I mean, it's a lack of perspective, and it's the hubris that some scientists have that their work is the revealed word, and anything somebody else finds is just wild speculation. And that's one of the things serving my last 16 years as a government scientist, that a really valuable lesson to me in the federal government was that the risk assessors are kept separate from the risk managers, and here in the IARC we have the risk assessors voting on managing that risk

Dr. Gabrielle Lyon: 16:13

so what does that mean? Exactly? That

Dr. David Klurfeld: 16:16

means that they don't have the objectivity that's required of saying that we'll look at all the work equally. Rather, we're going to look at my work and say that that's more important than anybody else's work. And part of the problem of that group was you had to have relevant research to the question? In Hand, 11 of the 22 scientists were epidemiologists, so already everybody on the committee is outnumbered by people doing observational studies. Were they aware?

Dr. Gabrielle Lyon: 16:57

One would have to recognize the quality of that evidence, even if you are a career epidemiologist,

Dr. David Klurfeld: 17:05

nutritional epidemiologists believe that they have a different standard from everyone else, and that's why nutritional epidemiology is the Rodney Dangerfield of science. You know, it's not going to get the respect it has, because it doesn't deserve the should. It should have respect, but it uses methods that don't deserve respect to come to causative conclusions. You can certainly come to the conclusion that this should be researched more and that maybe there's a risk here. You know, I would have been happy to have voted that there's a possible risk here from consumption of processed meat, consumption of raw red meat, unprocessed red meat, I don't think has any identifiable cancer risk at all, but they claimed it did in their summary, and it was based exclusively on epidemiology. And the summary that you cited, that was in Lancet oncology, reported that the epidemiologists looked at 800 studies. Yeah, I see that here 10 studies. They only used 18 studies out of 800 out of 800 so 780 of them were thrown out because either they didn't show anything, or they didn't show the right result, or whatever the reason was. In fact, I will tell you that that monograph was supposed to come out within six months of our meeting in France, and it took almost three years, and none of us on the working group saw the final result before it was published.

Dr. Gabrielle Lyon: 18:54

Were the 22 of you sitting all in the room talking through these things together.

Dr. David Klurfeld: 19:00

We were we were in the room in subcommittees for a few days, and then we were in the room as a full committee for several partial days. So the epidemiologists sort of worked on their own to come to a conclusion that the rest of us would agree to,

Dr. Gabrielle Lyon: 19:26

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Dr. David Klurfeld: 22:15

Well, among the epidemiologists, many of them were friends. Many of them had served on previous IARC committees, and almost all of them had already reported that either red or processed meat intake was associated with increased risk of colon cancer. And I think they saw this as an opportunity to reinforce the importance of their work. You know, this is a judgment call on my part. I mean, there was no obvious discussion that I heard saying we're going to nail red meat

Dr. Gabrielle Lyon: 22:58

cows are responsible for everything. Yes,

Dr. David Klurfeld: 23:00

but this, I think, was, was the attitude, you know, I came in more or less neutral. We the studies I had done on fat showed that increasing fat increased the risk of different kinds of cancer in rats that were given cars chemical carcinogens, but we had fed meat to rats, and didn't increase the risk at all. And in fact, the mechanisms, which we touched on just momentarily, were only shown in rats fed a calcium deficient diet, and not red meat, but blood sausage. Eating blood is not the same as eating roast beef,

Dr. Gabrielle Lyon: 23:43

yes, and this is so one of the people on the IARC committee published two papers feeding bacon to rats and given a chemical that induces colon cancer in these animals, and eating a diet high in bacon actually reduces the pre cancerous lesions. It seemed that the scientists also used animal studies to justify the biological mechanisms linking meat intake with colon cancer. And your response to that is, while these studies are being reported and then somehow getting out to the public in robust ways that the actual studies did not feed meat, but this blood sausage to calcium deficient rats, which I don't necessarily know the relationship between calcium deficient rats and and what the outcome would be, but I am very well aware that readers were not told of the actual way that the study was done.

Dr. David Klurfeld: 24:40

Well, for me, the calcium deficiency, I biochemically, I don't know what that meant to the rats, but it tells me it probably didn't happen in normal, healthy rats, if they have to use calcium deficient rats. Oh, that's interesting. You know, calcium is a major mineral in a lot of processes

Dr. Gabrielle Lyon: 24:58

I see. So it was almost set. To fail and whatever or set up for a particular

Dr. David Klurfeld: 25:03

outcome, I think you understand completely

Dr. Gabrielle Lyon: 25:06

where does that lead us now. So what was the actual scientific basis for that red meat classification?

Dr. David Klurfeld: 25:13

So it was the combination of the mechanism which was not demonstrated to occur in humans, but in sick rats, in combination with a very small number of papers that evaluated the association of meat with colon cancer, and in most of those papers, scientists are basically told by the editors and reviewers of the journals don't use causative language when you're describing Association. That's sort of a basic scientific approach. You can't show cause and effect from statistical associations. It's simply a statistical correlation. You know, there's a correlation between eating cheese and the number of divorces in the state of Maine.

Dr. Gabrielle Lyon: 26:08

I read that was a wonderful paper. I think that I became your number one fan after I read that, it was the consumption of margarine and the equivalent of how you would get divorced in Maine. It was unbelievable. We should definitely link that. What was the, what was the title of that paper? I think I

Dr. David Klurfeld: 26:24

have it here. Don't, don't recall, okay, title

Dr. Gabrielle Lyon: 26:27

of hilarious.

Dr. David Klurfeld: 26:29

But you can, you can show statistical associations. You know, when these studies are done, not one of these studies was ever designed to look just at fat, just at meat, intake, on cancer, it was to look at everything in the diet. So we have dozens of foods, scores of nutrients, maybe 100 disease related endpoints. So you have 1000s of 1000s of combinations, literally more than 100,000 potential comparisons that are made. And you know that the statistical standards p less than oh, five or a 5% chance of it being a real difference? Well, with 120,000 potential comparisons, you have 6000 potential false positives, more than the total number of papers that were examined in this exercise.

Dr. Gabrielle Lyon: 27:31

Did you have a sense when you were on the International Agency for Research on Cancer, did you go in there thinking one way or the other,

Dr. David Klurfeld: 27:44

I was skeptical. I would say, of the relationship, I didn't feel that it was as soft as it ended up being. Meaning what that you really could, couldn't decide anything on either bread or processed meat being causally related to any disease endpoint that we examined.

Dr. Gabrielle Lyon: 28:08

What about now? Oh, I think it's weaker. You think it's weaker?

Dr. David Klurfeld: 28:12

Yeah, I don't think it's gotten better with age.

Dr. Gabrielle Lyon: 28:18

Were you shocked at the outcome of this working group of

Dr. David Klurfeld: 28:23

what would shock is one of the words that went through

Dr. Gabrielle Lyon: 28:26

my brain. I'm sure all wasn't in there.

Dr. David Klurfeld: 28:30

I was really discouraged, you know, I really thought that well trained scientists would be more discerning in their take on the relationship between the observational studies and the end points of importance

Dr. Gabrielle Lyon: 28:53

when you began to question the group or the outcome of the group, what role do you think their personal biases played. Were these people that were, I don't know, vegetarian? Were there certain? Was it a, you know, were there activists? What kind of individual scientists were applying to be part of these committees?

Dr. David Klurfeld: 29:13

Well, a number of the scientists on the committee were vegetarians. In fact, the first night we were together, they had a dinner at a restaurant, and I sat next to someone who was the head of nutrition for the World Health Organization, and I said to her that I thought that people who are vegetarians should make a public disclosure on this committee if they're vegetarians. I felt that that was a intellectual conflict of interest, and she laughed and said, Well, I'm a vegetarian. So that was the end of our dinner conversation about what we ate. But it told me something that. So I paid attention to the meals that the other scientists who were on the committee were eating, and I would say at least half, probably two thirds of the people on the committee, I didn't count, but more than half, for sure, were vegetarians.

Dr. Gabrielle Lyon: 30:22

It becomes very challenging for the general population and even physicians like myself, who no longer do research and are not career scientists, when I see things you know, looking at papers that are quoted, I'm just going to give you an example. So this is, this is arguments that I hear against red meat consumption, and this is a large prospective study found that replacing red meat with plant protein was associated with a 10 to 19% lower risk of all cause and cardiovascular mortality based on data from over 131,000 participants, and that was published in 2012 are you? Are you aware of of that one? Yes, and there's even more. Maybe, perhaps you count. You can comment on that, but I want to read a few more statistics, because the reason I'm doing this is people like you, and with your credentials and your years decades in the field, are very different than the young influencer and even young scientist, because arguably, the science done now seems to be a little bit different. It seems as if there's a lot less randomized, controlled trials, a lot less rigor, but these are the statements and headlines that we're seeing. And then here's another one, colorectal cancer risks increased by 17% per 100 gram of red meat consumed daily according to another meta analysis. Do you care to comment on either of those two statements, because these are quite often quoted, sure.

Dr. David Klurfeld: 32:06

So the last statement about the 17% increase that comes from the IARC review, and that was the number from the epic study, the European prospective investigation on cancer, again, 10 years ago, was standard to do systematic review and a meta analysis that wasn't done by the IARC staff, but within six months of our meeting, another dose response systematic review and meta analysis was published, showing that if you're in the highest group of intake of red meat, not processed meat, but just red meat. It didn't matter if your highest intake was 20 grams a day or 200 grams a day, you had a similar risk, meaning the people eating the most had the worst outcome for colon cancer. So, but there's a tenfold difference there, and that doesn't seem to matter now, with the 130,000 or so that that's one of those Harvard studies,

Dr. Gabrielle Lyon: 33:17

seems to always be recycled. It is.

Dr. David Klurfeld: 33:20

And so the people who are eating the most red meat compared to the most plant protein, those are very different diets, not just they're not substituting plant protein for beef. They can do a statistical model that switches those but the people who are worried about their health and worried about following all the recommendations are the people who aren't smoking, who aren't sitting on their couch pumping aluminum every evening. You know, they're exercising. They're not smoking, they weigh less. They're following all the health recommendations. And for me, the aha moment was the publication from the NIH AARP study, which is more than a half a million people. There were 70,000 deaths, and they linked red meat consumption versus white meat consumption, white meat being poultry and fish, and the risk of every cause of death went up statistically significantly with red meat consumption. So we have heart disease, we have cancer, but we have accidents going up exactly the same amount as cancer. So tell me how eating a roast beef sandwich makes you get into a fatal accident. And there was another cause of all other causes, and there were 10 different causes of infection. Infections of chronic obstructive pulmonary disease and some other diseases that I'm just not recalling from 15 years ago that was even significantly higher than cancer or accidental deaths, and in the white meat group, all causes of death were significantly lower, except heart disease. It didn't seem like eating chicken decreased your risk of heart disease, but what it tells me is there are other health behaviors that haven't even been thought about that and certainly not measured in these studies, but the epidemiologists say, oh, there are always confounders. But we measured height, weight and asked people how much they exercise, therefore don't worry about it. And that's simply nonsense. That's just poor quality research.

Dr. Gabrielle Lyon: 35:58

When you see papers like that come out, and you hear and you see them recycled, and you think about the effect that that kind of perspective will have on our youth. Do you have a thought as to how to course correct? And you've also been involved in the US Dietary Guidelines? I'm curious as to how that came about.

Dr. David Klurfeld: 36:21

Well, I think part of the problem is grading the strength of the evidence, and that I would have liked to see for the IARC committee. Did, did create it? One, two, A, 2b, and three and three was, we can't determine the carcinogenicity. But interestingly, when I was on that working group, there was a fourth category of, it's not carcinogenic. And there, in the decades that they had been doing these reviews for IARC, there were roughly 1000 reviews, and one chemical, one out of 1000 was scored category four, not carcinogenic, and they eliminate IARC eliminated that fourth category sometime in the last five years. So what this says is there's a change in philosophy from IARC that's gotten, in my estimation, worse. If we investigate you, you're guilty. It's whether or not we can prove it, because you can't now be assessed as not causing cancer, and this is problematic for coffee, which reassessed just a few years ago.

Dr. Gabrielle Lyon: 37:42

Tell me about that. Is that why you see signs, if you're in California, you see signs that coffee has some compound in it that could cause cancer, right?

Dr. David Klurfeld: 37:52

And, you know, I forgot it was in the early 1990s it was a probable carcinogen. And then in 2018 it was re reviewed after lots of criticism that just never let up, and it was deemed a possible carcinogen. And so by California prop 65 it's known to the state of California to kill you. It's just nonsense.

Dr. Gabrielle Lyon: 38:21

It seems as if it's gotten worse, again, not better. What would you well, how, you know, I think I want to shift a little bit to the US, the dietary guidelines, and how you got involved in that, because I'm assuming, from what I know about you, is that you've really tried to make improvements and really ask transparent conversations. How did you get involved in the US Dietary Guidelines, and what was your role in the USDA? Okay, so

Dr. David Klurfeld: 38:50

I joined the USDA in 2004 and I was involved with four different guidelines, and 510, 15 and 20, and sort of different roles. My job at USDA was the national program leader for human nutrition research. I oversaw six human nutrition research centers around the country, roughly 600 scientists, 80 something million dollar a year budget.

Dr. Gabrielle Lyon: 39:20

That's tremendous. By the way, we were the tremendous.

Dr. David Klurfeld: 39:23

It was a lot of work, but a really joyful job, have to say, a lot of really creative people who were, for the most part, there to find the right it shouldn't see the right answers, to find the answers

Dr. Gabrielle Lyon: 39:38

whether they were right or wrong. I really, I really appreciate that statement,

Dr. David Klurfeld: 39:41

and that's part of the problem that a lot of people come in thinking and rightly so. You have to hypothesize a particular way something's going to come out, but you have to be prepared to not have it come out the way you planned it to go. Out, in fact, that's what I learned as graduate student, that a good study always generates additional questions that you need to ask.

Dr. Gabrielle Lyon: 40:10

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Dr. David Klurfeld: 41:31

as a follow up. And I don't think modern science admits that anymore. It's we have an answer to this question. No more research is needed. Just listen to me and you'll be fine. So let's come back to the dietary guidelines. A lot of it. First, the dietary guidelines are written by a small office in the USDA, which I had some connection to, but was not part of, and a small office at Health and Human Services, which, again, I had some connection to, but was not part of. Most of the people writing the guidelines are dieticians, not scientists, very well intentioned people, not necessarily trained in the details of experimental design, so not necessarily capable of interpreting some of the weaknesses that you need to pay attention to. In the last 2020, guidelines that I participated in, I was given a fancy title of CO executive secretary of the dietary guidelines. I actually there were no other co executive secretaries, so I don't actually know

Dr. Gabrielle Lyon: 42:49

who your counterpart was. I don't know what

Dr. David Klurfeld: 42:51

that meant, but I was in charge of do, of overseeing the peer reviews of the systematic reviews that were first implemented then by the USDA to evaluate a number of research questions. They had 62 questions, and only 30 of them were evaluated with a systematic review, in part because it just took so long. There wasn't enough manpower, money,

Dr. Gabrielle Lyon: 43:21

they didn't have chat GPT at the time, no.

Dr. David Klurfeld: 43:26

And that, you know, there's always this perception outside the government, oh, you know, there was a conspiracy by the food industry telling the USDA to back off and that, you know, we would hurt the sales of beef or or or Velveeta cheese or something that's nonsense. You know, certainly, the food industry is very, very interested more so than the public in the Dietary Guidelines for Americans. But and they are allowed to submit written comments, just like anybody in the public is they're allowed to make oral statements, just like anybody in the public is, but nobody from the food industry who can and a number of people contacted me during these processes, probably with the hope that I would see their point of view. But nobody ever said to me, I want you to put the word in for whatever food I'm selling. No. Nobody had the nerve or stupidity to do that, but the public thinks, and a lot of nutrition scientists claim that's standard practice,

Dr. Gabrielle Lyon: 44:34

meaning what exactly I send you an email that says, I really want you to add, I don't know, almond juice, because I think would that be something? What would be an example?

Dr. David Klurfeld: 44:46

Well, I don't think you would do it with an email, because Freedom of Information Act makes made all of my emails public knowledge. And in fact, that happened to me more than once where some activist group asked for seven. Years worth of emails to and from a dozen or more different groups and individuals, which amounted to 10s of 1000s of emails that our Freedom of Information Officer and I had to go through I do, which was harassment. As far as I'm concerned, they found nothing. Why would

Dr. Gabrielle Lyon: 45:18

they what what happened there. So you went to work for the USDA to contribute to the dietary guidelines you over, you were overseeing 600 scientists and millions and millions and millions of dollars to try to put together a recommendation or a pathway for people is that did I

Dr. David Klurfeld: 45:44

most of the work that we did in the human nutrition research program did not contribute to the Dietary Guidelines for Americans, but it did contribute to general nutrient requirement research, which would

Dr. Gabrielle Lyon: 46:04

then hopefully inform the guidelines. Exactly, yeah, and were you harassed by your findings? And were you publishing what was take me through a little bit about the history. So you would oversee all these scientists. They would, they present to you the studies that they were working on, or come to you for experimental design? You guys would meet

Dr. David Klurfeld: 46:26

sure all of the above. I mean, I had to approve in any research plan for the five year cycle that our research worked on, and if it didn't get my okay, it didn't move forward. And so there's sort of a check and balance against scientific creativity versus

Dr. Gabrielle Lyon: 46:50

authenticity. Yeah, that's really challenging. I can only imagine how many studies were, you know, during that time you're there for what, 12 years,

Dr. David Klurfeld: 46:59

16. But who's counting?

Dr. Gabrielle Lyon: 47:03

I mean, was that just hundreds, 1000s? How many? Oh, yeah,

Dr. David Klurfeld: 47:08

there were we grouped scientists together, so we might have 80 to 100 plans for the 600 scientists in a given year.

Dr. Gabrielle Lyon: 47:18

And you would have that that I could see being, I don't know if it's a challenging position, but you would have to be able to balance, you know, if someone's talking about plant protein versus red meat, which is exactly what you were doing, or various other nutrients, and I could see where you'd have to that would be a lot of scrutiny,

Dr. David Klurfeld: 47:35

absolutely. And in fact, we had a lot of research looking at the value of adding different plant compounds and different fruits and vegetables to the diet, both in people and in test animal models, because that's really the only time you can totally control the diet, unless you're locking people up. And our nutrition research centers actually had inpatient facilities

Dr. Gabrielle Lyon: 48:01

to do that. We did that at Wash U, yeah.

Dr. David Klurfeld: 48:05

Wash Wash U is Penn State. Wash you there, Pennington in Baton Rouge. There are very limited number of these metabolic wards that can do good quality nutrition studies, but all of the six human nutrition research centers, USDA brand, had that capability.

Dr. Gabrielle Lyon: 48:24

What were some of the surprising findings during that 16 years? Wow? Or was there any that really stood out to you, or that led to a bit of harassment, where an activist group wanted to see seven years of emails.

Dr. David Klurfeld: 48:44

Well, the harassment was actually because one of my responsibilities was to chair a working group of government scientists with industry scientists to create a public private partnership to fund a large long term human feeding study, and I was assigned by the Under Secretary for Research at USDA to chair this committee. So I sent an email around to the scientists that somehow fell into the hands, and in the email, basically said, here's an editorial. I believe it was in the British Medical Journal that says, here's why nutrition scientists are against public private partnerships that we need to move forward in a medical journal, and I so it's public record. I said, just read this. You know, it addresses the task we've been assigned by the undersecretary. And somehow this fell into the hands of an activist group and for any reason they can ask. Of freedom of information for any amount of correspondence. And you know, if they asked for emails with one person over six months, they're looking for something. But they asked for seven years with dozens of people in organizations. Was there a reason why harass? Well, I felt it was harassment. They were looking for something which they apparently didn't find. Because this was many years ago. They never published anything, so I'm assuming they found nothing.

Dr. Gabrielle Lyon: 50:34

What do you think some of the biggest myths are about nutritional research,

Dr. David Klurfeld: 50:41

wow. Okay, the biggest myth is what you see in the news media, whether it's traditional news media or online influencers, it's picking up a single association study, an observation of not cleaning your fingernails leads to 10 points lower IQ. Well,

Dr. Gabrielle Lyon: 51:09

that explains it.

Dr. David Klurfeld: 51:10

And you know, everybody starts scrubbing their nails with a brush and Clorox, because that's what the study said. But you know, it might, it's probably because somebody who walks around with dirty fingernails is maybe working manually and not reading and not learning. You know, there's other things to think about. And again, if, if there's one study that's Hmm, that's interesting, maybe we should test it a second time, and I would not change my diet based on a single study, even if it's a controlled feeding study, because most controlled feeding studies are what we call efficacy under a planned, controlled set of conditions, it works, but under your lifestyle, it may have no connection whatsoever. Under a larger group of 2000 people, maybe we don't see anything, but we can only afford to feed 20 people for two weeks. So you know, there's this nuance that the public doesn't understand, and scientists sort of blindly ignore.

Dr. Gabrielle Lyon: 52:31

What would you tell someone who really wants to learn and they'll get a study, and it's interesting, because right now, myself and many others, we educate in short sound bites, and we do our very best. What is a responsible way that you see to be able to educate the public when we recognize that? You know, it's not just one study and it's not it's not even just two studies, it's really a body of literature.

Dr. David Klurfeld: 53:01

So I've been doing this for almost 50 years, and I'm a lot less certain about anything in nutrition today. I mean, clearly we know a lot about nutrient requirements, but I'll give you an example. I can tell you what your vitamin C requirement is, more or less, but if you're a cigarette smoker, it's really different than if you're a non smoker, if you're living in a polluted place, it's more than if you're living out In the woods somewhere. So I need to know a lot about your personal lifestyle, and that's one of the things where nutrition is going towards personalization. We have this food is medicine. Great, sound bite, but I'm not sure food is medicine. I believe food can stave off the need for medicine. Food can prevent you from requiring medicine. So in some ways, it's like medicine, but it's not the equivalent of taking a statin drug to lower your cholesterol, right? You know you can. You can use diet to drop your serum cholesterol five or 10% but if you have genetically high cholesterol, unfortunately, you're going to rely on drugs, and it's really effective. But to prevent a heart attack, we talk about in medical research, we talk about the number needed to treat, you know, almost everybody's shouldn't say, the vast majority of people's serum cholesterol is lowered by taking statins. But to prevent a heart attack, you probably need to treat 30 to 50 people to prevent one heart attack.

Dr. Gabrielle Lyon: 54:58

You know, then, when we think about the gut. Guidelines, and the guidelines make really mass generalizations. How? How do you think about that? How do you think about the Dietary Guidelines and the recommendations that that we're seeing?

Dr. David Klurfeld: 55:14

This is one of the real problems that we have, that if, if guidelines are more personalized, then maybe there's no single set of rules for anybody, and you can sort of get around the recommendations and wait

Dr. Gabrielle Lyon: 55:32

how, how would that be? So for So, the way I think about it is they will say, again, saturated fat, just because that seems to really derail everything. If the diet is 10% or less, should be saturated fat. But you know, I'm not sure where that science came from. Are you Yes, where

Dr. David Klurfeld: 55:55

it came from the air. So when dietary recommendations were first starting the American Heart Association sort of ruled the world, and I was a member of the Heart Association for decades, and finally abandoned them. I refused to give them $1 anymore, but the American average intake was 40% fat, and the agreement in the field was, we have to cut fat in half, which would be 20% and the agreement among the experts was, nobody will reach 20% so let's say make make the goal 30% it's halfway towards the real goal.

Dr. Gabrielle Lyon: 56:41

And where do they come over there, just for fun.

Dr. David Klurfeld: 56:46

Pretty much, you know, there's, there are very few populations on earth that are eating 20% fat. You know, in Thailand, the fat intake 50 years ago was around 20% fat, but protein was also a little bit lower. They were eating a lot of rice. You know, that's one of the things that white food is bad for you. You know, sugar a is not a metabolic poison. Rice does not make you fat. You know, a third of the world was slim living with rice as their basic staple food, until their diets sort of crapped out by getting westernized, by doing less physical activity, by moving to big cities, there are lots of changes that the confounders that we talked about earlier all change at the same time. So you can't pick out one or two things. There's six or 10 things that happen simultaneously. So to come back to the fat levels, the interim target for the Heart Association with 30% and so 10% fat from SATs, monos and polys just pulled out of the air. So our saturated fat intake has been for several years now around 11% not anymore than that. It used to be 14% back when we were eating 40% fat. So we've reduced significantly, in part because the meat industry has raised lower fat pigs and trimmed beef more, but in large part because processed food formulas have changed, because the food industry pays attention to the guidelines, the public doesn't, on a good day, one out of 20 Americans meets the dietary guideline recommendations. On a bad day, everybody's thumbing their nose at them so but the food industry, when the guidelines said low fat, everything made fat free cookies, those are not health foods. You know, that's just another crappy choice, and it's fine for cookies to be an occasional snack. It's not fine to eat a sleeve of cookies every afternoon with a glass of low fat milk.

Dr. Gabrielle Lyon: 59:27

When the guidelines came out, obviously, they've been going on for quite some time. What is the evidence, the quality of evidence that the guidelines contain?

Dr. David Klurfeld: 59:39

Well, it's actually hard to know from the first multiple sets of guidelines, which are small pamphlets.

Dr. Gabrielle Lyon: 59:47

When did they first come out?

Dr. David Klurfeld: 59:49

Was it 1980 Yeah, there was actually a 1977 set of dietary guidelines from the McGovern committee. But the official Dietary Guidelines for Americans. I began in response to the McGovern Committee, which was done by Senate staffers.

Dr. Gabrielle Lyon: 1:00:05

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Dr. David Klurfeld: 1:01:35

So scientists gave their expert opinion in like, a nine page pamphlet. Nobody knew what the evidence was. It was just a bunch of friends got together in the room and put together what they thought were and so

Dr. Gabrielle Lyon: 1:01:52

this is 1980 Do you think people recognize that? No,

Dr. David Klurfeld: 1:01:55

of course not. So it was, you know, it was, it was, don't eat too much salt, don't eat too much sugar. Wasn't defined what too much meant. And I have to say, I can't define that for you. Eat more fruits and veggies, eat less fat, eat less saturated fat. I don't remember what all the others were that might have been it. So that's 1980 and let's fast forward to 20, 2040, years later, the guidelines have gone from a nine page pamphlet to 150 page book with lots and lots of science behind it, but the recommendations are exactly the same. I know the wording has been tweaked, but the government has been locked into the same. Don't eat any fat, or you'll get fat, which we know was wrong, but school lunch prioritizes skim milk and low fat milk. You can't give full fat milk to kids on a school lunch because the guidelines mandate that

Dr. Gabrielle Lyon: 1:03:00

the guidelines that came out in 1980 didn't seem to have scientific basis. It seems like the American Heart Association had quite an influence. Because again, and please correct me where I'm missing the mark. Here started at 40% fat, then went to 30. Then somehow there was a, you know, the ultimate target was 20, but individuals felt like it was never going to get there. But these guidelines have not changed drastically. I mean, I think recently, they said high quality protein for younger, for infants, or something youthful. I have to, I have to look because from my perspective, and I think from yours, they haven't changed. You're

Dr. David Klurfeld: 1:03:45

right. And there are a couple of problems that initially, the guidelines tried to make one diet that all Americans were supposed to eat, that I think is a bankrupt plan to begin with. You know, there are so many other reasons you hardly anybody eats just for nutrition. You know, there's, you know, all the different reasons people eat, and nutrition is far down the list. Taste and cost, convenience, culture are far more important than nutrition. Everybody, when they're asked is, oh, yeah, I'm in for nutrition. It's good stuff. But then when you ask them, Well, what did you choose? You know, doesn't look so nutritious, because they don't know how to cook, they don't have time to cook, they can't afford what they really want to buy. There's lots and lots of problems with that.

Dr. Gabrielle Lyon: 1:04:39

So if the guidelines haven't changed since the 80s, and it doesn't reflect new scientific research. What would you like to see be re evaluated?

Dr. David Klurfeld: 1:04:50

Oh, from the ground up, I'll tell you. One thing that I would love to see is have a grade for the strength of evidence. There is a system where the acronym. G, R, A, D,

Dr. Gabrielle Lyon: 1:05:02

E, is medicine. We had Bradley Johnson on the podcast, sure, one of the people behind that, another one of

Dr. David Klurfeld: 1:05:08

my widely accepted in medicine, completely disregarded in nutrition. There's you see that occasionally, but rarely in nutrition, and it's sort of poo pooed in nutrition, because nutritional epidemiologists always say nutrition is so hard, we need different standards. And my answer is, No, you don't. You need the same standards as other fields of science. Just don't claim that you have the same quality of evidence. If the guidelines, the way they are, were given a grade of maybe, maybe not, meaning a C or a C minus, I wouldn't be beating them about it.

Dr. Gabrielle Lyon: 1:05:51

You know, I'm looking at a summary here, and I'm going to share this with you. It's so fascinating. 1980 guidelines focused on fat reduction, exactly what you said. It seemed like there was this saturated fat cholesterol to prevent heart disease. The low fat craze happened 1992 Do you remember what happened 1992 food guide pyramid? Oh, yes, that seemed to be a disaster. The thinking was grains should form the base six to 11 servings, and fats were placed as the top to be used sparingly. 90s to 2000 fat reconsidered Sugar and Carbs came under scrutiny, scrutiny. Then the USDA introduced my pyramid in 2005 from 2010 to now. And then, of course, 2011 the my the My Plate came out replaced the food guide pyramid with this way of visualizing a balance. The recommendation was, again, this is grouping last, I don't know, 15 years healthy eating patterns, whatever that is, Mediterranean, dash, plant based, emphasis, limiting added sugars and sodium. So this is 10% of daily calories. One thing that is so obviously missing here is, where is the conversation about dietary protein? Those numbers haven't, have not changed.

Dr. David Klurfeld: 1:07:15

There actually is a conversation that occurred with the current lead being developed guidelines that it will be out sometime in 2025 and I'm not really happy with the approach that was taken by the Advisory Committee, which are the university folks who are supposedly giving advice that the guidelines will Follow. The guidelines don't always follow the advice from that committee, but there was a concept of ounce equivalents for carbohydrates developed, and that made perfect sense to me, because you have something like a ready to eat dry cereal that might have 10% water in it, and you're comparing an ounce of bran flakes to an ounce of bread. Well, bread is 65% water. That's not the same as dry cereal. So you have an ounce equivalent of carbohydrates, where you take the ounce of actual carbs in however many ounces of those two foods. That seems reasonable. Yeah, that seems fine, but that was applied to proteins, and now they're saying, based on nitrogen content alone that, and you know, probably better than I do, that that's not a Good marker of your protein status, that that is and because all the dietary RDAs for protein are set in groups of healthy young men consuming high quality protein, meaning animal proteins, almost exclusively dairy or egg protein, and generally isolated From the other components of those foods, so it's pure protein, really easily digested. And then you're saying that a plant protein with the same grams of nitrogen as the equivalent to an isolated animal protein just doesn't pass the laugh test.

Dr. Gabrielle Lyon: 1:09:21

But yet, here we are, right, and it hasn't changed, which is which is really terrifying, if you could make a recommendation, and then were you able to make recommendations when you were working at the USDA, by the way, so you were overseeing all these scientists, would you get this information and then pass it to someone that would then take action on it. How does that flow work?

Dr. David Klurfeld: 1:09:48

Okay, most of the scientists that I oversaw would publish in peer reviewed scientific journals. So that's how they would disperse their information. The other mechanism. Was through government reports, and my program analyzed the data on diet from the NHANES annual surveys. Can you share about what that is? Sure NHANES is another one of those government acronyms that you need a dictionary for. It's the national nutrition health and sorry, natural nutrition, health and Examination Survey, and it's a snapshot in time of 5000 people, and they get 224 hour dietary recalls. And there are different quality dietary recalls, not all of them are the same quality. The ones that are used in NHANES are really the best. There are

Dr. Gabrielle Lyon: 1:10:50

those are the best start to interrupt. Those are the best that they are. But do you think they're good?

Dr. David Klurfeld: 1:10:56

They're the best that we have? Actually, the USDA nutrition program did a study published in the 1980s that, depending on what nutrient you want to estimate you need between three and 3524

Dr. Gabrielle Lyon: 1:11:19

hour recalls three to 35 to make it, to really be able to get a good sign,

Dr. David Klurfeld: 1:11:24

to know what the actual intake of an individual is. To do a group average, you need three to 524, hour recalls. Almost nobody does three to 524. Hour recalls, it's one or two. NHANES does two. And in NHANES, they do an in person interview with food models so the subject can estimate the size of the portions they're eating when they go home. They have a little book with life size pictures of those food portions. If there's some university professor who's doing the same thing, they don't have either of those aides. So

Dr. Gabrielle Lyon: 1:12:06

it's the best for what we have, right? Do you find that the data that they would get from that would be flawed, or is there some level of confidence? Because the NHANES data set is quoted all the time, I quote it, it's the best that we have. You know, for example, if someone says, Well, I don't know, 20% of adults, 20% of women at any given age are deficient in protein. I mean, is that number, right? Well, it's kind of the best that we have.

Dr. David Klurfeld: 1:12:37

So NHANES data is used for a particular purpose, which we'll explain in a second, but it's also misused constantly, probably more so than the way it's properly used. NHANES is a snapshot in time of the average intake. It's not you get a distribution of intake from that, but it tells you relatively limited amounts of information about sub populations. And so what do

Dr. Gabrielle Lyon: 1:13:11

you mean by that? That's interesting. You're interested

Dr. David Klurfeld: 1:13:14

in populations that are increased risk of deficiency, increased risk of certain diseases. So ethnic minorities, young women who generally have more iron or calcium deficiency because they're not choosing beef or dairy.

Dr. Gabrielle Lyon: 1:13:32

How could they with the headlines that they're hearing? Seriously? Yeah,

Dr. David Klurfeld: 1:13:37

I mean, that's part of it, you know. I'm not asking somebody why they're avoiding it. You know, if somebody's avoiding food for nutritional purposes, I can generally argue against those choices, but if it's for ethical purposes or religious purposes, I'm not going to argue against that. That's a personal decision. You know, if it's for environmental purposes, I don't think the data are solid on life cycle analysis of producing different kinds of food. You know, people driving to the grocery store have a much bigger environmental impact than the growth of anything that's produced for them to eat, and people just don't get it.

Dr. Gabrielle Lyon: 1:14:22

That is really fascinating. We will touch on that the NHANES data. What would be an appropriate use for the NHANES data, if someone was communicating science, or if we're having discussions about this? So

Dr. David Klurfeld: 1:14:38

lately, over the last decade, it's been noted that more and more young women have lower iron status, not necessarily Frank anemia, although anemia has increased, but lower iron reserves, and that's corresponded to decrease. And red meat, particular, and other sources of bioavailable iron. That's another distinction between plant protein and animal source protein is bioavailability of the protein that it's just not as available from plant sources as it is from animal sources, and it's particularly true for minerals and vitamins that are considered nutrients of risk. So we have calcium, we have iron, we have zinc, vitamin B, 12. You know, young women and older people tend to be deficient in all of those either low, low marginal status, or deficient in all of those nutrients we just mentioned, including protein. You know, one of the myths is that we eat too much protein, and I don't know where that came from. Young men clearly do eat as a group. Clearly do eat more protein than the requirement is set

Dr. Gabrielle Lyon: 1:16:09

at, but the requirement is set at a minimum based on that nitrogen balance number.

Dr. David Klurfeld: 1:16:13

You're right about that and but there's a problem in understanding that, you know, if you're a couch potato, maybe the protein requirement is close to what's really needed, but if you're exercising, you clearly do need more. If you're over the age of 65, or 70, you clearly do need more. If you're a growing kid who should be out playing every afternoon, you clearly do need more, and you're not going to get it from eating plant substitutes, because you have to eat a lot more of that stuff, and you're still not getting the nutrient balance that you have from the amino acid profile and the other nutrients In animal source foods. I'm not saying you can't be a healthy vegetarian. You absolutely can be, but you have to be a well educated vegetarian who plans carefully.

Dr. Gabrielle Lyon: 1:17:10

You wrote one of my favorite papers of all time, and it was, it was a commentary, as is beef a healthy food? Do you? It was just such a wonderful and maybe the title is not totally right, and I'll drop it in here, but it was just so well written in this idea that it's not just about protein. We talk about protein, but that's just the start. It is these bioavailable sources of iron, zinc, vitamin A, vitamin D, that, you know, it's so beyond just the protein aspect. How do you see that informing our decisions? Because you see headlines seem to contradict themselves. How do you see individuals making good choices in terms of what is necessary?

Dr. David Klurfeld: 1:17:55

It makes it harder in lots of ways, and one of the minerals we haven't mentioned is selenium. Turns out beef is about the source of half the Selenium in the United States and US soil is enriched in selenium, so wheat, grown in the US is a decent source of selenium, but it's still nowhere near as good as the Selenium from beef, but wheat grown in Italy has zero selenium. So if you're buying imported Italian pasta, it might taste good, but you're getting no Selenium. Selenium is an important antioxidant. It's involved in a number of enzymatic pathways in the body. There's no USDA table for selenium values, you know? It's sort of an orphan mineral. There just isn't enough information about it, you know. So there nutrition is an endlessly complex science. It's not rocket science. It's tougher than rocket science. You know, you have stuff coming out one end and stuff going forward in the other end, and if it doesn't explode, it all works with nutrition. There's, you're making hundreds of choices a day in your diet, and there's hundreds of consequences metabolically going on in your body. So it's short term, long term effects of nutrition. You know, it's not overwhelming. You could be paralyzed as a result of all of that. And I don't want people to think that's the way to approach it. Well,

Dr. Gabrielle Lyon: 1:19:41

I actually really love what you said, that white food isn't bad. Rice is not the end of the world. Sugar isn't going to kill you. These things are, they are very sensationalized. And even thinking about, I know you had mentioned before we started recording even the Women's Health Initiative. For those listening, it was a 750 million study, a seven $50 million study, and the biggest chunk of that study was what 20,000 women on a low fat diet and 30,000 women on their usual diet for nine years. And the outcome, again, it said, no difference in risk with colon cancer following a low fat or a typical higher fat American diet. And why do I bring this up? Because there's a lot of confusion out there online in terms of different groups. You said something when we first started talking that I think was really profound. You show me the name of someone, and I'll tell you what their outcome and conclusion is going to be, and that becomes extremely detrimental to the public. And you show me the name of the influencer, and I already know what the answer is going to be, which is challenging, because I suppose looking at the other side, people could say that about me, and they could say that about you, and they could say that about Don Lehman, but I will also say that there's a collective amount of high quality research that maybe we don't know exactly how much protein I need or you need. We We know over time what that would trend towards, and that we know that this, there's, there's the animal products, that they're different than, say, the plant products. When you were, you involved in the Women's Health Initiative, well,

Dr. David Klurfeld: 1:21:35

I was supposed to be, what happened? I was asked to be a member. Do you like how I led into that very sneaky of you, I was asked to be a member of a committee from the National Cancer Institute that would review the design of the Women's Health Initiative nutrition trial. There was also the hormone replacement therapy component of it, but as you mentioned, the biggest part was the nutrition study, and was half a billion dollars, unbelievable, and it was a failure, basically, for the low fat intervention. We

Dr. Gabrielle Lyon: 1:22:13

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Dr. David Klurfeld: 1:24:12

not just colon cancer, but no no effect on breast cancer, no effect on heart disease, meaning a low fat diet. Low fat diet had no benefit on this. Now, the argument is that the women reduce their diets the fat in their diets in the first couple of years, and then they slowly added it back. Whether or not that's true, that's not really sure. In fact, that's probably speculation, but it's one of the only two intervention studies that I brought up to the IARC panel of a controlled feeding trial, and one of the epidemiologists said, but that study wasn't designed primarily to red meat. And I said, Yes, that's correct. It was the. Signed as a low fat diet, but meat intake was cut by half. That's important. That's a huge drop. And my response, which I didn't think of it immediately at the time we were in this conference, was that not one of these epidemiology studies that indicts meat was designed to look at red meat. They were all designed to look at whatever they can find in the diet. That's statistically significant,

Dr. Gabrielle Lyon: 1:25:32

that's really challenging. You did introduce the concept of the beef matrix. I have quoted you many times. And what is that? And why does it challenge the mainstream view of saturated fat and cholesterol?

Dr. David Klurfeld: 1:25:47

Well, the beef matrix is the physical structure of the food that we call meat, and so it includes muscle, connective tissue, fat. It includes cell membranes. Give you an example from the dairy industry. They have funded a lot of nutrition research for decades, and they've actually in both the US and Europe, and they've actually shown that the fat in dairy is in a membrane structure called the human milk fat globule membrane, and it has a really different effect from eating butter, which is just the fat that's dripped out by heating dairy products in in the beef matrix, you can extract beef tallow or the beef Fat and extract that out of beet, but it's not necessarily the same as what you get from eating beef that whether whether it's ground up in a processed food or not, doesn't make a difference. Whether it's from the beef or pork that's or chicken that's ground up, all of that's the structure, and it differs based on each species will have a different molecular composition. That's fascinating. And it includes, you know, say heme iron will be different in beef, pork and poultry,

Dr. Gabrielle Lyon: 1:27:44

you mean the amount versus the bioavailability or the all of the structures within that tissue.

Dr. David Klurfeld: 1:27:51

There's really no heme iron in poultry to speak of. But in pork, we'll have some, and beef will have a lot more and so. But we talk about iron, we don't talk about bioavailable iron. Yeah, and that's key, that maybe you need to eat less beef to get the same iron value. You're not eating meat just for iron, but you need less of it than you do eating boneless skinless chicken breast, according to the guidelines for Americans,

Dr. Gabrielle Lyon: 1:28:24

are you talking a little bit about the other nutrients, like creatine, carnosine and serine, some of these other bioactive compounds?

Dr. David Klurfeld: 1:28:36

Sure. In fact, one of the podcasts I listened to on the flight in today was about creatine. And there's certainly, if you're physically creatine is not considered essential, because the body can make it. But I think there are enough studies to strongly indicate not to just to suggest that if you're physically active, if you're an athlete, having more creatine is valuable for you. There's suggestive data that creatine helps cognition, yeah, and I don't know if that's solid enough to make a recommendation about dietary change or not. You know, a lot of those recommendations for creatine are basically being extrapolated to take grams and grams of this as a supplement. I'm not a big fan of most supplements. I would prefer people to get their nutrition first from foods and only secondarily from supplements. Now, if you're going to be a vegan, supplements are now a new food group for you. You can't live healthily without supplements.

Dr. Gabrielle Lyon: 1:29:50

Yes, it would be very challenging. And I really like how you talk about you're talking about the nutrients, not just the protein, not just the micronutrients, but other but more about these. Bioactive compounds. And to be fair, there's bioactive compounds in, say, a meat food group and other bioactive compounds in a plant food group also probably not interchangeable, agreed, and that becomes important in the context of overall diet. One of the things that you have mentioned is that the guidelines really are based on weak evidence and that that can cause harm. Where do you think that we've gone wrong in US Dietary policy

Dr. David Klurfeld: 1:30:31

by not admitting that I'm right and everybody

Dr. Gabrielle Lyon: 1:30:34

else is wrong? Is Don layman here,

Dr. David Klurfeld: 1:30:38

no, I think we say over and over that nutrition is different, it's tough, and it is absolutely but don't say we have different standards of science because of that. You know, we we have to be willing to pull up our pants and say, you know, we're wading through some muck here, and that we can't be certain about this, but this is our best guess based on science today, I would love the discussion paper of every published research study to begin with, based on what we know today. You know the public thinks that every study that's publicized is the final word, whether it's about olive oil or roast beef or whatever, you know this is what I've got to do to change my diet to be healthier. And I can guarantee you that nobody has the final word on any food,

Dr. Gabrielle Lyon: 1:31:38

and probably because it's just evolving, sure that the right would that be a reason as to why there's always this

Dr. David Klurfeld: 1:31:44

evolution? It's both that it's evolving, but we're also looking for new endpoints to measure. You know, people aren't as interested anymore in measuring serum cholesterol the way they were with diet studies, because we have drugs to control serum lipids now, so we're trying to control other things, and we're making believe that we're controlling aging. You know, I think we can actually extend health span. I'm not sure we can expand

Dr. Gabrielle Lyon: 1:32:20

lifespan.

Dr. David Klurfeld: 1:32:21

Lifespan, you know, I'm if I'm a sickly 95 year old, you know, I'm ready to say goodbye. If I'm a healthy 95 year old, maybe I want to hang on a couple of more years. So these are problems, and of course, there's no guarantee in what shape you're going to be

Dr. Gabrielle Lyon: 1:32:38

in, and you could get into an accident. Absolutely. Or you could

Dr. David Klurfeld: 1:32:41

eat margarine only if you're eating too much roast beef.

Dr. Gabrielle Lyon: 1:32:46

Why are randomized control, randomized control trials so difficult to do? And why do you think that we're doing or are we doing less of them?

Dr. David Klurfeld: 1:32:54

Oh, absolutely, we're doing less, and we're doing only short term trials. We're not we're not going to do long term trials that give the answers you and I would like to see, for a couple of reasons, it's too expensive, takes too long. Nobody wants to wait 20 years for the answer. And

Dr. Gabrielle Lyon: 1:33:12

what if you're wrong? You know, I did two years of research at Washington. Do you know Sam Klein? Yeah, sure. So I was in SAM Klein's labs, and he, he is so lovable, for sure. And, you know, we're doing, we're working on one study, and I don't know. I think I came in in year two, did another two years, and I don't think the data never got published. I cannot imagine, and it was one, you know, it was also in the metabolic work. I cannot imagine doing a 20 year study and then, oh, you know what? I don't know. I don't think we're gonna publish. So

Dr. David Klurfeld: 1:33:39

if you're going to design an RCT, a randomized control trial with something good, what are you going to compare it against the something bad? Well, if that's unhealthy, that's unethical to compare with something bad. So you got something good against something that's not so good. So now you got a small difference, and you want this to be the only difference that you're going to randomly assign people to, are they going to listen to you for the next 20 years and make that one change? I kind of doubt it, especially if it gets a lot of publicity, like a lot of the dietary studies have gotten, where people see in the literature or in the news media that olive oil is good for you? Well, I'm dumping my soybean oil. I'm going to only use olive oil from now on, even though they're in the soybean oil group. Your experiment is no longer valid. Gosh, what

Dr. Gabrielle Lyon: 1:34:37

do you think we could do going forward? What is the biggest change that we could make to improve nutrition research or even our understanding.

Dr. David Klurfeld: 1:34:47

I think we need better metabolic markers, and the science is evolving in that area. You know, we're looking at what are called Small metabolites in the blood. The problem is. Is that they're more qualitative than quantitative. So if you eat a pound of salmon, I can point to 12 different things in your blood that changed. But if you eat four ounces of salmon, nothing happens

Dr. Gabrielle Lyon: 1:35:15

when you say qualitative versus quantitative. What do you mean when it comes to these compounds? You

Dr. David Klurfeld: 1:35:20

need a ginormous jolt to your system to show a difference. It's you're not seeing a dose response.

Dr. Gabrielle Lyon: 1:35:28

Or do we have to get better, more sensitive testing that would

Dr. David Klurfeld: 1:35:32

help, but I'm not sure. Already the tests that measure these small metabolites, mass spectrometry, really, really sensitive. Yeah, you know, 75 years ago, when I arc was started, you can measure parts per 1000. Now you can measure parts per

Dr. Gabrielle Lyon: 1:35:50

trillion. Oh, so that isn't improved. They

Dr. David Klurfeld: 1:35:53

didn't even, they didn't even think about the tiny, tiny amounts of stuff were exposed to back when the law was set in the 1950s that anything that causes cancer in an animal or human has to be banned from the food supply. So another thing that wasn't taught when I was in school was the intestinal microbiome. They were bacteria. Living inside all of us, the same number of cells in our intestine that are in our entire body. They're cranking out all kinds of chemicals that actually get absorbed and participate in normal metabolism and have marked health effects. When I was a student, the colon was supposed to absorb water and electrolytes and nothing else,

Dr. Gabrielle Lyon: 1:36:51

right? Oh, I'm excited that you're mentioning this. And so what

Dr. David Klurfeld: 1:36:55

we do to measure that now is, well, here poop in this cup, and we'll measure the bacteria that in your intestine? Well, if you're pooping it out, maybe you know your large intestine is six feet long. Your small intestine is 20 feet long. There's a lot going on in your ileum, bacterially speaking, that we never measure. We're not even doing the Model T version of the microbiome at this point. We're also analyzing who's there. So I actually was in the human gut microbiome project. You were enough. So another thing you were I did a food frequency questionnaire on myself, and it misfortune a cup, though, no, I just had to send them a little poop sample.

Dr. Gabrielle Lyon: 1:37:47

Didn't need to poop in a cup, but that's that's fascinating. So

Dr. David Klurfeld: 1:37:51

they measured my poop. They told me who lives there. And I have no idea what that means. There were 80 or 90 bacterial species, but I don't know what metabolically they're doing, and there are about 1200 bacterial species that live inside human beings. So my 100 might be different from your 100, or we might overlap by 20 or 30 or by 70. But with that number, and the numbers of bugs, with the zillions of bugs, we have, just imagine the differences, just in who's there and what they could potentially

Dr. Gabrielle Lyon: 1:38:36

do. That is an excellent point. And frankly, that from my opinion, again, I don't have evidence to support that this, but I think that that's what makes the human body so adaptable to different dietary choices. I don't know if you've seen some of the there was early work looking at the extraction of a largely plant based diets, some of these bugs generating essential amino acids.

Dr. David Klurfeld: 1:39:04

Yeah, I think you're absolutely right that this is, again, a problem that the field has that nobody's willing to admit. It's very complicated with that. Yeah, we don't have, we don't have an answer for this. You know, I think I said to you earlier that I'm a lot less certain about any nutritional endpoint than I was when I was doing this for five or 10 or 15 years. Was

Dr. Gabrielle Lyon: 1:39:33

there a moment that changed it for you?

Dr. David Klurfeld: 1:39:37

There certainly was a moment in my decision to no longer accept observational studies as being really important. Tell me, well, this was the 2009 the NIH ah AARP study, American Association. See for retired persons, more than a half a million people, more than 70,000 deaths recorded. And the population was divided into men and women, into red meat eaters and white meat eaters by into five different levels of intake. And so there were tables and tables that you had to wade through, and I basically summarized these in a couple of publications and put it in into a graph that made it easy to interpret it. So it's not exactly matching the average in the tables, but it's very close, and the red meat eaters all had significantly increased deaths from heart disease, total mortality, deaths from cancer, deaths from accidents, and deaths from all other causes, the white meat eaters had significantly reduced deaths from everything on that list except heart disease. So again, it's the confounders. We need a lot better measures of the confounders in the willingness for nutrition researchers to admit that we have to measure these things and quantify them, and that takes a lot of questionnaires. It takes a lot of staff support, and makes the data more difficult to interpret, because it's now complicated by all these factors, and everybody agrees that we have to measure sex and age. Those are sort of the basic things in epidemiology. And we've gotten to the point where we all measure body mass index and try to adjust for that. But if we're adjusting for body mass index, how does that play into exercise? How does that play into cigarette smoking? They're all related to body mass index, positively or negatively. So if these confounders are correlated, then how do you treat those statistically? It's a really complex problem, and in the area of food intake, red meat in particular, we dichotomize the intake into step wise patterns of intake. And so this NIH AARP study had five levels of intake, but meat is not a step wise intake. You don't say, Okay, today, I'm having 50 grams. Tomorrow, I'll have 20 grams. The next day, can have 70 grams. That's not the way it works. And so that's a meaningless distinction, and would only be meaningful if there was truly a biologically meaning, meaningful endpoint that differentiated 50 from 100 grams of meat intake,

Dr. Gabrielle Lyon: 1:43:10

I see. So the example to that would be that we could, this is probably not a meaningful endpoint. But the example to that would be the, I don't know, anabolic response shows that, you know, from 50 to 100 or something like that. And then that would translate to making this up, you know, one pound of muscle or something absolutely that. Is that, how you would think about it.

Dr. David Klurfeld: 1:43:36

That's right. But none of the short term markets translate for chronic disease risk. I mean, this is really, in my estimation, the Achilles heel of nutrition research, that we don't have intermediate biomarkers for anything in cancer. The only thing that the FDA accepts is colon polyps as an indicator for risk of colon cancer. That really

Dr. Gabrielle Lyon: 1:44:03

complicates everything. Yes, do you, I mean, what would a meaningful endpoint be? It wouldn't even be hscrp inflammatory marker, because it's not a, you know, it's a marker,

Dr. David Klurfeld: 1:44:19

right? Exactly. It's non specific. Inflammation is a risk factor that CRP is elevated in people who are obese, but it's in increased in people who have infections. You know, that's the thing, that in obesity, CRP might go up 50% you know, if you have cancer, it might go up 75 100% you know, if you have an influenza, it's going up like 400 fold.

Dr. Gabrielle Lyon: 1:44:49

Would you say body fat percentage or muscle would be some kind of meaningful endpoint? It's tricky, because how would we define an endpoint? Would I mean, obviously, death? Is an endpoint. But how? How do we defer

Dr. David Klurfeld: 1:45:03

a lot of bio I'm not sure. Yeah, there are a lot of biotech companies that are looking for circulating plasma markers for cancer endpoints. In particular, you know, they they're trying to come up with a blood test that will diagnose 10 or 90 different kinds of cancer in advance of getting advanced cancer. Yeah,

Dr. Gabrielle Lyon: 1:45:27

we actually do in our clinic. We do it's called the Grail test, or the gallery, and that looks at 60 plus DNA methylation markers. It's very fascinating. I have a final question for you. I certainly could sit and talk with you for a very long time, and we're going to link some of your work and your papers. And I really strong. Are you on? You're on x right?

Dr. David Klurfeld: 1:45:52

No, I'm not. I left when a certain businessman bought it.

Dr. Gabrielle Lyon: 1:45:58

So you won't be able to find Dr Klurfeld, are you on any social media?

Dr. David Klurfeld: 1:46:02

No, I'm the world's biggest introvert, so really I think you're doing

Dr. Gabrielle Lyon: 1:46:07

great for an introvert.

Dr. David Klurfeld: 1:46:09

Well, thank you. My the agency that I was part of actually was a strong believer in the personality indexes, and so I actually scored the highest on the introvert scale of anybody ever in the history of ever in that agency. And so I always knew I was an introvert. So now I'm justified in saying, leave me alone. Okay,

Dr. Gabrielle Lyon: 1:46:33

fair enough. But you have a again, hundreds of publications that, and I'm going to link a few of my favorite this. This final question is really just a curiosity. You have had a decade. You've had decades long career, 5050, some years in Science and Government. What has been the impact for you again, about going against the grain, so to speak.

Dr. David Klurfeld: 1:47:02

Well, it it hasn't been good for my career. I'll tell you that. I mean, I've had a wonderful career. I've been acknowledged by a number of organizations with various awards. I've had grants from NIH, from the American Cancer Society, but I've been on review panels. I'm not bragging about all that

Dr. Gabrielle Lyon: 1:47:25

stuff. That's, let me brag about you. You again, you are, which is, I would argue that we only select the finest scientists and the people that I think really contribute, because the world needs to hear you and yeah, so you don't have to brag or say anything. All of those things are true.

Dr. David Klurfeld: 1:47:42

But I believe, among the movers and shakers in the nutrition field, I'm not taken seriously. I'm one of those contrary naysayers. And in fact, the fellow that I was my postdoctoral mentor, fit the same mold, and he was really prominent in the nutrition business, but also didn't always get invited back. You know, I remember being invited to the American Heart Association to speak, and they paid my way in the mid 1980s and I said, Well, dietary cholesterol is not really important for changing your serum cholesterol, and if looks could kill I would have been dead on the spot. I was never invited back.

Dr. Gabrielle Lyon: 1:48:28

I have to tell you something. You might not like this, because it might have to you might have to change your introverted nature, but I believe quite the contrary, I would say among your peers, you are very well respected and have done a tremendous amount of work. So again, that might not be good news to you, because you might be getting calls for interviews and things of that nature, but really, you have been very courageous and tremendous in the work that you've done. And I am extraordinarily grateful and so grateful that you agreed to come on the show and really, really well done. Well. Thank you very much. If today's conversation gave you a new perspective on food nutrition science or how we shape public health policy, consider sharing it with someone who values evidence over headlines. And if you are hungry, keep learning alongside us, be sure to follow the show you.