Making Sense Of Conflicting Claims From Diet Gurus – Dr. Stephan Guyenet and Dr. Mario Kratz

Content By: Ari Whitten & Dr. Stephan Guyenet and Dr. Mario Kratz

In this episode, I’m re-releasing an episode with Dr. Stephan Guyenet and Dr. Mario Kratz, two impressively experienced nutrition researchers with a wide range of expertise, about their organization Red Pen Reviews, a non-profit dedicated to publishing unbiased, scientifically accurate reviews for current nutrition books hitting the market.

Today, we focus on two popular but controversial books—Dr. Steven Gundry’s The Plant Paradox and Carnivore Code from Dr. Paul Saladino.

This podcast was originally published on August 27 2022

Table of Contents

In this podcast, Dr. Guyenet, Dr. Kratz, and I discuss:

    • How difficult it is to parse out accurate versus inaccurate and biased information and the regulated and systematic role of Red Pen Reviews in clearing up the confusion
    • The 3 focus areas Dr. Guyenet and Dr. Kratz use to score the books they review and the importance of each
    • How the health claims made in Carnivore Code compare to research AND anecdotal reports of people eating the diet…and how the main claim that humans evolved to be carnivores compares to evolutionary evidence
    • Possible downsides or even dangers of the carnivore diet and if these caveats are discussed in the book
    • The full truth of the claim that elevated LDL is not a cardiovascular concern if a person has excellent metabolic health
    • Does a nose-to-tail carnivore diet provide all the nutrients you need each day?
    • The Plant Paradox’s primary claim that certain plant lectins lead to approximately 50 diseases…plus, what a lectin actually is!
    • What current research tells us about lectins triggering leaky gut, inflammation, and autoimmune disease 
    • The health status of people who eat large amounts of lectin-rich legumes, tomatoes, and other nightshade vegetables
    • Could lectins and other plant foods be stressful BUT ALSO beneficial at the same time
    • Practical ways to evaluate the nutrition information you take in every day so you can more easily consider what’s accurate and what’s likely not

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Ari Whitten: Hey, this is Ari. Welcome back to The Energy Blueprint podcast. I am very excited for today’s show. I’m going to be talking to two world-class nutrition experts all about a problem that I’m sure you know about, which is the world being inundated with a huge amount of conflicting and contradictory nutrition information, everything from vegan diets being the best for health to carnivore diets being the best for health and every variation in between those two extremes.

Are things like, “Is dairy good or bad for you? Is gluten good or bad for you? Is red meat good or bad for you? Are vegetables good or bad for you?” Vegetables and herbs like curcumin or phytochemicals like sulforaphane or resveratrol and things of that nature. I think within the realm of nutrition, there’s some diet book that demonizes basically everything. It used to be the case up until a few years ago that everything conceivable other than water and non-starchy, colorful vegetables were demonized by someone somewhere.

Now we’re at a point where even non-starchy vegetables have been demonized heavily in some circles. I think the list right now is really just water and that’s it. That’s the only thing that is agreed upon by all different diet gurus and nutrition experts. There’s also a big distinction I think between what kinds of ideas are popular in the general public at any given time, what kinds of diets are trending, and what kinds of dietary beliefs people have at any given point in time.

For example, that fat is bad and we should avoid fat. Then it became, no, actually sugar and carbohydrates are the real problem. You should go low carb and you should go keto, or you should go paleo, or you should go carnivore, or, really, animal foods are bad and you should go vegan. There’s all these different competing dietary ideologies, all of which have their own group, oftentimes, a very cult-like group of people who worship at the altar of this dietary ideology almost as if it’s a religion and attack everybody who challenges it.

I’m sure, for example, there will be some people who try to attack me for touching this topic and for inviting people on my show to discuss some of the things that we’re going to discuss today, yet it’s simply the case that there is genuinely a lot of information out there in nutrition circles that is simply not an accurate representation of the science. Either there are what appear to be very overt and deliberate misrepresentations or sometimes it’s happening by accident. People simply leave stuff out or people cherry-pick the research on a particular topic to give a misleading impression of what the overall evidence on that topic says.

Overall, this is a really important topic and there are some people namely Dr. Stephan Guyenet, who is a neurobiologist and obesity researcher whose work I followed for over a decade now. Someone I respect enormously and whose work had a huge impact on me, in my thinking, starting about a decade ago. He’s got a website now called Red Pen Reviews. It’s a nonprofit organization that is dedicated basically to publishing unbiased, scientifically accurate reviews for different nutrition diet books that are hitting the market.

They have a system for how they score these books on scientific accuracy in terms of the healthfulness of the diet. They do reference checks where they actually check the scientific references that these books are citing, see if they’re misrepresenting things. They’re also seeing if claims are being made in that book where maybe they cherry-picked the research and maybe there’s a whole bunch of studies that were left out of that book that say otherwise, that contradicted claims being made in the book.

All of this is, in my mind, a vitally important service for mankind to get access to accurate information about this incredibly important topic for our health, which is nutrition. We need adequate nutrition to be healthy and to be disease-free and to live a long life, and we need to have accurate, non-cherry-picked, non-misrepresented scientific information on those topics. Red Pen Reviews is really dedicated to that. I think they’re doing an incredibly important service.

I’m personally donating to them. I want to encourage you all to donate to them. I have no vested interest here financially whatsoever, this is just something I think is very important. I personally feel passionate enough to want to donate to this cause because I think it’s, as I said, incredibly important for helping people get accurate information on the topic of nutrition to prevent disease, to live a long life, to be healthy and happy, especially in a sea of misinformation that’s out there.

I want to encourage you all to consider donating to them. I think you’re going to be very impressed by what you hear in this episode. We’re going to be covering two books in particular. One is Dr. Gundry’s book, The Plant Paradox, which is all about the idea that lectins in plant foods are a major cause of disease in humans. The other book, which is in a similar vein, is The Carnivore Code by Dr. Paul Saladino where the central claim is that the most optimal human diet and the ancestral diet is something approximating a carnivorous diet, mostly or entirely animal food-based diet.

The idea that by eating more that way and by excluding a lot of plant foods, which are explained in this book, many plant foods but not all necessarily have compounds in them which are unhelpful and that by excluding them and moving more in the direction of a carnivorous diet that that’s more the optimal human diet for health and longevity and for feeling good and well-being.

The central claims in those two books were analyzed by Red Pen Reviews and they did in-depth reviews on them. We’re going to be talking about that in this episode. Let me just tell you a bit about the two people that I’m hosting in this episode. The first is Dr. Stephan Guyenet. He’s the author of this book, The Hungry Brain, which is a vital reading, which is must-read material for anybody who is interested in understanding the real causes of why humans get fat, what’s causing the obesity epidemic, and what we need to do to lose that. It is not a particular specific diet, it’s really just explaining the physiology and the neurobiology that’s going on in how people accumulate large amounts of excess body fat.

As I said, he’s a brilliant neurobiologist who has had a huge impact on my own thinking. He specializes in the neuroscience of obesity and he’s an advocate for information accuracy in health communication. He received a bachelor’s of science in biochemistry from the University of Virginia, and a PhD in neuroscience from the University of Washington, where he remained as a postdoctoral fellow studying neuroscience of obesity. His scientific publications have been cited more than 4,000 times by his peers. His book, The Hungry Brain, was named one of the best books of the year by Publishers Weekly and called “essential” by The New York Times Book Review.

He’s the founder and director of Red Pen Reviews, which publishes the most informative, consistent, and unbiased health and nutrition book reviews available. The other guest also works for Red Pen Reviews and he sent me his CV, which I had to pull information out to create some bit of a bio. The CV is 20 pages long. It would be hard to do justice to, but here’s a few highlights.

He has a master’s of science in nutritional sciences from the University of Bonn in Germany. He has a PhD in nutritional sciences from the University of Bonn in Germany. He has been involved in arteriosclerosis research at the University of Münster in Germany. He did his postdoctoral fellowship around arteriosclerosis research. He is a senior research fellow of medicine in the division of metabolism, endocrinology, and nutrition at the University of Washington, or was for a period of time. He’s held a number of different roles as involved in research and directing various research institutes or bodies within different universities.

He’s worked as an assistant professor in the School of Public Health Department of Epidemiology at the University of Washington. He’s been associate director in the Immunology and Inflammation Core at the University of Washington. He’s been an associate professor in the Public Health Sciences Division in the Cancer Prevention Program. He has been an adjunct research associate professor of medicine at the University of Washington and he’s been a professor of public health nutrition at the University of Washington, and he’s a published scientist having done nearly 100 studies related to nutrition and human health. That’s just a short version of all of his long list of credentials.

Fascinating, brilliant, extraordinarily knowledgeable people who are commenting on the details of these two books in a very scientific and nuanced way and I think also very charitable way. I think you’ll get a lot of really important takeaways from this conversation. With all of that said, enjoy the episode.

What is Red Pen Reviews And What Do They Do?

I would like to give you guys the floor to talk a little bit about your work with Red Pen Reviews. What are you guys doing? If you want to say a few words beyond what I just said.

Dr. Stephan Guyenet: Yes, thanks for having us on. I’ll kick it off here. As I think most people recognize, there is an enormous amount of information out there on nutrition and health. Some of it is accurate, and some of it is not. One thing I like to say is that the popular nutrition publishing sphere is an exploding volcano of nonsense. In reality, what it is, is that it’s just very variable. Some of the information is good, some of the information is not good, and it’s surprisingly hard to tell the good from the bad even for a knowledgeable person. You can’t be an expert in everything.

You could be a knowledgeable person reading a book that’s a bit outside your area of expertise and you could get totally taken in by some compelling sounding ideas. Most people just don’t have the time or energy to do scientific literature searches to evaluate the claims that are made, to look up citations that are cited in the book to see if they’re being used accurately in the book, and when you do that, it can really change your perception of the claims that are in a book.

What do you do? You look up reviews of a book online, maybe you find some on Amazon, maybe you find some that were published in a newspaper, The Atlantic, New York Times, some respectable outlet, but they generally don’t do reference checks either, and they’re usually not written by experts in that area as well. How reliable are those? If you have one person who says it’s good and another person who says it’s bad, how do you arbitrate between those?

We wanted to just go back to the drawing board and create a system that would solve all these problems at once and bring book reviews into the 21st century, I guess, would be a way to put it. We created this system that it’s a structured review method that gives semi-quantitative scores for scientific accuracy, reference accuracy, and healthfulness. We apply the exact same method to each book; you get these numerical outputs that are very easy to understand and that can be compared between different books.

We use a lot of methods that are drawn from the scientific method like random sampling. We randomly choose 10 citations to evaluate from the book so that whatever we’re looking at is really representative, we’re not cherry-picking ones to make the book look bad or make it look good, it’s really random. Then peer review is another thing we apply. All of our reviews get reviewed by a second person to get an extra pair of eyeballs on them.

I think there are just many, many ways in which this method is superior to the method that is usually applied when books are reviewed, which is to say no method. We really hope that it will provide better information to people who are looking to purchase books, as well as creating better incentive structures for the health and nutrition publishing industry.

Ari: Very well said. I also want to ask you on that note in case anyone is skeptical of what you’re doing, maybe he’s thinking what are your hidden financial interests that you may have. Obviously, it’s become a huge issue with the amount of even peer-reviewed scientific literature that has financial conflicts of interest that is funded by pharmaceutical companies. If anybody’s interested in that I recommend a book by Ben Goldacre called Bad Pharma. It’s rampant, and this is a huge issue in science.

What if somebody is skeptical and is thinking, “Well, maybe you have some kind of vested interest in selling your book,” (which I gave a little endorsement of), or some other thing, “You’re funded by so and so.” Anti-red meat vegan group or pro dairy group or whatever. Do you have any words to say on that?

Stephan: Yes. I guess the first thing is, I would invite people over to my house to see my 2006 Toyota Sienna minivan.

It’s the car that I drive. I think that if I were raking in bucks, I’d probably be driving something different. More to the point is that Red Pen Reviews is a 501(c)(3) nonprofit organization. We are federally recognized as a nonprofit, which means that part of our — our organization is founded around the principle of serving the public, not serving ourselves financially. That is legally part of the foundation of our organization.

It doesn’t exist to put money in our pockets. In fact, the organization is run very much on a shoestring. Literally, not a single person has made a single cent so far in the history of the organization. The only transfer of money that has occurred is out of my bank accounts into the organization.

Ari: Maybe you need to start soliciting some shilling for some of these-

Stephan: Yes, exactly. It sounds a lot more– [crosstalk]

Ari: -more reviews.

Stephan: Yes. I think people are right to be concerned about bias to some degree. I’m a human being, I don’t want to give the impression that I have no biases and that I’m 100% objective. That wouldn’t be an accurate thing for anyone to say, but we have this method that strives to minimize bias. That is something that I can say, is that we have a concrete, structured method that is designed in part to minimize human bias and that we lay out everything that we did, every detail of how we came to the scores that we came to. Our method is published on the website. It’s all transparent for people to be able to judge for themselves.

Ari: Excellent.

Dr. Mario Kratz: Can I add there?

Ari: Yes, please, Mario.

Mario: Actually, we have these meetings once a quarter. By the way, thank you for having me as well, Ari. We have these meetings once a quarter and I’d say a good chunk of the time, every single meeting with the entire team, we’re discussing these types of issues, how can we make sure we’re removing as much as possible the influence of others’ financial interests.

For example, one thing we do is, if someone reviews a book, we make sure that both the primary reviewer and the peer reviewer don’t have any, not even financial interests, but also, if they’ve spoken out publicly very much against a certain diet, we feel like that may be perceived as, “Okay, maybe they have some kind of issue going on here. Maybe someone else should review that book.”

We’re really trying to make sure that the reviewer and peer reviewer go into the book review with a white piece of paper, little else written on it yet in terms of other entanglements with that subject matter, which is hard, because we’re all having graduate degrees, at least, in nutrition, so we may have published on a certain issue. We’re trying to do our best in that regard to make sure that the reviews come out unbiased and certainly not influenced by external financial or other interests.

The Carnivore Code

Ari: Excellent. I’ll just add on a personal note, having read, I think pretty much all of your views, that I think you guys do a great job of that. Without any further ado here, I want to jump into the two books that we’re going to be talking about, both very popular diet books, and both scored extremely poorly based in your review system. The first one is Dr. Steven Gundry on The Plant Paradox, talking a lot about lectins. Then the other one is Carnivore Code from Dr. Paul Saladino.

We’re going to jump into the Carnivore Code first. Again, for everybody listening, I’d recommend actually reading their review on the site on You can see the text review there if you want. We’re going to talk about some of the detail of that. First of all, can you guys talk about what is a carnivore diet from this perspective and what are the central claims that are made in this book?

Stephan: Yes. Typically, a carnivore diet is a diet that includes only animal flesh. Sometimes it also includes eggs. Then, if people are less strict about it, they might include other things like dairy or maybe a limited amount of plant foods. If you look at The Carnivore Code, for example, he lays out several different versions of the carnivore diet. The one that he describes as the pinnacle is a purely carnivorous diet, and it is a nose-to-tail carnivore diet. You’re eating muscle meat, you’re eating a variety of organs, including liver and pancreas and other organs, but you’re not eating any plant foods. You’re not eating any dairy.

That is what is presented as the pinnacle in that book, although I think how people define it can vary. The claims that are made about it are basically everything. There are claims about a wide variety of major diseases in there. It makes claims about treating obesity and preventing obesity, diabetes. It makes claims about autoimmune disease. It makes claims about mental health conditions, particularly depression and mood. It makes claims about well-being and performance, not just disease but actually how well you’re thriving in life.

The book talks a lot about kicking butt, about how this diet is going to make you kick butt. It makes a really wide variety of claims. This reflects the claims that are seen in the broader carnivore community online. If there’s a disease, there’s a claim that the carnivore diet has prevented or reversed it somewhere online.

What Is The Optimal Human Diet According To Research

Ari: Okay. My question, which is a very broad one, and I’m sure we could delve into 100 different subtopics within this, is how do those claims stack up against the evidence? Is there any particular place you want to start? Maybe, what about the claim that if the pinnacle of what is the most optimal human diet is an entirely or almost entirely animal food organ meat-based diet, there should be some kind of evolutionary anthropological track record of humans evolving as carnivores. We should be able to go to hunter-gatherer civilizations that still exist in the world today and verify that that’s true. I know you’ve written a lot about this and Staffan — is it Staffan Lindberg? …

Stephan: Yes, Staffan Lindberg.

Ari: I know you’ve written a lot about his work many years ago. I remember reading your articles of this is a researcher who traveled all over the world and visited hunter-gatherer tribes and very rigorously tracked what they were eating. What does that research tell us about the claim that humans are supposed to be carnivores or that’s the most optimal diet for us?

Stephan: Just to take a little step back before I dig into that, this is a central claim that you find in the book and more generally in the carnivore community, that humans evolved as carnivores. The part of the rationale for the diet is that this is the natural diet for humans and therefore it is optimal. I think that is a claim that does not hold up very well when you look at the archeological and anthropological evidence.

If we look at the archeological evidence, which is directly relevant to what our distant ancestors ate, it’s pretty spotty, first of all. You really have to piece together very limited evidence to get a picture of what’s going on, but there is quite a bit– From the evidence that does exist it suggests that typically plant foods were consumed. However, there was a lot of variability across time and space in the amount of animal and plant foods that were consumed.

I think one thing that is true is that there was a period where we substantially ramped up our animal food consumption during our evolution. If you go back to the last common ancestor that humans have with chimpanzees, which was something like seven million years ago, that was probably an animal that ate a largely vegetarian diet. Maybe a little bit of meat every now and then, probably some bugs, but probably mostly leaves and fruit.

As the genus Homo emerges, you see that you have humans that are hunting animals; you have bones with tool marks on them. Humans today, obviously, we’re very skilled hunters. If you look at hunter-gatherer societies around the world, humans are typically apex predators. Clearly, there was an evolution that happened there toward more meat-eating. However, that doesn’t mean that we were pure carnivores.

If you look at the record, you see, even in times and places where it was believed that people were primarily eating animal foods, for example, Neandertals during the Ice Age in Western Europe, even they were eating plant foods. If you look at the tooth plaque from their teeth, you can find all kinds of plant foods embedded in it. They were eating a wide variety of different plant foods. It was probably a mostly animal-based diet, but it was not a purely carnivorous diet. That much is clear.

Then if you look at hunter-gatherer cultures that have been characterized within the historical period as well as ones that currently exist, you see that, again, there’s a wide variety of diversity, but almost all of them eat plants. The only ones that eat little or no plant foods are the ones that are living in the Arctic where there is little or no plant foods. Pretty much anywhere where humans existed, where edible plants existed, which was almost everywhere, people were apparently eating plants.

Again, there’s a lot of uncertainty. Like most of the archeological record, we don’t really have direct evidence from, it’s just snippets here and there, but I would say that the pattern that emerges really suggests that we have always eaten plant foods and that only in certain specific contexts were plant foods small or occasionally nonexistent proportion of the diet.

What Studies Tell Us About Modern Hunter-Gatherer Diets

Ari: What about modern hunter-gatherer tribes that have been studied around the world and their diets?

Stephan: Only a few of them, the ones living in the Arctic like the Inuit had diets that were low or possibly no plant foods. Even the Inuit, there are entire cookbooks full of traditional Inuit plant recipes that have been published. It’s not like they were even pure carnivores either. Maybe some groups were. I’m not sure. I know some anthropological accounts suggest that they didn’t eat plants, but clearly, many of them did eat plants when available. They went to great lengths to obtain them. They would go out and pick tiny little berries on the tundra and preserve them for the winter.

Can you imagine how much work that is? Greens and they would eat seaweed. They would eat the stomach contents of caribou. They were going to great lengths to get the meager amounts of plant foods that were available in their environment. I would think that’s because those were nutritionally valuable, but I don’t know.

Ari: What about other groups? What you just said might be relevant to someone who is of Inuit ancestry. Maybe there’s a valid case that they should be something approximating a carnivorous diet, but what about groups that are in Africa or South America or Central America that have been studied or [crosstalk]?

Stephan: It’s highly variable. If you look broadly at the evidence, it’s highly variable. If you look specifically at the groups that have been the most thoroughly characterized, where you really have had anthropologists, in detail, characterizing their diets, following them around all day, seeing not just what they’re bringing back to camp but what they’re eating when they’re out hunting, maybe they have handfuls of berries here and there, things like that. When you look at those kinds of studies, you see a diet most often that is actually predominant in plant foods. Usually, with a good amount of animal foods. Again, highly variable, but there can be quite a bit of animal foods.

They were definitely not vegetarians. However, most of these cultures that have been really characterized deeply in terms of their diet were eating predominantly plant foods.

Ari: Can you give a few specific examples? Let’s say the Hadza, the Tukisenta, the Tarahumara, the Simane. I know you’ve written quite a bit about some of those findings.

Stephan: Yes. The one that I have most top of mind is the Hadza of Tanzania. There’s also the Kung Bushmen in Botswana. I’m not sure if they’re still hunter-gatherers or not. I think their culture was expiring, but at least their traditional way of life. Those are two cultures that have been characterized in great detail that ate predominantly plant foods.

Does The Carnivore Diet Really Prevent And Cure Common Diseases of Lifestyle

Ari: Okay. Got it. What’s the next central claim in the book or maybe another way of looking at this question? We were just looking at, “Okay, what is the anthropological evidence or evidence from hunter-gatherers that have been studied that are still alive to support the claim that the natural evolutionary human diet is mostly or all meat and animal foods?” That claim doesn’t stack up very well to the evidence. What about looking at modern nutritional science and this claim that the optimal, most healthy human diet is mostly or entirely carnivorous diet? What is the evidence that he cites in the book to support that this diet prevents or cures many different diseases?

Stephan: There is no direct evidence that is cited in the book or not cited in the book on key long-term health impacts of this diet. There are no randomized controlled trials with health outcomes for this diet, so really most of what we have, almost everything, in fact, on this diet is a combination of speculation and anecdotal reports. That said, the anecdotal reports are quite impressive. I think they’re pretty intriguing, so I don’t want to completely dismiss those.

There was actually a study that collected these anecdotes published in– let’s see here, got it in front of me– Current Developments in Nutrition. They used a survey method to survey people eating a carnivore diet. They found these communities of carnivore dieters on Facebook, et cetera, and they just asked them a bunch of questions by survey about what they eat and how the diet has impacted their health.

I’m looking at Table 3 here, and there’s a long list of conditions. Obesity, blood lipid abnormalities, cardiovascular disease, autoimmune disease, neurological problems, oncologic problems, which means cancer. What it’s showing is that a high proportion of these people are reporting improvements in these conditions. In this survey, a high proportion of people are saying that, “My diabetes got better. I lost weight. My cancer got better, neurological conditions got better.” Basically, anything you could look at and also markers of well-being improved in these people, and then they have some blood measures as well.

I think if you take this at face value it looks really, really impressive. You would say, “Wow, this diet can do just about anything.” I think it’s important to keep in mind that this is a very self-selected group of people. These are the people who responded to the survey, which are the people that are in these carnivore diet communities, which are the people who did the best on the diet. It’s really selecting for people who did the best. It’s not representing the people who started the diet and got worse and then dropped out. I think it’s really not so straightforward to interpret this.

I think one thing that I want to highlight as well is that– The evidence is based on basically speculation and anecdote. However, this is a diet that would be expected to do certain things. This is speculation but I think we can logically speculate that a diet that is high in protein that cuts out pretty much all processed foods, pretty much all variety and is very low in carbohydrates, it’s probably going to cause weight loss. That’s logical. That’s probably true. That very low carbohydrate and the weight loss is probably going to help blood sugar control and diabetes. Those are two things about the diet that I believe are probably true.

Ari: Given that excess body fat, all being overweight and obesity contributes to poor metabolic health in such profound ways and leads to increased propensity for so many different metabolic diseases, that mechanism by itself, really any diet that causes a profound amount of weight loss could be expected to have an array of different health benefits. Is that accurate to say?

Stephan: Yes, I think so. I think that would be logical to suppose that would be true. I’d have higher confidence if we had direct evidence of that on the carnivore diet specifically. The other thing that we would expect from this kind of diet is that it would increase LDL cholesterol, which is a risk factor for cardiovascular disease, because typically people are eating a large amount of saturated fat from meat, particularly red meat, and they’re not eating much polyunsaturated fat, which lowers LDL cholesterol. You would expect that to increase LDL.

That is what you see in these data, people who start on the diet, they typically experience a marked increase in LDL cholesterol. I would say that gets us into thinking about what some of the downsides of this diet could be. One of the possible downsides is that it could increase cardiovascular disease risk.

Ari: Got it. Okay. What are some of the kinds of things that you’ve read as far as the anecdotes around changes people see in their blood lipid profiles?

Stephan: I’m sorry, can you repeat the question, please?

Ari: Yes. As far as some of the stories that you’ve seen the anecdotes of people on the diet, what kinds of changes do people typically see as far as changes in blood lipids, cholesterol, and so on?

Stephan: I think it’s highly variable. Some people don’t see changes in — typically you would see a reduction in triglycerides just because of the carbohydrate reduction, but in terms of the LDL, I think it’s highly variable. Some people report that there’s no change in LDL. Other people see this massive, massive increase in LDL. Obviously, my concern would be focused on the people who see that massive increase. If somebody goes on a diet and their LDL doesn’t change and their blood lipids look good overall, I don’t think I would be very concerned, but for these people who see absolutely massive increases, including the author Paul Saladino, he is one of these people. Let me see if I can–

Ari: What has he said about his personal increase in cholesterol in his LDL? I think that I’ve heard him explain why he thinks that that’s not a concern. What do you think of his explanation and how that stacks up to the overall body of evidence on that topic?

Stephan: First of all, LDL cholesterol above 190 mgs per deciliter is considered very high. 190. His is 533 mgs per deciliter. We’re talking about truly extreme LDL cholesterol levels. Essentially what he says is that LDL is not harmful in the context of a carnivore diet because when you’re in good metabolic health, which according to him, the carnivore diet creates good metabolic health, when you’re in that state, the LDL doesn’t actually contribute to cardiovascular disease because of different properties of the LDL particle and different properties of the endothelium.

It’s possible that that could be partially true. Metabolic health does have an independent impact on cardiovascular disease risk. LDL is not the only risk factor for cardiovascular disease. To the extent that the carnivore diet might improve some of these other markers, it’s possible that it could attenuate or even prevent the increase in risk from elevated LDL, but I think once you’re getting into levels of LDL like Saladino has, where they are just extraordinarily elevated, I would be pretty surprised if there was anything else that could make up for that increase in risk. That’s just massive.

Essentially, to state it simply, it’s an argument that’s based on speculation, not evidence. There’s no evidence that the carnivore diet prevents the harmful effects of high LDL. It’s pure speculation, and I would say it’s speculation that’s not very well supported, based on the evidence that we have.

Mario: Can I chime in here as well, Ari?

Ari: Yes, please.

Mario: I think this is really an issue that’s debated very widely, and I think, to some degree, misunderstood because– What we need to understand is that LDL is associated, we think causally, with cardiovascular disease. Then there’s a whole bunch of other risk factors. Let’s say blood pressure, your blood glucose levels, and so forth. They all, we know, independently contribute to the cardiovascular disease risk. That certainly remains true.

If now you go on a carnivore diet, then your LDL may rise, but if some of the other parameters improve, you may still be better off, depending on how they all change as Stephan said. I think the one big claim that I’ve seen made in this community of people following a keto diet or a carnivore diet is that, for some reason, that if these other parameters change, that that would also somehow change the relationship of LDL cholesterol to cardiovascular disease. In science, we call this effect modification, where now, for some reason, your blood glucose levels are normal, and that means suddenly there is no association anymore between LDL cholesterol and cardiovascular disease.

To the best of our knowledge currently and what the science says, there’s really absolutely no reason to believe that that is true. I think there are studies going on right now to test this specifically, and I’ve seen some observational analyses already that show quite clearly that the relationship between LDL cholesterol and cardiovascular disease risk is present no matter what your metabolic health is, no matter what your triglycerides are, no matter what your blood glucose levels are.

I just want to make sure people don’t get confused about this. If you look at the entirety of the risk, sure, you’ve got to look at all the risk factors, but the argument that there’s effect modification by other factors on the relationship between LDL cholesterol and cardiovascular disease risk, there’s absolutely no evidence whatsoever for this.

Ari: That is to say if you had LDL levels of 530, no matter how good your other markers of metabolic health are, how lean you are, you would be deeply concerned about that.

Mario: I certainly would. I think it’s just way too high. Of course, I think people could say, “Yes, if I had 530 and also had diabetes and my blood glucose was out of control and my blood pressure was very high and I was a smoker,” all these other risk factors, then your risk would be even higher. No one is arguing that that wouldn’t be true. In other words, yes, in some ways, you’re well off on the carnivore diet if you’re losing weight and if your blood glucose is well under control, but the argument that your LDL cholesterol levels suddenly don’t matter anymore if you’re otherwise metabolically healthy, I think is, if you ask me frankly, wishful thinking.

Ari: Okay. I’ve read the book as well and there are some things that jump out to me as pretty significant and pretty concerning. I want to read one quote from the book here. He says, this is a comment on telomeres, which are a marker that’s been linked with the rate of biological aging.

He says, “What sorts of things are associated with longer telomeres? For both vegetarians and non-vegetarians, it’s all the great lifestyle stuff we’ve previously discussed. Exercise, adequate sleep, moderate sunlight exposure, finding meaning in our lives, and a tight-knit community. It’s no surprise that Buettner the author of the Blue Zones books found these as commonalities between his Blue Zones, the longest-lived populations. Guess what? When it comes to food, there’s only one thing that has been correlated with longer telomeres, and it’s not plant foods, it’s red meat.”

After I read that, I spent, I just went on Google Scholar and looked at nutrition and telomeres. Within about five minutes, literally no more than five minutes, I found over a dozen studies completely disproving this finding.

Numerous studies showing that red meat and processed meats are either not linked at all with telomere length or have a negative effect, and lots and lots of studies showing that numerous kinds of plant foods, vegetables, berries, nuts, things like that were the only foods in those studies that were linked with longer telomeres. To me, this brings up another issue. It’s one thing to go into the literature and have one reasonable interpretation of the evidence and it’s another thing to just completely distort the facts and what that evidence says.

Do you guys have any comments on that issue?

Stephan: Yes. My main comment is that this book received a scientific accuracy score of 28%, so 28 out of 100. I would say that’s pretty consistent with what you’re saying there.

Ari: Yes. Okay. Were there any other glaring issues or examples of things like that that you found concerning in the book?

Stephan: Yes. We have the scientific accuracy score; we have the reference accuracy score, and we have healthfulness. Our method for scientific accuracy is to select three representative claims in the book and evaluate those in enough depth to see how well they hold up. We evaluated the claim that humans evolved as carnivores, only occasionally eating plants as fallback foods to avoid starvation. We evaluated the claim that dietary fiber is not helpful for constipation, and we evaluated the claim that high LDL cholesterol on a carnivore diet is not harmful.

None of those claims faired very well. The one that faired the least poorly is the dietary fiber claim because I think the evidence is mixed on that. That’s what we think paints a pretty representative picture of the book is that it makes very strong claims. When you go and evaluate the evidence underlying those claims, it tends not to support those claims very well.

Ari: Yes. I think that there are examples of diet books out there that are making claims that are maybe largely aligned with the body of evidence on that topic and where the author does a lot of logical speculation of piecing things together; they have their own hypothesis of why this effect could occur, and they’re doing a lot of logical speculation overlaid on top of the evidence that they’re presenting.

That could be one way which someone could be downgraded on your analysis, the way you guys are doing these reviews, you could say, “Ah, that claim or that hypothesis isn’t really supported by the scientific evidence but it might be a reasonable and logical, mostly valid form of speculation, speculative as it may be.”

It seems to be another distinct category when someone is basically just overtly distorting what the science actually says, where you have a body of scientific evidence and someone is just completely ignoring it and then cherry-picking one study that says what they want to say, they ignore the dozen others that contradicts it, and then they present to you the one as if it’s representative of the full body of evidence. That seems to me to be a totally different category of misrepresentation distinct from some degree of logical speculation.

Stephan: It’s very common. Sometimes it’s intentional, and sometimes it’s not. We have these cognitive biases. I think sometimes people don’t even realize they’re doing it, but that’s what systematic literature searches are for so that you can evaluate and correct those types of biases, and that’s what we try to do. I think what people really get dinged for hard is not just speculating, it’s presenting speculative ideas as not speculative ideas.

If someone says, “Hey, I have this idea. I really don’t know if it’s true or not but it’s an interesting idea. Here is my argument for it.” That will be scored quite differently than someone who says, “Hey, here’s what the facts are,” but in fact it’s just speculation.

Do you guys have any other thoughts on the carnivore diet as far as possible downsides of this? I know we’ve touched on that already, but are there any other possible downsides of doing this diet or things that people should be concerned about?

I know that obviously there are certain essential nutrients that many people would say we get from plants. People on a carnivore diet would say, “No, you can also get those nutrients in adequate amounts if you eat nose to tail.” There’s also issues around fiber and gut microbi ome. I’ve heard people say there could be a risk of permanent damage based on completely extinguishing certain species of gut microbes that need fiber. Any thoughts around those kinds of issues?

How The Carnivore Diet May Lead to Nutrient Deficiencies

Stephan: Yes. What we did to evaluate this was we put the suggested meal plans in The Carnivore Code through– We focused on the ones that it presented as optimal, the nose-to-tail purely carnivorous diet. We put that through software that analyzed the nutritional composition of it. What we found was that it actually was nutritionally inadequate for a number of vitamins and minerals, including magnesium, manganese, potassium, vitamin C, vitamin E, and vitamin K. If a person chose not to consume an additional calcium supplement, which is recommended in the book, then there would also be a lack of calcium in the diet.

You could argue about whether the recommended intakes are accurate, maybe you don’t need to get that much, but I think, certainly, if you take the recommended intakes at face value it is substantially nutritionally inadequate for a number of vitamins and minerals. I think this may have something to do; I don’t know if this is related. It’s not hard to find anecdotes of people who tried the diet and just didn’t feel good. If you just do a quick Google search, you find that a lot of people tried the diet and didn’t feel good and they stopped eating it. Actually, Paul Saladino is one of those people. If you look at what he eats now, he’s eating large amounts of honey, and he’s eating white rice.

Ari: I was with him about a year ago, he was visiting with a mutual friend of ours and I sat with him. Ended up having a discussion/debate in person, but mostly very cordial and respectful. He ate a bunch of beef and he ate two mangoes while he was sitting with me.

Stephan: Yes, fruit too. I forgot to mention that. Right. He has his reasons for that. The reason that I’ve heard him state publicly is that he feels better when he includes these other foods in his diet. I don’t doubt that he got benefits from a purely carnivorous diet. That’s what he says in his book. I don’t question that, but there was something that was not optimal for him about a purely carnivorous diet relative to the diet that he’s on now. That’s something you see from a lot of people. Carbohydrate is not an essential part of the diet, but I think a lot of people do better with some carbohydrate versus zero.

Ari: Yes. It’s interesting for me to consider this just from a semantics perspective because having some meat and a couple of mangoes in a meal might be similar to a meal that I might have but I wouldn’t tell people that I’m eating a carnivore diet. I wouldn’t claim that the definition of that diet is a carnivore diet. I would imagine, I don’t know this for sure, but I would imagine probably a lot of people who eventually do that they start incorporating more and more plant foods to the point where they’re eating an omnivorous diet but they’re convincing themselves that they’re eating some kind of carnivore diet. Do you understand what I’m saying?

Stephan: Yes, absolutely. I agree with that but I think often they do end up still being on a very meat-heavy diet, and I think that’s still true for Saladino. It’s not like he has just returned to eating a standard American diet, but certainly, yes, it’s not a carnivorous diet in a sense that — in a sense that is literally not. It is an omnivorous diet.

Ari: Right. I definitely don’t think it’s typical to a standard American diet but I would say it’s more similar to my diet, someone who eats quite a bit of animal foods but also eats an abundance of different plant foods. There are certain categories of the plant foods that I eat that they would stay away from, for example, root vegetables and things like that. The last aspect of this that I think maybe is worth commenting on is just the modern nutritional science.

What is the evidence that supports the idea that people eating more plant foods have poor health outcomes? What is the evidence that people eating more plant foods, provided they’re eating unrefined, unprocessed plant foods, to rule that out as confounding variable, but what’s the evidence around people who eat more unrefined plant foods and health outcomes? Does that support or contradict the claims made in the book?

Stephan: Most of the research that’s been done, and I think Mario probably would have some good thoughts on this as well, but most of the research that’s been done has really been more focused on disease prevention than well-being and kicking butt, which is a central claim of the book. I think if you’re looking at from a disease prevention standpoint, the evidence overall, you’d have a really hard time making an argument that diets high in unrefined plant foods increase the risk of common diseases like obesity, type 2 diabetes, cardiovascular disease. I think you would have a pretty easy time making the reverse argument that they’re actually protective.

Certainly, that’s what you see in observational studies. That’s what you see in randomized controlled trials typically, that are looking at biomarkers like blood lipids and body weight and glucose, but that’s not to say that that’s the only path. There’s the low carbohydrate diet trials where you’re restricting at least certain types of plant foods and you could see benefits there, particularly in the realm of diabetes management and obesity management.

Then if we look at components of plant foods, things like fiber and polyphenols, generally in studies, those are found to cause health benefits in animal studies, human studies. I don’t think we have knockout evidence that these compounds reduce health risks, but the evidence that we have does point in that direction. Mario, any other comments you want to add there?

Mario: No. I absolutely agree. I think whether you look at legumes or vegetables specifically, but I’d say even fruit and whole grains where it’s a little less clear, both in observational studies, we see these associations with better health outcomes. Also, if you gave me a little bit of time I could probably find you at least 50 intervention trials where people started eating more legumes, more vegetables, for example, and very specific health outcomes improved. If you look long enough, you’ll probably find something where there’s a negative association, but the claim made by Dr Saladino that plants are toxic or partly toxic is, I think, in my opinion, not at all supported by the existing data.

I think we’re going to talk about some of these potential toxic components when we talk about The Plant Paradox. I’m not saying there’s nothing in plants ever that could harm you. That’s certainly also flawed. I think we’re creating a false dichotomy in a way where we’re saying there’s some toxic things in plans and that means plans are always to everyone, under all circumstances, toxic. That in my mind is just really not supported by the actual evidence.

The Link Between Vegetable Consumption And Diseases Of Lifestyle

Ari: Have you guys ever seen a study that showed that lower levels of vegetable consumption was linked with lower rates of heart disease and cancer, and neurological disease, and things of that nature?

Mario: I can’t remember off the top of my head. Sometimes it’s just novel when people look at these associations. Also, I think it’s for sure we have a certain view in the sciences that maybe people don’t even look at questions that way like that. If someone’s a critic of nutrition science, I agree with most of it. I think there’s a lot of limitations and issues. If you have hundreds of studies pointing one way, and then to say, “These are all weak studies,” it’s actually exactly the opposite. I’m not sure that’s a mindset that’s going to get you to the actual truth.

Ari: Let me ask the question in reverse. Have you ever seen studies that show that higher levels of consumption of vegetables are linked with lower rates of cancer and heart disease, and neurological disease, and diabetes, and obesity, and other diseases?

Mario: Yes, of course. That’s the norm. As I said, there’s easily hundreds of observational studies. As I said, easily 50 intervention studies probably as well. Admittedly, many of these using surrogate endpoints of disease, but some actually using heart disease endpoints and seeing positive changes.

Ari: Okay.

Stephan: There was actually, I figured it’d be worth mentioning, a recent randomized controlled trial that was particularly notable in this regard. They used cocoa flavonoids or flavanols, which is a type of polyphenol compound found in cocoa. They gave it as a supplement to people for an average of, I think 3.6 years. Huge study, tens of thousands of people. They found signs that it may have reduced cardiovascular events in these people. If you look at it, honestly, it’s a mixed bag. The primary outcome was not quite statistically significant. There was a trend toward reduction in all cardiovascular events.

Some of the secondary outcomes were statistically significant, but if you look in The Carnivore Code, he’s arguing that these compounds are actually harmful. Whereas this trial is an actual randomized controlled trial with real cardiovascular outcomes, not biomarkers, suggesting if anything, that these compounds are beneficial. I think, if you wanted to be real hard-nosed you could say, “This doesn’t provide much support that they’re beneficial,” but it certainly doesn’t suggest that they’re harmful under any circumstances. I think this is what the literature on these plant compounds looks like as a whole. I think that’s pretty representative of what it looks like.

Ari: There seems to be a problem when you try to take an individual study, it’s almost like this attitude of pretending like there is no body of nutritional scientific evidence that has been created for the past several decades by new nutrition scientists all over the world, and then taking each individual study that you encounter, and saying, “That one’s limited by this. There’s this wrong with it and that wrong with it. Look at this aspect of it.”

There is a need, in my opinion, to look at an entire body of evidence, and to your point, Mario, that you were just making a minute ago, what is the direction of the overall, all of these studies together, both observational and randomized controlled studies, what direction are they pointing in? If they’re virtually, all pointing in a particular direction, does it make sense to conclude “no, all of those studies are garbage? Actually, the complete opposite is true.”?

Mario: Yes. I agree with you.

Ari: Do you guys have any final thoughts on The Carnivore Code?

Stephan: The only thing I’ll add is that I think the anecdotes are intriguing. I don’t want to completely discount the possibility that there could be something there that’s worth scientific study. That’s what I put in my review is there’s very little evidence, the claims are grossly exaggerated for this diet. That doesn’t mean that there’s no benefits. I think it’s possible that these anecdotes are pointing in a direction where we could learn something scientifically.

What are Lectins?

Ari: Well said. I agree. Particularly for certain subsets of people who — I have seen people who have reported that they’ve had longstanding gut issues, that veganism made them feel terrible, and they react horribly to many different kinds of plant foods. For that subset of people, excluding plant foods may very well be a huge breakthrough for them feeling better.

Let’s get into Dr Gundry’s book, The Plant Paradox, on lectin. First of all, can you guys talk about what lectins are?

Mario: I was a primary viewer of The Plant Paradox, so I’m going to take that here primarily, but Stephan, feel free to chime in anytime. Lectins are just proteins that are very ubiquitous in nature. Humans make them, animals make them, plants make them. There’s a lot of different structure. Lectins are not one family that’s defined by its structure. It has a lot of different structures, but one thing they all have in common is that they bind sugar. They have at least one binding side for sugar, many times more binding sides. Commonly, lectins are referred to as sticky proteins.

They’re proteins that if you added them to something biological, say to a cell culture, they stick to stuff, because say cells, for example, express proteins on their surface, and these proteins often have sugars, let’s call them sugars for simplicity sake, sugars attached on their surface. That allows these lectins to bind to these sugars. Sometimes people even say lectins are a type of class of molecules that can help us read what is sometimes called the glyco code, the code of sugars attached to molecules on the surface. Because these sugars actually do affect sometimes the function of these proteins and so forth. They’re very specific, usually, every lectin is very specific for one particular kind of sugar.

Ari: What claims are made about lectins in the book, in The Plant Paradox?

Mario: The central theme is that The Plant Paradox claims that lectins from particular plants, and specifically plants that we have not been able to evolve to throughout evolution, so plants that were introduced into the human diet just in the last 10,000 years or so, that we are not adapted to dealing with them, and that they are causing a large number of diseases. There’s pages and pages of listing, I think, 50 or so diseases ranging from autoimmune disease to diabetes, obesity, heart disease, all kind of Parkinson’s, Alzheimer’s.

Basically, it’s, you could almost say the vast majority of most chronic diseases that we’re all at some point suffering from, the claim is that lectins play a role or a causal agent in the development of those diseases. The argument, I think, because it’s a complex topic, to break it down a little bit for people following this discussion, is such that the argument is there’s lectins in these plants, and we’ll get to which plans are particular critical. Then we eat them, they get into our gastrointestinal tract. These lectins are not digested properly. They get into a bloodstream.

There they attach to cells that have all these different– Specifically to specific cells based on what sugar they’re specific for. Then the immune system reacts basically to those lectins and causes inflammation in those areas, and destruction. That then causes, depending on which cell and which tissue type has been bound to by the lectin, causes destruction in those types of tissues. To maybe take this apart a little bit, so to start from the beginning, the plants that are particularly the focus here in this book, are those, as I said, that have just been introduced into the human diet in the last 10,000 years or so.

Particularly legumes, they are by far the richest source of lectins, whole grains, nightshade family vegetables. Those are tomatoes, eggplants, potatoes, peppers. Cucumber family vegetables; squashes, pumpkins, cucumbers, and so forth. Those are the core foods that according to The Plant Paradox have the highest concentration of plant lectins that our bodies are not well adapted to. That part is definitely true. If we look actually at the evidence, there’s huge evidence and showing very nicely, actually, we don’t know the concentrations in many cases, but lectins are very abundant, particularly in legumes and grains.

That part is definitely true. Then the issue is that when we eat those foods, the claim is we may be ingesting those. Here’s, I think, where we need to take a closer look at the evidence, because when you, say, eat a legume, you typically cook it. If you, say, take a kidney bean out of a package, you really cannot eat it raw. That’s actually an interesting tidbit that maybe many people are interested in. If you were to try to eat, say, raw kidney beans, they’re really highly toxic, and you may end up in a hospital. In other words, the argument that lectins are toxic to people definitely holds water.

It’s true. We should not be eating large amounts of these lectins. That’s exactly why humans have developed techniques to cook these foods. If you cook them properly, so,

to stick with this example, kidney beans, if you soak them and then cook them long enough, or particular if you cook them in a pressure cooker, you reduce 98%, 99% of the lectins in the kidney beans. I’d say there’s some lectins potentially left, small amounts, very small amounts, and we can discuss later whether that may be an issue. First thing for people to understand is yes, lectins are toxic. They’re not desirable.

At the very least, they’ll give us some digestive issues. We can get diarrhea, abdominal cramping, if you eat lectins. Humans usually have evolved ways to process foods in a way that dramatically reduces the concentration of lectins in all of those foods. Actually, I will take that back, it’s not all of those foods. In legumes, we usually cook them. If you cook them long enough and they’re ready for you, you feel like you can eat them, their lectin content is usually very, very low, a small fraction of what it was at the beginning. For grains, similarly. If we soak or ferment a grain and then cook it, again, it reduces the lectin content to almost entirely.

There are some foods obviously that we eat that are not maybe prepared that way. Peanuts come to mind because very often we may be eating peanuts just briefly dry roasted. Dry roasting is likely to not entirely destroy the lectins to the same degree as we see, say, with cooking or pressure cooking kidney beans. Others are, say, tomatoes or peppers, because the lectins are actually in the skin or the seeds. Say, with tomatoes, you usually do eat the whole tomato, which includes the skin and the seeds. If you eat that raw, you will be exposed to some tomato lectin. Maybe let’s keep that in mind that usually we will have some exposure to some of these lectins.

Ari: There’s debating a few different directions to go from here. Let’s talk about what you just mentioned a minute ago, which is, is that a risk? Is it a risk to consume some small amount of lectins? Let’s say someone’s thinking after listening to what you just said, that beans have these toxic compounds called lectins. Even if I cook them, they’re still 1%, 2%, 3% of these poisonous lectins in there. Am I going to be harmed by that? What does the research say about consuming a very small amount of lectins, and the potential for harm from that? Maybe connecting that to the broader literature around populations that consume large amounts of lectin-rich foods, and long-term health outcomes.

Mario: Short answer is we really don’t know. There’s lots of research to be done, I feel. The biggest issue that I think I had with the book is that claims were made that were partially supported by something in the literature, cell culture experiments, mostly animal experiments in mice. Then the claims were exaggerated. They were translated to human disease where in usually most cases there was absolutely no evidence linking them. Let’s use one specific example. Let’s use maybe peanuts because I mentioned that earlier. Peanuts are often eaten just dry-roasted.

The degree to which lectins are reduced in a food are related to how long it’s cooked, the pressure which it’s cooked, and if it’s wet versus dry-cooked. A peanut basically being roasted briefly and not with water, and not with pressure, you would expect there’s some percentage of the peanut lectins still in the peanut when we eat it. There’s good research for most lectins actually, that lectins are poorly digested. That’s an important finding actually that I found very interesting because when I was in graduate school in nutrition 25 years ago, I was taught proteins are digested in the stomach.

What arrives in the small intestinal tract is just basically amino acids or little, shorter snippets, what we call polypeptides, not the intact immunogenic protein anymore. It looks very clearly there’s good evidence for peanut lectin, good evidence for tomato lectin, good evidence for garlic lectin that they pass through the gastrointestinal tract mostly undigested. You can detect them in the stool in animals. There’s good reason to think this could be true in humans as well. I think that’s already an interesting thing that certainly distinguishes lectins as a somewhat different type of protein.

There seems to be something in its evolution that it has evolved to be resistant to digestion. Peanut lectin, I think we can fairly assume, will get to our small intestinal tract, to the site where it’s absorbed, in a way that is fairly intact. Now, the book basically says lectins in general trigger what is called leaky gut. That would include that the epithelial cells in the gut basically open up a little bit, and larger molecules can just enter. Again, I’d say there’s evidence for this in animals, no evidence in humans whatsoever. For peanut lectin, we can clearly say that it does enter the bloodstream because there is at least one paper I’m aware of.

Then in which we can find intact peanut lectin actually in the blood that you can detect with antibodies. Most people actually carry antibodies against peanut lectin in their blood. There’s clearly been exposure in those people to intact immunogenic peanut lectin. Immunogenic, meaning it’s an intact protein that our immune system can react to and bind, create an immune response to. All of those facts we know for peanut lectin, and they’re all very interesting actually. I would say I think that already is a cause for concern.

Beyond that though in humans, we know nothing. There’s no link ever that I’m aware of, linking peanuts to — I’ve looked quite thoroughly actually, even yesterday night, still to see how– Because I’ve reviewed The Plant Paradox three years ago, so I wanted to make sure maybe there’s some killer new science that we now have. There’s nothing that I could find that actually says, “Now, if this peanut lectin gets into the blood, what does it do there?” The Plant Paradox would argue now, it can maybe attach to some tissue. There’s again, evidence from cell culture that peanut lectin can attach to the cartilage and joints.

What you would expect then, if that were to happen, is that the peanut lectin attaches to the cartilage and joints, and the immune system attacks. Somehow in the process of the inflammation that develops, partly destroys the joint. Maybe that could be one of the contributing factors for something like rheumatoid arthritis. Then what we would expect to see is that peanut consumption would at least loosely, at some point, be associated with rheumatoid arthritis. I’m not aware of any such study. I’ve looked specifically for those types of links.

As we know, particularly in observational studies in nutrition, if there’s one critique, then that we may be looking at too many of these links. You can find association studies for almost anything. Vitamin K is linked to Alzheimer’s or osteoporosis. People look at everything. If it’s positive, it’s going to be sure to be published. I think actually that is somewhat of a concern with nutritional epidemiology. In spite of that, I have not been able to find really any evidence that that’s the case. That’s an important one. Because it gets into the blood and the immune system may respond to it, it’s a large stretch then to now say, it is the cause of an autoimmune disease.

I think that’s important for people to understand. We can do similar things. I’ve done similar things, say, for legumes. We look at legumes, could well be that small amounts of lectins remain in the legumes even if they’re properly cooked, or tomatoes which we often eat raw, as I said earlier. It’s possible, again, that they actually do get into our bloodstream, that they trigger an immune response. I’m very open actually to the possibility because I studied as a researcher for a long time. Low-grade chronic inflammation.

It’s really important for us to try to be open to all different types of sources of that inflammation because really we don’t know in many cases what causes these inflammatory diseases. I’ve really been open to the idea, could this be true? I’m still open. I think it’s really an interesting hypothesis, is how I would frame it. When we look at populations that eat the most, say, tomatoes, or the most legumes, for most health outcomes, including those that according to The Plant Paradox are caused by these lectins, we actually see the opposite of what we would expect if that was true.

Ari: If I can summarize paraphrasing and maybe adding a bit of my own commentary here, someone listening to this might still be very concerned about eating lectin-rich foods, given everything that you just said. They might still be thinking, “It sounds there’s a pretty reasonable case that these lectins could potentially be really harmful and poisonous to us, and it sounds like cooking is not a perfect solution. This other thing about humans probably not digesting a lot of lectins also may not be a perfect solution. Maybe it’s better for me to avoid these lectin-rich foods.”

(So given that someone may still be thinking that), what does the literature say more broadly about populations that consume foods like legumes that are very rich in lectins, or lots of tomatoes, maybe raw tomatoes, things like that? Based on looking at that level of research or randomized controlled studies where they maybe have a group of people with, let’s say diabetes, introduce legumes into their diet, and then they track biomarkers over a few months. What do those kinds of studies tell us about the relationship of lectins to human health?

Mario: It’s very clear that in all the kinds of studies that I’m aware of, observational studies, let’s say, let’s start with that people and populations who eat the most, say, legumes typically have good health outcomes associated with that. People who eat more vegetables, including nightshade vegetables, have better health outcomes associated with that. In intervention studies, people who increase their consumption of legumes, or people who increase their consumption of vegetables, including nightshade vegetables, have improved health outcomes associated with that, including for example, reduced levels of inflammation commonly.

Again, I’m not familiar with any study really that would suggest that, say, eating legumes is the thing that gives you autoimmune disease, and cutting out legumes will cure these autoimmune diseases. What I was just discussing is I feel like in science we need to be open to new ideas. I’ve been dismayed sometimes by scientists who hear something like this about lectins, and without ever looking into the literature they immediately say, “Rubbish. It’s all rubbish. Lectins are great. We should be eating all these foods.” Yes, I’d say we should be eating all these foods. If viewers or listeners want to know, I do. I eat plenty of legumes and vegetables.

Ari: After reviewing this book in-depth, and after spending a lot of time looking at the literature, specifically being open to and trying to find evidence that supported a link between consumption of lectin-rich foods and these various diseases like the claims in the book were making, after spending all that time doing that, you are still eating lots of lectin-rich foods.

Mario: Yes. I just make sure I prepare them properly. I think that’s an important point. I think it’s important for people to understand the science behind this. There is science, mostly in animals, that suggest these lectins, if we eat them, they can get into our bloodstream, that they’re bad. We have no evidence whatsoever in humans. That’s, in my mind, this huge jump that the book makes, where it takes a large body of evidence from cell culture and animals, and translates it to humans. The important part here as well is if you look actually…

I probably read close to 200 papers on lectins, and the animal literature specifically. If you’re a researcher, how do you test with lectins have negative health effects? You order some isolated lectins from the chemical company and put it into the animal’s food. I’m not kidding. Those animals in studies that have shown, for example, that lectins may cause what we call leaky gut, they’re using lectin concentrations that are hundreds of fold higher than what we would ever be expected to eat. It’s almost certain that those findings are not really translatable to the human situation where we’re actually eating food, or mice being fed uncooked beans.

Actually, that’s another very common method. I think we need to be very, very careful. The dose makes a toxin, that’s for sure. If we study a model just to understand some basic science– I’m not saying the model is wrong. I think it’s good that they’re doing these studies, but then if someone comes along and reads these studies and immediately draws conclusions to not ever eat these foods again, even though the concentrations that we would be exposed to in properly prepared legumes, for example, are maybe 1% or less of what is used in these studies.

I think that’s a problem. That way, in the end, we can make the case for almost any food that it has some negative health effects. If we’re focusing on that one negative health effect that’s been shown, let’s say with meat, we can focus on the fat and the saturated fat content and say, “It may raise LDL cholesterol, so better not eat meat.” If we focus on lectins, we’re not going to eat any legumes and vegetables, and in the end we’re going to end up eating nothing. That’s a silly approach, right? What we really need to look at is the totality of the evidence.

The totality of the evidence right now tells us, I’d say with a high degree of confidence, that legumes are good for us if they’re prepared correctly. Whole grains and vegetables, good for us if we prepare them correctly. I think it should be the take-home message of people. As a result, in our review, the scientific claims made in the book didn’t fare all that well. People who are interested in this should really look into it. Just because I’m saying I’m open to these ideas, I’m looking at the literature, doesn’t mean at all that the claims that these lectins actually are the cause of chronic disease, are supported by anything really.

How Some Toxins May Improve Health

Ari: You brought up so many good points there. A few things I want to comment on. One is I saw a funny meme recently where they showed a picture. I’ll tell you what the picture was in a second. It was a picture and it had text written on it that said, “Vegan, sugar-free, dairy-free, paleo.” Da, da, da, da, da, a bunch of other things. That was a picture of a plate with several ice cubes on it and nothing else. I think to your point that you were making a minute ago of if we’re fearful of this and we’re fearful of that, and we’re fearful of this, we’re ending up in a position where everything is bad for us.

We also, I think, need to consider, I’ve seen a lot of evidence of this in the people that I work with, we need to consider the effects of the nocebo effect, and whether– This is the placebo effect but in reverse, for people listening who have never heard that word. The idea that having a certain belief that consuming something can harm you will actually harm you, will actually lead to very real harm because you believe that is so.

I think that there is a strong case to be made that in many instances, people can have a level of stress and anxiety, and fear around consuming certain foods where the negative emotions that they have around it are actually far more harmful than the food itself, even if that food, let’s say sugar or saturated fat, or something like that, may actually have some true negative physiological effects. I think lectins is a good example of that. Certainly the idea that we’re talking about with the carnivore diet, that plants are full of toxins, and most plants are things that are going to be harmful because they have these toxins in them.

I think these kinds of ideas are not only not aligned with broader body of scientific evidence but are potentially harmful by virtue of creating nocebo effects where none should exist.

That’s one thing I wanted to mention.

The other thing is the idea of potentially a biphasic dose response. To your point that you were making a minute ago where everything could be harmful when you do experiments in this kind of way, where you take isolated extracts and give them dosages that are 100 fold greater than what’s natural in the context of, let’s say, a human diet.

For reference, everything could be harmful in this context. Someone could go get sun exposure. If you get too much sun exposure, you cause DNA damage and get sunburn, you can potentially get skin cancer. Yet the sun is also profoundly beneficial for health when in the proper dose. If you consume two gallons of water in the next 10 minutes, you can cause permanent brain damage and put yourself in a coma and die from water. Right? Everything is like that.

Exercise is like that, if you do too much exercise, you take a sedentary person, tell them to go run a marathon, they may have a heart attack and die, or they may cause so much muscle damage that they have rhabdomyolysis and have a huge amount of harm for that. None of this means that sun is harmful or water is harmful, or exercise is harmful. It means that, as you said, that dose makes the poison. It also begs the question, what if lectins, in the proper dose, not proper dose, but in a low dose, might not only not be these horrible toxins, but might actually be beneficial like many things are in low dose?

Even if you look at the hormetic research, there’s crazy things like radioactive compounds and mercury, heavy metals and things like that that have been shown to be beneficial when dosed in tiny doses. I’m skeptical of the idea that something is just toxic, period. There are certain examples of that, but something that humans have been consuming for very long periods of time, I’m skeptical of the idea that consuming very small amounts of it are going to be just horrible toxins for us. Do you have any thoughts on really anything that I just threw out there?

Mario: I think those are very good points. I can actually cite from the review on this last point you made, and that is that if you look at the scientific literature, you’ll actually find a lot more papers looking into potential beneficial, specifically anti-cancer effects of lectins. Then you find linking lectins to health problems in humans. Personally, I will say that is probably because lectins are somewhat toxic, and the idea is they may be more toxic to fast-growing cancer cells. In my mind, that’s not a great point in favor of lectins. I think we should still try to limit them.

As you said, people living in fear of very small amounts of lectins that may still be in the cooked kidney beans, they’re going to miss out on the greater benefit of actually eating a diet rich in those foods because based on everything we know, the beneficial impacts of eating those foods far outweigh the potential risks that we, I think, should be considering. At this point, they’re just potential and theoretical risks because there’s really not– If at least there was a few observational studies that said, “Peanut consumption is associated with rheumatoid arthritis, or kidney bean consumption is associated with,” but none.

You’ll find none of these. Really, the only thing that’s been published is one conference abstract by the author of The Plant Paradox that is very short on details, in which he describes cases of patients in his office that have gone in his Plant Paradox program, and have reversed some diseases or seen some health benefits from it. It’s a 200-word abstract or something like that. It’s really not the kind of peer-reviewed, high-quality evidence that I think anyone would want to base any important decision on.

Stephan: You mentioned the ice cube example. This brings up something that I think is pretty interesting from The Carnivore Code, which is that Saladino even argues that tap water is riddled with toxins and we shouldn’t be drinking tap water. There’s very much a focus on purity of the things that you’re putting in your body to a very extreme degree in that book, like any trace of any kind of toxin is enough to rule out the consumption of a food or beverage.

I think that, to your point about the psychological impacts, and by the way, I’m not discounting that some people might benefit from this diet. I’m not saying that’s not the case, but I think we have to consider potential harms too of developing this extreme purity mindset. Some might call it orthorexia, where you develop an unhealthy psychological relationship with food. That’s a risk psychologically, and that psychological risk could also bleed into physical risks as well because of the connection between the two.

Ari: Well said. I have some personal experience with that. That’s why this issue is personal for me. I would say I generally agree with, and I would imagine you do too, at least to a large extent, Stephan, the wanting to have only pure things going into your body. I’m extremely health conscious. I’ve been studying nutrition for over 25 years since I was a kid, since I was 13. I’ve tried really every extreme diet out there imaginable. I’ve spent periods of–

I’m older and wiser now, but I’ve spent periods of time where each phase that I was in where I went vegan, or I went to a low-carb keto, or I went here, or I went there, in every phase, I can watch myself be utterly convinced that this diet is the one true best diet. Now I’ve finally found the truth. Now I realize that these particular kinds of foods really are toxic and I have to get rid of them completely. I’m an extreme personality in the sense that I’m drawn to those kinds of extremes, so I implement them full force with a level of obsessiveness.

It absolutely has resulted in periods of time where I’ve been orthorexic where I’ve been causing myself pretty intense nocebo effects. There’s so much stress around the purity of everything. The concern, the fear of harms of this for that food. Thank God I’m in a more mature, wiser, older relationship with food now where I’m more relaxed about all that, but I’m also still — there’s a balance with also still being quite health conscious.

Like the water for example. I filter my water. I do want pure water, but I also don’t have a really unhealthy fear of if I drink some bottled water every now and then, or water they give me while I’m on a plane traveling. I’m not definitely afraid of that or something like that. Yes, I think it’s interesting how you have to find that balance between being health conscious but not creating harm by being orthorexic and neurotic about the whole thing.

Mario: I agree. I think we should have a much better, more positive attitude towards our food. Ultimately, it’s wonderful that we have such a rich — particularly we in Western countries, like we have such a rich, fairly affordable selection of nutritious foods. Just to look at everything and mostly see lectins and phytates, and saturated fatty acids, I think that’s it. What kind of way to live is that?

It’s almost like you see everyone you meet as a potential criminal. I like to have a much more positive attitude towards things, and including food. We should be open to potential negative effects and study them, and know about them. I think what we’re seeing a lot in this box is a type of exaggeration of various theoretical and potential risks that I agree could potentially be harmful in the long run to people.

Ari: It’s worth saying this directly, I think. This is I think an important thing to bring up. There are massive financial incentives for people to distort the scientific literature. Diet books, that’s a big business. There’s always, going back decades now, there is a massive financial incentive for someone to come out with the next big thing that goes viral. The next diet that becomes like a low-carb Atkins trend or a keto trend, or a paleo trend, or one of these big trends. If you start that trend, you can make many, many millions of dollars by convincing people that that new diet that you’ve discovered is the one true best diet.

Stephan: I think there are psychological incentives too. I think that the people who write these books that are successful, they become revered. I think for some of these people, that’s also a major incentive. Also painting a simple story that is cognitively the path of least resistance. I think there’s a powerful psychological incentive as well as the financial incentive.

Ari: I just found how to remain in the scientific position. Of course, you have to do what you just said.

Stephan: It’s the charitable position too, trying to give people the benefit of the doubt. With Red Pen Reviews, we just really try to stick with the evidence, how well is it supported, and not worry about what people are thinking or what their motivations might be.

Ari: Right. Sorry, go ahead, Mario.

Mario: I think that’s important though. I think this focused on we’re evaluating scientific claims, not people. I think what you said is still a very important, Ari. All I would like to add to this is I think it’s maybe good idea for consumers of any content, be it online or in book form to maybe ask themselves sometimes, what’s the motivation here? What am I being sold specifically?

I think that’s maybe a good thing to have somewhere in the back of your mind. We try to stay out of this because for Red Pen, personally, I think it’s better if we don’t attack people and we don’t try to attack whatever their motives may be, but just focus on the claims and whether they’re based on evidence. That’s how we’ve decided to go about it.

Ari: Yes, absolutely. I think that’s the smart way to do things. Do you guys have any final words on The Plant Paradox? Anything you want to add to that before we conclude?

Mario: No, I think we’ve said main things. Maybe one thing I would like to add, and that is, because people may be confused about getting some of the messages. They may hear from people like this book, the author and this other says, “I’ve reviewed as well the blood type diet book for Rep Pen, which also basically argues that lectins are bad for you, but they have a qualifier. They say lectins are only bad for you depending on what your blood type is. People may be confused hearing this and then hearing all these excess stories.

Sometimes celebrities saying, “I cured my Hashimoto’s thyroiditis or my XY disease by going on this diet.” Then they hear from scientists saying, “No, everything’s good. You eat your legumes, it’s all fine.” I’m hoping that we can convey a bit more of the complexity of science and say, “At this point, the totality of the evidence very clearly says there’s a lot more health benefits associated with eating these lectin-rich foods. Just make sure they’re well prepared.” If you have health problems right now, that’s maybe the one qualifier would say.

Let’s you do have an autoimmune disease and you do eat a lot of a certain lectin-rich food, and you’re not sure if it’s properly prepared. Let’s say you do eat peanuts regularly, or you do eat raw tomatoes all the time. For some reason, you have some health issues you can’t figure out. Just experiment maybe with leaving these specific foods out. Don’t then immediately jump to a conclusion that all lectin-rich foods are bad and go on a diet that suddenly doesn’t have any legumes, any grains, any nitrate, because it’s possible that you’re going to do more harm by doing that.

I think a targeted approach to say, “I learned from this. I’m aware some foods may actually have higher concentrations of lectins if they’re not properly prepared, not cooked fully.” I think peanuts and tomatoes are the two that really come to mind because they may still have somewhat higher lectin concentrations in the form, that we experiment with maybe cutting these out for maybe a couple of months or something like that to see, does it help me at all? We’ll be open to that, but I think in general this approach of theoretically something could be bad, so let’s cut out a third of the human diet or something like that, it’s a little bit–

It’s not a proportionate response to the actual degree of evidence. The degree of evidence, you could say, is you have maybe a little bit of evidence that theoretically something could be going on there. It’s an interesting class of molecules, but then our response is like this, like, “That doesn’t make any sense to me.” I think we need a measured way to handle this. Understanding this well, and then having a measured response, is, I think, the right way to handle these types of things in general.

The Issues With Nutrition Studies

Ari: Actually, this reminds me of one other thing I wanted to bring up earlier that I think is important, in the context of really both of these two diets that we’ve talked about. That is that there can be subsets of people who are the exception to the rule, who maybe don’t show up in the broader body of scientific evidence. In other words, let’s say we have a body of evidence saying seafood consumption is really beneficial for health, but here’s this guy over here who eats three cans of tuna every day. Now he’s got mercury poisoning, and now he’s suffering really severe consequences from consuming that seafood.

That’s someone who he’s over there going, “Hey, but I’m eating seafood and I feel terrible.” Then we respond to him, “Look at this body of evidence. Clearly, it’s not the seafood, because we know that seafood is linked with beneficial outcomes.” I think the same could be true with lectins, for example. You can have some subset of people that do genuinely react negatively to, let’s say, nightshades, and they have joint pain from them.

That doesn’t show up in the broader body of evidence since most people experience only beneficial effects or mostly beneficial effects from that. I just want to bring that up. The same could be true with the carnivore diet. Again, there’s a subset of people that might react negatively to almost any plant food if they have dysbiosis and severe gut dysfunction, or something like that. If you guys want to follow on that with anything.

Stephan: I think related to that, as I mentioned earlier, the scientific literature is mostly concerned with the relationship between foods over disease risk. Are you going to develop type II diabetes, obesity? Are you going to have a heart attack? I think there are a lot of other health-related conditions that people have that aren’t really very well represented in the scientific literature and remain quite mysterious. Irritable bowel syndrome or other digestive distress that people experience regularly. Low energy levels, depression. Even aside from depression, just not feeling very good.

I think that those are the places where people might not be thriving and we don’t really know why, and the scientific literature doesn’t have anything to say about it, or maybe not much to say about it. I think there’s room for some of these things to be correct. Particularly if we’re thinking about digestive health. It’s not at all implausible to me that there are certain plant compounds that don’t play well with certain people’s digestive tracts or microbiota, and that eliminating those would be helpful.

Maybe eating a pure carnivore diet is like bringing a gun to a knife fight. It’s certainly not implausible to me that that could be a way that some people get helped. Maybe some people have a really totally messed up microbiota, and minimizing the microbiota by not eating plant foods is helpful to them. I think there are a lot of gaps in our knowledge here that relate maybe not so much to disease risk but more to how do we thrive as human beings. I don’t want to discount the possibility that some of these ideas could be correct, at least for some people. I think there’s potentially a lot more to learn here.

Ari: Well said. Mario, do you want to say anything?

Mario: No. I’m just nodding. I agree with everything that you said. I think exactly the same thing. That’s why I said be selective. If you have some issues, and say, you eat a lot of tomatoes or peanuts in that particular example, I said, again, based on the research I’ve done, I think it’s theoretically possible. That could cause some issues for some people. That’s why I think it’s important to maybe get that more measured message out there and not say, “Oh, no. No worries. They’re all good,” because that creates this huge contrast with the claims made that are out there that say lectins are terrible and they’re destroying your health.

I think the truth actually is, based on what we know, I wouldn’t say in the middle, but there’s a little bit to this. We shouldn’t totally discount the literature on lectins. At least tell people, “If you have health issues, just look a little bit at what you’re eating. If you eat a lot of lectin-rich foods that are not fully cooked, maybe experiment with leaving this out.” I totally agree. I agree with what Stephen said as well. I think these are maybe good takeaway points to say we should try to find a balance in how we view these things rather than just having these extreme views that we’re drawn to because they promise a quick fix, a quick solution.

Red Pen Reviews

Ari: I think that’s a very nice way to wrap up. The last thing I want to mention here is just the work that you guys are doing, Red Pen Reviews. Obviously, we described what this is all about at the beginning, but I want to just say a personal word, that I think this is really one of the most important things that is going on right now in the world of nutrition and the interface between nutrition science and the general public, what the general public believes about nutrition. As I was getting at earlier, making my guests uncomfortable, a lot of these financial disincentives, financial incentives I should say, have led to a lot of misinformation.

Just rampant competing contradictory claims by many different diet gurus. There’s lots of stuff out there that’s just wrong, or maybe has a grain of truth in it, but is 90% wrong, and is not an accurate representation of the scientific evidence even though the diet book author is claiming themselves to be in possession of the truth. I think the work that Red Pen Reviews was doing to review these books, and that the public can have a place to go to verify the accuracy or inaccuracy of some of these different claims, I think is an extraordinarily important service for the general public.

I personally love what you guys are doing. I’m going to be supporting you guys personally with a donation of my own. I also want to let listeners know that, as you mentioned earlier, you drive your Toyota Sienna minivan. [chuckles]… Obviously, you guys are doing good work. You’re doing extremely important work, but you’re not being rewarded financially for it. Please just have a few words with our listeners as far as how they can support you.

Stephan: Thank you so much, Ari. I appreciate that. A very simple, effective way to support us is to donate to Red Pen Reviews. It’s an organization that operates really on a shoestring. We are currently transitioning to paying reviewers a modest sum for each review. This is a way for us to incentivize reviews and improve our ability to recruit. It’s really a very modest amount but it really helps for us to be able to do that in terms of incentivizing these reviews and increasing the volume of reviews that we can produce, and so donations are really, really helpful.

The other thing is spreading the word. If you can just go to our website, check out our reviews, join our mailing list. Then when we publish these reviews, spread them around social media. Share them with your friends. It’s amazing the number of people that I meet who are into nutrition and haven’t heard of Red Pen Reviews. I’m just amazed. There are still people who need to hear about us. The third way is for people who have a master’s degree or equivalent or higher in nutrition, we are always looking for new reviewers. If you are interested, please contact us and apply. Maybe you can join the team.

Ari: Awesome. Thank you guys so much for coming on. Thank you for all the extra time, a good two hours of your day. I really appreciate it. I think it’s a very important service that you guys are doing for the world, so thank you so much. Thank you for being so nuanced and balanced, and charitable with how you spoke about everything today. I really appreciate everything you guys are doing, so thank you. I hope to do this again maybe after you do a couple more diet book reviews. We can talk about those too. I can have you back on the show.

Mario: Thanks so much, Ari. It was fun talking to you. I hope this was useful to people. Thanks for the invite.

Stephan: Thank you.

Show Notes

Intro – 00:00
Guest Intros – Dr. Stephan Guyenet and Dr. Mario Kratz – 00:52
What is Red Pen Reviews And What Do They Do? – 11:49
The Carnivore Code – 20:07
What Is The Optimal Human Diet According To Research – 23:19
What Studies Tell Us About Modern Hunter-Gatherer Diets – 28:20
Does The Carnivore Diet Really Prevent And Cure Common Diseases of Lifestyle – 31:40
How The Carnivore Diet May Lead to What Are Lectins – 1:05:40
How Some Toxins May Improve Health – 1:27:40
The Issues With Nutrition Studies – 1:44:24


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