GreenSmoothieGirl Logo
Lose 10 Pounds in 10 Minutes. Add 10 Years to your life.
Our beautiful template for infinite variety of greens and superfoods in your smoothies—print this and eliminate the need for recipes! Get it now for free!

Ep. 156: Reviewing “Grain Brain,” “The Plant Paradox” and “The Bullet-Proof Diet” with Stephan Guyenet, PhD

Robyn Openshaw - Nov 06, 2019 - This Post May Contain Affiliate Links

Vibe Podcast 156 Stephan Guyenet

Dr. Stephan Guyenet researches whether fad diet books are useful, or not, based on scientific evidence. This is a really interesting interview, learning what his team of researchers discovered, diving into three trendy nutrition books that millions of people have purchased and read.


Check out Red Pen Reviews


  • [04:54] Frustrated by the “science” in fad diet books? It’s hard to evaluate the claims in popular health and nutrition books because there’s no standard to compare them to, and online reviews are little help. Luckily for us, Dr. Guyenet and Red Pen Reviews are working to change that.
  • [19:10] There are kernels of truth in most of them. Many diets will help you lose weight and improve your health in some way (because cutting out unhealthy foods does that!) But the scientific evidence to those claims of “why” are almost always stretched, or wrong.
  • [23:43] Is Grain Brain scientifically accurate? The author David Perlmutter makes strong claims that carbohydrates, gluten, sedentary behavior, and insufficient sleep is causing dementia and brain-related problem. But the strong science is not there to back it up.
  • [33:28] What about The Plant Paradox? The book claims that pretty much all obesity and chronic disease is caused by a class of substances called “lectins.” The author Steven Gundry claims that the scientific literature strongly supports this; the Red Pen Researchers say not even close.
  • [51:38] And finally, how is Bulletproof? Author Dave Asprey suggests his special coffee and lots of oils is the secret to losing weight and higher brain power. After analysis of his scientific accuracy, it only scored a 34% (and that’s higher than the two others!)


This transcript has been edited for clarity.

Robyn:  Hey there. It’s Robyn Openshaw. Welcome back to the Vibe show.

Before I jump into this week’s interview, which is pretty cool, I want to just drip a little teaser on you that I had the nephew of the president, John F. Kennedy on the show. He is the son of Senator Robert Kennedy Sr., he is Robert F. Kennedy Jr. He’s an attorney and an activist (he’s not the Chappaquiddick guy. He’s the son of the Chappaquiddick guy, if I’ve got it right).

[Robert F. Kennedy Jr.] has pledged the rest of his life to advocating for better safety in vaccines, and better information and better reporting, and getting pharma out of the mix with the testing because they suppress a lot of results. They cherry pick the data and they’re way, way, way too involved with the regulatory agencies. And now they’re even controlling public platforms like Google, Netflix Amazon, Facebook, Pinterest; people getting banned, lots of books and movies getting eliminated from the public views so that we cannot buy them or view them or read them.

It’s a very interesting time to be alive if you care about medical freedom. And we’ve got former pharmaceutical executives who get six figures to seven figures annually manning the FDA, the CDC, the vaccine administration, all the way up to the parent organization, Health and Human Services.

Today I’m introducing Stephan Guyenet, who is a researcher and a science consultant; he has a PhD in the neuroscience of obesity.

I came into contact with his work when I read an article in the Seattle Times that talked about his Red Pen Reviews, where he and another researcher with at least a master’s degree in nutrition review a major best-selling health or diet book, and really dig into the references. They basically do a multi-part review and then there’s a peer of the main reviewer to give it an overall rating on several different scales.

Today in this interview, we’re going to go through three books. That’s all we had time for. We go through their evaluation of the very popular book, Grain Brain. Then we go through Steven Gundry’s, The Plant Paradox (he just wrote another bestseller that’s a companion book to that). And then we go into The Bulletproof Diet.

I think you’ll find this very interesting. As you know, I have a major objective here on this show of digging into the science on a variety of things. I don’t have a dog in this fight with any of these three authors or their claims, and neither does Dr. Guyenet. So let’s get into it.

Welcome to the Vibe show, Dr. Stephan Guyenet.

Dr. Guyenet:      Thank you. Good to be here, Robyn.

Robyn:  I have been super interested to talk to you ever since I read this article in the Seattle Times about what you call “the volcano of nonsense” that is most of the books that are coming out on the bookshelves that people are gobbling up by the millions. And there were a few of them that caught my eye.

There is a cover photo on that article in the Seattle Times that shows four books, and I know pretty much all the authors (I don’t actually know the Plant Paradox guy; I don’t know that guy, but the other ones I do). And I have had serious misgivings about some of the nutrition information that’s out there, and that people are believing it because it’s in a book and the book is the New York Times bestseller or whatever it is.

Tell me about Red Pen Reviews and what inspired you to create it, and what that’s all about. And your qualifications, so we know how committed you are to really diving deep into these pieces of research.

Dr. Guyenet:      Sure.

I’ll start with myself just so people know a little bit about who I am.

I have a background in biochemistry, undergrad, and then my PhD work was in neuroscience. I continued as a postdoc at the University of Washington studying the neuroscience of body fatness and eating behavior. And that really got me into the world of health and nutrition, particularly as it relates to eating behavior and body fatness.

Since then I’ve been doing various things that all revolve around evidence evaluation. So basically the different things that I do professionally revolve around evaluating scientific evidence. And one of the things that I’ve found frustrating over the year — and I think this is a really common frustration for people, this is not just me — is that it’s really hard to evaluate the claims and popular health and nutrition books because we know that a lot of them are incorrect, right?

You have one book on the shelf and then the book right next to it is saying the opposite. So, one of them has to be wrong. This is a frustrating situation for people who are looking for accurate information.

I termed this “the exploding volcano of nonsense” and the author of the Seattle Times article, Carrie Dennett, picked up on that. This reflects my frustration and a lot of people’s frustration with the state of the health and nutrition publishing sphere.

But I do want to acknowledge that it’s not all nonsense, there’s a lot of good stuff out there as well. But the problem is how do you separate the wheat from the chaff? How do you tell what is good evidence-based information that will promote your health versus low-quality information that might harm your health. Or, might just erode your understanding of science or erode the broader public’s understanding of science.

I think that’s another big problem here, because you can have books that give advice where, if you follow that advice, it will improve your health. But it could be based on complete mumbo jumbo and conspiracy theory ideas that will actually erode your understanding of your body and the natural world.

The ideal scenario is that you have books that are giving you the right advice and justifying it using the right scientific information. That’s really what everyone would like to see. That’s the problem that I perceive — and that I think a lot of other people perceive — and that’s compounded by the fact that it’s really hard to get good information about these books.

Where do you go if you want to evaluate a popular health and nutrition book? Do you read a review on Amazon? Those are basically useless. Honestly, as someone who can quickly evaluate books that are in my own scientific field of expertise, when I look at the reviews on books related to that, I’m like, this is just garbage on Amazon.

The problem is that people don’t have the expertise. They’re paying attention to whatever aspects of the book caught their attention. It’s not comprehensive, it’s not accurate. And it’s not comparable across reviews for different books. If you look at health and nutrition books on Amazon, almost all of them are between four and five stars for books that are selling reasonably well. So, regardless of how good or bad a book is factually, it’s going to get a good review on Amazon overall.

Those reviews are essentially useless. And then we have reviews in newspapers that really aren’t that much better in, in major media outlets, including really respectable ones like the New York Times or the LA Times. They’re generally written by journalists who don’t have a background in that area. And again, who just write — and I’m not saying they don’t have any value, sometimes they do — but they often will miss things.

They generally don’t check references to make sure that the author is using them accurately, and they write about whatever aspects of the book suit their fancy. So, you could have a totally different review coming out from the New York Times than from the LA Times or the Washington Post because a different person wrote those reviews and they’re using a totally different method to evaluate it. That is invariably very subjective.

This is the problem that we’re facing. This has been an ongoing source of frustration for me for a long time.

Eventually, a few years ago I came across the work of this guy Seth Yoder, who is part of our organization now (Red Pen Reviews). And what he did was something very simple. He was taking these health and nutrition books and he was going through reference, by reference, by reference, every reference in the book — and just looking up the reference and seeing how well it supported the claim that the author was using it for.

It was super regulatory because some of these books that had gotten so much praise in major respectable media outlets, once you look up the references, it’s like wow, this person is really stretching it. Really stretching it in a way that is obviously, I would say, unethical. I would use that term.

I saw this and I was like, this is really regulatory. This simple technique right here is really shining a light in the way that these thousands of other reviews on Amazon and everywhere else are just not able to do.

I said, “How can we take this method and make it simpler, make it faster (because it is insanely time consuming to do that), make it simpler and faster, more reproducible, more unbiased, and more informative. Basically, how can we make this all around better?”

I gathered together a team of nutrition scientists — people who had a master’s degree or higher in nutrition or related field, something that relates to the things these books write about — and we designed this Red Pen Reviews method.

What it is — this is really the core of what we do — this method is a semi-quantitative expert book review method. Semi quantitative: what that means is we have basically a scoring guide that assigns numbers to our judgements about different areas of the book. For example, does the strength of the author’s claim of this particular claim line up with the strength of the evidence that person is citing? And then score that between a zero and a four.

If the author says, “Food X prevents cardiovascular disease,” and then we look at the reference she cites and it doesn’t say that, or it’s some really weak finding, then maybe we would score that a one. Opposed to if the strength lined up really well, then we give it a four. That’s just an example of what I mean by a semi-quantitative scoring rubric.

We’re putting numbers to this and we have this fixed review method that we apply the same way to every book, and every book gets a score using the same method.

In fact, that score is broken up into three categories: scientific accuracy, where we select three claims and evaluate them, three key claims of the book. Then there’s reference accuracy where we randomly select 10 references and evaluate those. And then there’s healthfulness where we apply some criteria to determine how healthy that diet is going to be.

At the end of the day, what you get is these percentage scores in each of those three categories, and then average together you get the overall score.

When you land on the Red Pen Reviews page, the first thing you see is like Rotten Tomatoes-type display where you have percentage bars (if you guys are familiar with that movie website), you get percentage bars that give you a lot of the information you want to know in like five seconds.

You just glance at that and right away you’re like, “Oh, okay. I know whether this person is making scientifically accurate claims. I know whether they are supporting their references or supporting their arguments with accurate references. And I know whether this diet will likely improve my health.” Boom, in like five seconds.

Below that is all the supporting information where we explain how we rated those books.

This is, in my opinion, the most informative and consistent and unbiased health and nutrition book review method that currently exists. We review a book, you get the scores. Those scores can be compared directly to other books. So you could say of all the weight loss books that we’ve reviewed, which one scored the highest? You can literally do that, compare numerically, quantitatively.

Whereas if you’re trying to figure out what’s a good weight loss book and comparing reviews on Amazon or reviews in newspapers or whatever, that’s going to be a very difficult task.

There are a lot of advantages to having this semi-quantitative review method.

Essentially, the big picture is we’re trying to give more power to readers, to consumers of these books to identify high quality from low quality. And we’re also trying to change the incentive structure of the publishing industry itself. Because this is really the fundamental problem that we’re up against, is there is no incentive to be truthful and accurate. And we can get into greater depth on what I mean by that. But I’ll just leave it at that for right now.

Robyn:  That was a good overview of what the problem is for the poor consumer out there who’s being bombarded with all these books.

Some of us are old enough to have been around when there are dozens and dozens of books being published back in the 1980s telling us the fat was going to kill us. Well, nobody’s buying those books now, and now we’ve moved on to books that tell us that fat is the only important macro-nutrient apparently.

We’ve got a 13-time New York Times bestseller who says — and I actually canceled my podcast interview with him an hour before, even though he’s probably would be the most famous guest I’ve ever interviewed because there was a quote in his book, and I really don’t think I’m paraphrasing here, it might have a word or two off — he basically said, “No human being should ever eat a carbohydrate.”

I just couldn’t interview him on my podcast because I felt like it was so out of integrity and so out of line with evidence that I canceled that interview. That’s a book that was his 13th New York Times bestseller, and I don’t think you’ve reviewed that one yet. We can have a side conversation about that one.

We’re going to be asking Stephen about several of the books that are either trending right now or have really captivated the imagination of Americans. I think you brought up a good point that with a lot of these books, it’s not like everything they say is categorically false. I call it “truth mingled with fiction.”

An example is — and I don’t think you’ve reviewed this one either because this one is not trending, it’s a 20-year-old book — I have a few times on my public platforms talked about the Blood Type Diet. People who’ve applied the council of the Blood Type Diet will often just rave about it and they’re very emotionally attached to it because they changed their diet to the prescription of the Blood Type Diet.

Well, the Blood Type Diet has been completely debunked by many people. And all you have to do is point out that, first of all, we’ve all intermixed and intermarried.

I don’t even think there’s going to be any more race really in a generation or two, we’re all marrying different races now. There’s all those political divides are coming down. I personally am with a person of a different race. And even though my family’s white all the way back to Adam, you can’t really say where did my ancestors come from and I should eat that.

Another thing is that every single blood type exists in every single indigenous people. That’d be an interesting one for you guys to review at some point.

What’s interesting is people will do the blood type diet that they were prescribed, and they’ll be like, “I feel great. So therefore,” (which is a logical fallacy), “therefore the blood type thing is a legitimate theory.”

And I say, “Wait a minute, take a look at all four of the blood type diets; all of them ban white flour and sugar and processed foods.”

That, all by itself — like one of them, you eat a lot of meat, one of them you eat no meat and is vegetarian — either way you’re getting rid of the processed foods. Everyone is going to feel better. Anyone going from the standard American diet to any one of those iterations of the Blood Type Diet is going to feel better.

That’s just to put a little fine point on, or an example on, what you said about the fact that people can go on these diets and feel better. Guess what? In 2019, all of the diets tell you to get off of sugar and garbage food. Am I right?

Dr. Guyenet:      Yeah, absolutely. I think this is an important point, and that is that all of these diets have a kernel of truth in them and sometimes more than a kernel of truth. Usually the truth lies more on the efficacy side of things than on the scientific accuracy side of things.

Maybe a diet, if you adopt it, it will help you lose weight. Maybe it’ll reduce your risk of diabetes or diabetic complications. But the evidence used to support the statements about the diet is used poorly, or is used a little too enthusiastically, or the effect size of the diet is greatly exaggerated. Things like that. I would like to give credit where credit is due.

Certainly, a lot of these diets probably are helping people to lose weight and feel better. But I really have a very low tolerance for science abuse. I don’t think it’s justified to be untruthful or inaccurate to people in order to convince them to go on some diet. I don’t think you have to do that. And I don’t think it’s a good idea to do that.

Robyn:  You were the primary reviewer on some of the reviews that you guys have written, and then you were the peer reviewer. Say just a little bit about what that is.

And then if I ask you a question about a specific nutrition book that everybody has been reading the last few years, you can qualify what you’re saying with, “I was this or that reviewer or not a reviewer at all.”

Dr. Guyenet:      We have this whole carefully defined method for reviewing each book. And in addition to that scoring rubric that I was mentioning, that gives numerical scores to different aspects of the book, we have this whole procedure that includes selecting a primary reviewer, which is the main person who is responsible for writing the review, and then a peer reviewer who checks his work.

We could just have one person responsible for each review, but we want these to be as informative and accurate as possible. And so we bring a second expert on to check that person’s work because even experts can make mistakes, and especially when they are examining topics that are outside of their area of expertise because when you’re a researcher, generally your main area of expertise is pretty narrow.

We’re reviewing a lot of different types of books and so it’s good to bring a couple of different brains together just to make sure that what we’re eventually going to publish is as solid as possible. Because really the success of our endeavor relies on having information that is as accurate and transparent as possible.

On the transparency side of things, I want to emphasize that we publish our entire review method on the website, so you know exactly what we’re doing when we review these books.

I was the primary reviewer on three of the six books that we have reviewed so far, and those books are Grain Brain, the Good Gut and The China Study.

Robyn:  And then you were a peer reviewer on some others.

These are the ones I’m going to ask you about today: I’m going to ask you about Grain Brain, The Plant Paradox, and Good Gut. And I might touch on Bulletproof if we have time. I haven’t read these reviews, I want to go read them in more detail.

Wheat Belly came out, and I don’t believe that you’ve reviewed that one, but between Wheat Belly and Grain Brain, a lot of people have gotten off of processed foods and they feel amazing. So they’ve decided that the conclusions of those authors — which is that gluten is killing all of us (and there are other books out there too) and that all gluten in all of its forms should be avoided like the plague — that idea has so captured our mindset that it’s now a multibillion dollar industry. These gluten-free processed foods, which now we have found out are four times higher in arsenic for instance. We may be just swapping one set of problems for another.

Talk to me about what you learned reviewing Grain Brain.

Dr. Guyenet: Grain Brain was written by David Perlmutter who is an MD, a neurologist, if I recall correctly. And a very charismatic person who, in addition to his books, he has these TV specials and videos and it’s really this whole empire, this Perlmutter empire of diet advice. And essentially what he focuses on is dementia. Particularly Alzheimer’s disease, but also other types of dementia.

Dementia is a huge problem, right? Dementia is not something that anyone wants to get, but there’s a pretty good probability that as we age we will get dementia, and we don’t really have a super clear understanding of why that happens, in terms of what’s the contribution of lifestyle versus genes and what lifestyle elements are contributing to it. There’s a lot we still don’t know about dementia.

Essentially Dr. Perlmutter has stepped into this void and has this very enthusiastic vision of what is causing dementia. According to him (and by the way, it’s not just dementia; this is a whole spectrum of brain related problems that includes headaches and depression and ADHD and all kinds of other brain related issues) he suggests that this is all caused essentially by carbohydrate and gluten, as well as sedentary behavior and insufficient sleep.

Not only does he suggest that this is what causes dementia and other brain related problems, but he suggests that science has clearly established that this is the case, that basically there’s tons of really clear research that shows that he is right.

He’s not just saying, “Hey, I’m speculating, this is an idea that maybe this is what’s going on.” He was saying this is what’s going on and this is what the scientific evidence suggests.

We evaluated his claims.

The three claims that I evaluated for the scientific accuracy section are that eating carbohydrates increases the risk of dementia; B) that high levels of blood cholesterol are healthy for the brain, this is another one of his central claims; and three, that gluten is a major cause of many brain conditions like dementia and depression and ADHD and all the other things that he mentions.

Overall these claims did not fare very well at all. His scientific accuracy score was 20%, which is pretty close to as poorly as you can score without having the literature literally contradict everything you say. I would say his claims about cholesterol are the most egregious.

The first thing you have to understand — and he’s not the only one who claims this, that high cholesterol supports brain health — the first thing you have to understand is that the brain makes all of its own cholesterol onsite. It does not rely on blood cholesterol for its own cholesterol. So the idea to this idea from the get-go is physiologically implausible.

On top of that, you see that people with higher cholesterol in midlife actually have a higher risk of dementia in later life. The claim is really pretty much backwards.

When you look at gluten specifically — this is one of the major claims of the book — I used to be pretty suspicious of gluten myself and I just have been mostly unconvinced of that over time by the scientific literature as it’s continued to expand on this.

We have at this point randomized controlled trials on top of randomized controlled trials showing that gluten really doesn’t seem to do a whole lot unless you have Celiac disease. At least in the short term. And then in the long term there’s just not really much evidence at all.

All of these things that people say about gluten are pretty much purely speculation, pretty much totally hypothetical. Except for, of course, Celiac disease, which is a very well established autoimmune disease that is caused by gluten and let’s not trivialize it. This affects 1% of the population. So that’s a pretty big public health burden right there.

But when you try to extend that to these other things, particularly saying, “This has been supported by science,” there’s nothing behind it. That was not well supported,

Robyn:  They’re going to be people listening to this who are having a big mental resistance right now. And they’re saying, “No, I got off of gluten and I felt better.”

I want to point out that if you get off of gluten, then you’re getting off of a lot of products that contain, for instance( probably the most interesting thing) is that anything that’s wheat is also sprayed twice with Roundup these days (or glyphosate). Maybe that’s why. Or there are a number of other reasons that it may be why you feel better getting off of all products that contain any gluten that don’t come to that primary assertion of the author of Grain Brain, which is: it’s the gluten.

Dr. Guyenet: Yeah. And let me just say also that I don’t think the evidence we have right now, it doesn’t completely rule out the possibility that gluten could be harmful for some people under some circumstances. There’s a lot of things that we really can’t say right now.

I don’t want to overreach and say that we know for sure that gluten doesn’t do anything bad. I don’t think I can make that statement either. I can’t say categorically that people who feel better from excluding gluten, I can’t say categorically that that’s not due to the gluten.

However, I think there are other explanations that are possible for that, that are perhaps a bit more likely. And I want to start this off by relating an anecdote.

We had — I don’t remember the gentleman’s name — but he organized this thing called “gluten-free January.” This was a number of years ago. And he asked for my help with it. Basically, just asking people to go gluten free for one month in January and just see how they feel.

I had the idea, well, we should give questionnaires to people before and after and we should compare how they feel before and after. Compare how their weight changed, how their digestive health changed, how their energy level change, et cetera, et cetera.

We found incredible differences. Basically the more excess weight you had, the more you lost, the lower your energy level was, the more energy you gained. People’s digestive health improved, people’s mood improved. Almost everything we measured got better from going gluten free. So I think there’s a good case to be made that it actually is helpful. But is that because of the gluten?

There’s a lot of other confounding variables. Think about what you’re cutting out. When you cut out gluten, you’re cutting out some of the most calorie dense, highly palatable, unhealthy foods in the entire diet. And you’re just cutting out a lot of things in general. So it’s not really that surprising that people are going to lose weight, that they’re going to start feeling better because they’re suddenly cutting out a broad swath of the most unhealthy foods in our diet.

Even if you ignore the gluten completely, or if you think it’s completely neutral, those are still unhealthy foods that we shouldn’t be eating all the time. And I’ll tell you the single largest source of calories in the U.S. diet is grain-based desserts. So things like this — I know this sounds shocking, but this is actually true based on questionnaires — the number one source of calories is things like cakes and cookies and pastries and donuts.

Nobody thinks that’s healthy. Everyone knows that that is a horrible thing for you to eat on a regular basis. And if that’s your single largest source of calories and you cut it out and that’s the one of the least healthy things in your diet, yeah, you’re going to feel better.

That doesn’t prove that gluten is not part of the explanation. There could be some effect that the research just hasn’t come up with yet.

This is the type of thing that we really try to respect at Red Pen Reviews. We try to respect the limits of our knowledge. We can’t say that gluten is not harmful, but the evidence does not support these broad sweeping ideas that it is super harmful.

Robyn:  I think there’s another empire-builder and this is the model for people who (I don’t know if you know this, you probably do) write books these days is, the book is the Trojan horse; but then there’s all the products on what we call the “back end.” And another empire is Plant Paradox guy. He’s a medical doctor.

I actually got the Plant Paradox because so many people were coming to me about it, asking me questions. I was like, “Well, I’m going to read it,” and I read it and I would go look up the references that he would point to. Because I think the average person isn’t going to go look up the references and they’re just going to go, “Wow, there’s 30 pages of references at the back of this book. This must be true. This book must be true.”

I started looking them up and the handful that I did look up made me stop. My interest ended in reading the book, and after a few chapters I stopped reading it because the references weren’t proving his point. And I thought, because I’m a former university professor, I was like, “Oh, this is one of those guys who always padded his bibliography in high school and college and just counted on the fact that the teacher never looked up the references, and it was just like, ‘Oh, that’s a nice quantity of references. I’m going to give this guy an A if he can argue his case.'”

That was my frustration with the Plant Paradox. The idea behind it is that foods containing lectins, which are huge swaths of the whole foods plant based world. I’m talking about legumes; your split peas, beans and lentils. Those are off-limits in his diet. There’s even nuts and seeds and quite a few vegetables.

If you took everything with lectins out of the picture, you’d be left with the mostly meat-based, and a very limited diet.

Of course, there’s people who are saying, “I felt better on it.” And again, remember we’re getting rid of the donuts and the bagels like Stephan’s talking about.

But I’ve noticed, Stephan, that there’s an empire there too. I’ve seen Dr. Gundry running retargeting ads on anybody who’s been to his Facebook pages. And anything to do with his book, running retargeting ads, selling a — wait for it — lectin-blocker supplement.

Tell us what you learned digging into his work.

Dr. Guyenet: Yeah, absolutely.

This is interesting, the business plan that underlies these books. I’m vaguely aware of it, but I’m not enough of a businessman or marketer to have capitalized on that myself. Nor do I really have any desire to do that. But I think you’re absolutely right.

The book itself — and this is just a little tangent here — the book itself generally is not the most profitable part of a successful book. The profitable part is the things that you can get people to buy as a result of reading your book, which I think the most popular one is supplements. And Gundry sells a lot of supplements. He is an MD.

Essentially what the book claims is that pretty much all obesity and chronic disease is caused by these, this class of substances called “lectins.”

This is a type of substance that is able to bind certain types of sugars, especially the sugars that are out on the outside of your cells. Outside of your cell wall, there’s all kinds of these complex sugars. These substances can bind to those. And in some cases, they can be harmful.

There is a lectin, for example, in raw red kidney beans that will kill you if you eat a bunch of undercooked or raw kidney beans. And every now and then it happens. People actually do occasionally die from eating undercooked red kidney beans. Now of course, if you cook them sufficiently, the lectin goes away and then there’s no known health consequences.

Let me just specify that Mario Kratz, who’s one of our reviewers, was the primary reviewer on this. I was a peer reviewer, so he knows this better than I do. He’s a professor at the Fred Hutchinson Cancer Research Center here in Seattle. Really great researcher. But essentially, he did a really deep dive on the scientific literature. And again, this guy, this gentleman Gundry, claims that the scientific literature strongly supports what he says.

This is the template that this type of book uses; they make these claims and they suggest that those claims are very well supported by scientific literature. And this, like you said, this is difficult for the average person to sort out because the average person does not know the literature and will not be looking up the references. So there’s all these claims, people are making these huge claims and it’s hard to know which ones are true and false.

Essentially there was no substantial evidence of any kind supporting his claims about lectins. Yes, lectins are a thing that exist. Yes, occasionally there are ones that are super toxic, like the ones in red kidney beans, if they’re not properly prepared, but there’s basically no evidence that lectins in the quantity — in the context that is relevant to this book — has any of the effects that are claimed in the book.

No evidence that it contributes to obesity. No evidence that lectins and common foods contribute to cardiovascular disease, et cetera, et cetera, et cetera. Basically, it’s totally unsupported. However, that doesn’t mean that none of it could possibly be right. This is another case where the scientific literature just doesn’t really tell us a whole lot.

We have a lot of basic research on lectins. What are they chemically, what do they do to cells in a Petri dish, stuff like that. But we don’t have years-long randomized controlled trials where you put people on a low lectin diet versus a high lectin diet. We don’t have that evidence. So you just can’t really say with any certainty one way or the other.

That said, I think it seems pretty unlikely that he’s correct, simply because we do have randomized controlled trials that change the intakes of some of these foods like fruits and vegetables or nuts, things like that. And so far those types of foods seem more beneficial than anything. If we’re looking at things like bio-markers of cardiovascular health changes in weight, there are some randomized controlled trials that looked at actual cardiovascular outcomes, like heart attacks. And generally, increasing unrefined plant foods reduces that risk.

I would say that, even though we don’t have definitive evidence one way or the other on lectins themselves, I think when we’re talking about the whole foods that do contain those lectins, it’s pretty hard to make a convincing argument that those are a major cause of obesity and disease based on the evidence that we currently have.

This book got an overall score of 49%. One of the lowest that we’ve given out. It got a scientific accuracy score of 26%, which again is pretty tough to get lower than that in our scoring rubric. Most of the evidence that we evaluate would have to say literally the opposite of what you’re claiming to get much lower than that.

Robyn:  Wow. That’s amazing.

Dr. Guyenet: Yeah. Basically that is a score that is consistent with claims being almost totally unsupported. Reference accuracy is 63%. Generally these books tend to do decently to well on reference accuracy. Like when we randomly select references, they’re not usually totally out to lunch in how they cite those things. They just use those references to support larger arguments that they don’t necessarily support. And then for healthfulness, we gave it a score of 58%.

Healthfulness-wise, I don’t think it’s actually as bad as it might seem superficially because it actually does continue to include fruits and vegetables. And he’s not recommending just a meat-only type of diet. He’s just restricting it to certain types of plant foods that are low in lectins.

Yes, you probably could eat a reasonably healthy diet while following his advice; however, it would be really hard to do because he cuts out most foods and everything you buy has to be like grass-fed and organic and etcetera that most people can’t afford. He creates this very high bar for eating.

Robyn:  That’s what I said, is it becomes very becomes a very restrictive diet. And it’s not that he says you have to eat lots of animal products. It’s that when you eliminate legumes, nuts, seeds and a lot of vegetables, you’re going to end up — of course you’re not supposed to eat processed foods either because like we said, nobody’s advocating for those — you are going to by default get way out of line in terms of your ratio of how many animal products you’re eating relative to the good healthy whole foods in the plant kingdom.

That’s really the issue. It’s not that he’s saying to eat too much meat, it’s that you’re just going to be out of so many options of the things that provide the calories and the bulk if you eat mostly plant-based like I do, and like we advocate for here. So, it’s more about that.

We just have to get really real about what happens when you take these whole entire classes of whole plant foods off the table (per the Plant Paradox if you’re going to follow his plan).

Dr. Guyenet: My view is that if you’re going to go to extreme lengths like that, you have to have pretty good supporting evidence. And I don’t think the case here.

I think what he has is this really novel idea, an idea that is very different from what everyone else is claiming causes obesity and chronic disease and whatever. And he has a fix, which is a super restricted diet that probably does help people, at least temporarily, just because it’s a restricted diet and helps people eat less and cuts out junk food.

He’s got this really unique concept and platform that I think helps him be really visible and popular. But, I think, in my opinion, at the expense of scientific accuracy.

Robyn:  That really is the point that I want to bring out of all this, is that a bestseller is created by saying something new. And how much more is there to say that’s new about the field of wellness and nutrition.

I’m super committed at and on this podcast to just keep reiterating what the basics are and keep pulling people out of the little bunny trails and saying, “Let’s talk about what we actually know about nutrition,” because people aren’t doing that. People aren’t doing the basics. They want to get into these strange minutia of whether I should eat this seed or nut because it has lectins in it, or whatever.

I want to point that out that a lot of times the reason a book is trending is because he’s saying something new, and if he’s saying something all that new, we should use our critical thinking skills to assess whether it’s actually true or not.

Dr. Guyenet: I agree with that, and I want to add that I think that’s part of the twisted incentive structure that drives book authors and publishing and the publishing industry to create this exploding volcano of nonsense.

Robyn:  And the exploding volcano of nonsense really has everything to do with the fact that [books] — I’m a 16 time book author, so I’m way inside this world; I make very little money on my books and couple of them are bestsellers and do very, very well, even one that’s a 10 year old book; I still get royalties for it, but it wouldn’t support having employees at all — books are just ubiquitous. Self-publishing has made it so that everybody’s an author, everybody’s an expert.

Then there’s the fact that books have been like a free lead magnet so that people can get folks to opt in and then sell them something on the back end. Just be aware of that.

Authorship used to be a big uphill battle and you used to have to get a big publishing house to take notice of you. And a lot of the barriers to entry have come falling down. That’s why you see a lot of goofiness and a lot more books being published, and people aren’t willing to pay for books or they might be willing to pay five bucks for a book or 10 bucks for a book.

That’s neither here nor there, too, about evaluation of whether a specific book is relevant.

Dr. Guyenet: I think that’s part of it. That’s part of the problematic incentive structure. Other parts of it are that essentially there’s no accountability. So if someone makes false claims, that doesn’t come around to them in a negative way, generally. If anything, it can help their sales. Because if you’re making really strange, unusual claims, like Plant Paradox, that actually gets more eyeballs onto your book. It potentially gets more people to buy your supplements or whatever.

It’s not like in the scientific literature where you have tons of knowledgeable people who are scrutinizing every word you write. And if they don’t like what you’re saying, it doesn’t get into the scientific journal, or you don’t get your grant or whatever. I’m not saying that process is perfect either by any means, but it creates a lot more accountability for the information that is being published in the scientific literature. And that is not there in the popular press.

When I wrote my book, there was no fact-checking of my scientific claims of any kind. I sent my chapters to experts myself to have them fact check it, but no one required me to do that and that that’s not how the industry works. I don’t want to say they don’t care at all, because probably they do at least a little bit. Maybe somebody cares. But they don’t care enough to do anything about it really.

What’s driving everything is the sales volume. They want books ultimately that are going to sell well and make money for the organization. I’m sure all else being equal, they would rather those books be factually accurate. But that is just not high on the priority list.

That’s what we’re trying to do with Red Pen Reviews: create that accountability structure where, Hey, if you publish something that is not accurate, it’s actually going to matter to your bottom line. Hopefully it’s going to matter to your bottom line because consumers are going to read this, and they are going to not purchase this book.

It’s going to be embarrassing for the author because it will be exposed publicly. There will suddenly be accountability that causes people to think twice before writing stuff like that, and causes publishers to think twice before publishing it.

But I don’t want to paint it in just a negative light. It’s also positive, in the sense that our website is there to help authors write better books to begin with. And we would rather have that happen than have them write books that are not accurate and then we give them a bad review. Our entire method is published in entirety on our website. And if you write your book with that method in mind, it’s going to be a better book.

That’s part of what I see as our work, to actually support authors to write better books to begin with rather than having to point out problems after the fact.

Robyn:  I agree.

We’re about out of time, so I wanted to go over Good Gut.

I have not read that book; I did do episode 140 just recently reviewing the microbiome tests, or the poop swab test, where you send your poop into a lab and they tell you what you should eat. And I came to similar conclusion that you have on some of these books; just going to these three microbiome companies, their actual references, and taking a look at whether those references actually support the claims that they’re making or show any clear clinical evidence that their tests are really anything valuable that you actually want to get tested. And I’ve come to some similar conclusions to the conclusions you’ve made of the two books you’ve talked about so far.

But I think I’ll leave Good Gut in favor of — and I haven’t read any of these reviews, are where you can read these in detail — just with the few minutes we have left, why don’t you tell us what you discovered digging into Bulletproof, which is the idea that you drink coffee and add MCT oils (or I think pretty much like refined coconut and Palm oils; he used to have Palm oils and I think now it’s just a blend of refined oils in the coffee) that it’s a great way to lose weight and have higher brain power.

What did you learn reviewing that?

Dr. Guyenet: I was the peer reviewer on this, and Seth Yoder was the primary reviewer.

This book did not fare that great. It got an overall score of 49%, scientific accuracy of 34%, which is certainly better than Grain Brain and Plant Paradox, but still not so good. Reference accuracy of 70%, and helpfulness score of 43%.

Essentially, it’s a type of low carbohydrate diet that he advocates for. It includes the consumption of this specific brand of coffee that Asprey sells, that is purportedly low in fungal toxins, that he claims affect your physical and mental performance.

This is a very performance-oriented book. It’s not as oriented toward disease prevention. It’s more like, how do you perform your best in life? It’s very focused around consuming saturated fat too, like coconut and butter fat and those types of things.

I would say that the most unique angle that this book has is the mycotoxin angle. This idea that there is fungal toxins in the foods that we eat that affect our performance. And there are fungal toxins that are relevant to health. For example, aflatoxin is one that some people may have heard of. It can be present in peanuts and corn and certain other things, certain other foods.

However, it’s measured and regulated in the American food system. So it’s usually not much of a concern here. In some other countries it can be, but basically, it’s a carcinogen that increases your risk of cancer, particularly liver cancer.

What he is saying is “No, no, no, it’s not just about cancer. It actually makes your brain and your body not work as well. Makes you not perform as well. And we’re drinking it every day in our coffee.”

And it’s true, there is a little bit of mycotoxin and coffee. But the truth is there’s toxins in everything we eat. There’s toxins in everything we eat. The question is how much toxin are we ingesting and how toxic is the toxin at that level of ingestion?

Basically, there’s no evidence at all to support the idea that these very low levels of fungal toxin affect our performance. And that includes a study that Asprey himself conducted; a really strange scenario actually.

He recruited experimental subjects from his audience and had them drink his coffee versus Starbucks coffee and had them do a variety of cognitive tests in collaboration with (I forget what university, Stanford or something) but it was never published in a peer reviewed journal. And if you look at the actual experimental design, it’s actually not capable of supporting the claims that he makes about it without getting into detail.

We get into detail in the review if people are interested.

The big like angle that he has that underlies, I think, probably a lot of his profit (because the coffee: he’s selling it) I think that angle is poorly supported.

The rest of the book — not to say that people wouldn’t gain some benefit from the advice, maybe they would — I think it’s, it’s fairly shaky in the way that it uses science.

Robyn:  Interesting.

Well, we could just go all day. I would love to hear more about the others; I know you’re fairly new and you have six book reviews out, but I know that you have more in the works. And you probably won’t even be to keep up because there’s so many fad diets and fad nutrition advice coming out!

But thanks for doing the very best job you can to be a neutral evaluator of these many claims because they confuse my audience. We’re talking to a quarter of a million people every week (not even including on social media, there’s another quarter of a million there), and we’re hearing from them how confused they are about all the different advice they get.

You’re doing a great service.

Tell everyone where they can find you and subscribe. I’m going to be watching and waiting for new reviews to come out myself.

Dr. Guyenet: If you go to on the homepage, if you scroll down, there’s a box where you can sign up for email alerts. We’ll send you an email every time we publish your review.

I also announced them on Twitter. My handle is @whsource. So every time we do a review, I will announce that as well as other news related to Red Pen Reviews.

I also want to say that we’re a registered charitable organization and we’re trying to do a public service. And if people listening believe in what we’re doing, please make a donation. We made that very easy through PayPal on our website.

That money goes to paying the reviewers to do those reviews. These are very time intensive reviews that are being done by very, very busy people. And so I’m trying to create the best possible incentives for people to write these reviews. And part of that includes paying them a modest sum for their work. If people can donate, that improves our ability to incentivize reviewers to do these reviews, and to get more reviews onto our site.

Robyn:  I appreciate that very much, and thanks so much for coming on the Vibe show today, Dr. Stephan Guyenet.

Dr. Guyenet: Thanks for having me.


Related article: It’s a Long and Winding Road to Good Nutrition!


One thought on “Ep. 156: Reviewing “Grain Brain,” “The Plant Paradox” and “The Bullet-Proof Diet” with Stephan Guyenet, PhD”

Leave a Comment
  1. Suzanne says:

    I’m super curious…Robyn, you mentioned a 13 times NY Times bestselling author whose interview you cancelled at the last minute because of something said in one of his books, how people should never eat another carb, or something similar to that. What author is that?

Leave a Reply

Your email address will not be published. Required fields are marked *

Skip to content