Studies show people who eat red meat also tend to engage in behaviors that are perceived to be unhealthy. Find out why these behaviors impact the possibility of developing heart disease more than the TMAO and Neu5Gc compounds found in red meat.
People who eat red meat are engaging in unhealthy behaviors that have led to their gut flora being screwed up in the first place. Those could include eating fewer fruits and vegetables, eating less soluble fiber, fermentable fibers in general, eating more processed and refined flour, and eating more sugar and industrial seed oils. And wouldn’t you know it; we do have studies that show that the average person who eats more red meat—we’re not talking about Paleo dieters here because that’s not the average person—but the typical American who eats a lot of red meat also engages in those other behaviors that would be bad for the gut flora. Those behaviors, each of them, have been associated in separate studies with undesirable changes in the gut microbiota.
In this episode:
3:57 What Chris ate for breakfast
8:29 The truth about red meat and TMAO
17:36 What is the Neu5Gc compound?
24:02 Diet and behaviors
Links we discuss
- 9 Ways to Prepare Plantains
- Special Report: The Truth About Red Meat
- Red Meat and TMAO: Cause for Concern, or Another Red Herring?
- National Geographic: Evolution of Diet
Steve Wright: Good morning, good afternoon, and good evening. You are listening to the Revolution Health Radio show. I’m your host Steve Wright, co-author of SCDlifestyle.com. Before we get rolling, I just want to let you know that this show is brought to you by 14Four.me. What is this? If you haven’t heard of it yet, you definitely need to go over to 14Four.me and check it out. It is a 14-day healthy lifestyle, sort of reset program. I’m sure you’ve been through a few holiday seasons; I have myself. I know that it’s very hard, due to travel, food, just different holiday parties, staying up late. Typically, everything gets out of sorts for me: my exercise routine, my sleep routine, even my food. I can fall off the wagon sometimes with all these not healthy treats sitting around the house. Anyway, going into January, 14Four.me might be something you want to look into, where for 14 days, Chris has put together this amazing program where you focus in on stress, diet, movement, and sort of your lifestyle and everything. Basically, you’re going to hone in. For 14 days, Chris Kresser is going to hold your hand as you move through resetting this portion of your lifestyle. So if you’ve always kind of wondered how to put all the pieces of the puzzle together, Chris went ahead and created this step-by-step program for you. With me today on the podcast, as always, is Chris Kresser, integrative medical practitioner, healthy skeptic, and New York Times bestselling author. Good morning.
Chris Kresser: Hey, Steve. I’m glad I’m here and it’s not somebody else on my podcast.
Steve Wright: That would be weird.
Chris Kresser: We’ve got a red meat question today. You know, it doesn’t matter how many red meat podcasts or articles I write. There will always be more red meat questions and more to say about red meat, because there’s always a new attack against red meat, with some new mechanism or new idea about how red meat is going to kill you. Long ago, I accepted that the defense of red meat was just part of my job description and something that I’ll probably be doing until the day that I die—hopefully, not of a heart attack caused by eating too much red meat.
Steve Wright: Some days, Chris, I’m just like, “You know what? You’re right. You should eat all of the poultry, because I want all the red meat for myself.”
Chris Kresser: That’s right.
Steve Wright: Go and take it from me.
Chris Kresser: Yeah. Because I don’t know if you’ve been hearing about this, but there have been a few articles lately about peak chocolate, how the production of chocolate is not keeping up with demand, and that in five years’ time, we could be having a major chocolate shortage, which was really, really bad news, for me at least. And I take responsibility for contributing, because they said that people who eat really dark chocolate are the biggest offenders. That’s definitely me.
Steve Wright: Gosh, Chris!
Chris Kresser: Because it takes more cacao to make dark chocolate than it does to make those lame Hershey milk chocolate bars that have been the mainstay for many years. Then I read an article yesterday about peak olive oil. Now that people have gotten the message that saturated fat is bad for you and really switched over to olive oil as the main oil in cooking, they’re struggling to keep up with that. Peak red meat is not going to happen any time soon, given the prejudice against it. So I think you’re safe, Steve.
What Chris ate for breakfast
Steve Wright: Whew, okay. Well, before we get to the actual question—which isn’t a charged topic for you at all, I can tell—did you have anything for breakfast this morning?
Chris Kresser: I did. Actually, we made these plantain pancakes. So I finally wrote that post. I don’t know if you saw it.
Steve Wright: Yeah, I did.
Chris Kresser: It’s about nine ways to prepare plantains. You know, that’s such a versatile starch. One of the ways that I talked about in the post was making pancakes. What’s amazing about this is they’re not only gluten-free and grain-free, they’re also nut-free and completely flour-free. So they’re pancakes that are just made essentially with the green plantains themselves and eggs in a blender. There’s a few other things put in there as well, but it’s basically like having scrambled—you know, it’s no different from a nutritional perspective than having scrambled eggs and plantains whole, except they’re all blended up together. Then I typically will put some blueberries in them when I put them on the griddle, and of course, some butter, sometimes some fermented cream as well. Today, we just had the plantain pancakes with blueberries, butter, and some bacon.
Steve Wright: Speaking of cooking with oil, what kind of oil did you lay down to cook those in?
Chris Kresser: Expeller-pressed coconut oil. Definitely one of my favorite oils for cooking. The temperature was 300. That’s well below the smoke point for expeller-pressed coconut oil. I like the expeller-pressed coconut oil because it doesn’t have the strong coconut flavor that extra virgin does, and it also has a higher smoke point. So it’s a better choice for this.
Steve Wright: Perfect.
Chris Kresser: That was it. Some listeners might be thinking, “Well, that’s pretty much plantains and eggs, the same breakfast you have every day, in a different form.” Yes, that’s true. But it’s all about textures. That’s all I’m going to say.
Steve Wright: And moving on to the question!
Chris Kresser: This one’s from Patrick. Let’s give it a listen.
Patrick: Hi, Chris. My name is Patrick. I just read an article on the last National Geographic magazine. There’s an article about Paleo diet. There’s a study here about red meat. I’m going to quote that. “Recent studies confirm older findings that although humans have eaten red meat for two million years, heavy consumption increases atherosclerosis and cancer in most populations. And the culprit isn’t just saturated fat or cholesterol. Our gut bacteria digest a nutrient in meat called L-carnitine. In one study, digestion of L-carnitine boosted artery-clogging plaque. Research also has shown that the human immune system attacks a sugar in red meat that’s called Neu5Gc, causing inflammation that’s low level in the young, but that eventually could cause cancer. ‘Red meat is great, if you want to live to 45,’ says Ajit Varki of the University of California, San Diego, lead author of the Neu5Gc study.” What’s going on there?
Chris Kresser: Patrick, if you haven’t seen this already, go to ChrisKresser.com. There should be—I think there is an eBook on red meat. I should know this. But if there’s not an eBook, there’s a special report. If you search for “Chris Kresser red meat,” you’ll see tons of articles that we’ve done about red meat. I’ve addressed both of your questions: TMAO, which is what you’re getting at with carnitine, which we’re going to talk about today; then Neu5Gc, which is the compound that’s supposed to cause inflammation and give us cancer when we eat red meat. So I’ve actually already addressed those in writing, with lots of references. If you want to check that out, you can see the series on red meat. But we’ll quickly—or maybe not so quickly, given that it’s me we’re talking about here—go through this stuff and get to the bottom of it. We’re not going to address everything about red meat because that would take several podcasts. We’ve already done that. We’re just going to focus on these two issues: TMAO and Neu5Gc. Then you can get all the information you want in the eBook or the special report. Okay.
The truth about red meat and TMAO
This whole idea L-carnitine and TMAO being a new mechanism by which red meat can kill you, really kind of got a lot of attention after a study was published in the journal Nature last year or the year before. The authors of that study had published previously a paper proposing that a chemical called trimethylamine N-oxide—so we’re going to call it TMAO for short—increases the risk of heart disease. TMAO is easier to say. So in the study, the researchers hypothesized that eating red meat might increase levels of TMAO in the bloodstream, which would, in turn, ramp up your chances of having a heart attack. Okay? The study that we’re discussing here, the one in Nature, found that those who eat red meat produce TMAO, whereas vegans and vegetarians who hadn’t eaten meat for at least a year do not produce TMAO. On the surface, that sounds pretty damning for red meat, right? If you red meat, you produce more TMAO. More TMAO means you get a heart attack. Okay.
Steve Wright: For sure.
Chris Kresser: The mechanism that the researchers argued was causing this is that eating red meat alters the gut flora in some way that predisposes towards producing TMAO. However, there’s another explanation that I think is a lot more plausible, which is that people who eat red meat are engaging in unhealthy behaviors that have led to their gut flora being screwed up in the first place. Those could include eating fewer fruits and vegetables, eating less soluble fiber, fermentable fibers in general, eating more processed and refined flour, and eating more sugar and industrial seed oils. And wouldn’t you know it; we do have studies that show that the average person who eats more red meat—we’re not talking about Paleo dieters here because that’s not the average person. But the typical American who eats a lot of red meat also engages in those other behaviors that would be bad for the gut flora. Those behaviors, each of them, have been associated in separate studies with undesirable changes in the gut microbiota.
Steve Wright: Just to be clear, the Nature study was not the Paleo diet versus the vegetarian diet?
Chris Kresser: No.
Steve Wright: It was your average, standard American versus a vegetarian.
Chris Kresser: Vegetarian and vegans, yeah.
Steve Wright: Perfect. You know what? That’s a great sample group. These researchers are just—Nature is going downhill, man. Nature is really going downhill.
Chris Kresser: In other words though, to summarize as well, the problem is not the red meat; it’s the gut bacteria. There are several lines of evidence to support this. Number one, the red meat eaters in the study did not produce TMAO after taking a course of antibiotics. So it showed that if the antibiotics kill the unhealthy gut flora that’s responsible for the TMAO production, and then you eat red meat, then you don’t produce TMAO. That clearly shows it’s really about the gut flora. Second, it’s supported by data indicating that a breakdown in intestinal barrier, which occurs in dysbiosis and SIBO, can increase heart disease by elevating the number of circulating LDL particles in the bloodstream. We’ve talked about that before, where essentially, leaky gut leads the liver to produce more LDL particles because they have an antimicrobial effect. Then that increase in LDL particles can increase the risk of heart disease. But there’s actually another, more fundamental problem with this whole TMAO-heart disease theory. That is this: The evidence that links TMAO production to eating red meat, and serum TMAO levels to heart disease, is not as cut-and-dried as the authors of this paper suggest. The Nature paper on TMAO had data from two studies. There was an epidemiological or observational study on humans, and then there was a clinical study on mice. Now, the human study compared one single vegan that they managed to convince to eat steak for the study, to five representative meat eaters. So we’re talking about a sample size of six people with only one in the vegan group.
Steve Wright: Holy cow!
Chris Kresser: That’s hardly adequate to draw firm conclusions from, right? Then the mouse study used a carnitine supplement. And it’s well-established in the scientific literature that free carnitine, like you would get from taking carnitine supplements, increases TMAO production. But previous studies have not shown that eating carnitine-rich foods like red meat have that impact on TMAO. As we know, taking a single isolated nutrient in the form of a supplement can have profoundly different effects than eating that nutrient in the context of a whole food. On the contrary, there’s a study in 1999 that found that out of the 46 different foods that were tested, including red meat, there was only one food that actually elevated TMAO levels in the human participants. That food was seafood.
Steve Wright: Really?
Chris Kresser: Yeah.
Steve Wright: I thought you were going to say kale.
Chris Kresser: Seafood. In fact, halibut generated 107 times as much TMAO, or more TMAO, as red meat. This makes sense because trimethylamine, which is the precursor to TMAO, is naturally present in seafood. So if you’re eating the precursor to TMAO, you’re going to see a large increase in TMAO production. Of course, Steve, that explains why fish consumption is so strongly associated with heart disease.
Steve Wright: It is. You know, I’ve heard that the latest New York Times article … I’m just kidding.
Chris Kresser: Not! Wait a second. Fish consumption is strongly inversely associated with heart disease.
Steve Wright: Oh my gosh, my head’s exploding.
Chris Kresser: So we would have to account for if TMAO is this evil nutrient that causes heart disease, then why doesn’t eating more fish cause a serious increase in heart attack? There’s definitely something wrong with this story. Finally, even if it’s true that people following a Paleo diet, rather than just the standard American crappy diet that screws up your gut flora, have higher levels of TMAO than vegans and vegetarians, that’s not proof that TMAO causes heart disease. This is one of these classic cases of correlation is not causation. You can see that people with heart disease have high levels of TMAO, but do we know that it’s the TMAO causing the heart disease? Could it be the development of heart disease increases TMAO levels? Or could it be that some other factor that led to these people getting heart disease also led to increased TMAO levels? In fact, Chris Masterjohn explored a number of those factors in a really long article he wrote about this. There are definitely genetic factors that contribute to higher TMAO levels. There are certain medications that contribute to that. Race makes a difference. What race you are determines, in some part, your TMAO levels, which, of course, is tied to genetics. So there are a lot of different things that can affect TMAO that have nothing to do with diet. Furthermore, if we’re talking about diet, the only food that really significantly increases TMAO is fish, which is a food that has been shown to be, probably more than any other food that we could think of, protective against the development of heart disease. So I think we can, at least for now, close the book on the red meat-TMAO-heart disease link, because it’s really not plausible the way that it’s been presented so far.
Steve Wright: And if there’s one other thing to consider, it’s that last time I checked, no one has really just completely mapped it out and said, “This is exactly how heart disease is created.” So to link it back to one singular factor is such a reductionist point of view from science.
Chris Kresser: Yeah. And the authors of the study are long-time vegetarians and vegans. Some of them, they’re plant-based diet advocates. That doesn’t, again, invalidate the study any more than it would if a researcher was following a Paleo or a low-carb diet and did a study. But human beings are just—it’s really hard for us to avoid confirmation bias. That’s one of the problems with scientific research. For those of you that are new to this concept, confirmation bias basically means that we search for information that confirms our biases and we filter out information that doesn’t. It’s something I’m constantly guarding against, but I’m not perfect and I make that mistake. I know for a fact that others do as well. So it’s a tricky thing about this messy scientific process.
What is the Neu5Gc compound?
Let’s move on to Neu5Gc. It’s called Neu5Gc. I don’t know if I’m actually pronouncing it correctly because I’ve only ever read papers with it. I’ve never heard somebody say it out loud. So we’re calling it Neu5Gc.
Steve Wright: I like it. I can pronounce that. Neu5Gc.
Chris Kresser: Certainly easier than spelling it every time I say it. What is it? It’s a monosaccharide—that’s a single sugar—that acts as a type of signaling molecule in mammalian cells. One of its functions is to help the immune system distinguish between self and foreign cells. Humans actually lost the ability to produce this Neu5Gc millions of years ago through a genetic mutation, although we still produce a compound that’s closely related called Neu5Ac. But humans are unique in this respect, because most other mammals still do produce Neu5Gc, which is why that compound is found in mammalian meat that humans eat. When we consume red meat and milk products, we incorporate this compound, at least some of it, into our own tissues, especially tissues that grow at a fast pace: a developing fetus, epithelial and endothelial tissues, and tumors, either benign or malignant tumors.
The concern is that most of us have anti-Neu5Gc antibodies circulating in our blood. Some researchers have suggested that these antibodies react with the Neu5Gc in our tissues to create chronic inflammation, leading to chronic diseases like cancer. Essentially, we’re having almost like an autoimmune reaction against the meat. And through molecular mimicry, because we have the Neu5Gc in our tissues, then in a similar way to gluten intolerance, we’re getting attacked against our own tissues, not just the Neu5Gc in the meat itself. The problem with this hypothesis is that researchers are nowhere near proving it. It’s a theory; certainly an interesting theory, but the research is at the very early stages. We need studies to confirm or refute these hypotheses. Most of the studies that have been done, if you actually read the full text of the paper, acknowledge that. They say, “At this point, these results are preliminary. We need lots more research. It would be irresponsible to draw conclusions from this.” But of course, the media does not pick up on that nuance. The media does not like nuance.
Steve Wright: Do they ever read the whole study or is it just the abstract? I’m not sure.
Chris Kresser: Yeah. I mean, I think it’s a pretty rare science reporter these days that reads and understands the full text of the study before they write. Most people are just taking stuff off the wire, it seems like to me. Like I said, nuance doesn’t sell. It’s black-and-white, sensational stuff. That’s what generates clicks. Clicks are what generate the ad dollars. Unfortunately, that’s how it goes.
So in any role in chronic inflammation that Neu5Gc might have is still speculative. But when you see these articles that cite this research, they neglect to acknowledge that limitation. And whenever we talk about a new theory like this, this is where the evolutionary lens, once again, comes in so handy. We talk about this on almost every show. The beauty of the evolutionary or ancestral perspective on health and illness is that it can resolve conflicts that we see in modern clinical research. This is a great example. Or in a situation where you have some studies that say one thing and other studies that say the exact opposite. If it’s not clear from looking at the body of modern clinical evidence that we have what the answer might be, then we can look at the anthropological record, evolutionary biology, archaeological record, and we can see if that sheds additional light on the question.
For example, in this case, if we have the idea that red meat causes inflammation and chronic modern disease, then we would expect to see inflammation and chronic modern disease in populations traditionally that have eaten a lot of red meat, right? Pretty simple and straightforward. Don’t need to be a rocket scientist to figure that out. Well, when we look at traditional diets, there are cultures like the Maasai in East Africa, who we’ve discussed before, that, in fact, ate a diet that essentially, you couldn’t design a diet higher in Neu5Gc because their diet consisted mostly of red meat, blood, and milk from the animals that they raised. They raised cows, they’re a pastoralist culture. They eat mostly cow parts: the meat, the milk, and the blood. Those are all high in Neu5Gc. So we’d expect the Maasai to have diabetes, heart disease, autoimmune disease, allergies, asthma, all these chronic inflammatory diseases, cancer, out-of-control cancer and tumor growth. That’s not what we see at all. In fact, those diseases are practically nonexistent in the Maasai people. So either you have to come up with some magical protective mechanism that these Maasai have that nobody else has that prevents them from getting chronic disease when they eat so much Neu5Gc, or we have to seriously question this theory that Neu5Gc is a problem. Because if you see examples of cultures that are eating red meat and don’t have these conditions that you would expect with chronic inflammation, then that’s a serious hole in the theory. Again, this is where the evolutionary perspective can be so helpful. It can also be helpful when you’re looking at, like I said, modern evidence that’s somewhat conflicting.
Diet and behavior
Let’s talk about the data on red meat and mortality, the overall risk of death. When you study the research on this topic, you find that the intake of fresh red meat—so red meat that hasn’t been processed, smoked; just fresh red meat—it’s inconsistently associated with higher cardiovascular disease risk. In other words, some studies say it is associated and other studies say it’s not associated. If there is any effect, even in the studies that say it is, the effect size is really small. But when we look at, once again, the anthropological record and see evidence of cultures who ate a lot of red meat and didn’t have heart disease, or heart disease is practically nonexistent, that’s another piece of evidence in this puzzle suggesting that it’s not red meat, but it may be something else that people who eat more red meat, on average, are doing that’s contributing to this increased risk. This is known as the healthy user bias. It’s the scientific way of explaining the phenomenon we’ve been talking about, where people that engage in one behavior that’s perceived as healthy, whether it is or not, are more likely to engage in other behaviors that are healthy. Of course, the flipside of that is also true. Those that engage in behaviors that are perceived to be unhealthy, like eating red meat, which has been demonized for so many years, are more likely to smoke cigarettes, not exercise, not eat fruits and vegetables, eat lots of processed and refined flour, drink too much. Good studies will, of course, attempt to control for at least some of these factors, but there’s no way that they can control for all of them. Some of them, they haven’t even tried to control for. An example is the gut microbiome. What’s the status of the gut microbiome of people who are eating these things?
Steve Wright: Man, wouldn’t it be shocking if they actually bought into that idea and started recruiting, for instance, a vegetarian who exercises and a red meat eater who exercises?
Chris Kresser: The closest study I’ve seen to that was—and I think we’ve talked about it before; it was pretty ingenious—they just studied people who shopped at health food stores. It doesn’t guarantee that they’re all health-conscious, but they’re health-conscious enough to be shopping at a health food store. Then they separated them into vegetarians/vegans and meat eaters/omnivores. They found there was no difference in mortality between those two groups at all. So I’d love to see more studies like that. Whether we will or not comes down in large part to who’s going to fund those studies. Maybe with some of the crowdsourced trends that are happening in science now, that would be possible. Anyways, I’m going to stop there. We could go on and on about red meat. I hope we’ve addressed Patrick’s main questions, which are related to TMAO and Neu5Gc.
I, for one, eat plenty of red meat. I think there are some potential concerns with red meat. People who have hemochromatosis or a tendency to store too much iron might need to be careful with red meat. I think charring red meat at high temperatures often is probably not a good idea, because there’s some fairly compelling research suggesting that that can produce carcinogenic compounds. So cooking methods probably matter. Eating a diverse diet that includes seafood, poultry, and red meat is probably a good idea. They all have different nutrient profiles. But so far, I have not seen any evidence that convincingly links red meat—outside of other potentially unhealthy lifestyle behaviors—to disease, whether we’re talking about cancer, heart disease or any other disease. Red meat is one of the most nutrient-dense foods that we can eat. I’m not saying goodbye to red meat any time soon. And at least from an evidence-based perspective, I don’t think you should either.
Steve Wright: I would have to agree.
Chris Kresser: Plus, it’s delicious.
Steve Wright: I was going to say, I think a good steak is just too delicious.
Chris Kresser: Yeah. Slow-cooked brisket, some of the cuts that you can throw in a slow cooker are just amazing after they’ve been cooked for a long time.
Steve Wright: So true, so true. It can’t taste that good and be bad for us. Anyways, this has been a great summary, Chris. I really appreciate you kind of bringing it home here in an audio version, for you to distill these posts down. I think that’s going to help people. For those skeptics who haven’t been convinced, definitely go check out those links that Chris has been talking about, because he’s exhaustively been defending red meat for many years now.
Chris Kresser: And it does get exhausting.
Steve Wright: I get a little exhausted.
Chris Kresser: But I’m happy to do it.
Steve Wright: Awesome. Thanks, everyone, for listening this week. If you want more red meat updates in-between these episodes, make sure you’re following Chris on social media. You can go to Facebook.com/ChrisKresserLAc and Twitter.com/ChrisKresser. Chris, thanks so much.
Chris Kresser: Thanks. Thanks, everyone. See you next time.
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