Dr. Mark Hyman is a practicing family physician, medical advisor for Bill and Hillary Clinton, and a #1 New York Times bestselling author of multiple books on nutrition and wellness, including Eat Fat, Get Thin and The Blood Sugar Solution. Chris Kresser, M.S., L.Ac is a globally recognized leader in the fields of ancestral health, Paleo nutrition, and functional and integrative medicine, and is the author of the New York Times best seller, Your Personal Paleo Code. The two recently sat down to talk about the diet humans were designed to eat, and why fat and butter might be good for you after all.
Mark: Recently, there was this big headline in the news that said, “If you eat meat, you’re at a higher risk of death than if you eat plant protein.” Does that mean all of us should become vegans? How do we interpret this data?
Chris: It’s confusing. One week it’s “Butter is bad for you,” the next week it’s “Butter is good for you.” Same thing with animal products. I think we have to be careful with epidemiological or observational data, which basically involves taking a whole bunch of people and asking them to report what they ate on a questionnaire, which is really sketchy.
There have been studies on food frequency questionnaires that have shown them to be completely unreliable measures of food intake. Memory is sketchy. That’s one problem.
The second problem is these things called “confounding factors.” Let’s say we see [that one] group of people ate a lot more meat, and then they had more heart attacks and earlier death. What else were they doing or not doing? Maybe they weren’t exercising as much. Maybe they were smoking more cigarettes. Maybe they weren’t sleeping as much. Maybe their general awareness of health was just lower overall because historically, red meat has been seen as a bad food.
Researchers attempt to control for those confounding factors. They try to remove smoking and drinking from the equation. The truth is, it’s nearly impossible to control for all of the confounding factors.
Here’s an interesting one: the gut microbiome. We now know that gut health plays an incredibly important role in so many different aspects of our overall health, including heart disease and cancer. Nobody’s controlling for somebody’s gut microbiota.
Mark: Let’s get a poop sample and see what’s going on.
Chris: Exactly. When I look at the health claims, I use what I call a three-legged stool to evaluate the claim. One is the modern, peer-reviewed scientific literature. Evidence-based medicine is something that I completely support, but it’s not the end all, be all. There are problems with the way that scientific research is done.
Mark: People think that if it’s published in a journal, if it’s reported in the news, then it must be true.
Chris: If only that were the case.
Mark: If you pull back the veil on these studies, who funded the study? How was it designed? These are important things that are often not immediately evident. I think we often can draw the wrong conclusions from the data. Even the data, sometimes, isn’t reported correctly.
Chris: Oftentimes, I’ll read the conclusion of a study, and then I’ll read the full study, and I’ll see that the author’s conclusion doesn’t even match the data. Researchers are humans. They often have a certain perspective or point of view, [and] it’s really hard for that not to seep into the way that that study’s designed and reported.
Mark: [So] you’ve got your three-legged stool.
Chris: We’ve got the three-legged stool. Modern research is one, but this is where an ancestral evolutionary perspective is so important. We know that all organisms are adapted to survive and thrive in a particular environment, right? We can look back and say, “What is the natural diet for human beings? What is the diet that we evolved to eat?” Guess what? It involves animal protein. It’s primarily meat and fish, wild fruits and vegetables, nuts and seeds, and some starchy plants. That’s what humans ate for the vast majority of our evolutionary history. It doesn’t make any sense that animal protein would be problematic for us, if you look through that evolutionary lens.
Mark: [But] people might say, “People died at 40 [back then].”
Chris: That’s a popular misconception. It’s true that our ancestors had shorter lifespans on average than we did today. Think of what they were dealing with that we’re not. They had trauma, warfare. They were sleeping outside. They had to deal with freezes and cold spells, infections, lack of emergency medical care, higher infant mortality rates. [But] anthropologists have looked at populations that had the most rudimentary access to medical care, [and they] enjoyed lifespans that are equivalent to our own today. The difference is, they didn’t acquire all of the inflammatory diseases that characterize our old age today. They were relatively healthy until they died.
“It doesn’t make any sense that animal protein would be problematic for us, if you look through that evolutionary lens.”
Mark: Okay, you’ve got the two legs of the stool. Evidence based, evolutionary [lens]…
Chris: Then, clinical experience. If I recommend a vegan and vegetarian diet to 100 people, a lot of people are not going to do well. Then I have them reintroduce meat in a paleo type of diet. I see them improve and feel better. That means something to me as a clinician.
Mark: I was recommending low fat diets for years. I mean, I thought the evidence was there. [But] I never saw the kinds of results that I’m seeing now. People get off insulin in five days. People lose 100 pounds.
I think those three legs are really important. The National Institute of Health is actually pioneering the standards by which we can look at an individual and compare them to themselves before and after some intervention.
Chris: That may be the future of research. If we’re going to look at functional medicine as an intervention, we do more than one thing at a time. That old research paradigm isn’t going to work. We need to look at before and after with individual people and see what the changes are.
Mark: One of the things people don’t realize is that during the time they’re doing [a] study, if meat is seen in the culture as bad, the people who want to take care of themselves and exercise and eat well are not eating meat.
Chris: The healthy user bias.
Mark: The other part is that the people that don’t give a crap about their health are eating lots of meat, because they don’t care and they’re doing all these other bad habits.
Chris: One of the best studies I’ve seen that dealt with the healthy user bias looked at people who shopped at health food stores only. Guess what? There was no difference in lifespan or risk of disease for [those] who ate meat and didn’t eat meat.
Mark: They both had their risk reduced in half. That was like 11 thousand people. It was not a small study.
The other thing is that this was an observational study, meaning it cannot prove cause and effect. If you wake up every morning and the sun rises, it wasn’t because you woke up. It’s correlation. In these studies, they show correlation, not causation. It’s really crappy for the journalists not to elucidate that this does not prove anything.
Chris: This is why people are turning to blogs like yours and mine to get this information. Most of the people who are reading my blog are better educated about science than a lot of the so-called “science reporters.”
Mark: Right. There was another study showing that people who had higher protein diets have less belly fat and higher HDLs, which goes along with lower risk of heart disease. What do you make of that? It’s sort of the opposite of this other study, right?
Chris: I believe it. I’m an advocate of a paleo diet, [which] tends to be higher in protein. Protein is the most satiating of all macro nutrients. That means, when we eat it, we feel full, we feel satisfied. This explains why high-protein diets are associated with weight loss, and weight loss is associated with improvement in metabolic function. If you’re overweight, the fastest way [to] improve your markers, your LDL, your HDL, your triglycerides, is to lose weight. A higher protein diet is a great way to lose weight.
Mark: Higher fat too?
Chris: Yes, most of the time.
“The research on dairy fat is overwhelming at this point. Full fat dairy is consistently associated with metabolic benefits.”
Mark: What do you think is more important, the protein or the fat?
Chris: The research suggests that where a low carb diet has been effective, it may be in part because it was a high-protein diet. The protein, I think, is a crucial part of that equation. Then, whether higher fat, moderate carb, or moderate fat is the best option is an individual question. This is why there’s been so much controversy saying low fat or high fat is better. There is no one answer for everybody.
Mark: We’re all different, imagine that.
Chris: Crazy concept. Overall, the research shows, at least in the short term, a lower carb, higher fat diet will be more effective for more people.
Mark: You’re not worried about the saturated fat in meat?
Chris: I love the saturated fat in meat. It’s what makes it taste really good. I’m not worried about it.
50 years ago, the dominant paradigm was that saturated fat is harmful. It increases the risk of heart disease because it increases your blood cholesterol. Now, many large reviews have shown that saturated fat not only doesn’t affect blood cholesterol on average, it [also] doesn’t increase the risk of heart disease, and may even have an inverse association with stroke. In other words, the more saturated fat you eat, the lower your chances of having a stroke.
Mark: That other study found that in 3,000 people over 15 years, those with the highest levels of dairy fat in their blood have the lowest risk of diabetes by 40 to 50%.
Chris: Yeah, the research on dairy fat is overwhelming at this point. Full fat dairy, but not non-fat or low fat, is consistently associated with metabolic benefits, cardiovascular benefits, lower risk of diabetes, lower risk of heart disease, and lower risk of stroke.
Mark: It’s true. There are some experts who say, “It’s really not true that this is the story, because we dramatically increased our intake of fat. We have increased our intake of meat. That’s what’s correlating with this epidemic of obesity and diabetes and heart disease.” That’s true, but our consumption of red meat has gone dramatically down, [by] over half. Our consumption of butter, lard, and tallow has been cut in half or more. Our consumption of eggs is dramatically reduced. What has increased is our intake of chicken, and our intake of vegetable oils.
Chris: Soybean oil.
Mark: Soybean oil is very inflammatory. It also seems to be associated with increased cardiovascular harm.
I was with Dr. Joe Hibbeln in Washington. He was saying, “Even though it’s white meat, chicken is actually bad for you because of all the Omega-6 fats. [The chickens] are eating all these grains that have inflammatory vegetable oils.” He says they’re trying to design chickens with Omega-3 fats in them, like a chicken-fish.
“If I could sum it up in three words, it’s just eat real food.”
Chris: It’s ironic because that’s always been perceived as the healthy meat, right?
Let’s loop back to a topic that’s hot in the news. A couple of weeks ago, there was a review article by Dr. Mozaffarian and PLS. They reviewed six hundred thousand people in 15 studies. They were like, “Gosh, there doesn’t seem to be a lot of evidence that butter is bad. In fact, there seems to be an inverse correlation with diabetes and no effect on heart disease.” What do you make of that?
Chris: The conclusion was very cautious. It was like, “There’s no evidence to support butter restriction.” They didn’t go into all the evidence that suggested eating butter isn’t just not harmful, that it actually may be beneficial.
Mark: May be helpful?
Chris: Yeah. It may help you prevent diabetes. The mechanisms are not fully understood, but they’re thought to involve beneficial fats that dairy fat has, like natural trans fats. We’ve heard all about the bad artificial trans fats, but conjugated Linoleic acid, for example, is a natural trans fat that seems to have health benefits.
Mark: Weight loss, diabetes, cancer.
Chris: Absolutely, and butter has nutrients that are hard to get elsewhere in the diet, like Vitamin A and Vitamin K2—especially if the butter is pasture raised, grass-fed. One wonders… if the study had just looked at pasture raised, grass-fed butter, the results probably would have been even better.
Mark: What about the people who say, “Oh, saturated fat’s inflammatory. It seems to activate inflammatory pathways in the body, and you should be concerned about it?”
Chris: It definitely does if you’re a mouse.
Mark: In animal studies, it seems to be a problem. But what if you’re a human?
Chris: This is where it all comes down to context. If you are a human, and you’re eating large amounts of saturated fat, and you’re also drinking Big Gulps and eating Cheese Doodles and muffins and cookies and pizza, then the combination of those acellular carbohydrates is like mainlining sugar. It’s feeding the harmful bacteria in your guts, creating a dysbiotic state, which then leads to what’s called “metabolic endotoxemia.” It’s a proliferation of bad bacteria that produce endotoxins. Those endotoxins then cause a leaky gut. They cause our gut to become permeable. They get into the bloodstream and it creates an inflammatory state.
Mark: I call that sweet fat. It’s ice cream, donuts, french fries. It’s starch and sugar combined with fat. Bad news.
Chris: If you’re eating a standard American diet and you’re eating high saturated fat, it’s probably not going to do you any favors.
But if you’re going to show that saturated fat causes metabolic endotoxemia, and you’re going to argue, therefore, that it’s inflammatory, then you have to account for the observational data that show that, on average, saturated fat is not increasing the risk of heart disease.
Mark: Right, doesn’t make sense.
Chris: How do you explain that? There must be some other mechanism that is countering that mechanism. That’s what happens when you get too focused on the details, you can lose sight of the big picture. There’s one other thing, which is that studies have shown that a higher fiber intake can mitigate the potentially adverse effects on the gut flora of a high fat diet.
Mark: What you’re saying is so key. If you eat saturated fat, and you have plenty of Omega-3s, and lots of fiber, and not a lot of starch and sugar, no problem. If you’re eating saturated fat with no fiber, no Omega-3 fats and tons of sugar, you’re in trouble.
Chris: Yes, exactly. We have 50 years of data that supposedly told us that saturated fat was harmful. Then we have newer, better designed, more comprehensive studies that did a better job of controlling for the healthy user bias, [which] show us that it’s not. If I could sum it up in three words, it’s just eat real food.
Mark: Very few steps from the field to the fork.
This conversation has been edited and condensed.