The investigative journalist uses hard science to examine the history of saturated fat’s bad reputation. Excerpted from “The Big Fat Surprise: Are Butter, Meat and Cheese Healthy?” August 7, 2014.

NINA TEICHOLZ, Author, The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet
In conversation with RONALD M. KRAUSS, M.D. Senior Scientist and Director, Atherosclerosis Research, Children’s Hospital Oakland Research Institute; Adjunct Professor, Department of Medicine, UCSF and Department of Nutritional Sciences, UC Berkeley

NINA TEICHOLZ: For 50 years, we’ve felt guilty about eating red meat, creamy cheese, butter, whole-fat dairy and fried eggs. We’ve been avoiding these foods because they contain saturated fat, and saturated fats are supposed to be the number one dietary culprit in causing heart disease. These foods are naturally high in fat, and we also believe that fat makes you fat, so we avoid them.

My plan tonight, through an analysis of the science and the history, is to try to take some of the guilt out of those guilty pleasures.

Where do our ideas about fat come from? It really goes back to the 1950s when the nation was in a panic over the rising tide of heart disease, which had seemingly come out of nowhere in the early 1900s to become the nation’s number one killer. President Eisenhower himself had a heart attack in 1955 and was out of the Oval Office for 10 days. So there was a tremendous sense of urgency about the need to find an explanation for what might be causing heart disease.

There were a number of different ideas. Some were that it was excessive stress, vitamin deficiency or automobile exhaust. However, the winning theory was proposed by one scientist, whose name was Ancel Keys, a pathologist at the University of Minnesota. He came up with the idea that it was saturated fats that caused heart disease. They would raise your total cholesterol; therefore, they would clog your arteries and cause a heart attack. This was called the diet-heart hypothesis.

The American Heart Association—their advice has long been considered the gold standard for fighting heart disease—and the nutrition committee had been openly skeptical of Ancel Keys’ ideas. But then, [Keys] managed to get himself appointed to the committee, and, just a year later, he was able to swivel the committee around to follow his own views. In 1961, the American Heart Association issued the country’s very first anti-saturated fat advice to middle-aged men, telling them to cut back on meat, cheese and full-fat dairy as their best strategy to avoid heart disease.

But what, at the time, was the evidence that supported this hypothesis? In 1961, it really boiled down to one study that, coincidentally, had been done by Ancel Keys. It really was the Big Bang of all nutrition studies, because it was a time when the whole field was in its infancy and very little science had been done.

[Keys] did this heroically pioneering effort called the Seven Countries Study. He studied almost 13,000 men in seven countries, including Europe, the United States and Japan. And he found what he had hoped to find, which was a correlation between low consumption of saturated fat and the risk of having a heart attack.

But his study has since been analyzed by a number of critics, and the methodological problems that have been found are really quite significant, calling into question the whole study itself. For one, he deliberately chose countries that he knew would support his hypothesis: he chose countries like Italy and Greece, where he knew that they had a low consumption of saturated fat and low rates of heart disease, while avoiding France, Germany, Switzerland, where they ate a lot more saturated fat, but also had low rates of heart disease.

Then there’s the problem that he had tremendous problems with his dietary and survey data. He ended up throwing out all of his dietary surveys, ending up with a sample of only 500 men out of nearly 13,000. His star data subjects, who ate only 8 percent of all their calories as saturated fat and had low rates of heart disease, were on the island of Crete. He and his researchers sort of fell in love with the island of Crete, but they only got reliable dietary data from 33 or 44 men there. None of those sample sizes were statistically significant.

Even with all of those problems aside, it was what’s called an epidemiological study, which shows association and not causation. That’s a really important theme that runs throughout the history of nutrition science: it’s very hard to [study] nutrition science, especially [to run] the kind of clinical trials that really [provide] the firm, hard evidence that can be used to establish causation. It’s hard to feed people; it’s expensive. It’s hard to get people to change their diets over any period of time. And in the absence of that kind of harder data, it’s this soft epidemiological data, this associational data, that has been made to suffice. That really started with Ancel Keys and his Seven Countries Study.

But of course it wasn’t just one man and one study. There are many scientists, and obviously, expert scientists, so how did this idea get propelled along? The short answer is that it really became institutionalized and hardened into dogma before those clinical trials could be conducted, so opinions were formed and the policy was set before the science was actually done.

The same group came to control the allocation of research grants, and they’d carry out the studies that were funded by those grants, and they would review each other’s studies. They sat on the editorial boards of the research journals. Everyone really got on board with this “cholesterol bandwagon,” as it was called by the editors of the Journal of the American Medical Association. They said that an almost embarrassingly high number of researchers boarded the cholesterol bandwagon. It was an overly narrow, fervent embrace of cholesterol to the exclusion of all other biochemical processes that might cause heart disease.

That was in 1967. It was the same select group of experts who were influential in the late 1970s in advising the U.S. Senate when they took up the subject. Senator George McGovern led a committee, and the outcome of that committee’s work was the conclusion that a low-fat diet also restricted in meat and dairy products should be recommended, not just for middle-aged men, but for all Americans over the age of two. That led the USDA to issue the very first dietary guidelines in 1980. Dietary guidelines are the basis of the food pyramid that you probably all know. So now you have all the giant wheels of the massive federal government working behind this one hypothesis, that saturated fat and cholesterol cause heart disease. All of the accompanying agencies got in line behind it because that was the wheel of the government.

So, in this environment where institutions, research dollars and other investments were all lining up behind one idea, it was very hard to do good science or to be a good scientist. Scientists are trained to try to confront their biases and to constantly question and challenge their beliefs. The great philosopher of science, Karl Popper, described it: “The method of science is the method of bold conjectures and ingenious and severe attempts to refute them.” But this was an environment where the exact opposite was going on.

A bias set in amongst experts: they selected data points in their favor, and they ignored those that were not in their favor. It’s called selection bias, and it is fairly stunning to see this at work over the decades of nutrition science since the 1960s.

There are really four major clinical trials that are supposed to be the bedrock proof of the diet-heart hypothesis. [These trials] showed that vegetable oils did successfully lower total cholesterol. In some of the trials there was actually a reduction in cardiac events, but there were significantly higher rates of death from other things, including cancer, and higher rates of gallstones. All of that was so worrying that in the early 1980s, the National Institute of Health had a series of expert panels to try to figure out what that was about, and they couldn’t. Overall mortality in the two groups was the same, so these trials could not demonstrate that you could lengthen your life by cutting back on saturated fats.

But at a certain point, there was just no turning back. There were literally billions of dollars in research funds invested in this hypothesis. Careers were founded upon it, institutions depended upon it, and too much institutional energy and research money had already been spent trying to prove this hypothesis. By the mid-1980s, the critics were basically silenced. Through a mixture of politics, bias, personal ambition and bad science, a consensus had been sealed up.

What was the role of the food companies? I’m often asked: Where were the meat, egg and dairy producers? Why did they not stop this? Weren’t they so powerful? To which I answer: They were powerful—they are powerful—and they did try, but it turns out the big manufacturing companies are more powerful. Companies who, since the 1940s, have known the importance of influencing nutrition science: General Foods, Quaker Oats, National Biscuit Company, Corn Products Refining Company.

But I have to say that the mistakes that were made were really primarily ones of science. Scientists are the gatekeepers on expert panels publishing public health advice. And I truly believe that they really believe their recommendations. It’s just that the initial science was weak, and they jumped the gun on it, and the science could never catch up.

So what are the unintended consequences? Is there a link between this dietary advice and the load of disease that we’re suffering from today? I think there are basically two unintended consequences.

One consequence is that we’ve increased vegetable oils as we’ve been told. Before 1900, the only fats that American housewives cooked with were butter and lard. We ate in 1900 pretty much 0 percent of our calories as vegetable oils. Now we eat 7 or 8 percent of all of our calories as vegetable oils. These oils have brought with them a number of unknown issues. When they’re hardened, through a process called hydrogenation—to make Crisco, which was introduced in 1911, and then margarine, both hugely successful products—one of the byproducts of that is trans fats, the health effects of which we only have really started to understand relatively recently.

It’s been known since the 1940s that when these vegetable oils are heated, they produce toxic oxidation products: more than 100 of them have been found in a single piece of chicken fried in vegetable oil alone. And these toxic products appear to produce huge inflammatory effects and possible gastric damage, amongst many other things. Our state of understanding, our reckoning with the science, is pretty much where we were with trans fats back in the 1970s.

One of the unsung good qualities of saturated fats is they are solid at room temperature. They’re stable; they do not oxidize when heated. It used to be that McDonald’s fried their French fries in tallow. Now, we have switched over to vegetable oils, about which we know so little. That’s one of the unintended consequences of getting rid of saturated fats.

The other major unintended consequence is the increased amount of carbohydrates that we eat. In retrospect, it seems obvious this would happen: if you take meat, cheese and eggs off the plate, foods that have historically been at the heart of our meals, what fills the empty space? The answer is pasta, grains, potatoes, and these are all very high in carbohydrates. The USDA instructed us to do this: that giant bottom slab of the USDA food pyramid is all grains, bread, pasta.

The problem with carbohydrates is that they break down into glucose in the bloodstream. Glucose triggers the release of insulin, and insulin seems to be the king of all hormones for sucking away fat. In fact, experiments on animals show it’s almost impossible to get fat without insulin, and chronic exposure to insulin seems to be what leads to type 2 diabetes. Again, it’s carbohydrates that are the main cause of insulin release in your bloodstream.

It seems like fat does not make you fat. That seems like just a tragic homonym. The fat we eat—we’ve always thought it was the fat we get. Same word, but there does not seem to be a connection. The idea that fat doesn’t make you fat, that overall we shouldn’t be limiting fat, seems to kind of have percolated into the expert community. But there’s still a strong belief that saturated fat, the kind in meat, cheese, butter, dairy, eggs, causes heart disease and is bad for you.

Beyond the argument that saturated fat isn’t bad for you, can you make the argument that saturated fat is actually good for you? Should we not just stay away from these foods as a measure of caution, or are there arguments for eating meat, dairy, butter, eggs, cheese? I think there are.

One [argument] is that these foods are extremely nutritionally dense. Certain vitamins such as B6 and B12 are uniquely available in animal foods. Other vitamins, A, D, E and K, can only be absorbed when they’re accompanied by fat. So if you’re drinking skim milk, you’re not fully absorbing these vitamins, and without those vitamins, you’re not absorbing the minerals. Animal foods are really the naturally occurring, perfect package of vitamins and minerals, together with the fat needed to absorb them. Red meat turns out to be far more nutrient-dense than chicken; red meat contains selenium, folate, iron, zinc, which are barely present in chicken. So these animal foods really deliver a powerful dose of healthy nutrition that is not so easily available from plant foods.

These foods are almost essential if you want to eat a diet higher in fat. Over the past decade there have been a lot of clinical trials comparing a high-fat, carbohydrate-restricted diet to a low-fat diet. The high-fat diet really performs much better in terms of weight loss, diabetes and heart disease markers. How do you get to a high-fat diet? Unless you’re Italian peasants drinking bowlfuls of olive oil, it’s hard, though not impossible, to eat a high-fat diet without eating animal foods.

Also, these foods are uniquely satiating, which is to say there’s something about fat and protein we don’t really quite understand but that fills you up. [Scientists] have tried to make prisoners overeat on meat, and they just cannot. The [prisoners in the studies] look at a stack of pork chops and cannot eat any more. Whereas experiments have found, it’s very easy to overeat on carbohydrates – on pasta, popcorn. Those foods are not as naturally satiating. So it could very well be that because we’ve so greatly reduced animal foods over the last 30 years, we’re all walking around in a state of being hungry, trying to fill up on carbs.

We do eat more calories now than we did 40 years ago. Why is that? Did we all become gluttonous? Why did our grandparents have an easier time of not being gluttonous? It’s possible that we’re just not eating enough fat and protein, and we’re trying to fill ourselves up on carbohydrates.

One other [argument] in favor of saturated fats: Before the epidemics of heart disease, obesity and diabetes, these fats were at the centerpieces of meals for thousands of years. From Athena laying down a fat goat in the chine of a great wild hog rich in lard for Odysseus, to Isaiah prophesizing in the Old Testament that the Lord would make unto all people a feast of fat things, of fat things full of marrow, to Pip’s theft of a pork pie in Great Expectations, it is very hard to find people eating salads in history and in the history of literature.

Nutrition science has really ignored this history at our peril. It’s time to welcome these nutritious and delicious foods, guilt-free, back into our lives.

RONALD M. KRAUSS: Here’s a question that I think touches on the idea of establishing causality from the kind of evidence that we have in nutrition: Instead of saturated fats, do you believe that processed foods are a leading cause of obesity and heart disease?

TEICHOLZ: “Processed foods” is a highly unspecific term. You can process vegetable oil, that’s one thing; you can process flour, that’s another thing; you can process meat, that’s something else. Those all have very different kinds of macronutrient contents, so I think it’s kind of a vague term.

KRAUSS: Part of the issue is that there’s specificity at the level of a food that can’t easily be deconstructed from its individual components. Processing is one of those things that carries with it the stigma of losing something that’s natural in the whole food itself. I believe it touches a little bit on the vegan question because such diets can be consumed using whole wheat and natural foods that avoid some of the types of processed foods that I think we are concerned with, such as carbohydrates. How do we quell environmentalists and animal rights activists and feed the world’s population on this healthy diet?

TEICHOLZ: The environmental, ethical questions around eating animal foods are huge. The scope of my book was: What is healthy? And that took years and years of research. There’s so much discordance and disagreement about what a healthy diet is. I feel like we need to get to some agreement and understanding of [what is healthy], and then figure out how to make those foods sustainable. How do you raise animal foods sustainably in a way that is ethical and humane?

KRAUSS: What is your opinion on the high-fat, low-carb Mediterranean diet?

TEICHOLZ: What I suggest in my book is that it might be possible that any higher fat diet is healthier than a low-fat diet. The Mediterranean diet does seem to be healthier than a low-fat diet. It’s possible that there are other high-fat diets and other traditions in Sweden, in Holland, in other places where they eat a lot of fat, and people might want to eat their own ancestors’ diet rather than have us all eating a Mediterranean diet.

KRAUSS: There is the potential, in the sound bite coverage of this whole topic, to swing from one end of the pendulum to the other. There’s evidence on the other side that would suggest that we should be increasing our intake of saturated fat, which could be done in ways that we don’t yet know the consequences of.

TEICHOLZ: You get to the absolute heart of the issue here, which is that saturated fats have been unfairly condemned. The evidence seems to have dissolved. So if you have false evidence against something, let it out of jail, right? Why keep it in jail? Why force it to prove itself to a higher standard than, say, broccoli or kale? Why should it be forced to be the subject of a two-year-long clinical trial high in saturated fat? It’s like keeping somebody in jail and saying, “You need to show good behavior, even though all our evidence against you is gone.”

I do not make the argument that people should be going out and eating sticks of butter. There are people making this argument, but I don’t. But I think this is really at the heart of the issue, and it’s again where I draw upon the lessons of history and examples of populations who have been healthy, historically, because I think nutrition science has ignored that historical record.