Who do you look to for information about health and nutrition?
Certainly, conventional advice – advice that is provided in influential publications such as the U.S. government’s Dietary Guidelines for Americans – can be trusted.
If only it were that simple.
A combination of flawed studies, political bias, hidden data, and clever marketing by the food industry led to the demonization of dietary fat and the birth of the low-fat craze – a trend that has lasted decades.
That trend is likely a major cause of most of the serious health problems so many people are experiencing today.
To better understand where the advice to avoid dietary fat came from, a short nutrition science history lesson is necessary.
Minnesota, Seven Countries, and George McGovern
The idea that dietary fat was bad for health didn’t start until around 1940, when some scientists and physicians started to suspect that diets high in saturated fats and cholesterol were linked to heart disease. This was based on their interpretation of some early research and speculation.
Then along came Ancel Keys.
Keys was a scientist who studied the influence of diet on health. One of Keys’ major research projects was known as the Seven Countries Study, which was conducted from 1958 to 1964. For that study, he and his team gathered data on the diets, lifestyles, and health of 12,770 middle-aged men in Italy, Greece, Yugoslavia, Finland, Netherlands, Japan, and the United States.
There were problems with the study’s design: there was no objective basis for the countries chosen by Keys. Did he intentionally choose those he suspected would support his hypothesis? It’s hard to say for sure, but Keys knew that the French and Germans had relatively low rates of heart disease, despite living on a diet rich in saturated fats – and he chose to leave those countries out of his research. In addition, chronic diseases usually take decades to develop, and studies that track them are usually follow participants for much longer than 6 years (15+ years is more common).
Nevertheless, Keys claimed his findings showed a correlation between intake of saturated fats and deaths from heart disease, but even some supporters of his hypothesis were skeptical and said his “evidence” was inconclusive.
Keys conducted another study called the Minnesota Coronary Experiment (MCE), which seemed to confirm what he found in the Seven Countries study, and prompted the federal government to recommend low-fat diets to the entire nation.
But the full story of the MCE should serve as a cautionary tale, a lesson that teaches us just how difficult it can be for new evidence (or even the full truth) to see the light of day when it contradicts widely held theories and beliefs.
The MCE was a major controlled clinical trial that was conducted from 1968 to 1973 and was led by Keys and Dr. Ivan Frantz. They studied the diets of more than 9,000 people at state mental hospitals and a nursing home to compare the effects of two diets. One group of patients was fed a diet intended to lower blood cholesterol and reduce heart disease. It contained less saturated fat, less cholesterol and more vegetable oil (corn oil, which is an unsaturated fat that is common in many processed foods). The other group was fed a more typical American diet (meals rich in saturated fats from milk, cheese, and beef).
The researchers intent was to show that removing saturated fat from people’s diets and replacing it with polyunsaturated fat from vegetable oils would protect them against heart disease and lower their mortality.
The special diet did reduce blood cholesterol in patients. While it didn’t seem to have any effect on heart disease, researchers said they suspected that a benefit would have appeared if the experiment had gone on longer.
There was “a favorable trend,” they wrote, for younger patients.
Even though some studies did not support what came to be known as the “diet-heart hypothesis” (also referred to as the “lipid hypothesis” or “fat hypothesis”), and there was no actual proof of a link between dietary fat and cardiovascular disease, the ideology picked up speed.
But it wasn’t pushed upon the public at large until 1977 – that’s when the U.S. Senate’s Select Committee on Nutrition and Human Needs, chaired by George McGovern, published its report titled Dietary Goals for the United States. That report encouraged people to switch to nonfat milk and limit the consumption of butter and eggs. Some scientists remained skeptical of these suggestions, but the advice spread like wildfire anyway.
By 1980, the idea that a low-fat diet could help reduce risk of heart disease and cancer was generally accepted within the scientific community. The World Health Organization and the Surgeon General promoted the diet.
The principles of that special diet — less saturated fat, more vegetable oils — are still recommended by the Dietary Guidelines for Americans, the government’s official diet guidelines, and have been widely accepted as nutrition gospel for decades.
But the data from the MCE was never fully analyzed.
Until now, that is.
From a Basement to the BMJ
Several years ago, Dr. Christopher E. Ramsden, a medical investigator at the National Institutes of Health, learned about the long-overlooked study. He contacted the University of Minnesota in hopes of reviewing the unpublished data.
Dr. Robert Frantz, the MCE lead researcher’s son and a cardiologist at the Mayo Clinic, found a box marked “Minnesota Coronary Survey,” in his father’s basement. He turned it over to Dr. Ramsden for analysis.
What Ramsden and other investigators from the National Institutes of Health and the University of North Carolina found during their analysis surprised them: the patients who lowered their cholesterol, presumably because of the special diet, actually suffered more heart-related deaths than those who did not.
The findings clash with conventional dietary recommendations that advise a diet low in saturated fat to decrease heart risk. Current dietary guidelines say to replace saturated fat with vegetable oils and other polyunsaturated fats, in hopes of lowering cholesterol.
“Incomplete publication has contributed to the overestimation of benefits and underestimation of potential risks” of the special diet, the researchers wrote.
“Had this research been published 40 years ago, it might have changed the trajectory of diet-heart research and recommendations,” said Daisy Zamora, a researcher at UNC and a lead author of the study, which was published in the BMJ.
It isn’t clear why the full data from the MCE was never published, but some say it is possible that Frantz and Keys didn’t publish the findings in full because they were so “contrary” to the popular scientific beliefs of the time.
In their findings, Zamora and Ramsden wrote:
There would have been little or no scientific or clinical trial literature at the time to support findings that were so contrary to prevailing beliefs and public policy. And, finally, it is possible that medical journal reviewers would not have accepted study results for the reasons cited above.
Steven Broste, now a retired biostatistician, was a student at the University of Minnesota and used the full set of the MCE data for his master’s thesis in 1981.
He told The Washington Post that at least part of the reason for the incomplete publication could be human nature. Frantz and Keys had a theory they believed in – that reducing blood cholesterol would make people healthier. The idea was widespread and was to be adopted by the federal government in the first dietary recommendations. So when the data they collected conflicted with their theory, they may have been reluctant to believe what their experiment revealed, Broste explained.
The results flew in the face of what people believed at the time. Everyone thought cholesterol was the culprit. This theory was so widely held and so firmly believed — and then it wasn’t borne out by the data. The question then became: Was it a bad theory? Or was it bad data? … My perception was they were hung up trying to understand the results.
The younger Dr. Frantz told The New York Times that his father was probably startled that there seemed to be no benefit in replacing saturated fat with vegetable oil.
When it turned out that it didn’t reduce risk, it was quite puzzling. And since it was effective in lowering cholesterol, it was weird.
After collecting all the data from the Minnesota trial, Zamora and Ramsden combined it with four published randomized, controlled trials that also substituted saturated fat with vegetable oils high in linoleic acid. Like the Minnesota trial, this additional meta-analysis found there was no benefit to switching to these oils when it came to death by coronary heart disease – or death by any cause.
Why linoleic acid-containing oils (which include corn oil, safflower oil, soybean oil, sunflower oil, and cottonseed oil) would lower cholesterol but worsen or at least fail to reduce heart attack risk is a subject of ongoing research and much debate. Some studies suggest that these oils can cause inflammation, a known risk factor for heart disease and a multitude of other health problems. There is also some evidence they can promote atherosclerosis when the oils are chemically modified in a process called oxidation.
“Altogether, this research leads us to conclude that incomplete publication of important data has contributed to the overestimation of benefits – and the underestimation of potential risks – of replacing saturated fat with vegetable oils rich in linoleic acid,” said Zamora.
Dissenters Silenced and Shunned
The fat-hypothesis has always had critics, but most were ignored or shunned.
Years after the Seven Countries Study findings were published, the lead Italian researcher, Alessandro Menotti, went back to the data. He found that the food that correlated most closely with deaths from heart disease was not saturated fat, but sugar.
This was in line with what one of the most outspoken critics of the fat hypothesis – Dr. John Yudkin – had been saying for years.
In 1957, Yudkin, who was a British physiologist and professor of nutrition, presented a hypothesis that presented an alternative to the one made by Keys.
Yudkin looked at the data on heart disease and was struck by its correlation with the consumption of sugar, not fat. He carried out a series of laboratory experiments on animals and humans, and observed, as others had before him, that sugar is processed in the liver, where it turns to fat, before entering the bloodstream.
As early as 1967, Yudkin suggested that the excessive consumption of sugar might result in a disturbance in the secretion of insulin, and that this in turn might contribute to atherosclerosis and diabetes.
Yudkin’s warning that it was not dietary fat, but sugar, that was a major contributor of the development of conditions such as obesity, diabetes, and heart disease was criticized and ridiculed by the food industry and other researchers – including Keys.
In 1972, Yudkin published the book Pure, White and Deadly, which was a huge success, much to the dismay of the food industry.
“If only a small fraction of what we know about the effects of sugar were to be revealed in relation to any other material used as a food additive,” wrote Yudkin, “that material would promptly be banned.”
In 1973, Yudkin was called from London to testify before McGovern’s congressional Dietary Guidelines committee. It took most of its evidence from America’s nutritional elite: men from a handful of prestigious universities, most of whom knew or worked with each other, all of whom agreed that fat was the problem – an assumption that McGovern and his fellow senators never seriously questioned.
Yudkin presented his alternative theory about heart disease, and a reportedly confused McGovern asked the scientist if he was really suggesting that a high fat intake was not a problem, and that cholesterol presented no danger.
“I believe both those things,” replied Yudkin.
“That is exactly the opposite of what my doctor told me,” said McGovern.
The last paragraph of Chapter 1 of Yudkin’s book begins, “I hope that when you have read this book I shall have convinced you that sugar is really dangerous.”
This message was extremely unwelcome to the sugar industry and manufacturers of processed foods. These firms employed a number of methods to impede Yudkin’s work. The final chapter of Pure, White and Deadly lists several examples of attempts to interfere with the funding of his research and to prevent its publication.
It also refers to the scathing language and personal smears that Keys employed to dismiss the evidence that sugar was the true culprit. Keys wrote, for example:
It is clear that Yudkin has no theoretical basis or experimental evidence to support his claim for a major influence of dietary sucrose in the etiology of CHD; his claim that men who have CHD are excessive sugar eaters is nowhere confirmed but is disproved by many studies superior in methodology and/or magnitude to his own; and his “evidence” from population statistics and time trends will not bear up under the most elementary critical examination. But the propaganda keeps on reverberating …
Yudkin was promptly shunned, called names, uninvited to international conferences, and censored, as The Telegraph explained in John Yudkin: the man who tried to warn us about sugar:
The British Sugar Bureau put out a press release dismissing Yudkin’s claims as “emotional assertions” and the World Sugar Research Organisation described his book as “science fiction”. When Yudkin sued, it printed a mealy-mouthed retraction, concluding: “Professor Yudkin recognizes that we do not agree with [his] views and accepts that we are entitled to express our disagreement.”
Yudkin was “uninvited” to international conferences. Others he organised were cancelled at the last minute, after pressure from sponsors, including, on one occasion, Coca-Cola. When he did contribute, papers he gave attacking sugar were omitted from publications. The British Nutrition Foundation, one of whose sponsors was Tate & Lyle, never invited anyone from Yudkin’s internationally acclaimed department to sit on its committees. Even Queen Elizabeth College reneged on a promise to allow the professor to use its research facilities when he retired in 1970 (to write Pure, White and Deadly). Only after a letter from Yudkin’s solicitor was he offered a small room in a separate building.
Unfortunately, this smear campaign didn’t affect just Yudkin: by the end of the 1970s, he had been so discredited that other scientists were hesitant to publish anything negative about sugar for fear of being similarly attacked.
Where does this leave us?
Recent research on dietary fat and sugar sure make it seem like the recommendations of the last few decades are, well, backwards. Demonizing fat led the food industry to add sugar to their new low-fat and no-fat products to make them palatable.
We have been consuming less fat and more sugar, when we should have been doing the opposite.
Yudkin died in 1995, but his work is finally being vindicated by new discoveries and a growing body of research. Diets high in sugar have been linked to the development of heart disease, obesity, type 2 diabetes, non-alcoholic fatty liver disease, kidney disease, cancer, deficiencies in cognitive health, and cell aging.
One recent study showed that “ultra-processed” foods make up more than half of all calories consumed in the US and almost all of our added sugar intake.
The moral of this tragic story is this: we can’t rely on the government to provide us with accurate information about nutrition. That’s not going to happen – Big Sugar is a large, powerful, and wealthy industry that has been using Big Tobacco-style tactics to influence policy and ensure that government agencies dismiss troubling health claims against their product for decades.
Our health – and that of our families – is in OUR hands.