Several people posted comments or sent emails with links to articles about a “rediscovered” study from the 1960s. Let’s look at some quotes from the Washington Post article:
It was one of the largest, most rigorous experiments ever conducted on an important diet question: How do fatty foods affect our health? Yet it took more than 40 years — that is, until today — for a clear picture of the results to reach the public.
The fuller results appeared Tuesday in BMJ, a medical journal, featuring some never-before-published data. Collectively, the fuller results undermine the conventional wisdom regarding dietary fat that has persisted for decades and is still enshrined in influential publications such as the U.S. government’s Dietary Guidelines for Americans. But the long-belated saga of the Minnesota Coronary Experiment may also make a broader point about how science gets done: it suggests just how difficult it can be for new evidence to see the light of day when it contradicts widely held theories.
The difficulty lies in the fact that scientists are freakin’ liars.
The story begins in the late 1960s and early ’70s, when researchers in Minnesota engaged thousands of institutionalized mental patients 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. The other group was fed a more typical American diet.
Just as researchers expected, the special diet reduced blood cholesterol in patients.
Well then, those patients whose cholesterol dropped must have suffered fewer heart attacks and lived longer.
Today, the principles of that special diet — less saturated fat, more vegetable oils — are recommended by the Dietary Guidelines for Americans, the government’s official diet advice book.
And have been since 1980 – because of all the solid evidence supporting switching from animal fats to vegetables oils, doncha know.
Yet the fuller accounting of the Minnesota data indicates that the advice is, at best, unsupported by the massive trial. In fact, it appears to show just the opposite: Patients who lowered their cholesterol, presumably because of the special diet, actually suffered more heart-related deaths than those who did not.
The higher rate of mortality for patients on the special diet was most apparent among patients older than 64.
In other words, within the group most likely to suffer a heart attack in the first place. Hooray for vegetable oils that lower our cholesterol!
It’s not exactly clear why the full set of data from the Minnesota experiment was never published.
Oh, I think I can guess.
“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.
And that’s why it wasn’t published.
The results of the study were never touted by the investigators. Partial results were presented at an American Heart Association conference in 1975, and it wasn’t until 1989 that some of the results were published, appearing in a medical journal known as Arteriosclerosis.
Amazing. A big, expensive study is conducted to test the hypothesis that switching from saturated fats to vegetable oils will reduce heart disease by lowering cholesterol. The results show the opposite – at a time when many Americans were being encouraged to follow exactly that advice. What kind of lousy @#$%ing scientist would bury the results instead of publishing them?
The lead investigators of the trial, noted scientists Ancel Keys and Ivan Frantz, are deceased.
You’ve gotta love Ancel Keys. The guy conducts an observational study by giving two dietary questionnaires to a whopping 30 or so people in seven countries. From this itty bitty dataset, he decides he’s proved that saturated fats cause heart disease. Meanwhile, he tries to destroy the careers of other researchers who question his findings.
Then when his own clinical study – involving thousands of patients – shows that switching to vegetable oil increases heart disease and overall mortality, he clams up and doesn’t publish the results. What an awesome scientist he was.
In an exceedingly strange turn of events, data from a clinical trial dating from the 1960s, long thought to be lost, has now been resurrected and may contribute important new information to the very contemporary controversy over recommendations about dietary fat composition.
“Exceedingly strange” has now happened twice.
One trial that actually tested the hypothesis was the Sydney Diet Heart Study, which ran from 1966 through 1973. In the trial, 458 men with coronary disease were randomized to a diet rich in linoleic acid (the predominant omega 6 PUFA in most diets) or their usual diet. Although total cholesterol was reduced by 13% in the treatment group during the study, all-cause mortality was higher in the linoleic acid group than in the control group. However, in the original publications, and consistent with the practice at the time, deaths from cardiovascular (CVD) and coronary heart disease (CHD) deaths were not published.
Now, in a new paper published in BMJ, Christopher Ramsden and colleagues report that they were able to recover and analyze data from the original magnetic tape of the Sydney Diet Heart Study. The new mortality findings are consistent:
• All cause: 17.6% in the linoleic group versus 11.8% in the control group, HR 1.62, CI 1.00-2.64)
• CV disease: 17.2% versus 11%, HR 1.70, CI 1.03-2.80
• CHD: 16.3% versus 10.1%, HR 1.74, CI 1.04-2.92
People who switched to the vegetable did worse all around: higher all-cause mortality, higher mortality from cardiovascular disease in general, higher mortality from heart disease. But as with the Minnesota study, the results didn’t see the light of day for decades. The explanation offered was that a computer data tape was misplaced and only found 40 years later.
What a strange coincidence. We have two large, well-controlled studies conducted around the same time. Both show that switching from saturated animal fats to vegetable oils actually leads to higher mortality rates (including deaths from heart disease), despite lowering cholesterol significantly. A total poke in the eye for the Lipid Hypothesis. And somehow, the results of both studies were buried for 40 years.
No wonder the researchers who crunched the “lost” Minnesota data wrote this:
Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid.
I interpret “incomplete publication” as a polite version of scientists are freakin’ liars.
Naturally, researchers who’ve spent years promoting the switch from saturated fats to vegetable oils immediately called a press conference to offer their apologies and a promise to re-evaluate their positions.
Kidding! Of course that didn’t happen. Here’s what did happen:
“The bottom line is that this report adds no useful new information and is irrelevant to current dietary recommendations that emphasize replacing saturated fat with polyunsaturated fat,” Walter Willett, chair of the nutrition department at Harvard University, said in a blog post from the school. “Many lines of evidence support this conclusion.”
He characterized the new analysis of the old experiment as “an interesting historical footnote.”
So Willett, like Ancel Keys, considers his observational studies to be rock-solid evidence, but dismisses clinical trials if the results undermine what he already “knows.”
As Max Planck said, science advances one funeral at a time. Ancel Keys is dead. A few more funerals, and we may finally see the Lipid Hypothesis end up on the Scrap Heap of Wrong Ideas, where it clearly belongs.