Does saturated fat increase our risk of heart disease? For forty years, doctors have advised Americans to avoid animal fats and stick to polyunsaturated vegetable oils, for heart health. But there's more and more skepticism about that recommendation. The Food Guys share news of a study from forty years ago which sheds new light on the topic.
Greg Patent and Jon Jackson travel back to the mid-1960s, when an alarming rise in the number of heart attacks led scientists to look for causal links between diet and heart health.
Based on the results of his 1970 "Seven Countries" study, American nutritionist Ancel Keys concluded that dietary fat - especially saturated fat - was to blame for high serum cholesterol and thus for heart attacks. British physiologist John Yudkin disagreed, naming sugar, especially fructose, as the cause of heart disease as well as cavities, obesity, liver disease, and some forms of cancer.
Later, critics of the Seven Countries study pointed out that although 22 countries were studied, Keys's thesis found supportive data in only 7 of them - and residents of these seven countries didn't just eat little saturated fat; they also ate very little sugar.
Yudkin's 1972 book, "Pure, White and Deadly," argued that dietary fat and saturated fat are harmless. He was quickly attacked by Keys. Greg sums up what followed: "Keys won." In response to the work of Keys and other advocates of low fat consumption, in the 1970s, the food industry successfully manufactured a huge market for its own processed foods, which contained little saturated fat but lots of sugar. What Yudkin warned of has followed: a sharp increase in obesity, Type 2 diabetes and heart disease among Americans.
For decades, Yudkin's point of view was nearly silenced. But recently, the tide has turned. It's not just that sugar is viewed increasingly as the culprit; today, there's waning agreement among doctors about the role played by dietary saturated fat in raising levels of low-density lipoprotein (LDL) cholesterol, the kind associated with plaque buildup in the arteries.
Recently, Christopher Ramsden at the National Institutes of Health analyzed a forty-year-old study whose results had never been fully published. From 1968 - 1973, the Minnesota Coronary Experiment placed nearly 9,500 participants on diets heavier in either animal fats or vegetable fats, and compared death rates between the two groups. From The Atlantic, Julie Beck's June 2016 article, "Is Vegetable Oil Really Better For Your Heart?" explains:
The Minnesota Coronary Experiment was a study conducted from 1968 to 1973, a rare randomized controlled trial testing this idea. It looked at a population of nursing home and mental hospital residents, some of whom were given a diet that replaced saturated fats with corn oil and corn oil margarine.
The researchers conducted autopsies as part of this study, but the results of those were never reported or analyzed as part of the original study published in 1989. It’s not clear why. But a new study, published by the BMJ, looks at the MCE data in more detail.
Christopher Ramsden at the National Institutes of Health became interested in the older study, and got in touch with Robert Frantz, the son of MCE’s lead author, Ivan Frantz. Frantz the younger found the old MCE data in his mother’s basement and sent it to the NIH. Ramsden, Robert Frantz, and several others analyzed it (though some of the autopsy records are still missing) and found that while the people who had their saturated fat traded for vegetable oil did see a reduction in cholesterol, this was not associated with lower mortality rates from heart disease.
In this new analysis, researchers also suggest the high-linoleic acid, low-saturated fat diets seem to have had a negative effect for participants over 65. This latter claim—that vegetable oil could actually be worse than butter for mortality—is not very strong, though, given all the missing data.
“We don’t know if this difference is statistically significant and that’s really important,” says Daisy Zamora, a researcher at the University of North Carolina and a co-author of the study. “What we really can say from this though is that the intervention diet did not have a benefit.”
"There was evidence forty years ago that saturated fats have very little effect on heart disease - and yet, these studies were suppressed. Why?" asks Greg. Jon adds: "Ramsden - sort of the Indiana Jones at NIH - finds there's no accounting for how these studies vanished."
Had this research been fully published forty years ago, how might it have changed the trajectory of the diet-heart theory and all the dietary recommendations and trends that have followed?
"I don't think you need to look at butter or sour cream or whipping cream as villains anymore," says Jon.
"You have to do it in moderation," Greg points out. "This is not license to eat a pound of butter because you feel like it."