Earlier this month, the medical journal BMJ published a re-evaluation of a 40-year-old study that concluded that saturated fats cause high cholesterol and heart disease. This look into the past included previously unpublished data that was never before seen by the public. It gets even juicier: The data actually contradicts conventional wisdom about the relationship between saturated fat, high cholesterol, and heart disease.
In the study, 9,000 institutionalized patients were given one of two diets at random. The first was a diet low in saturated fats and rich in things like vegetable oil, and the second mimicked a typical American diet that's high in saturated fat. As the researchers hypothesized, the special diet reduced blood cholesterol levels in the patients. Although the special diet didn’t seem to have any effect on heart disease, the researchers believed that they would have seen reduced rates in these patients if the experiment gone on longer. Makes sense right? Maybe not. The recently published full results actually prove that the exact opposite is true. The low-saturated fat group actually experienced higher rates of heart-related deaths than those who ate the quintessential American diet. Yes, you read that right, a diet low in saturated fat = an increased risk for heart disease. These results were especially prominent in subjects over the age of 64. Mind. Blown.
Confused? Well, you’re not alone—for decades, we’ve associated saturated fat with heart disease because that’s what it seemed research indicated. In fact, The Dietary Guidelines for Americans still supports this idea, suggesting that Americans limit their intake of saturated fat and use more vegetable oils.
The researchers who re-evaluated the initial study concluded that the absence of the data over the past 40 years have led to some serious misunderstandings. “Had this research been published 40 years ago, it might have changed the trajectory of diet-heart research and recommendations,” said study author Daisy Zamora. On the other side of the equation, however, experts who have been strong supporters of the campaign against saturated facts were quick to criticize the new findings. Walter Willett, chair of the nutrition department at Harvard, recently wrote in a blog that these new findings are irrelevant to the current dietary guidelines. He argues that’s because current guidelines don’t say to cut out saturated fats altogether, instead, they recommend replacing saturated fat with a type of “good fat” known as polyunsaturated fat.
It's not totally clear why the data was not published, and we may never know since the lead researchers, Ancel Keys and Ivan Frantz, have since passed away. One theory is that the trial results went against the firmly believed notion that saturated fat hurt heart health. That said, it’s quite possible that for that very reason, the researchers questioned their results and never fully understood them.
Christopher Ramsden, the lead author of the new review, urges caution in drawing definitive conclusions about the new analysis. He did, however, say that the research suggests that saturated fats "may not be as bad as originally thought." (Translation: Saturated fat may not be the worst thing ever, but you still shouldn't scarf down an entire pizza or go on a fast-food burger bender.) One conclusion we can draw from the new discovery with certainty, however, is just how difficult it is for data that contradicts conventional thought to reach the public.