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The ‘Dangers’ of Saturated Fat — Weighing in on the Recent Controversial Study
By Sharon Palmer, RD

When Walter Willett, MD, DrPH, chair of the department of nutrition at the Harvard School of Public Health, took the stage on March 14 at Healthy Kitchens, Healthy Lives in St Helena, California to speak about nutrition recommendations for optimal health, he ominously announced, “There will be a meta-analysis coming out next week. There are egregious errors in the meta-analysis, but it will make the headlines, and it will be very confusing.”

Although Willett couldn’t identify the study before its publication date, he reported that he was concerned regarding the media attention the saturated fat–related story would receive. 

Sure enough, on March 18, the systematic review and meta-analysis was published in the Annals of Internal Medicine, concluding that evidence doesn’t support the current heart health guidelines encouraging high consumption of polyunsaturated fats and low consumption of saturated fats. The study was based on a pooled analysis of 76 individual studies that looked at how different fats influence the risk of cardiac events. When the researchers compared people with the highest and lowest saturated fat intakes, they found no clear difference in the risk of heart disease and cardiac events. They also found no difference among those who consumed high or low levels of unsaturated fats.

The moment the study was published, headlines started popping up proclaiming that saturated fat is no longer bad, and that the 2010 Dietary Guidelines, which recommend limiting saturated fats in lieu of unsaturated fats, should be changed. The study opened the debate about whether saturated fat has been unfairly relegated to the “naughty list.”

But several prominent scientists have publicly criticized the study, and several major errors in the study have been identified. One error occurred because the study authors incorrectly identified a study on omega-3s, a type of unsaturated fat, that they included in the meta-analysis to show a negative effect when it had shown a strong positive effect. Another error included omitting two important studies on omega-6 fatty acids (unsaturated fats) from the analysis.

Furthermore, the study didn’t take into account what people consumed when they reduced their saturated fat intake. For example, previous research has indicated that if people replace saturated fats with refined carbohydrates, their risk of heart disease can increase.

The study was revised to address the error regarding the correlation of omega-3s to risk of coronary outcomes, but that wasn’t enough, according to Willett, who has called for the study to be retracted, with the same level of media coverage surrounding the retraction as the original study.

Penny Kris-Etherton, PhD, RD, a distinguished professor of nutrition at Penn State University, reported that the data from this study conflicts with a large evidence base showing benefits of unsaturated fats and adverse health consequences of saturated fats.

David Katz, MD, founding director of the Yale University Prevention Research Center, wrote an article for the Huffington Post to explain the results of this study to the public, reporting that the study essentially showed two things: You can’t get a good answer to a bad question, and there’s more than one way to eat poorly. He added that good dietary guidance focuses on eating foods within the context of an overall diet, not about particular nutrients, with this new study focusing on the latter.

According to Katz, the researchers set off to answer an inappropriate question by looking at the intake of specific fatty acid categories and disease risk without taking into account what people consume when they reduce their intakes of these fatty acids. He stressed that evidence supports that dietary patterns low in saturated fat but also high in vegetables, fruits, beans, lentils, nuts, seeds, and whole grains are linked with dramatic reductions of chronic disease risk. 

It’s important to remember that the 2010 Dietary Guidelines, which call for limiting saturated fat to less than 10% of calories, is based on a body of evidence linking these fats to cardiovascular disease risk. More research needs to occur before we can discount this information.

— Sharon Palmer, RD, is a Los Angeles-based foodie, the author of The Plant-Powered Diet and Plant-Powered for Life, the editor of the Environmental Nutrition newsletter, and a contributing editor at Today’s Dietitian.