Nearly a decade ago, I traveled to New York to meet with the Atkins diet folks to discuss a book project, but I was quickly shown the door after I broached the subject of saturated fat. Can’t we tweak the program a bit, I wondered aloud, to emphasize olive oil over artery-damaging fried pork rinds?

Fast-forward 10 years, and researchers are still debating whether saturated fat is devil or angel. A new re-analysis of a decades-old clinical trial involving 458 male heart patients found that those who were randomly assigned to eat a diet rich in polyunsaturated vegetable oils instead of saturated animal fats had a bigger drop in their cholesterol levels over a three-year period than those who stuck with their usual diet — but they also had more heart disease deaths.