The media love contrarian man-bites-dog stories that purport to debunk long-established beliefs and advice. Among the most popular on the health front are reports that saturated fats do not cause heart disease and that the vegetable oils we’ve been encouraged to use instead may actually promote it.

But the best-established facts on dietary fats say otherwise. How well polyunsaturated vegetable oils hold up health-wise when matched against saturated fats like butter, beef fat, lard and even coconut oil depends on the quality, size and length of the studies and what foods are eaten when fewer saturated fats are consumed.

So before you succumb to wishful thinking that you can eat well-marbled steaks, pork ribs and full-fat dairy products with abandon, you’d be wise to consider the findings of what is probably the most comprehensive, commercially untainted review of the dietary fat literature yet published. They are found in a 26-page advisory prepared for the American Heart Association and published last June by a team of experts led by Dr. Frank M. Sacks, professor of cardiovascular disease prevention at the Harvard T.H. Chan School of Public Health.

The report helps to explain why the decades-long campaign to curb cardiovascular disease by steering the American diet away from animal fats has been less successful than it might have been and how it inadvertently promoted expanding waistlines and an epidemic of Type 2 diabetes.