Exposing the myths—and truths—about saturated fat.

When it comes to breaking science, I try to keep an open mind. But when I read statements like “It’s become clear that natural saturated fats are good for you” (in a major food magazine last year), I blink. In the professional groups I’m involved with—including the American Heart Association—the idea that saturated fats increase the risk of heart disease is an unquestioned, fundamental principle.

Saturated fats—found mainly in fatty meats, butter, cheese and whole milk—are “saturated” with hydrogen atoms, which gives them a rigid structure and makes them solid at room temperature. (Unsaturated fats—those in nuts, olives, fish and vegetable oils—are fluid at room temperature.) Most experts agree that saturated fats raise levels of LDL (“bad”) cholesterol in the blood. That’s damaging to the heart and arteries, we believe, since excessive LDL accumulates in artery walls and can trigger inflammation, eventually leading to a heart attack or stroke. That would seem to be the end of the story—or is it? I decided to evaluate some common assumptions.

“All saturated fats are bad.”

It’s easy just to lump all saturated fats into one “heart-threatening” group, but the reality is that there are many different kinds of saturated fats in foods. Some research suggests that certain types are more harmful than others. For example, a handful of studies show that while coconut oil, rich in lauric acid, raises blood levels of LDL (“bad”) cholesterol, it also raises HDL (“good”) cholesterol slightly. Stearic acid, a type of saturated fat that makes up about half the fat in dark chocolate and accounts for 15 percent of the fat in beef, doesn’t raise LDL at all. Experts consider stearic acid “neutral” when it comes to cardiovascular risk: it doesn’t help, but it doesn’t hurt either.

On the flip side, some saturated fats appear more likely than others to cause the buildup of fatty plaque in arteries. Palmitic acid, which is the main fat in palm oil and another saturated fat present in beef, is one such fat. But the fact that beef contains both “bad” palmitic acid and “neutral” stearic acid underscores the point that foods rich in saturated fats contain a mixture of different types.

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