Some messy studies made it look like swapping certain fats in your diet lowers heart disease risk, but when scientists did better studies, they found that wasn't really true.

Some studies said swapping certain fats in your diet is good for heart health, but they might have been wrong because other factors like different medicines or other diet changes messed up the results.

Swapping saturated fats (like butter) with certain vegetable oils in your food doesn't really lower your chances of having heart problems or dying early, according to big studies.

Eating less saturated fat doesn't seem to reliably help people live longer or avoid heart disease deaths, whether they're healthy or already have heart disease.

Eating less saturated fat didn’t help men who already had a heart attack live longer without another heart attack.

If people eat less fat—down to just 20% of their daily calories—but still eat lots of white bread, pasta, and sugar, it doesn’t make heart attacks any less common over eight years.