Replacing butter with oils like those in walnuts helps lower cholesterol because of the type of fat, not something special in the whole nut.

Eating walnuts or using vegetable oils instead of foods with saturated fats can lower bad cholesterol in people at risk for heart disease—by about 5 to 7%.

Swapping out bad fats like butter or fried food fats with healthy fats from walnuts can help your liver make less cholesterol and clear more 'bad' cholesterol from your blood.

If you're at risk for heart disease, swapping out saturated fats for healthier fats from walnuts or vegetable oils won't raise a specific blood marker (called Lp(a)) that's linked to heart problems.

If you swap out a little bit of the healthy fats in your Mediterranean diet (like olive oil) for walnuts, your bad cholesterol (LDL) and overall cholesterol go down a bit—which might help your heart.

If you're an adult with extra weight and a higher risk for heart problems, eating a special diet with less saturated fat and more healthy fats—like those in walnuts or vegetable oils—for 6 weeks can lower your bad cholesterol by about 10 to 15 points, no matter if the healthy fats come from whole walnuts or oils.