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.

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%.

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 instead of other healthy fats like olive oil may lower a dangerous blood fat called lipoprotein(a) in men with high cholesterol—but it doesn’t seem to help women the same way.

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.

Eating walnuts doesn’t really raise your 'good' cholesterol, even though it helps with other types of cholesterol. So while walnuts are heart-healthy in some ways, they don’t seem to boost HDL much.