Eating walnuts or using vegetable oils instead of foods high in saturated fats can lower a type of 'lighter' bad cholesterol that's less likely to cause heart problems — but it doesn't seem to change the 'denser', more harmful type of bad cholesterol in people at risk for heart disease.

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%.

Saturated fat raises LDL cholesterol, but mostly the 'bigger, fluffier' kind that doesn't clog arteries as much as the small, sticky kind.

Eating certain fats can change your 'bad' cholesterol — saturated fats go up a little, but monounsaturated fats go down, even if you're already healthy.

Eating walnuts can make the 'bad' cholesterol in your blood healthier by filling it with good fats, without making it more likely to cause damage—like adding armor instead of fuel to a fire.

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.