The major fat constituent in most vegetable oils, including corn, safflower, sunflower, and soybean oils, which are all liquid at room temperature. Polyunsaturated fat actually tends to lower LDL cholesterol levels but may also reduce HDL cholesterol levels.
A "good" fat, polyunsaturated fats are fatty acids that have been shown to lower blood cholesterol levels. Polyunsaturated fats can be found in sunflower, safflower and soybean oils. Omega 3 fatty acids, which have been shown to help prevent heart problems, are one of the most health-protecting polyunsaturated fats. Fatty fish's (like herring, mackarel, and salmon), green leafy vegetables, flaxseed, soy, canola oil, and walnuts are all good sources of Omega 3's.