Time for an Oil Change?

A stroll down the cooking oil aisle of your local supermarket may leave you shaking your head. So many choices… olive, corn, canola, safflower. The list seems to go on and on. Which do you choose?

Before answering that question, it helps to know a bit about cooking oils in the first place.

Fats and oils are made up of "building blocks" called fatty acids. Each type of fat or oil is a mixture of different fatty acids:

• Saturated fatty acids are found primarily in animal sources such as meat and poultry, whole or reduced-fat milk, and butter. Some vegetable oils like coconut, palm kernel oil, and palm oil have saturated fats. Saturated fats are usually solid at room temperature.
• Monounsaturated fatty acids are usually found in vegetable oils such as canola, olive, and peanut oils. They are liquid at room temperature.
• Polyunsaturated fatty acids are found mainly in vegetable oils such as safflower, sunflower, corn, flaxseed, and canola oils. Polyunsaturated fats are also the main fats in seafood. They are liquid or soft solids at room temperature. Specific polyunsaturated fatty acids, such as linoleic acid and alpha-linolenic acid, are called essential fatty acids. They are necessary for cell structure and making hormones. The body does not manufacture its own essential fatty acids; they must be obtained from the foods we eat.
• Trans fatty acids are formed when vegetable oils are processed into margarine or shortening. Sources of trans fats in the diet include snack foods and baked goods made with partially hydrogenated vegetable oil or vegetable shortening. Trans fatty acids also occur naturally in some animal products such as dairy products.

Eating too many foods high in saturated fat may increase blood levels of LDL (bad) and total cholesterol. High blood levels of LDL and total cholesterol are risk factors for heart disease.

Trans fatty acids act like saturated fats and raise LDL cholesterol levels; they may also lower HDL (good) cholesterol in the blood. High levels of HDL are protective against heart disease.

Eating foods high in monounsaturated fatty acids, on the other hand, may help lower LDL cholesterol levels and decrease risk of heart disease. Eating polyunsaturated fats in place of saturated fats decreases LDL cholesterol levels.

While we should do what we can do stay away from saturated fats and trans fatty acids, taking in a combination of monounsaturated and polyunsaturated fats keeps us nutritionally balanced, says K.C. Hayes, professor of biology at Brandeis University.

Fats and oils actually play an important role in how our body works, adds Cindy Moore, MS, RD, director of nutrition therapy for the Cleveland Clinic and spokeswoman for the American Dietetic Association. "Fats and oils provide a concentrated source of energy for the body. Fats are used to store energy in the body, insulate body tissues, and transport fat-soluble vitamins -- A, E, D, and K -- through the blood. They also enhance the taste, aroma, and texture of food, and contribute to a feeling of satiety, or fullness."