Dear Dr. Komaroff: All fats once were considered bad. Now there are good fats and bad fats. How can I tell the difference?
Dear Reader: Saturated fats and trans fats are bad fats. They boost your chances of developing heart disease by increasing your blood levels of LDL (bad) cholesterol and triglycerides. Trans fats are even worse – they also reduce your HDL (good) cholesterol. Cutting back on saturated and trans fats can help prevent and control heart disease.
Saturated fats mainly are found in meat and whole-fat dairy foods. Limit red meat, particularly processed meat, and full-fat dairy products such as butter, cheese and ice cream. Choose nonfat or low-fat dairy products and lean cuts of meat.
Trans fats are found in margarine, particularly hard stick margarine, commercially baked goods such as cookies and crackers, and in many fried foods. There is no safe level of trans fats, and you should eat as little of them as possible. To do so, avoid packaged foods where the package label says they contain “partially hydrogenated” oils, and look for the amount of trans fats on the Nutrition Facts panel.
The good fats are polyunsaturated and monounsaturated fats. Good fats can help lower LDL (bad) cholesterol and prevent heart disease.
There are two types of polyunsaturated fats: omega-3 fatty acids and omega-6 fatty acids. Omega-3’s come mainly from fish, especially fatty fish like salmon and sardines. But you can also find them in flaxseeds, walnuts and canola oil. Omega-6 fatty acids are present in safflower, soybean, sunflower, walnut and corn oils.
Good sources of monounsaturated fats are olive oil, peanut oil, canola oil, avocados and most nuts.
Dr. Anthony Komaroff is a physician and a professor at Harvard Medical School. To ask a question or for more information, go to askdoctork.com.