DEAR DOCTOR K: All fats were once considered bad. Now there are good fats and bad fats. How can I tell the difference?
DEAR READER: You've asked a great question. For years, you probably heard that fats were bad for you and carbohydrates ("carbs") were good. That is wrong. We all need both fats and carbs in our diet. There are no proven health benefits, in general, from substituting carbs for fats.
What we need to pay attention to is eating primarily "good fats" and "good carbs," and minimizing "bad fats" and "bad carbs" -- and not eating too much even of the good fats and carbs. Calories still do matter.
So what are the bad fats and the good fats?
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 good HDL cholesterol. Cutting back on saturated and trans fats can help prevent and control heart disease.
Saturated fats are found mainly 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 non-fat or low-fat dairy products and lean cuts of meat.
Trans fats are found in margarine, particularly hard stick margarine, commercially baked goods like 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.
We have a lot more information on good and bad fats in our Special Health Report, "Healthy Eating: A Guide to the New Nutrition." You can learn more about this report at my website, AskDoctorK.com, and also order it by calling 877-649-9457.
As with all things, practice moderation. Fats should make up less than one-third of your total daily calorie intake. A reasonable and simple general plan is:
- Minimize red meat;
- For protein, instead of red meat choose fish, poultry, nuts, and legumes such as peas and beans;
- Use liquid vegetable oils in cooking and at the table;
- Eat one or more omega-3 fatty acid-rich foods every day: fish, walnuts, canola, soybean or flaxseed oil.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.
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