Polyunsaturated fats come mostly from plant sources like nuts, seeds and vegetable oils. Two well known polyunsaturated fats are the omega-3 and omega-6 fats. These fats are liquid at room temperature and often stay liquid when refrigerated. Fish is also good source of polyunsaturated omega-3 fats, especially cold water, oily ocean fish. This is why you should eat fish at least three times per week. While most red meat is low in polyunsaturated fats, animals raised on grass instead of corn-based feeds have meat that has more polyunsaturated fats and lower in fat in general.
The essential fatty acids are so named because you need to get them from your diet. Your body can make many of the fats it needs from other types of fatty acids, but the omega-6 and omega-3 polyunsaturated fatty acids must come from the diet.
Omega-6 fatty acids come from vegetable oils, nuts and seed oils. Most people get plenty of these fats from their diets -- usually more than enough.
While the omega-6 fatty acids are common in a typical Western diet, the omega-3 fatty acids are often deficient. Many experts believe that eating a diet with too many omega-6 fats and too few omega-3 fats increases your risk for inflammation and chronic disease.
Getting enough omega-3 fatty acids from your diet or as dietary supplements will help to reduce inflammation, regulate heart rhythm and keep your cholesterol levels normal. When you don't get enough of the essential fatty acids in your diet, you may have dry skin, dry hair and increased inflammation.
Trans Fats
Most trans fats are created artificially by a process called hydrogenation. It involves heating regular vegetable oil and forcing hydrogen atoms onto the polyunsaturated fatty acid molecules. This process turns the oil into a solid substance and improves the shelf life of the fat.Fully hydrogenating a vegetable oil will make it firm and not create trans fats. However, the firmness of the fat makes it difficult to use in cooking. Partially hydrogenating an oil makes for a softer product and is still widely used in baking and processing foods. Examples include stick margarine and partially hydrogenated frying oils. Trans fats are commonly found in donuts, snack cakes, cookies and processed foods.
Artificially created trans fats are the unhealthiest of fats, even worse than saturated fat. Eating too many trans fats has been linked to increasing your risk of cardiovascular disease.
Not all trans fats are created in the lab. Small amounts of natural trans fats occur in milk and beef. Conjugated linoleic acid is a well-known natural trans fat. The natural trans fats do not appear to be as unhealthy as the artificial trans fats.
This Week's Assignment
In your next lesson, you will learn about choosing healthy fats. For this week, I would like you to keep track of the different types of fat that you eat. This includes fats found in red meat, poultry, pork, fish, milk, cheese, cream, nuts, seeds, oils, dressings, and possibly desserts and snacks.
This Week's Quiz
You can test your knowledge of fats with this quiz: Quiz Five - Functions of Fat and Types of Fats
This is lesson five of the basic nutrition - macronutrients e-course. Up next, lesson six is about fat digestion and choosing healthy fats. You may sign up for the whole e-course at Basic Nutrition - Macronutrients
Sources:
United States Department of Agriculture. "National Nutrient Database for Standard Reference." Release 20. September 2007.
Gropper SS, Smith JL, Groff JL. "Advanced Nutrition and Human Metabolism." Fourth Edition. Belmont, CA. Wadsworth Pub Co. 2005.
Otten JJ, Hellwig JP, Meyers LD. "Dietary Reference Intakes: The Essential Guide to Nutrient Requirements." IOM, 2006.
Harvard School of Public Health. "Fats & Cholesterol." 2007.
