Fat is needed by the body in small amounts for important functions. Some dietary fats, such as mono-unsaturated fats, are healthier than others, such as saturated fats or trans fats. Replacing saturated fats with unsaturated fats helps lower blood cholesterol levels. Most unsaturated fats come from plant sources. These types of fats are a good source of essential fatty acids. Like all types of fats, they should be eaten in moderation.
Unsaturated fat can be either monounsaturated or polyunsaturated. These fats come mostly from plant sources and are liquid at room temperature. Foods high in monounsaturated fat include avocados, olives, and peanuts. Canola, olive, almond, hazelnut, and peanut oils are also high in this type of fat.
Foods high in polyunsaturated fat include fatty fish, nuts and vegetable oils such as safflower and sunflower. Omega-3 fatty acids are polyunsaturated fatty acids. They are found in certain cold-water fish such as salmon, mackerel, albacore tuna, sardines, and lake trout. Omega-3 fatty acids may help prevent heart disease because they lower triglycerides and reduce blood clotting. They may also lower blood pressure and prevent arrhythmias.
Trans fats are made up of trans fatty acids. They are formed when vegetable oils are processed into margarine or shortening through a process called hydrogenation. Hydrogenation makes the fat solid at room temperature. Stick margarine and vegetable shortenings are examples of hydrogenated products.
Foods high in trans fatty acids include french fries, donuts, crackers, and cookies. However, recently, as the health risks of trans fats have become known, more snack products without trans fats have become available. In fact, trans fats have been banned in New York City restaurants since December 2006.
Both kinds of unsaturated fat can be used in place of saturated fat in the diet. This substitution helps to lower levels of total and LDL cholesterol in the blood. All types of fat should be eaten in moderation. The effect of monosaturated fats was studied in the DELTA Study. DELTA is short for Dietary Effects on Lipoproteins and Thrombogenic Activity.
When monosaturated fats replace saturated fat in the diet, they improve cholesterol levels. They reduce triglycerides, total cholesterol, and LDL, that is "bad" or "lethal" cholesterol. They increase HDL, that is, "good" or "healthy" cholesterol. good carrier for cholesterol.
Polyunsaturated fats supply essential fatty acids (EFAs). The body does not make these fatty acids and must get EFAs from food. EFAs are needed for normal growth and development in children and for healthy skin. EFAs are vital to the human brain and central nervous system. They also produce hormone-like substances that help regulate blood pressure, blood clotting, and the immune system.
Trans fats raise LDL cholesterol levels and may also lower HDL cholesterol in the blood. They tend to raise total blood cholesterol levels but not as much as more saturated fatty acids.
The National Heart, Lung, and Blood Institute recommends that no more than 30% of an individual's daily calories come from fat, and no more than 10% from saturated fat.
Some diet tips that can help with appropriate fat intake include: Choose mayonnaise and salad dressings that contain no more than 1 gram of saturated fat per tablespoon.Eat at least five servings of fruits and vegetables each day.Eat fewer processed snacks and sweets, including crackers, cookies, and pastries. These contain partially hydrogenated oils, which means that trans fats are present. Look for labels that read "no trans fats".Eat more fish. Good choices include fatty fish such as salmon, lake trout, herring, sardines, mackerel, and albacore tuna. These offer heart health protection. The American Heart Association recommends eating a 6-ounce serving of fish twice a week. Grill or bake to avoid adding extra fat and calories.Eat no more than 6 ounces of lean meat or skinless poultry each day. Loin and round cuts of meat have less fat. Trim visible fat from meats before cooking. Broil, bake, roast, poach, steam, saute, stir-fry, or microwave to reduce the amount of fat. Follow the American Heart Association guidelines for margarine. It should have no more than 2 grams of saturated fat per tablespoon. Liquid vegetable oil should be the first ingredient. Use liquid or tub margarines rather than stick margarine. The stick form is higher in saturated fat and trans fats. Incorporate more breads, cereals, grains, pasta, and dried beans into meals.Limit fats and oils to a total of no more than five to eight servings a day. This amount may be lower if weight loss is needed. Typical serving sizes are 1 teaspoon of vegetable oil or margarine or 2 teaspoons of diet margarine. A serving is also 2 teaspoons of mayonnaise or 3 teaspoons of nuts.Use unsaturated oils, margarines, and spreads in place of saturated fat products, such as butter or hydrogenated shortening. Check labels on oils and margarines for amounts of saturated, polyunsaturated, and monounsaturated fats.
The American Dietetic Association's Complete Food and Nutrition Guide. Roberta Larson Duyff. Chronimed Publishing, Minneapolis, MN, 1996
The American Dietetic Association. Skim the Fat: A Practical and Up to Date Food Guide. Chronimed Publishing, Minneapolis, MN, 1995.
The American Heart Association. Website. The Details: Fat and Fatty Acids.
Duyff, R., MS, RD, CFCS. (1996). The American Dietetic Association's Complete Food&Nutrition Guide. Minnesota: Chronimed Publishing.
Mahan, K, MS, RD, CDE&Escott-Stump, S., MA, RD, LDN. (2000). Krause's Food, Nutrition,&Diet Therapy (10th ed.). Pennsylvania: W.B. Saunders Company.