Fat (also known as lipid) is one of the three classes of nutrients. The other two are proteins and carbohydrates. The major function of fat is to provide energy for the body. Pound per pound, fat contains more energy (calories) than protein and carbohydrates. There are three types of fat; triglycerides, cholesterol, and phospholipids.
Fatty acids consist of chains of carbon atoms linked together by chemical bonds. On one end (terminal) of the carbon chain is a methyl group (a cluster of carbon and hydrogen atoms). On the other terminal is a carboxyl group (a cluster of carbon, oxygen, and hydrogen atoms). The chemical bonds between carbon atoms can be either single or double bonds. Single bonds have more hydrogen molecules around them than double bonds. These chemical bonds determine whether a fatty acid is saturated or unsaturated. Fatty acids also come in different lengths: short chain fatty acids have fewer than six carbons, while long chain fatty acids have 12 or more carbons.
Fatty acids serve as energy for the muscles, heart, and other organs, as building blocks for cell membranes, and as energy storage for the body. Fatty acids that are not used up as energy are converted into triglycerides. A triglyceride is a molecule formed by attaching three fatty acids onto a glycerol compound that serves as a backbone. Triglycerides are then stored in the body as fat (adipose) tissue.
Saturated fatty acids contain single bonds only. Fats containing saturated fatty acids are called saturated fats. Examples of foods high in saturated fats include lard, butter, whole milk, cream, eggs, red meat, chocolate, and solid shortenings. An excess intake of saturated fat can raise blood cholesterol and increase the risk of developing coronary heart disease.
Monounsaturated fatty acids contain one double bond. Examples of foods high in monounsaturated fat include avocados, nuts, and olive, peanut, and canola oils. Scientists believe that increased consumption of monounsaturated fats (for example, eating more nuts) is beneficial in lowering LDL cholesterol (bad cholesterol) and lowering the risk of coronary heart disease, especially if monounsaturated fats are used to substitute for saturated fats and refined sugars.
Polyunsaturated fatty acids contain more than one double bond. Examples of foods high in polyunsaturated fats include vegetable oils, corn, sunflower, and soy.
Essential fatty acids are polyunsaturated fatty acids that the human body needs for metabolic functioning but cannot produce, and, therefore, has to be acquired from food.
Omega-3 fatty acids are a class of essential polyunsaturated fatty acids with the double bond in the third carbon position from the methyl terminal (hence, the use of "3" in their description). Foods high in omega-3 fatty acids include salmon, halibut, sardines, albacore, trout, herring, walnut, flaxseed oil, and canola oil. Other foods that contain omega-3 fatty acids include shrimp, clams, light chunk tuna, catfish, cod, and spinach.
Omega-6 fatty acids are a class of essential polyunsaturated fatty acids with the initial double bond in the sixth carbon position from the methyl group (hence, the "6"). Examples of foods rich in omega-6 fatty acids include corn, safflower, sunflower, soybean, and cottonseed oil.
Omega-3 and omega-6 fatty acids are also referred to as n-3 and n-6 fatty acids, respectively.
Trans fatty acids (trans fats) are made through hydrogenation to solidify liquid oils. Heating omega-6 oils, such as corn oil, to high temperatures creates trans fats. Trans fats increase the shelf life of oils and are found in vegetable shortenings and in some margarines, commercial pastries, fried foods, crackers, cookies, and snack foods. The intake of trans fatty acids increases blood LDL-cholesterol (bad cholesterol), decreases HDL cholesterol (good cholesterol), and raises the risk of coronary heart disease.
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Archived: March 20, 2014
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