Oils

The edible oils are all liquid fats extracted from vegetable sources, with the exceptions of coconut, palm, and palm kernel oils. They are virtually 100 percent lipid, or fat, and most are high in unsaturated fat and low in the saturated component (10?20 percent). Commonly used oils include almond, avocado, corn, olive, peanut, safflower, sesame, soybean, and sunflower. Olive oil, a monounsaturated oil, is the main vegetable oil, possibly along with the newly available canola (rapeseed) oil, that should be used for cooking; most of the other oils contain more polyunsaturated fats and should not be heated. Polyunsaturated means that the oils have more than one unsaturated bond available in their carbon chain to which hydrogen atoms can be attached. These oils should be used on salads and other dishes in their cold-pressed form or consumed with extra vitamin E to prevent oxidation. The polyunsaturated fats may actually help to reduce blood cholesterol rather than raise it and, more importantly, can improve our ratios of LDL and HDL cholesterols to help reduce cardiovascular disease risk. These vegetable oils do not contain cholesterol.


All of the vegetable oils are liquid at room temperature except coconut oil, one of the few saturated vegetable oils. When the unsaturated vegetable oils are ?hydrogenated? through a special industrial process, they become partially saturated, as in the solid vegetable margarines. These are usually fortified with vitamin A and have other additives, and they tend to function differently in the body. They may increase blood cholesterol and thus, the risk of cardiovascular problems; they have been associated with increased cancer risk as well. The animal fats?lard, butter, and chicken fat?have a much higher percentage of saturated fats and more cholesterol, and these fats are implicated as well in these chronic, serious cardiovascular diseases and cancer.


All of the vegetable oils contain nine calories per gram of pure fat, and one tablespoon of vegetable oil contains about 120 calories, so they should be used sparingly by people concerned about weight. These oils are rich in essential fatty acids, particularly linoleic acid, which is also present in the foods from which these oils are extracted. Linoleic and linolenic acids are needed for the growth and maintenance of our cells, tissues, and entire body. Other than vitamin E, which is found in these vegetable oils, they contain negligible amounts, if any, of other nutrients, such as
the B vitamins and minerals. Some of the oils richer in vitamin E are soybean, safflower, cottonseed, corn, and wheat germ.


Oils can be used in salad dressings, in sauces, in baking, and in cooking food. To repeat the important point about cooking with oils, heating the polyunsaturated oils is not recommended, as heat may affect their chemical structures, making them less usable and more difficult for our body to process (they are also possibly carcinogenic). Overall, it is ideal not to fry foods but to add the uncooked oils after cooking the food. In general, the saturated fats are more stable when used in cooking, but are not the healthiest for us. I recommend either canola or olive oils, which are monounsaturated and more stable vegetable oils, or butter when cooking or sautéeing foods.


Though usually slightly more expensive, the least refined oils, most often called ?cold-pressed,? are the best. As heat and chemicals are not used in extracting them, they retain more vitamin E and are less likely to break down in the processing. For regular use, I do not recommend the refined or partially hydrogenated vegetable oils, the vegetable shortenings, or really very much margarine either.


Overall, the vegetable oils should contribute a higher percentage of the total fat in our diet than they currently do, as this would increase the proportion of polyunsaturated to saturated fats, which is helpful. But total blood cholesterol is influenced most by total fat intake, so for best health we should reduce our total fat intake. (The topic of fats in our diet is discussed in detail in Chapter 4, Lipids.)

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Elson M. Haas MD Written by Elson M. Haas MD

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