Trans monounsaturated fatty acids and serum cholesterol levels

Article Abstract:

When oils are hydrogenated (the addition of hydrogen atoms to open double bonds between molecules), liquid vegetable oils become solid fats. This a useful way of preventing spoilage and adding bulk or texture to food. Hydrogenation is also used to produce margarine and shortenings. The principle fatty acid in vegetable oils is linoleic acid, which contains 18 carbon atoms and two double bonds (abbreviated 18:2). When linoleic acid is hydrogenated, the double bonds open and a group of more saturated (with fewer double bonds) fatty acids are formed, including oleic acid (18:1); elaidic acid (18:1), formed in a rigid ring similar to an unsaturated fatty acid; and stearic acids (18:0), a saturated fatty acid with no double bonds. Molecules containing double bonds can take on one of two configurations: cis configuration places the two hydrogen atoms on the same side of the double bond; trans configuration positions them on opposite sides of the double bond. These configurational, or stearic, differences effect various physical and physiologic aspects of the fat produced. The physiologic effect of the three classes of fatty acids saturated, monosaturated, and polyunsaturated cause different effects within the body. Saturated fatty acids have been associated with elevation of cholesterol levels and with cardiovascular disease, particularly atherosclerosis (hardening of the arteries). However, the situation appears to be far more complex. Some saturated fats do not raise cholesterol concentrations when compared with the monosaturated oleic acid (which has been thought to be neutral). Medium chain fatty acids such as 8:0 compounds and stearic acid do not raise cholesterol levels as much as oleic acid. Thus, it is no longer correct to view all saturated fatty acids as cholesterol-raising compounds. An article in the August 16, 1990 issue of The New England Journal of Medicine (Mensink and Katan) strongly indicates that trans fatty acids increase the concentration of cholesterol and lower protective concentrations of high-density lipoprotein (HDL). Trans fatty acids occur infrequently in nature, and the American diet contains 3 to 4 percent of trans fatty acids. The deleterious effects could be obviated by re-blending margarines and shortenings to reduce the level of trans fatty acids. A group of suspected or confirmed deleterious fatty acids include palmitic acid, myristic acid, trans monosaturated fatty acids, and lauric acid. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects

Article Abstract:

When oils are hydrogenated (the addition of hydrogen atoms to open double bonds between molecules) liquid vegetable oils become solid fats. This is useful as a means of preventing spoilage and adding bulk or texture to foods. Hydrogenation is also used to produce margarine and shortenings. Recent studies have emphasized reducing hydrogenated fats in human diet and the value of monounsaturated (containing one double bond between two adjacent carbon atoms) fatty acids in reducing the blood levels of cholesterol and low-density lipoproteins. Molecules containing double bonds can take on one of two configurations: cis configurations place the two hydrogen atoms on the same side of the double bond, and trans configurations position them on opposite sides of the double bond. These configurational, or stearic differences, effect various physical and physiologic aspects of the fat that is formed. The physiologic effect of the three classes of fatty acids saturated, monounsaturated, and polyunsaturated (more than one double bond) are assessed in a study of 48 women and 27 men. One of the volunteers, mostly young students, had a history of elevated blood pressure, for which she was being treated. Volunteers were examined, received numerous blood tests, and their eating habits were recorded before the experiment began. The subjects followed three different diets, each for three weeks. One diet was high in oleic acid, another in trans isomers of oleic acid, and the third in saturated fats (lauric and palmitic acid). During the course of the experiment, numerous blood samples were taken and analyzed; of particular interest were the levels of cholesterol, high-density lipoproteins, low-density lipoproteins and ratios among these levels. Trans fatty acids were related to increases in blood cholesterol concentrations and low-density lipoproteins, and with reductions of protective high-density lipoproteins. Thus, the ingestion of monounsaturated fatty acids with the trans configuration may have adverse health effects. Patients at high risk for atherosclerosis should consider decreasing their intake of trans fatty acids. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Fish and heart disease

Article Abstract:

Eating large amounts of fish or fish oils may not reduce the risk of heart disease. Most seafood contains polyunsaturated fatty acids called omega-3 or n-3 fatty acids. Epidemiological studies have demonstrated reduced mortality from heart disease in some populations that eat fish regularly. But a 1995 study found that men who eat six servings of fish a week had the same risk of heart disease as those who only ate one serving a week. All of the men who ate some fish had a lower risk of dying from heart disease as those who ate no fish. Consuming fish oil in capsules appeared to have no effect on risk of heart disease. Omega-3 fatty acids appear to reduce blood levels of fats called triglycerides, but have no effect on low-density lipoprotein cholesterol. High levels of this type of cholesterol are often linked to heart disease.

Editorial, Heart diseases, Seafood, Nutritional aspects, Fish oils in human nutrition, Fish oils

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