Fish consumption, fish oil, lipids, and coronary heart disease

Abstract

Reducing intake of saturated fat and dietary cholesterol and avoiding excess calories, which can lead to obesity, remain the cornerstore of the dietary approach to decreasing risk of atherosclerotic vascular disease. During the past 20 years, however, there has been renewed interest in other dietary components that might favorably improve lipid profiles and reduce risk of coronary heart disease (CHD). Fish and fish oil, rich sources of omega-3 fatty acids, have sparked intense interest in both epidemiological studies, which suggest a favorable effect on CHD, and metabolic ward studies, which show a striking improvement in lipid profiles in hyperlipidemic patients. Confusion has resulted from clinical trials of fish oil in patients with CHD, which did not corroborate early observational findings, and newer results, which suggest clinical benefit due to a mechanism independent of lipid effects. Fish and other marine life are rich sources of a special class of polyunsaturated fatty acids known as the omega-3 or n-3 fatty acids.1 2 They are so named because the first of the several double bonds occur three carbon atoms away from the terminal end of the carbon chain. The three n-3 polyunsaturated fatty acids (n-3 PUFAs) are alpha linolenic acid (LNA), eicosapentenoic acid (EPA), and docosahexenoic acid (DHA). LNA is an 18–carbon chain fatty acid with three double bonds; in the form of tofu, soybean, and canola oil and nuts, it is an important plant-based source of n-3 PUFA for vegetarians and non–seafood eaters. EPA and DHA are very long–chain fatty acids obtained from marine sources. These, along with n-6 polyunsaturated fatty acids (n-6 PUFAs) that cannot be synthesized from nonlipid precursors such as linoleic acid, are considered essential fatty acids that must be consumed in the diet. The n-6 PUFAs are obtained primarily from plant sources, especially seeds. Arachidonic acid is …