Abstract
Essential fatty acids (EFAs) are linoleic acid (18 : 2 n-6) and α -linolenic (18 : 3 n-3) acid, and a series of polyunsaturated fatty acids (PUFAs) derived from them. The desaturationelongation products appear to have more potent functions than the parent molecules. Since minimum requirement of EFAs is 11.2% of energy intake as linoleic acid and 0.4% as α-linolenic acid, the EFA deficiency rarely happens insofar as we eat regular meals. The main functions of EFAs include structural constituents of the membranes, precursors of icosanoids and a barrier of skin permeability. When considering the physiological effects, intake of EFAs should be far more than the minimum requirement. EFAs appreciably relate to the development of various degenerative diseases such as atherosclerosis, immune disfunction and carcinogenesis. The amount and the balance of dietary n-6 and n-3 PUFAs are indeed important to prevent and improve these diseases. Desaturation of linoleic and α-linolenic acids are regulated ingeniously and influenced by a number of factors. In addition, there is a strong interference in the metabolism between n-6 and n-3 PUFAs. Although enormous efforts have been paid to acknowledge the optimum balance and composition of dietary n-6 and n-3 PUFAs, many questions still remain to be solved.
