| [ Summary ] |
Over a period of almost 50 years there has been an increase in the intake of fats and oils in Japan and concomitantly the incidence of diabetes, hyperlipidemia and cardiovascular diseases have been elevated. In European countries, a reduction in total fat consumed to 30% of the total energy consumption has been advocated. However in Japanese dietary recommendations, we advocated 20 to 25% as fat energy ratio for population. There have been reports that an increase in the intake of saturated fatty acids elevates serum cholesterol concentrations and mortality from coronary heart diseases. There is increasing evidence that n-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) may have beneficial effects on a number of CHD risk factors and may reduce risk of death from atherosclerotic diseases. Monounsaturated fatty acids, such as oleic acid (cis 18:1) and linoleic acid(18:2 n-6) reduce serum cholesterol concentrations, however linoleic acid and arachidonic acid (20:4 n-6) in LDL particles are easily oxidized in the arterial walls. LDL particles, rich in oleic acid, are not modified to the same extent as those rich in linoleic acid. We recommended the ratio of polyunsaturated to saturated to monounsaturated fatty acids be 3/3/4 and the ratio of n-6/n-2 fatty acids be 4.
Dietary polyunsaturated fatty acids, notably EPA, function as ligand activators for PPARα, the transcription factor responsible for the induction of genes involved in lipid oxidation and thermogenesis, and suppress the expression and nuclear localization of SREBP-1, the nuclear factor responsible for the transcription of lipogenic genes. We examined the effects of the long-term ingestion of dietary diacylglycerols (DG) compared with triacylglycerols (TG) in a double-blind controlled study of human lipid metabolism. In contrast to TG, DG apparently suppressed accumulation of fat and possibly reduced the risk of diseases associated with visceral fat obesity. |