THE EFFECT OF DIETARY-FAT, ANTIOXIDANTS, AND PRO-OXIDANTS ON BLOOD-LIPIDS, LIPOPROTEINS, AND ATHEROSCLEROSIS

A number of primary and secondary prevention trials, including angiogr aphic studies, have indicated that a decrease in dietary saturated fat and cholesterol produces a decrease in the blood levels of cholestero l and low-density lipoprotein (LDL) cholesterol, leading to a decrease in coronary artery disease (CAD). Increasing evidence indicates that the oxidation of LDL in human beings is atherogenic. Of the three majo r antioxidants, vitamin E, beta carotene, and vitamin C, the evidence is strongest that vitamin E (at a minimum dose of 100 IU/day) has a st rong and independent inverse association with CAD. Selenium and flavon oids also have antioxidant properties, but their association with CAD in human beings is equivocal. Two pro-oxidants, homocysteine and iron, have been found to be associated with CAD. Blood homocysteine levels can be lowered significantly by an increase in dietary folic acid. Cli nical trials are needed to assess expeditiously the effect of antioxid ants, particularly vitamin E, and of folic acid on CAD and atheroscler osis. The substitution of monounsaturated fat for saturated fat lowers LDL and makes it less susceptible to oxidation without decreasing hig h-density lipoprotein (HDL) cholesterol. Studies in transgenic mice in dicate that apolipoprotein A-I, the major protein of HDL, may inhibit the oxidation of LDL. Dietary trans fatty acids at the level consumed by many Americans can increase LDL cholesterol and may decrease HDL ch olesterol. Individuals who have CAD or have family members who have pr emature CAD have delayed clearance of dietary fat, as judged by studie s of postprandial triglyceride metabolism. The importance of decreasin g dietary saturated fat and cholesterol is well established, but a num ber of other factors appear to influence the risk of CAD significantly and provide important areas for future investigation to improve preve ntion and treatment through better nutrition.