Influence of n-6 versus n-3 Polyunsaturated Fatty Acids in Diets Low in Saturated Fatty Acids on Plasma Lipoproteins and Hemostatic Factors

Modification of dietary fat composition may influence hemostatic variables, which are associated with increased risk of coronary heart disease (CHD). To address this question, we performed a controlled feeding study on 26 healthy male nonsmoking subjects with diets of differing fat composition. For the first 3 weeks, the subjects were given a diet calculated to supply 30% energy as total fat8% as monounsaturated, 4% as polyunsaturated, and 16% energy as saturated fatty acids, respectively (saturated diet). This was followed immediately by two diets taken in random order, each of 3-week duration and separated by an 8-week washout period on the subject's usual diet. Both diets were calculated to supply 30% of energy as fat14% monounsaturated, 6% as polyunsaturated, and 8% energy as saturated fatty acids. They both provided 5 g (approximately 1.7% energy) more of polyunsaturated fatty acids than the saturated fat diet; in one diet as long-chain n-3 fatty acids (n-3 diet) and in the other as linoleic acid (n-6 diet). Fasting plasma lipids, lipoproteins, and hemostatic factors were measured on the final 3 days of each dietary period. In a subset of 9 subjects the postprandial responses to a test meal were studied on the penultimate day of each period, each meal having the fat composition of its parent diet. On the n-3 diet compared with the n-6 diet, plasma triglyceride, HDL3 cholesterol, apoprotein AII, and fibrinogen concentrations were lower and HDL2 cholesterol concentration was higher (P = .0001, P = .003, P = .0001, P = .004 and P = .001, respectively). On both the n-3 and n-6 diets compared with the saturated diet, fasting plasma total and LDL cholesterol, apoprotein B, beta-thromboglobulin concentrations, and platelet counts were lower (P