Dietary-induced changes in fatty acid composition of human plasma, platelet, and erythrocyte lipids follow a similar time course.

The dietary-induced changes in the fatty acid composition of plasma, platelet, and erythrocyte lipids were measured as a function of time. Healthy adults consumed a diet rich in saturated fat (18% total energy, TE) for 19 d and then crossed over, without washout, to a diet rich in (n-6) polyunsaturated fat (10% TE) for a further 19 d. The fatty acid composition of plasma and blood cell lipids was measured in blood samples collected from fasting subjects on d 0, 1, 2, 5, 8, 12, and 19 of consuming the diet rich in (n-6) polyunsaturated fats. The linoleic acid composition of all plasma, platelet, and erythrocyte lipids increased to a plateau within 19 d, reaching at least 70% of maximum within 5 d. The maximum increase in linoleic acid composition of erythrocyte phosphatidylcholine was 3.8 mol% at d 12; the increase at d 1 was 2 mol% and at d 5 was 3.2 mol%. The decrease in pentadecanoic acid composition followed a similar time course in all lipids with the exception of plasma phospholipids. Our results show that the time course of dietary-induced changes in erythrocyte fatty acid composition is similar to that in plasma and platelet lipids. These results provide convincing, albeit indirect evidence that the exchange of fatty acids from plasma to erythrocytes and platelets is a major determinant of their membrane fatty acid composition.