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The effects of unsaturated dietary fats on absorption excretion, synthesis, and distribution of cholesterol in man, J.'c/in. Invest. 49, 1135. 19. SIMONS, L. A. and MYANT, N. B. (1974): The effect of D-thyroxine on the metabolism of cholesterol in familial hyperbetallpoproteinaemia, Atherosclerosis (In press). 20. NESTEL, P. J. and BARTER, P. J. (1973): Triglyceride clearance during diets rich in carbohydrate and fats, Amer. J. din. Nutr. -26, 241. 21. KOHOUT M. KOHOUTOVA B. and HEIMBERG, M. (1971): The regulatidn of'bepatic trigly&ride metabolism by free fatty acids, J. biol. Chem. 246, 5067. 22. SABINE J. R. MCGRATH H. and ABRAHAM, S. (1968): Dietary fat and the inhibition of hkpatic lipogenesis in the mouse, J. Nutr. 98 312. 23. RL&T OF INTER-SOCIETY COMMISSION FOR HEART D~SE+E RESOURCES (1970): Primarv orevention of the Atherosclerotlc Diseases,-Ci~cuiat~on 42, A-35.' 24. CARLSON L. A. and B O~G E R , L. E. (1972): Ischaemic heart disease i ; relation to fasting values of plasma triglycerides and cholesterol, Lancet 1, 865.

Pork, enriched in linoleic acid content, was compared iwth conventional pork in the diet of three human subjects with respect to the plasma cholesterol concentration and the excretion in feces of neutral sterols and bile acids. Since the fatty acids in pork glyceride have an unusual positional distribution, the redistribution that might occur during the absorption and disposition of a fat meal was also studied. The plasma cholesterol was lower with polyunsaturated pork, the difference, 14 mg/100 ml plasma, being of the order expected from the change in polyunsaturated to saturated fatty acid ratio. On average, the excretion of neutral sterols was 57% greater with polyunsaturated than with conventional pork in all three subjects, and in this respect the results resembled the findings with polyunsaturated ruminant fats. During the absorption of pork fat, the high proportion of palmitate in the 2 position of lard triglyceride served as a useful marker, since human triglyceride carries mainly unsaturated fatty acids in that position. There were stepwise changes in the fatty acid composition at the 2 position of triglyceride as the fat was absorbed, transported through, and cleared from plasma, the palmitate being gradually replaced by oleate and linoleate. By contrast, the total fatty acid profile in the triglyceride changed relatively little, implying selective reacylation with palmitate at the 1 and/or 3 position. During the clearing of dietary triglyceride, the porcine triglyceride was thus converted to the form occuring in humans.