Effect of a diet low in saturated fatty acids on plasma lipids, lipoproteins, and HDL subfractions.

The effect on serum high density lipoprotein subfractions of a low fat diet with a high ratio of polyunsaturated-to-saturated fatty acids was studied in 38 middle-aged volunteers (19 men and 19 women) in North Karelia, Finland. The mean serum HDL2 cholesterol decreased from 32 +/- 2 mg/dl (mean +/- SE) to 28 +/- 2 mg/dl (p less than 0.001) during the experimental diet and returned to 33 +/- 2 mg/dl (p less than 0.001) after a return to the original diet. No changes were observed in the concentration of HDL3 cholesterol. A highly significant decrease was observed in serum apoprotein A-I concentration, but not in apoprotein A-II concentration during the experimental diet. It is concluded that a low-fat, high-P/S ratio diet lowers LDL and HDL2 cholesterol in healthy volunteers, but does not influence the level of HDL3 subfraction.