The comparative influence on plasma and tissue
lipids of dietary soybean and egg
lecithins, which have contrasting
fatty acid compositions, was studied in the hypercholesterolemic guinea pig. The polyunsaturated to
saturated fatty acid (P/S) ratios of the soybean and egg
lecithins were 3.4 and 0.38, respectively.
Hypercholesterolemia was induced by feeding guinea pigs a purified diet that contained 15%
lard enriched with 0.5%
cholesterol. Subsequently, guinea pigs were fed for six wk the same diet supplemented with either soybean or egg
lecithin as 7.5% of the diet. A control group continued to be fed the
lecithin-free diet. Parameters measured included
body weight and relative liver weight; in plasma, total
cholesterol,
high density lipoprotein cholesterol (HDLC),
phospholipid, and nonesterified
cholesterol; in liver, total fat,
cholesterol, and the specific activity of the catabolic
enzyme cholesterol 7 alpha-hydroxylase; (EC 1.14.13.17); and in the aorta,
cholesterol. Among the most noteworthy observations were the 49% decrease in total plasma
cholesterol of the soybean
lecithin group without decreasing HDLC and the 177% increase in HDLC of the egg
lecithin group without a significant increase in total
cholesterol compared with those values in the control group. These data suggest that dietary
lecithin is particularly effective in increasing the HDLC/total
cholesterol ratio in plasma. However, the absolute concentrations of those plasma
lipids seem to depend upon the
fatty acid composition of the
lecithin.