The role of fatty acid saturation on plasma lipids, lipoproteins, and apolipoproteins: I. Effects of whole food diets high in cocoa butter, olive oil, soybean oil, dairy butter, and milk chocolate on the plasma lipids of young men

The present studies were conducted to evaluate the cholesterolemic effects of whole-food diets high in stearic acid. In study no. 1, normocholesterolemic young men were fed diets high in stearic acid provided by cocoa butter (CB); oleic acid provided by olive oil (OO); linoleic acid provided by soybean oil (SO); and myristic acid (and lauric acid) provided by dairy butter (B). In study no. 2, different subjects with similar baseline characteristics were fed diets high in stearic acid provided by milk chocolate (C), CB, CB + B (4:1, MIX), and myristic (and lauric) acid provided by B. Both studies used a randomized, crossover, double-blind experimental design, and experimental subjects (n = 18 for study no. 1 and n = 15 for study no. 2) in each study consumed every diet for 26 days with a 1-month wash-out period between each experimental period. The diets provided 37% of calories from fat, of which 81% was provided by the test fat. Ten ounces (280 g) C was provided daily by the C diet. In study no. 1, the B diet was hypercholesterolemic, whereas the SO diet was hypocholesterolemic, compared with the other diets. The OO and SO diets were hypocholesterolemic compared with the CB diet. Low-density lipoprotein (LDL) cholesterol levels, in general, paralleled the changes in plasma total cholesterol levels. SO significantly decreased apolipoprotein (apo) B levels compared with the other diets. Plasma very-low-density lipoprotein (VLDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and apo A-I levels were unaffected by the experimental diets. Compared with baseline, the CB diet elicited a neutral cholesterolemic response, whereas the B diet was hypercholesterolemic and the OO and SO diets were hypocholesterolemic. In study no. 2, the C, MIX, and CB diets elicited a similar and neutral cholesterolemic response; however, all were hypocholesterolemic compared with the B diet. Since the CB and B diets had virtually identical quantities of long-chain saturated fatty acids (SFA; C_12:0 to C_18:0), we believe that CB is hypocholesterolemic compared with B because of its high proportion of stearic acid. Thus, stearic acid has unique effects on plasma total cholesterol levels compared with other long-chain saturated fatty acids; the mechanism by which stearic acid exerts this effect is not clear. We also have shown that linoleic acid has a more potent hypocholesterolemic effect than oleic acid and does not affect HDL cholesterol levels or HDL composition.