Intake of 25 g of soybean protein with or without soybean fiber alters plasma lipids in men with elevated cholesterol concentrations

Twenty-one mildly hypercholesterolemic men consumed a diet that was low in fat (<30% of energy) and cholesterol (300 mg/d) and were given muffins containing 25 g protein + 20 g dietary fiber daily from either isolated soybean protein + soybean cotyledon fiber, isolated soybean protein + cellulose, casein + soybean cotyledon fiber or casein + cellulose. All subjects progressed through the low fat, low cholesterol baseline period, lasting 2 wk, and then through all four dietary treatments, lasting 4 wk each, according to a Latin square design. Plasma concentrations of total, LDL, HDL and VLDL cholesterol, total and VLDL triacylglycerols, and apolipoprotein A-I and B were measured at the end of each period. When data from all subjects were analyzed, dietary treatments did not influence lipemia; however, in subjects with initial total cholesterol concentrations >5.7 mmol/L, both isolated soybean protein treatments resulted in significantly lower total cholesterol compared with the two casein treatments (P < 0.05). In addition, a negative linear relationship was observed when a subject's total or LDL cholesterol change after each of the soybean treatments was regressed against the subject's baseline cholesterol concentration (P < 0.05). Apolipoprotein A-I varied dependent on baseline cholesterol with no apparent pattern, whereas apolipoprotein B levels were not affected. Results indicate that consumption of 25 g soybean protein/d is associated with lower total cholesterol concentrations in individuals with initial cholesterol concentrations >5.7 mmol/L.