Background: Health claims link soy protein (SP) consumption, through plasma cholesterol reduction, to a decreased risk of heart disease. Soy isoflavones (ISOs), particularly in individuals who produce equol, might also contribute to lipid lowering and thus reduce SP requirements.
Objective: The objective was to examine the contributions of SP, ISOs, and equol to the hypocholesterolemic effects of soy foods.
Design: Nonsoy consumers (33 men, 58 women) with a plasma total cholesterol (TChol) concentration 5.5 mmol/L participated in a double-blind, placebo-controlled, crossover intervention trial. The
subjects consumed 3 diets for 6 wk each in random order, which consisted of foods providing a daily dose of 1) 24gSPand7080mg ISOs (diet S); 2) 12 g SP, 12 g dairy protein (DP), and 7080 mg
ISOs (diet SD); and 3) 24 gDPwithout ISOs (diet D). Fasting plasma TChol, LDL cholesterol, HDL cholesterol, and triglycerides (TGs) were measured after each diet.
Results: TChol was 3% lower with the S diet (0.17 0.06 mmol/L;P0.05) than with theDdiet, andTGswere4%lower with both the S (0.140.05 mmol/L; P0.05) and SD (0.120.05
mmol/L; P 0.05) diets. There were no significant effects on LDL cholesterol, HDL cholesterol, or the TChol:HDL cholesterol ratio. On the basis of urinary ISOs, 30 subjects were equol producers. Lipids were not affected significantly by equol production.
Conclusions: Regular consumption of foods providing 24 g SP/d from ISOs had no significant effect on plasma LDL cholesterol in mildly hypercholesterolemic subjects, regardless of equolproducing status. Am J Clin Nutr 2008;88:298 304.