Whole Soy Flour Incorporated into a Muffin and Consumed at 2 Doses of Soy Protein Does Not Lower LDL Cholesterol in a Randomized, Double-Blind Controlled Trial of Hypercholesterolemic Adults.

Padhi, E., Blewett, H.J., Duncan, A.M., Guzman, R.P., Hawke, A., Seetharaman, K., Tsao, R., Wolever, T.M.S., and Ramdath, D.D. (2015). "Whole Soy Flour Incorporated into a Muffin and Consumed at 2 Doses of Soy Protein Does Not Lower LDL Cholesterol in a Randomized, Double-Blind Controlled Trial of Hypercholesterolemic Adults.", Journal of Nutrition, 145(12), pp. 2665-2674. doi : 10.3945/jn.115.219873  Access to full text

Abstract

Background: Soy protein may reduce coronary heart disease (CHD) risk by lowering LDL cholesterol, but few studies have assessed whether whole soy flour displays a similar effect. Objective: The aim of this study was to assess the dose-response effect of whole soy flour incorporated into muffins on plasma LDL cholesterol in hypercholesterolemic adults. Methods: Adults aged 30–70 y (n = 243) with elevated LDL cholesterol ($3.0 and #5.0 mmol/L) were stratified by LDL cholesterol and randomly assigned to consume 2 soy muffins containing 25 g soy protein [high-dose soy (HDS)], 1 soy and 1 wheat muffin containing 12.5 g soy protein and 12.5 g whey protein [low-dose soy (LDS)], or 2 wheat muffins containing 25 g whey protein (control) daily for 6 wk while on a self-selected diet. Fasting plasma samples were collected at weeks 0, 3, and 6 for analysis of lipids (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides (TGs), glucose, insulin, C-reactive protein (CRP), and isoflavones, and blood pressure measurements were taken. Dietary intake was assessed at weeks 0 and 4 with the use of 3 d food records. Treatment effects were assessed with the use of intention-to-treat analysis with multiple imputation and LDL cholesterol as the primary outcome. Results: In total, 213 (87.6%) participants completed the trial. Participants were Caucasian (83%) and mostly female (63%), with mean 6 SD BMI 28.0 6 4.6 kg/m2 and systolic and diastolic blood pressure values of 122 6 16 mm Hg and 77 6 11mm Hg, respectively. Despite a dose-dependent increase in plasma isoflavones (P < 0.001), neither HDS nor LDS had a significant effect on LDL cholesterol compared with control (mean 6 SEM changes: control, 20.04 6 0.05; HDS, 0.01 6 0.05; and LDS, 20.04 6 0.06 mmol/L). There were no significant treatment effects on total or HDL cholesterol, TGs, CRP, homeostatic model assessment of insulin resistance, blood pressure, or the Framingham 10 y CHD risk score. Conclusion: Consuming 12.5 or 25 g protein from defatted soy flour incorporated into muffins did not reduce LDL cholesterol or other CHD risk factors in hypercholesterolemic adults. This trial was registered at clinicaltrials.gov as NCT01547585.

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