Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile

• Published in: The American journal of clinical nutrition Vol. 81; no. 2; pp. 397 - 408
• Main Authors: Zhan, S, Ho, S.C
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 01.02.2005; American Society for Clinical Nutrition, Inc
• Subjects: Biological and medical sciences; blood lipids; blood serum; cholesteremic effect; Cholesterol; Cholesterol - blood; cholesterol metabolism; Cholesterol, HDL - blood; Cholesterol, LDL - blood; Clinical trials; Diet; Dose-Response Relationship, Drug; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; high density lipoprotein; Humans; Hypercholesterolemia - blood; Hypercholesterolemia - diet therapy; isoflavones; Isoflavones - administration & dosage; Isoflavones - therapeutic use; Lipids; Lipids - blood; low density lipoprotein; Male; Nutrition; Plant Extracts - therapeutic use; Proteins; Randomized Controlled Trials as Topic; Sex Factors; Soy products; soy protein; Soybean Proteins - administration & dosage; Soybean Proteins - chemistry; Soybean Proteins - therapeutic use; Time Factors; Treatment Outcome; triacylglycerols; Triglycerides - blood; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Human; Isoflavone; low-density-lipoprotein cholesterol; meta-analysis; Lipids; randomized controlled trials; total cholesterol; Feeding; Metaanalysis; HDL cholesterol; Soy protein; Soy protein containing isoflavones; triacylglycerols; LDL cholesterol; high-density-lipoprotein cholesterol
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn.81.2.397

Background: Convincing evidence shows that soy protein intake has beneficial effects on lipid changes, but it is unclear which components of soy protein are responsible. Objective: We conducted a meta-analysis to identify and quantify the effects of soy protein containing isoflavones on the lipid profile. Design: Twenty-three eligible randomized controlled trials published from 1995 to 2002 were identified from the PUBMED data-base (National Library of Medicine, Bethesda, MD). Weighted mean effect sizes were calculated for net changes in serum lipid concentrations by using fixed-effect or random-effect models. Prespecified subgroup analyses were performed to explore the influence of covariates on net lipid change. Results: Soy protein with isoflavones intact was associated with significant decreases in serum total cholesterol (by 0.22 mmol/L, or 3.77%), LDL cholesterol (by 0.21 mmol/L, or 5.25%), and triacylglycerols (by 0.10 mmol/L, or 7.27%) and significant increases in serum HDL cholesterol (by 0.04 mmol/L, or 3.03%). The reductions in total and LDL cholesterol were larger in men than in women. Initial total cholesterol concentrations had a powerful effect on changes in total and HDL cholesterol, especially in subjects with hypercholesterolemia. Studies with intakes >80 mg showed better effects on the lipid profile. The strongest lowering effects of soy protein containing isoflavones on total cholesterol, LDL cholesterol, and triacylglycerol occurred within the short initial period of intervention, whereas improvements in HDL cholesterol were only observed in studies of >12 wk duration. Tablets containing extracted soy isoflavones did not have a significant effect on total cholesterol reduction. Conclusions: Soy protein containing isoflavones significantly reduced serum total cholesterol, LDL cholesterol, and triacylglycerol and significantly increased HDL cholesterol, but the changes were related to the level and duration of intake and the sex and initial serum lipid concentrations of the subjects.