Effects of soy and isoflavone interventions on plasma lipid profiles in postmenopausal women: an umbrella review

Background Although numerous meta-analyses have investigated the effects of soy and isoflavones on lipid profiles in postmenopausal women, a comprehensive evaluation of this evidence remains lacking. This umbrella review synthesized existing meta-analyses of randomized controlled trials to assess the certainty of the evidence. Methods We searched PubMed, Web of Science, Embase, and the Cochrane Database for studies published through April 22, 2026. Methodological quality was evaluated using AMSTAR-2, and evidence certainty was assessed using the GRADE approach. Results Seven meta-analyses comprising 21 associations were included. According to AMSTAR-2, two meta-analyses (29%) demonstrated moderate or high quality. Eighteen associations were supported by evidence of moderate or high certainty according to GRADE. Soy protein containing isoflavones and soy isoflavone extracts significantly reduced total cholesterol (MD = −0.12 mmol/L, 95% CI: −0.21 to −0.03). Soy isoflavones reduced low-density lipoprotein cholesterol (SMD = −0.11, 95% CI: −0.21 to −0.01). Furthermore, unfermented soy products significantly increased high-density lipoprotein cholesterol (MD = 0.06 mmol/L, 95% CI: 0.02 to 0.10). Conclusion Specific soy-based interventions, rather than general soy consumption, were associated with beneficial changes in lipid profiles among postmenopausal women. Systematic review registration CRD420251243075.