Can soy isoflavones in combination with soy protein change serum levels of C-reactive protein among patients with chronic inflammatory diseases? A systematic review and meta-analysis on randomized controlled trials.

Abstract

Background: C-reactive protein (CRP) is one of the most important markers for assessing inflammation status and its increased concentration in blood is associated with many chronic diseases in humans. The aim of this study was to reveal the effect of soy isoflavones containing soy protein on serum levels of CRP in adult population with chronic inflammatory diseases.

Materials and methods: We searched databases including PubMed, Cochrane Library, ISI Web of Science, Scopus, and clinicalTrials.gov up to March 2025. We used random effects model to calculate the heterogeneity and the overall effects.

Results: Twenty-seven articles were involved in the systematic review and twenty-two articles with thirty-four effect sizes were considered for meta-analysis. The overall estimates revealed that soy isoflavones containing soy protein significantly decreased serum levels of CRP in comparison with control group (weighted mean difference (WMD)= -0.49 mg/L; 95% confidence interval (CI): -0.74, -0.25; P = 0 < 0.001).

Conclusion: Although our results clearly showed soy isoflavones containing soy protein can have decreasing effect on inflammation in participants with chronic inflammatory disease, more large-scale and high quality interventional studies still need to be done to clarify our results.