Spirulina Supplementation Can Reduce Serum Levels of C-Reactive Protein: A Systematic Review and Meta-Analysis on Randomized Clinical Trials

Background: Emerging evidence suggests that Spirulina may reduce inflammation by modulating key cytokines, including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Accordingly, this study conducted a systematic review and meta-analysis to evaluate the effects of Spirulina supplementation on serum levels of inflammatory mediators in adults aged 18 years and older. Materials and Methods: Relevant randomized clinical trials (RCTs) were identified through searches of several databases, including the Cochrane Library, ClinicalTrials.gov, ISI Web of Science, Scopus, and PubMed up to August 2025. The pooled effects were calculated using the DerSimonian and Laird random-effects model. Statistical heterogeneity was assessed using I-squared statistics and Cochran’s Q test. Results: Eight studies met the inclusion criteria. The administered dosages of Spirulina varied from 1 g/day to 8 g/day, with intervention durations spanning 3 to 16 weeks. The pooled analysis demonstrated that Spirulina supplementation significantly reduced serum CRP concentrations compared with placebo group (weighted mean difference (WMD): –0.09 mg/L; 95% confidence interval (CI): –0.16 to –0.02). In contrast, Spirulina supplementation caused non-significant reduction in TNF-α concentration (WMD: –0.43 pg/mL; 95% CI: –1.44 to 0.59) and IL-6 (WMD: –0.44 pg/mL; 95% CI: –0.98 to 0.1). However, heterogeneity concerning all inflammatory mediators was significant. Conclusion: The findings of this study indicated that Spirulina supplementation significantly reduced serum CRP levels, whereas its effects on IL-6 and TNF-α were not statistically significant. Owing to the significant heterogeneity, further high-quality RCTs are needed to confirm these beneficial effects. PROSPERO Registration: The study was registered in PROSPERO (CRD42024606496).