Chlorella for health: evidence from a GRADE-assessed systematic review and dose–response meta-analysis

Chlorella species have attracted attention for their potential to improve cardiovascular and metabolic health; however, comprehensive evidence from controlled trials remains limited. A comprehensive search of PubMed, CENTRAL, Web of Science, Scopus, and EMBASE databases was conducted up to February 2025. Study quality and certainty of evidence were assessed using the Cochrane Risk of Bias and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tools, respectively. Thirty-three studies were included. Chlorella supplementation led to significant reductions in body fat (Weighted Mean Difference [WMD] = -0.72%; 95% Confidence Interval [CI]: -1.09, -0.35; P < 0.001), body mass index (WMD = -0.29 kg/m 2 ; 95% CI:-0.44, -0.15; P < 0.001), weight (WMD = -1.52 kg; 95% CI:-2.07, -0.97; P < 0.001), waist-to-hip ratio (WMD = -0.01%; 95% CI:-0.01, -0.01; P < 0.001), homeostatic model assessment of insulin resistance (WMD = -0.20; 95% CI:-0.33, -0.08; P = 0.002), insulin (WMD = -0.97 µIU/mL; 95% CI:-1.38, -0.55; P < 0.001), low-density lipoprotein-cholesterol (WMD = -5.70 mg/dL; 95% CI:-8.10, -3.31; P < 0.001), total cholesterol (WMD = -7.02 mg/dL; 95% CI:-9.78, -4.25; P < 0.001), alanine transaminase (WMD = -4.84 IU/L; 95% CI:-6.46, -3.21; P < 0.001), aspartate aminotransferase (WMD = -3.38 IU/L; 95% CI:-4.65, -2.11; P < 0.001), and lactate dehydrogenase (WMD = -14.13 U/L; 95% CI: -25.18 to -3.09; P = 0.012). Additionally, there were significant increases in high-density lipoprotein-cholesterol (WMD = 1.57 mg/dL; 95% CI:0.27, 2.87; P = 0.018). Chlorella supplementation demonstrates meaningful benefits for cardiometabolic health, with effects influenced by species, dosage, and participant characteristics. While this analysis has some limitations, further long-term studies are required to optimize its clinical application. Overall, Chlorella appears to be a promising supplement that may warrant inclusion in dietary interventions.