Efficacy and safety of huanglian wendan decoction as an adjuvant therapy for metabolic syndrome: a systematic review and meta-analysis

Background Metabolic syndrome (MetS) is a prevalent metabolic disorder with a rising global prevalence, serving as a risk factor for cardiovascular disease and type 2 diabetes. Huanglian Wendan Decoction, a commonly used formula in traditional Chinese medicine, has increasingly been used to treat MetS. This study aims to evaluate the efficacy and safety of Huanglian Wendan Decoction as an adjunctive therapy for MetS. Objective This meta-analysis aims to systematically evaluate the efficacy and safety of Huanglian Wendan Decoction in treating metabolic syndrome, thereby providing new approaches and insights for its management. Methods Literature searches were conducted using English-language databases (PubMed, Web of Science, Embase, and the Cochrane Library) and Chinese databases (China National Knowledge Infrastructure Wanfang, the VIP Chinese Science Journal Database, and the Chinese Biomedical Literature Database). The search period extended through 1 October 2025. Data were analyzed using RevMan 5.3 and Stata 17.0. The study protocol is registered in PROSPERO (registration number: CRD420251151304). Results A total of 17 randomized controlled trials, involving 1,549 patients, were ultimately included. Huanglian Wendan Decoction combined with conventional treatment for MetS significantly improved waist circumference (WC) (MD = −1.82 cm, 95% CI:−2.53 to −1.12, P < 0.00001), body mass index (BMI) (MD = −0.76 kg/m2, 95% CI: −0.99 to −0.54, P < 0.00001), systolic blood pressure (SBP) (MD = −6.62 mmHg, 95% CI: −7.58 to −5.66, P < 0.00001), diastolic blood pressure (DBP) (MD = −4.88 mmHg, 95% CI: −5.69 to −4.08, P < 0.00001), fasting plasma glucose (FPG) (MD = −0.71 mmol/L, 95% CI: −0.81 to −0.61, P < 0.00001), 2-h postprandial glucose (2 hPG) (MD = −0.71 mmol/L, 95% CI: −0.83 to −0.58, P < 0.00001), glycated haemoglobin (HbA1c) (MD = −0.47%, 95% CI: −0.68 to −0.26, P < 0.00001), triglycerides (TG) (MD = −0.38 mmol/L, 95% CI: −0.44 to −0.33, P < 0.00001), low-density lipoprotein cholesterol (LDL-C) (MD = −0.57 mmol/L, 95% CI: −0.73 to −0.42, P < 0.00001), and homeostasis model assessment of insulin resistance (HOMA-IR) (MD = −0.93, 95% CI: −1.09 to −0.78, P < 0.00001). However, conventional therapy demonstrated greater improvement in high-density lipoprotein cholesterol (HDL-C) (MD = 0.16 mmol/L, 95% CI: 0.14 to 0.18, P < 0.00001). Nevertheless, the safety of Huanglian Wendan Decoction combined with conventional therapy for MetS remains inconclusive, as the safety indicators showed no statistically significant differences (OR = 0.24, 95% CI: 0.03 to 2.26, P = 0.21). Conclusion According to the results of the meta-analysis, Huanglian Wendan Decoction combined with standard treatment for metabolic syndrome (MetS) offers greater benefits than standard treatment alone; it can control blood pressure, blood lipid levels, and blood glucose, improve waist circumference (WC) and body mass index (BMI), and reduce insulin resistance. Huanglian Wendan Decoction is relatively safe. However, due to the limited number and quality of the included studies, the data from this study remain uncertain; further large-scale, double-blind, randomised controlled trials are required to validate these findings. Systematic Review Registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251151304 . Identifier CRD420251151304.