Effects of probiotic or synbiotic supplementation on glycolipid metabolism in patients with coronary heart disease: a systematic review and meta-analysis

Abstract

Objective This systematic review and meta-analysis, combined with trial sequential analysis (TSA), evaluated the effects of probiotic/synbiotic supplementation on glycolipid metabolism in patients with coronary heart disease (CHD). Methods Randomized controlled trials published up to May 1, 2026, were systematically searched across major databases, including PubMed, Embase, Cochrane Library, Web of Science, MEDLINE, and ClinicalTrials.gov. Pooled analyses were performed using Review Manager 5.3, and TSA was conducted to assess the conclusiveness of evidence. Mean difference (MD) and risk ratio (RR) were calculated for continuous and dichotomous outcomes, respectively. Results Six trials involving 296 participants were included. Probiotic/synbiotic supplementation was associated with a reduction in fasting blood glucose (FBG) (MD − 19.25 mg/dL, 95% CI −32.28 to −6.22, p = 0.004) and an increase in high-density lipoprotein cholesterol (HDL-C) (MD 3.70 mg/dL, 95% CI 1.65 to 5.74, p = 0.0004) based on four studies involving 192 participants. No significant effects were observed on low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, total cholesterol, triglycerides, insulin, homeostasis model assessment of insulin resistance, quantitative insulin sensitivity check index, systolic blood pressure, or diastolic blood pressure (p ≥ 0.05). Although adverse event rates did not differ significantly (p ≥ 0.05), safety evidence was limited by few events and a wide confidence interval. TSA showed that the cumulative evidence for both HDL-C and FBG did not cross the prespecified monitoring boundaries or reach the required information sizes. The certainty of evidence for all outcomes was rated as low or very low. Conclusion Probiotic/synbiotic supplementation may be associated with increased HDL-C and reduced FBG levels in patients with CHD. However, given the negative TSA findings, low certainty of evidence, and lack of hard cardiovascular outcomes, changes in HDL-C and FBG cannot be regarded as direct evidence of cardiovascular benefit. Furthermore, generalizability is limited, as five of the six studies were conducted in Iran and only one in China, which may limit applicability to populations with different dietary patterns, microbiome profiles, ethnic backgrounds, or healthcare systems. The substantial heterogeneity in probiotic strains, formulations, doses, and treatment durations also limits generalization to probiotics or synbiotics as a whole. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251178187; identifier: CRD420251178187.