Effect of synbiotics on the cardiovascular risk factors in patients with non-alcoholic fatty liver: a GRADE assessed systematic review and meta-analysis

Abstract

Introduction: Several studies revealed that synbiotics have been beneficial in managing non-alcoholic fatty liver disease (NAFLD), but the findings are conflicting. We aimed to assess the effect of synbiotic supplementation on cardiovascular risk factors in patients with NAFLD.

Methods: A thorough literature search was conducted to identify relevant studies up to July 2024, including publications from Pubmed, Embase, Cochrane, Scopus, and the Web of Science. Standardized mean difference (SMD) was used, and data with a 95% confidence interval (CI) were presented.

Results: Sixteen RCTs were included, involving NAFLD patients and synbiotic supplementation. No significant effects were found on blood pressure (SBP: SMD - 6.68, p = 0.234; DBP: SMD - 4.31, p = 0.391), anthropometric measures (weight: SMD - 0.78, p = 0.126; BMI: SMD - 0.21, p = 0.182; waist circumference: SMD - 0.53, p = 0.095), or lipid profile (triglycerides: SMD - 3.67, p = 0.266; total cholesterol: SMD - 0.61, p = 0.059; low-density lipoprotein: SMD - 3.09, p = 0.215; high-density lipoprotein: SMD 0.49, p = 0.219). Synbiotics significantly reduced CRP levels (SMD - 1.83, p = 0.019) but had no significant effect on TNF-α (SMD - 1.95, p = 0.087). Synbiotic led to a significant reduction in weight following adjustment of publication bias (SMD - 1.16, p < 0.05).

Conclusion: Overall, synbiotic supplementation does not significantly impact blood pressure, anthropometric indices, or lipid profile parameters in patients with NAFLD, except for a significant reduction in weight after adjusting for publication bias. Synbiotic supplementation significantly reduces CRP levels but has no effect on TNF-α.

Keywords: Lipid profiles; Meta-analysis; Nonalcoholic fatty liver disease; Synbiotics.

Fig. 1

PRISMA flow diagram of selection studies

Fig. 2

Effects of synbiotic supplementation on blood pressure in patients with NAFLD. (A) Forest plot showing the standardized mean difference (SMD) and 95% confidence interval (CI) for the effect of synbiotic supplementation on systolic blood pressure (SBP). (B) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on diastolic blood pressure (DBP)

Fig. 3

Effects of synbiotic supplementation on anthropometric indices in patients with NAFLD. (A) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on body weight. (B) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on body mass index (BMI). (C) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on waist circumference (WC)

Fig. 4

Funnel plots for publication bias assessment in BMI

Fig. 5

Effects of synbiotic supplementation on lipid profile in patients with NAFLD. (A) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on triglycerides (TG). (B) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on total cholesterol (TC). (C) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on low-density lipoprotein cholesterol (LDL-C). (D) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on high-density lipoprotein cholesterol (HDL-C)

Fig. 6

Funnel plots for publication bias assessment in lipid profile. Funnel plots evaluating the presence of small-study effects for (A) TG, (B) TC, (C) LDL-C, and (D) HDL-C

Fig. 7

Effects of synbiotic supplementation on inflammatory biomarkers in patients with NAFLD. (A) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on tumor necrosis factor-alpha (TNF-α). (B) Forest plot showing the SMD and 95% CI for the effect of synbiotic supplementation on C-reactive protein (CRP)