Purpose: The gut–liver interaction suggests that modification of gut bacterial flora using probiotics and synbiotics may improve liver function. This systematic review and meta-analysis aimed to clarify the effect of probiotics and synbiotics consumption on the serum concentration of liver function enzymes.

Methods: PubMed (MEDLINE), Cumulative Index to Nursing and Allied Health Literature, and Cochrane Library (Central) were searched from 1980 to August 2017 for studies where adults consumed probiotics and/or synbiotics in controlled trials and changes in liver function enzymes were examined.

Results: A total of 17 studies (19 trials) were included in the meta-analysis. Random effects meta-analyses were applied. Probiotics and synbiotics significantly reduced serum alanine aminotransferase [− 8.05 IU/L, 95% confidence interval (CI) − 13.07 to − 3.04; p = 0.002]; aspartate aminotransferase (− 7.79 IU/L, 95% CI: − 13.93 to − 1.65; p = 0.02) and gamma-glutamyl transpeptidase (− 8.40 IU/L, 95% CI − 12.61 to − 4.20; p < 0.001). Changes in the serum concentration of alkaline phosphatase and albumin did not reach a statistically significant level. Changes to bilirubin levels were in favour of the control group (0.95 μmol/L, 95% CI 0.48–1.42; p < 0.001). Subgroup analysis suggested the existence of liver disease at baseline, synbiotics supplementation and duration of supplementation ≥ 8 weeks resulted in more pronounced improvement in liver function enzymes than their counterparts.

Conclusions: Probiotics and synbiotics may be suggested as supplements to improve serum concentration of liver enzymes, especially when synbiotics administered for a period ≥ 8 weeks and in individuals with liver disease.