By Carolyn Crist

They also improve quality of life and have a favorable safety profile, adding to their potential as a promising intervention for treating cirrhosis, the study authors wrote.

"As currently one of the top 10 leading causes of death globally, cirrhosis imposes a great health burden in many countries," lead author Xing Yang of the Health Management Research Institute at the People's Hospital of Guangxi Zhuang Autonomous Region and Guangxi Academy of Medical Sciences in Nanning, China, and colleagues wrote.

"The burden has escalated at the worldwide level since 1990, partly because of population growth and aging," the authors wrote. "Thus, it is meaningful to explore effective treatments for reversing cirrhosis and preventing severe liver function and even systemic damage."

Analyzing Probiotic Trials

Yang and colleagues conducted a systematic review and meta-analysis of 30 randomized controlled trials among 2084 adults with cirrhosis, comparing the effects of probiotic intervention and control treatments, including placebo, no treatment, standard care, or active controls such as lactulose and rifaximin. The studies spanned 14 countries and included 1049 patients in the probiotic groups and 1035 in the control groups.

The research team calculated risk ratios (RRs) or standardized mean difference (SMD) for outcomes such as HE reversal, Model for End-Stage Liver Disease (MELD) scores, safety and tolerability of probiotics, liver function, and quality of life.

Among 17 studies involving patients with different stages of HE, as compared with the control group, probiotics significantly reversed minimal HE (RR, 1.54) and improved HE (RR, 1.94). In particular, the probiotic VSL#3 — which contains Streptococcus, Bifidobacterium, and Lactobacillus — produced more significant HE improvement (RR, 1.44) compared with other types of probiotics.

In addition, probiotics appeared to improve liver function by reducing MELD scores (SMD, −0.57) but didn't show a difference in other liver function parameters. There were numerical but not significant reductions in mortality and serum inflammatory cytokine expression, including endotoxin, interleukin-6, and tumor necrosis factor-alpha.

Probiotics also improved quality-of-life scores (SMD, 0.51) and gut flora (SMD, 1.67). For gut flora, the numbers of the Lactobacillus group were significantly higher after probiotic treatment, but there wasn't a significant difference for Bifidobacterium, Enterococcus, Bacteroidaceae, and Fusobacterium.

Finally, compared with control treatments, including placebo, standard therapy, and active controls such as lactulose and rifaximin, probiotics showed higher safety and tolerability profiles, causing a significantly lower incidence of serious adverse events (RR, 0.71).

Longer intervention times reduced the risk for overt HE development, hospitalization, and infections compared with shorter intervention times.

"Probiotics contribute to the reduction of ammonia levels and the improvement of neuropsychometric or neurophysiological status, leading to the reversal of HE associated with cirrhosis," the study authors wrote. "Moreover, they induce favorable changes in gut flora and quality of life. Therefore, probiotics emerge as a promising intervention for reversing the onset of cirrhosis and preventing disease progression."

Considering Variables

Yang and colleagues noted several limitations, including a high or unclear risk for bias in 28 studies and the lack of data on the intervention effect for various types of probiotics or treatment durations.

"Overall, despite a number of methodological concerns, the study shows that probiotics can improve some disease markers in cirrhosis," said Phillipp Hartmann, MD, assistant professor of pediatric gastroenterology, hepatology, and nutrition at the University of California, San Diego.

"One of the methodological concerns is that the authors compared probiotics with a multitude of different treatments, including fiber and lactulose (which are both prebiotics), rifaximin (which is an antibiotic), standard of care, placebo, or no therapy," he said. "This might contribute to the sometimes-contradictory findings between the different studies. The ideal comparison would be a specific probiotic formulation versus a placebo to understand what the probiotic actually does."

Hartmann, who wasn't involved with this study, has published a review on the potential of probiotics, prebiotics, and synbiotics in liver disease. He and colleagues noted the mechanisms that improve a disrupted intestinal barrier, microbial translocation, and altered gut microbiome metabolism.

"Over the last few years, we and others have studied the intestinal microbiota in various liver diseases, including alcohol-associated liver disease and metabolic dysfunction-associated steatotic liver disease," he said. "Essentially, all studies support the notion that probiotics improve the microbial structure in the gut by increasing the beneficial and decreasing the potentially pathogenic microbes."

However, probiotics and supplements are unregulated, Hartmann noted. Many different probiotic mixes and dosages have been tested in clinical trials, and additional studies are needed to determine the best formulations and dosages.

"Usually, the best outcomes can be achieved with a higher number of strains included in the probiotic formulation (10-30+) and a higher number of colony-forming units at 30-50+ billion per day," he said.