A comprehensive review revealed that probiotics may not effectively restore gut microbiota composition following antibiotic treatment, despite demonstrating benefits in reducing certain antibiotic side effects.

In a study, published in Nature Reviews Gastroenterology & Hepatology, an international team of investigators from Europe, Israel, and the United States analyzed data from over 16,000 children and adults across randomized controlled trials comparing antibiotics with and without probiotics. The review concluded that while probiotics reduced antibiotic-associated diarrhea (AAD) from 19% to 8%, they did not reliably restore the gut microbiome to its preantibiotic state.

“Current evidence does not support the notion that probiotics can restore the microbiota to its preantibiotic state,” the study authors noted. Some probiotic strains, including Lactobacillus rhamnosus GG and Saccharomyces boulardii, showed limited effects on specific bacterial groups, but these results were inconsistent across the studies.

The review identified key challenges in microbiota restoration research, including:

• Lack of consensus on defining a "normal" microbiota

• Nonstandardized measurement techniques

• Substantial interindividual variability

• Technical limitations in current testing approaches.

While the analysis highlighted clinical benefits, including reduced risk of Clostridioides difficile—associated diarrhea, the mechanism behind these improvements remained unclear. The investigators emphasized the need for further study to determine whether probiotics can counteract the expansion of antibiotic resistance genes in the gut microbiome, a growing concern.

The findings also cautioned against marketing claims suggesting that probiotics can fully restore microbial communities following antibiotic use. Instead, the investigators stressed that probiotics’ benefits are limited to specific clinical outcomes rather than comprehensive microbiota recovery. Supported by the International Scientific Association for Probiotics and Prebiotics, the review—incorporating evidence through March 2023—represented the most detailed analysis of probiotics’ effects on antibiotic-disrupted gut microbiota to date.

This pivotal research underscored the complexity of gut microbiota restoration and provided critical insights for clinical practice and future probiotic development.

Conflict of interest disclosures can be found in the study.