Pooled evidence from a recent systematic review and meta-analysis suggests that probiotics may reduce antibiotic-associated diarrhea by as much as nearly 50%.

Probiotics — live microorganisms intended to have a health benefit when consumed — can maintain or restore gut microecology during or after antibiotic treatment in several ways, such as by competing for nutrients, inhibiting epithelial and mucosal adherence of pathogens, and introducing lower colonic pH that favors the growth of nonpathogenic species.

The majority of 63 randomized controlled trials (involving 11,811 participants) included in the current review used Lactobacillus-based interventions alone or in combination with other probiotics, including Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, and/or Bacillus ( JAMA. 2012;307:1959-1969).

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Probiotic use was associated with a 42% lower risk of developing diarrhea compared with control patients not using probiotics.

Although this result was consistent across a number of subgroup and sensitivity analyses, the investigators noted that significant differences across studies existed and that the evidence is insufficient to determine whether this association varies systematically by population, by antibiotic characteristic or by probiotic preparation.

The researchers also pointed out that in rare cases, probiotics have been linked to such serious adverse effects as fungemia and bacterial sepsis. Nevertheless, the evidence was strong enough to allow the investigators to conclude that probiotic administration is associated with a reduced risk of antibiotic-associated diarrhea.