Lactobacillus reuteri DSM 17938 has been studied across 7 health outcomes, with the strongest evidence supporting its use for reducing crying time in infants with colic (9 studies, high evidence strength). Typical studied doses range from 1×10^8 to 5×10^8 CFU daily, with effects often observed within 3–4 weeks. Research also explores benefits for abdominal pain, diarrhea, vomiting, and stool volume, though the evidence varies in strength and consistency.
Strongest evidence: The most robust finding is for reduced crying time in infants with colic, supported by high-strength evidence (8 of 9 studies beneficial, moderate effect size). Moderate-strength evidence exists for reduced abdominal pain in children with functional abdominal pain disorders (10 of 12 studies beneficial, small effect), reduced diarrhea rate in acute gastroenteritis (5 of 8 studies beneficial, mixed effect sizes), reduced diarrhea duration (5 of 5 studies beneficial, mixed effect sizes), and reduced vomiting frequency in infants (3 of 3 studies beneficial, small effect). Doses across these outcomes typically range from 1×10^8 to 2×10^8 CFU/day, except for crying time where doses up to 5×10^8 CFU/day were used.
Mixed or weaker evidence: Low-strength evidence supports reduced stool volume in children with functional constipation (only 1 of 3 studies beneficial) and reduced crying duration in infants with colic (2 of 3 studies beneficial but with mixed effect sizes). These findings are preliminary due to small study numbers and inconsistent results.
Effective dose patterns: A common dose range of 1×10^8 to 2×10^8 CFU/day appears across multiple outcomes (abdominal pain, diarrhea, vomiting). For crying time, the effective dose spans 1×10^8 to 5×10^8 CFU/day. Doses for stool volume and crying duration were not consistently reported.
Population insights: The vast majority of evidence comes from pediatric populations — infants with colic, children with functional abdominal pain disorders, and children with acute gastroenteritis. Few studies address adults, so generalizability beyond pediatric groups is unknown.
Notable caveats: Publication bias is a recurring concern, especially for outcomes where all or most studies are positive (e.g., crying time, vomiting). Null results from higher-quality RCTs suggest effect sizes may be smaller than early studies indicate. Condition specificity is important: for example, abdominal pain benefits were not seen in children with functional constipation alone. Several evidence bases are small (3–5 studies), limiting confidence in conclusions.
Across 19 clinical studies, no specific adverse events were significantly increased with Lactobacillus reuteri DSM 17938 compared to control. In 17 studies, there were no significant differences in safety markers such as crying time, stool consistency, weight, and other gastrointestinal outcomes, with several events showing beneficial trends. An additional 19 reports described the probiotic as generally well tolerated, including one study that explicitly stated it was not associated with serious adverse events.
Caveats: Most studies were conducted in infants and children over short durations (≤8 weeks), limiting long-term safety data. The evidence base is focused on efficacy endpoints; rare adverse events may not be captured due to sample sizes. Safety in immunocompromised individuals or during pregnancy has not been systematically assessed.