Lactobacillus Reuteri for Infant Colic

Research suggests that Lactobacillus reuteri DSM17938 may reduce crying and fussing in infants with colic, though the evidence is notably stronger for breastfed infants than for those fed formula. The body of evidence includes multiple randomized controlled trials, several meta-analyses, and a number of reviews, with most pointing in a supportive direction — one individual participant data meta-analysis pooling four trials found roughly 25 fewer minutes of daily crying in probiotic-treated infants, and a 2016 systematic review estimated a reduction of about 56 minutes per day — but at least one well-designed Australian trial found no benefit and even observed more crying in the probiotic group, and a colonization study raised questions about whether gut colonization by the probiotic is actually the mechanism at work. Studies indicate that feeding type appears to be a meaningful moderating factor, with breastfed infants consistently showing more favorable responses across trials while formula-fed infants show little to no consistent benefit, and one trial combining a specialized formula with L. reuteri actually performed worse than standard formula. Limitations across the literature include industry funding in several trials, small sample sizes, variability in study populations and outcome measures, and an incomplete understanding of the biological mechanisms involved, meaning that while the evidence is promising for breastfed infants, researchers and reviewers generally stop short of recommending universal use.