In “Colicky baby? Here’s a surprising remedy” (J Fam Pract. 2011;60:34-36), we summarized a 2010 double-blind randomized controlled trial (RCT) that found the probiotic Lactobacillus reuteri DSM 17938 reduced daily crying time in colicky, exclusively breastfed infants.1
A recently published RCT of the same probiotic by Sung et al2 adds to the body of evidence and suggests that the jury may still be out as to the value of probiotics for colicky babies.
The newer study (which also measured colic using modified Wessel’s criteria) included babies who were formula-fed as well as those who were breastfed. When researchers looked at all babies as a single group, those who received probiotics fussed significantly more than those who received placebo at nearly all of the postintervention time points. However, when they delved deeper, the researchers noted that an increase in fussing occurred only among infants on formula. On the other hand, the time that breastfed infants spent crying or fussing did not vary significantly between those who received probiotics and those who received placebo.
Both the 2010 and 2014 studies used valid RCT methods with low risk for bias, so we’re not clear why the results (especially for breastfed infants) differed. The 2010 study was done in Italy and required breastfeeding moms to avoid cow’s milk, while the 2014 Sung et al2 study was conducted in Australia and did not have this requirement, so environmental factors may have played a role. The reporting method in the Sung et al2 study—a well-validated, detailed diary of infant behaviors—may have led to less parent recall error than the diary used in the 2010 study. All in all, we can only conclude that it is unclear whether probiotics work to reduce crying in colicky infants.
A safe bet may be to avoid recommending probiotics for colicky formula-fed infants, since no study of this population has shown probiotics are effective, and in the Sung et al2 study, they appeared to worsen symptoms. For breastfed babies, there is no evidence of harm, and mixed evidence on whether probiotics help.