Sad news for sleep-deprived parents: probiotics may not quiet their colicky babies, a new meta-analysis suggests.

Evidence is still insufficient “to support probiotic use to manage colic, especially in formula-fed infants, or to prevent infant crying,” lead author Valerie Sung, MPH, and colleagues report in an articlepublished online October 7 in JAMA Pediatrics.

Colic, defined as excessive crying or fussing for no apparent reason, affects up to 20% of infants younger than 3 months, but its etiology remains unclear, write Sung, from the Murdoch Children’s Research Institute and Royal Children’s Hospital, Parkville, Australia, and coauthors. Some evidence points to an association with food allergies, but other data show differences in gut microflora between babies with and without colic. “The logical next step is to determine whether intervening to alter gut microbiota can effectively prevent or reduce infant crying,” the authors write.

Use of probiotics, products that use live microorganisms to confer health benefits, can change the infant gut environment and has been shown to suppress intestinal inflammation, strengthen mucosal barriers, and modulate gut contractility, any of which could produce uncomfortable symptoms and contribute to an infant’s irritability. In a meta-analysis, the authors sought to determine whether probiotics were better than no or standard treatment at reducing the duration of infant crying or distress, number of episodes of crying or distress, and proportion of infants with colic (crying or fussing for at least 3 hours a day, at least 3 days a week, for at least 1 week).

The authors identified 12 randomized, clinical trials including 1825 infants: 271 term babies with colic, 1534 term infants without colic, and 20 preterm newborns without colic. Five studies focused on probiotics specifically to manage colic, and 7 examined the use of probiotics to reduce infant crying. Some of the studies examined use of a single product, whereas others looked at the use of multiple products administered together. The products were administered as drops, capsules, or formula in a range of doses. All of the studies were placebo-controlled. Daily infant crying time was the most common reported outcome. The analysis was conducted according to guidelines from the Cochrane Handbook for Systematic Reviews of Interventions.

Mean daily crying time was significantly less in 2 of 7 trials in which probiotics were used to prevent colic; there were no differences between probiotics and placebo in the other 5 trials. Of the 5 trials examining probiotics in the management of colicky episodes, probiotics were significantly more effective than placebo in 3 trials in which Lactobacillus reuteri was administered in drops to breast-fed, full-term infants. Compared with placebo, probiotics were associated in those trials with a median reduction in daily crying time of 62.10 minutes (95% confidence interval [CI], −85.82 to −44.38 minutes; P < .001), but there was substantial heterogeneity among the trials. The authors conclude that the effect of probiotics in treating colic remains unclear because of the difficulty in comparing studies that examined vastly different products on different populations.

At least one outside expert agrees with this conclusion, despite some reservations about the authors’ methods. “The definition of colic was not rigorously controlled; there is likely to be no single cause of colic and no single treatment that is effective,” said Frank R. Greer, MD, professor of pediatrics, Wisconsin Perinatal Center, Meriter Hospital, Madison, Wisconsin. “The dosages and specific probiotic preparations were too variable[, and] whether they were given prenatally or not to both mother and infant after delivery also was extremely variable.” In addition, Dr. Greer told Medscape Medical News, “the authors did not use a validated methodology for recording the primary outcome, which was length of crying time.”

In Dr. Greer’s opinion, there is currently no place for probiotics in the management of infant colic. In contrast, he said, it has no serious adverse effects, “other than it adds unnecessarily to the cost of infant formula.”