Background: Infantile colic affects 3 to 28 percent of healthy newborns. It is characterized by fussy crying lasting three or more hours a day, for three or more days a week, for at least three weeks, causing distress to infants and their parents. The etiology of colic is poorly understood, but increased counts of gas-producing anaerobic gram-negative intestinal bacteria have been implicated, and lower counts of lactobacilli have been recovered in the stool of colicky infants. Previous studies suggested a benefit of lactobacilli supplementation compared with simethicone therapy. Savino and colleagues conducted a randomized controlled, double-blind study to test the safety and effectiveness of a particular lactobacillus strain, Lactobacillus reuteri (DSM 17938), in colicky infants.

The Study: Fifty full-term, colicky infants with birth weights of 2,500 to 4,000 g (5 lb, 8 oz to 8 lb, 13 oz) who were exclusively breastfed were recruited between two and 16 weeks of gestation. Infants with evidence of chronic illness, gastrointestinal disease, any antibiotic or probiotic use in the previous week, or any formula feeding were excluded. Mothers were instructed to avoid cow's milk in their diet during the study. Infants were randomized to receive 8 log₁₀ colony-forming units of L. reuteri (provided as a freeze-dried suspension in a mixture of sunflower oil and medium-chain triglyceride oil) or identical placebo. Five drops of the supplement and placebo were given 30 minutes before the first feeding of the day for 21 days. The primary outcome was a reduction in crying time to less than three hours per day by day 21. Secondary outcomes included the number of children who had a 50 percent reduction in crying time at days 7, 14, and 21. Intestinal microflora also were analyzed to determine the effect the probiotic had on select intestinal bacteria.

At enrollment, parents were interviewed to determine daily crying time, and the infant's growth parameters were measured. Parents kept a detailed daily diary to record crying times, stooling patterns, and any adverse effects. Fecal samples were collected at enrollment and on day 21.

Results: All but four infants in the placebo group completed the study, and no infants were withdrawn because of adverse effects. Median crying times were similar between the groups at baseline (370 minutes per day in the lactobacilli group and 300 minutes per day in the placebo group). Infants in the probiotic group had significantly reduced daily crying times (35 versus 90 minutes per day) by day 21 compared with infants in the placebo group, although there was still a marked decrease in the placebo group. Moreover, infants in the probiotic group had significantly less crying at days 7, 14, and 21. By day 21, only four of the 25 infants in the probiotic group cried for more than 180 minutes per day compared with 12 of the 21 infants in the placebo group. Stool samples confirmed the presence of L. reuteri in the treatment group, whereas no infants in the placebo group had the probiotic in their stool. There was a greater decrease in Escherichia coli counts in the treatment group compared with the placebo group.

Conclusion: The authors conclude that although all colicky infants improved during the course of this study, the probiotic L. reuteri is well tolerated and more effective than placebo in reducing colic-related crying.