Colic usually develops a few weeks after birth, generally abates on its own and rarely lasts beyond 4 months of age. (Bigstock)
Babies
Probiotics seem to do little to calm a colicky infant

THE QUESTION Though no one knows precisely what causes colic in babies, one long-held theory is that it is related to gastrointestinal distress. Given that, might the fussing and crying of a colicky baby be eased by giving the child probiotics, the so-called “helpful bacteria” thought to be good for the gut?

THIS STUDY involved 167 infants, 3 months old or younger, who had been born full-term and were otherwise healthy but had been seen at an emergency clinic for colic. (For the study, colic was defined as crying or fussing for at least three hours a day for three or more days a week.) They were randomly assigned to be given the probiotic Lactobacillus reuteri or a placebo, in liquid form, once a day for a month. In that time, colic symptoms declined steadily in both groups, with the daily duration of colicky episodes cut in half for 44 percent of the probiotic group and 48 percent of the placebo group. After a month, babies taking the probiotic cried and fussed 49 minutes more each day, on average, than did those taking the placebo. Laboratory analysis of fecal samples showed virtually no difference in gut bacteria and inflammation between infants who were and were not given probiotics. During the study, babies given probiotics also slept less (on average, 47 minutes a day less) than those given the placebo.

WHO MAY BE AFFECTED? Infants. Colic, estimated to affect 25 to 40 percent of all babies, usually develops a few weeks after birth. With the hallmark trait of chronic fussing and crying for no apparent reason, colic generally abates on its own and rarely lasts beyond 4 months of age. In addition to the theory about digestive-system issues, other theories about the cause of colic have included allergies, lactose intolerance, feeding and comforting methods, and whether the baby’s mother smokes or is anxious, although there’s little scientific evidence to support any of them.

CAVEATS Information on colic symptoms came from journals kept by the infants’ parents. Whether a different probiotic or a different dose would yield different results is unclear. Probiotics used in the study, a strain of one commonly used in the United States, were provided by BioGaia, a Swedish health-care company that makes them. Probiotics sold as dietary supplements do not need prior approval from the Food and Drug Administration, but their labels cannot contain health claims without the agency’s consent. The FDA has not approved any health claims for probiotics.

FIND THIS STUDY April 1 online issue of BMJ at www.bmj.com.

LEARN MORE ABOUT colic at www.kidshealth.org (enter parents’ site). Learn about oral probiotics and their uses at nccam.nih.gov/health.

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.