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Probiotics do not reduce the rate of colic in babies, a condition in which newborns cry for prolonged periods without a clear reason, a new study suggests.
The findings, which were published Tuesday (April 1) in the British Medical Journal, contradict the results of other trials that suggested probiotics had some benefit.
Infant colic means crying inconsolably for at least three hours a day, at least three days a week, for three weeks. It generally affects about 20 percent of babies. Though the condition typically resolves by the time a baby reaches 3 months old, the seemingly endless crying can cause breastfeeding problems, postpartum depression and other stresses for parents.
Although no one knows what causes colic, some researchers have suggested that intestinal distress and gut inflammation could play a role.
Incessant crying
Past studies have suggested that the probiotic supplement Lactobacillus reuteri improved stomach problems and colic in newborns. But not all of those findings came from blind studies; that is, the parents knew they were giving their children probiotics. The studies also looked at a selected group of infants, such as those babies whose mothers exclusively breastfed them (without giving any infant formula), and those infants who were on a dairy-free diet. [5 Ways Gut Bacteria Affect Your Health]To see how probiotic supplements affected a more representative sample of newborns who had colic, Dr. Valerie Sung, a pediatrician at the Royal Parkville Hospital in Australia, conducted a blinded experiment. She and her colleagues randomly assigned 167 breastfed or formula-fed infants to receive either an L. reuteri supplement or a placebo, for a month.
The researchers then asked parents to report on their babies' instances of fussing and crying at various points, up to 6 months later. The researchers also looked at family well-being and adjustment, as well as maternal mental health.
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In both groups, the amount of crying dropped over time, but the babies given the probiotic supplement fussed for an average of 49 minutes more per day, compared with those taking the placebo. The babies in the probiotic group who were formula fed were particularly fussy, according to the study.
The probiotic also showed no benefits for family or maternal well-being, or infant sleep, and didn't alter the babies' gut bacterial compositions, according to the study.
No benefit
It's not clear why this study found no benefit from probiotic supplements when past studies did show a benefit. However, one possible explanation is that parents of babies in past studies knew if their children were receiving probiotic supplements. So the parents, and therefore the studies, overestimated the benefit of the treatment, the researchers said.
It's also possible that the benefits of probiotics may be confined to babies on a dairy-free diet, the researchers wrote in their study.
Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.
Tia is the editor-in-chief (premium) and was formerly managing editor and senior writer for Live Science. Her work has appeared in Scientific American, Wired.com, Science News and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.