Probiotics do not help babies suffering with colic, a new study suggests.

Colic refers to excessive crying in an infant where there is no known cause. It is estimated to affect one in five babies and can have a major effect on families. While it usually resolves itself spontaneously when the child is three or four months old, the cause often remains unknown and no single treatment has proven effective.

According to Australian and Canadian researchers, some small trials had indicated that the probiotic, Lactobacillus reuteri, could treat colic in breastfed babies. These trials were very limited however, and the effect of the probiotic on bottle-fed babies remained unknown.

The researchers decided to investigate further.

They set out to assess whether Lactobacillus reuteri could reduce crying in 167 babies with colic. All were aged less than three months old and they included breastfed and bottle-fed babies.

Eighty-five of the babies were randomly selected to receive the probiotic, while 82 received a placebo, for one month.

The researchers assessed things like how long the baby cried for, how long they slept for, and the mental health of the mothers involved.

The study found that overall, babies who received the probiotic fussed much more than the babies who received the placebo, at all times that they were assessed from day seven to the end of the month

After one month, the babies on probiotics fussed or cried for an average of 49 minutes more than the placebo group.

The researchers noted that this increased fussing only occurred in bottle-fed babies, however the probiotic did not affect fussing or crying time in the breastfed babies. In other words, while they did not fuss more, the fussing time was not reduced either.

This marks the largest randomised controlled trial of the use of probiotics to treat colic. The researchers concluded that the probiotic ‘did not reduce crying or fussing in infants with colic, nor was it effective in improving infant sleep, maternal mental health, family or infant functioning, or quality of life.

As a result, they believe that probiotics ‘cannot be routinely recommended for all infants with colic'.

Details of these findings are published in the British Medical Journal.