Probiotics do nothing to help babies with colic, says an Australian paediatrician who has conducted a major study.
Dr Valerie Sung teamed up with Canadian researchers to test the increasingly popular theory that probiotics, or healthy bacteria, effectively soothe babies with the poorly understood condition.
They found no benefit at all in a placebo-controlled trial of 167 Australian colicky babies, 85 of whom were given the probiotic Lactobacillus reuteri.
There was no difference for breastfed babies compared with the placebo group. And formula-fed babies fussed more than their placebo counterparts, according to the study published in the British Medical Journal (BMJ).
The researchers did not test the findings of a 500-baby Italian study that shows benefits if Lactobacillus is given as a prophylactic for the first three months.
That study, published in the journal JAMA Pediatrics in January, showed significantly shorter crying spells and fewer stomach upsets.
Infant colic, or excessive crying, affects about 20 per cent of babies and is a major burden for families.
Although it usually resolves itself at three to four months, the cause is not known and there is no universally accepted treatment.
The idea that probiotics help is becoming increasingly mainstream, which is what prompted Dr Sung and her colleagues to conduct the study.
Their trial showed the probiotic failed to improve the babies' sleep, the mother's mental health or the family's quality of life.
Probiotics also did not change the babies' gut bacteria.
Previous smaller trials have suggested probiotics effectively treat colic in breastfed infants.
"The results from this trial are contrary to existing evidence and clearly demonstrate that probiotics cannot be routinely recommended," said Dr Sung of the Murdoch Childrens Research Institute.
She said it was still unclear whether they could benefit certain breastfed infants with colic.
An editorial in the same issue of the BMJ describes Dr Sung's study as "the most definitive and well designed" on the controversial topic.
The author, US Professor William Bennett, questions whether colic should be treated at all, given the lack of evidence.
"Babies cry," he writes.
Parents and their babies may be better served by studying interventions such as reassurance, family social support and the healing effect of time.