A first review to establish whether giving babies probiotics (Lactobacillus reuteri) is an effective way to prevent and manage colic concludes there is not enough evidence to say it does, especially in formula-fed babies. However, in the case of exclusively breastfed babies who cry excessively or have colic, it may be effective.

The systematic review, which covered 12 trials involving a total of 1,825 babies up to 3 months old, was led by Dr. Valerie Sung of the Murdoch Children's Research Institute and the University of Melbourne, both in Australia.

Dr. Sung and colleagues report their findings in the latest online issue of JAMA Pediatrics.

Infant colic, or excessive crying for no apparent reason, is very common and affects around 1 in 5 babies under 3 months old.

Babies with colic can cry for several hours a day, causing significant distress to both babies and their mothers, to the point of affecting their mental health.

The specific cause of colic is unknown, and the symptoms include crying, swollen stomach and drawing legs up to the belly, though these usually disappear when babies reach 3 months of age.

There is evidence that infants with colic have different gut bacteria to infants without colic, which would suggest treatments targeting gut microbes might help.

Evidence 'not enough'

Probiotics have been proposed as a treatment for infant colic because they have been shown to benefit humans by rebalancing the mix of microbes in the adult gut.

Of the 12 trials that Dr. Sung and colleagues reviewed, six found probiotics reduced infant crying, and six did not.

The researchers noted that five of the trials were treatment trials, three of which said probiotics was an effective treatment for colic in breastfed babies, one said it might work for formula-fed babies with colic, and another said it does not work for breastfed babies with colic.

Dr. Sung says the evidence from these studies is not enough to give a "definitive answer" to the question of whether probiotics are an effective treatment for colic and excessive crying in babies.

"The results were extremely mixed," she says, and called for "larger and more rigorously designed clinical trials," to look at the question, particularly for formula-fed infants.

Another study published in JAMA earlier this year suggested infant colic may be linked to migraines in later life.