London - Probiotics do nothing to help the vast majority of stomach troubles, a major review has found.
New US guidelines warn there is not enough evidence to advise the use of probiotics for almost any digestive problems.
Products such as yoghurts, drinks and capsules containing "beneficial" bacteria are supposed to boost our health.
But the review found only three very specific circumstances where certain formulations might work.
It stressed patients should stop taking the products for all other complaints. Probiotics have boomed in recent years.
Many customers buy probiotics believing they will boost digestion and solve stomach complaints.
But the review finds there is little evidence this is the case.
The guidelines, issued by the American Gastroenterological Association, said there are only three circumstances where evidence backs use of the products.
One is for the prevention of Clostridium difficile infection in people taking antibiotics. Another is to help stop necrotising enterocolitis – a bowel condition – in premature babies and a third is for the management of pouchitis, a complication of inflammatory bowel disease. Researchers said there is no evidence that probiotics help treat Crohn’s disease, ulcerative colitis or irritable bowel syndrome.
And they can do more harm than good for acute infectious gastroenteritis in children. Dr Grace Li-Chun Su, of the University of Michigan, who led the guidelines panel, said: "The supplements can be costly and there isn’t enough evidence to prove a benefit or confirm lack of harm.
"Patients taking probiotics for Crohn’s, ulcerative colitis or IBS should consider stopping."
She added: "While our guideline does highlight a few use cases for probiotics, it more importantly underscores that the public’s assumptions about the benefits of probiotics are not well-founded."
The 375-page review, published in the Gastroenterology journal, also raised concerns that probiotics are often marketed without evidence to back up claims. The authors wrote: "The industry is largely unregulated and marketing of product is often geared directly at consumers without providing direct and consistent proof of effectiveness. This has led to widespread use of probiotics with confusing evidence for clinical efficacy."
But dietitian Dr Carrie Ruxton, of the UK industry-funded Health and Food Supplements Information Service, said: "Dietary supplements sold over the counter, including probiotics, are aimed at general health, not for preventing or treating specific illnesses.
"The new advice...isn’t relevant to the majority of people using over-the-counter probiotics who simply want to ensure that they are modifying their gut bacteria towards more favourable species."