Two new rigorous placebo-controlled studies have concluded probiotic supplements do not confer any beneficial effects in easing symptoms of gastroenteritis in children. The trials found children's symptoms and recovery times were nearly identical whether they took probiotics or a placebo.

As research into the gut microbiome is booming, so is the nascent probiotic market. From probiotic supplements to enriched foods, the market for these popular products is estimated to reach over US$60 billion by 2023, yet there is a dearth of strong scientific evidence proving their worth.

Probiotics as a treatment for acute gastroenteritis in children has grown in popularity over recent years. A small volume of studies have been produced to validate this use but many have been funded by companies with stakes in probiotics. Lead author on one of the new studies, David Schnadower from Washington University, suggests much prior work has been small and there was a need for more rigorous independent research.

"Some smaller studies have indicated that probiotics may help, however, such studies had a number of limitations," says Schnadower. "We sought to provide independent and conclusive evidence for or against probiotic use in infants and toddlers with acute gastroenteritis."

The trials examined two popularly used probiotics: Culturelle – an over-the-counter product containing Lactobacillus rhamnosus GG (LGG), and Lacidofil – a combination probiotic containing Lactobacillus rhamnosus and Lactobacillus helveticus.

Each trial involved nearly 1000 children who presented to pediatric emergency departments with moderate to severe cases of gastroenteritis in the US and Canada. The children were all given a 5-day course of either the probiotic or placebo, and then followed-up over the next month. Across both trials the results found the probiotic made no difference in the subsequent duration of diarrhea or vomiting. Recovery times between placebo and probiotic subjects were nearly identical, as was the average time absent from day care.

"We tested many different scenarios — infants compared with toddlers, whether the patient had taken antibiotics, whether the gastroenteritis was caused by virus or bacteria, and how long the diarrhea had been going on before the treatment was given," says Schnadower on the LGG research. "We also had the probiotic independently tested for purity and strength. Every time, we reached the same conclusion."

This research is far from the last word on any general beneficial use for probiotics, but it does offer very strong evidence suggesting these specific probiotics confer no beneficial effects in treating gastroenteritis in children. This may seem like a narrow conclusion, but considering both doctors and parents are increasingly administering these probiotics to children as a treatment for gastroenteritis, this is welcome, solid research essentially debunking that particular use.

Probiotics may have other uses, such as preventing sepsis in newborns or reducing a child's risk of developing allergic or autoimmune disease when taken by a mother during pregnancy. That said, many claimed probiotic benefits do still lack rigorous scientific proof, and some studies are appearing to question whether these supplements may be doing more harm than good.

Phillip Tarr, co-author of the LGG study with David Schnadower, suggests at the moment parents shouldn't waste their money on probiotic supplements. At the very least if your child has an upset stomach, these results clearly reveal probiotics to be relatively useless.

"The results of the U.S. and Canadian studies were not ambiguous," says Tarr. "Probiotics had no effect on the children. Parents are better off saving their money and using it to buy more fresh fruits and vegetables for their children."

Both studies were published in the New England Journal Of Medicine with the LGG study here, and the Lacidofil study here.