WEDNESDAY, Nov. 21, 2018 (HealthDay News) -- When young children have a bout of "stomach flu," parents often turn to probiotics for help. But two new clinical trials suggest they are wasting their money.
Researchers found that probiotic formulas showed no benefit for babies and preschoolers with acute gastroenteritis -- a common gut infection that causes diarrhea and vomiting.
The findings contradict some earlier, smaller trials.
But researchers said those studies were generally "poorly done" and provided only weak evidence that probiotics worked.
The new trials, performed in Canada and the United States, were much better designed, said Dr. J. Thomas LaMont, a gastroenterologist at Beth Israel Deaconess Medical Center in Boston.
And the findings might change doctors' minds about suggesting probiotics for gastroenteritis, he said.
"Often, trials with negative findings don't get published," said LaMont. "These trials were published because they're expected to have an impact on clinical practice."
LaMont wrote an editorial accompanying the reports, which were published Nov. 22 in the New England Journal of Medicine.
Probiotic supplements contain live bacteria, the goal being to restore a better balance to intestinal bacteria and boost the immune system.
Despite the weak evidence, some medical societies do suggest probiotics as an option for kids' gastroenteritis -- partly because the products are considered quite safe.
So doctors do recommend them, and many parents try the heavily marketed products on their own, said Dr. David Schnadower, who worked on both trials.
As it stands, there is no way to stop the diarrhea caused by gastroenteritis, said Schnadower, a professor of pediatrics at Cincinnati Children's Hospital. The only treatments are fluids to prevent dehydration and, sometimes, anti-nausea medication.
"That's frustrating," Schnadower said. "Parents really want something to make this go away."
But based on the new findings, he said, probiotics are not the answer.
The U.S. trial tested a pediatric formulation of a probiotic marketed for "digestive health" called Lactobacillus rhamnosus GG, or LGG.
It included 971 children aged 3 months to 4 years who'd been diagnosed with acute gastroenteritis in an emergency room. The researchers randomly assigned them to receive either a five-day course of LGG or a placebo, in addition to standard care.
In the end, the study found, the probiotic made no difference. Children in both groups had diarrhea for an average of two days, and missed two days in day care.
Schnadower said his team looked at the findings from different angles -- including whether probiotics had different effects in kids who did or didn't get antibiotics, or whose infections were caused by a virus versus bacteria.
"No matter how we looked at it," he said, "probiotics were no better than placebo."
The Canadian study tested a probiotic combination -- L. rhamnosus plus L. helveticus -- in 886 children with acute gastroenteritis. The results were nearly identical to those from the U.S. trial.
None of that means probiotics are useless, according to LaMont. He pointed to a recent trial in rural India, where researchers gave newborns a probiotic or placebo for the first few days of life. The supplement lowered the babies' risk of lung infections and sepsis -- a severe complication of infection -- in the first two months of life.
But when it comes to acute gastroenteritis, LaMont said, probiotics may have no effect because kids' symptoms are usually short-lived anyway.
"These conditions get better on their own in about 48 hours," he said. "They're self-limiting."
Schnadower suggested that parents stick with some basic measures when a child has diarrhea and vomiting.
"Keep your child well-hydrated with fluids," he said, "and wash your hands regularly to lower the risk of spreading the infection."
And while probiotics are generally safe, Schnadower pointed to the cost.
"Is it worth spending money on a probiotic that's no better than a placebo?" he said. "You could spend it on fruits and vegetables and other nutritious foods instead."
Schnadower did stress that there's great promise in studying the "microbiome" -- the trillions of bacteria and other microbes that naturally dwell in the body and may play a key role in our health.
"But research into manipulating the microbiome for health is still in its infancy," Schnadower said. "The market for probiotics is huge, and it's growing much faster than the science supporting it."
He cited statistics showing the global market stands at about $37 billion.
In the United States, LaMont noted, probiotics are not regulated the way drugs are. They are considered supplements and do not have to be proven effective before hitting store shelves.
The U.S. National Institutes of Health has more on gastroenteritis.
SOURCES: David Schnadower, M.D., M.P.H., professor, pediatrics, Cincinnati Children's Hospital Medical Center; J. Thomas LaMont, M.D., gastroenterologist, Beth Israel Deaconess Medical Center, and professor, medicine, Harvard Medical School, Boston; Nov. 22, 2018, New England Journal of Medicine