Many parents give their kids probiotics when they get stomach bugs. But do these supplements really help curb the vomiting and diarrhea?
The answer — at least for two popular probiotics — appears to be: No.
"We have shown in two very large and rigorous studies that these particular probiotics do not work. They had no effect," says David Schnadower, a professor of pediatrics at Cincinnati Children's Hospital Medical Center.
Schnadower led one of the studies, a federally funded project conducted in the United States. He also helped with the second, a government-supported Canadian test. The results of both are being published in the New England Journal of Medicine.
Schnadower concludes "these particular probiotics shouldn't be used for gastroenteritis."
Gastroenteritis is the technical name for stomach bugs, which can be caused by viruses, bacteria or parasites. The ailment sends about 1.7 million kids to emergency rooms and hospitalizes 70,000 in the United States each year. Many more kids spend miserable days at home with their parents.
The theory behind the use of probiotics is that friendly bacteria could help the body fight off tummy troubles and reset the normal balance of microbes in the digestive system.
But based on the findings, Schnadower and others recommend against doctors suggesting parents use probiotics for their kids sick with a stomach bug or moms and dads trying them on their own for the same reason.
"If they don't work, don't spend your money on them," Schnadower says. "Spend your money on good food. Buy yogurt. Buy vegetables. Buy fruit. Kids will benefit from that more than buying bacteria in pills that have no strong evidence behind them to support their use." (Neither study found any safety problems.)
Others argue the studies are far from the last word and need to be considered in the context of previous research, some of which indicated the probiotics could be effective for some conditions.
"The conclusion from these two trials is not that 'probiotics don't work,' " Mary Ellen Sanders, executive science officer at the International Scientific Association for Probiotics and Prebiotics, wrote in an email. The group includes scientists and probiotic makers. "Scientists must consider the totality of evidence when evaluating the efficacy of any intervention, including acute pediatric diarrhea. It is not scientifically valid to ignore previous research when new studies are performed."
But i-Health, Inc., the company that makes Culturelle, one of the probiotics tested, raised questions about how the U.S. study was conducted. The firm also noted that previous research has supported the effectiveness of the probiotic.
"The findings should be considered with other clinical trials that have demonstrated positive outcomes," wrote Seema Mody, senior director of research and development at i-Health, Inc., in an email.
But the researchers who led the new studies argue the earlier tests were inferior. "We were hoping for positive trials — a cure for kids' diarrhea — but we need to accept reality," wrote Dr. Stephen Freedman of the Alberta Children's Hospital, who led the Canadian study, in an email.
At least one independent scientist agrees the new studies are definitive, at least for the specific probiotics conducted for this specific ailment. "These are important, very well-done studies," says J. Thomas LaMont, chief of gastroenterology at Beth Israel Deaconess Medical Center in Boston, who wrote an editorial accompany the studies. "These studies are likely to have significant impact towards eliminating use of medications that don't seem to work."
Schnadower, Freedman, LaMont and others stressed that the findings only apply to the two probiotic formulations tested in the study and only for gastroenteritis.
It's still possible that the probiotics tested in these studies might work for other health problems. It's also possible other probiotics might work for gastroenteritis or other conditions, they say. A recent study, for example, found a probiotic could help protect babies against sepsis, which can be life-threatening.
But probiotics, which consist of living bacteria, are being marketed for a dizzying array of ailments — from digestive problems to maintaining overall health and preventing chronic ailments like obesity and heart disease. Some probiotics are even being marketed to alleviate mental health conditions such as anxiety and depression.
The booming multi-billion-dollar probiotics market has been fueled by the explosion of research into the microbiome. The microbiome is the millions of friendly bacteria, viruses, fungi and other microbes that inhabit and are believed to help maintain a healthy human body.
But most of the probiotics research has consisted of small studies, many of which have been funded by companies that sell products. Probiotics aren't required to undergo review and approval by the Food and Drug Administration.
As a result, many scientists and clinicians have questioned whether there's enough evidence to support the myriad claims, and have called for high-quality independent examinations like the two new studies.
In the first study, Schnadower and his colleagues studied 971 children, ages 3 months to 4 years, who were treated for gastroenteritis at 10 U.S. emergency rooms. The children got either a probiotic containing the bacteria Lactobacillus rhammosus GG for five days or a placebo. That probiotic is sold over the counter as Culturelle.
There was no meaningful difference in how long parents said their kids' vomiting and diarrhea lasted, the researchers reported.
In the second study, researchers studied 886 children ages 3 months to 2 years old who came into six Canadian ERs with gastroenteritis. The youngsters got either a five-day course of a probiotic containing Lactobacillus rhamnosus R001 and Lactobacillus helveticus R0052 or a placebo. That combination is popular in southeast Asia.
Again, there was no significant difference among the groups.
"The rigor and magnitude of these two studies ... have moved the indicator quite a bit towards a conclusion that these two different preparations offer no benefit to this illness," wrote Phillip Tarr, a professor of pediatrics at Washington University in St. Louis who helped conduct the U.S. study, in an email. "It is time to move on."