Probiotic supplements containing "killed" bacteria might help some people with irritable bowel syndrome find relief, a new study suggests.
Experts said the findings add to evidence that certain probiotics can help some people with irritable bowel syndrome, or IBS. And it's the first trial to test a probiotic with bacteria that were heat-killed -- which, the researchers say, could make the supplement more practical to use.
IBS is a digestive disorder that affects an estimated 12% of Americans, according to the U.S. National Institutes of Health. It's thought to be caused by problems in gut-brain communication, affecting how the muscles of the digestive tract work. That results in bloating, abdominal pain, and either constipation or diarrhea (though some people have both).
The usual treatments include diet changes and medication to normalize bowel movements. Doctors sometimes also recommend probiotics -- supplements containing live bacteria.
"Normally, we ask patients to trial a probiotic for a month or so, daily. If there is no benefit, it's reasonable to try another brand," said Dr. Nicholas Talley, a gastroenterologist and professor at the University of Newcastle in Australia.
"The problem is," he added, "we do not have strong data to recommend one particular product over another."
And the existing evidence suggests that any IBS relief from probiotics is "modest at best," according to Talley, who wrote an editorial accompanying the study, which was published online April 8 in The Lancet Gastroenterology & Hepatology.
The trial tested a probiotic containing Bifidobacterium bacteria that had been heated to make them "non-viable." The point is to give the supplements a longer shelf-life than standard probiotics. That would make them easier to store and take when traveling, according to the researchers, who were led by Dr. Peter Layer of the University of Hamburg Teaching Hospital, in Germany.
Layer's team recruited 443 adults with IBS and randomly assigned half to take the heat-killed probiotic for eight weeks. The other half took an identical-looking placebo (inactive substance).
Overall, 34% of the probiotic patients reported an improvement in their pain, bloating and bowel habits during at least four of the eight weeks of treatment. That compared with 19% of placebo patients.
The study, funded by German probiotic maker Synformulas, does not answer the question of why some IBS patients improved with the treatment.
But, in general, there's been interest in using probiotics for the condition because studies show that patients often have a "clear change" in their gut microbiome, according to Dr. Elena Ivanina, a gastroenterologist at Lenox Hill Hospital in New York City.
The gut microbiome refers to the trillions of bacteria and other micro-organisms that dwell in the digestive system and help it function normally.
People with IBS tend to show decreases in bacteria like Bidifobacterium and Faecalibacterium, said Ivanina, who was not involved in the study.
But, like Talley, she said there are important unknowns, including which particular probiotics work best.
"Recommendations within the gastroenterology literature have suggested taking probiotics 'as a group' to improve IBS symptoms, with no further guidance," Ivanina said.
She called the new findings "welcome," because they give insight into how well this particular probiotic strain works, and whether a non-viable form can have an effect.
But why would a killed probiotic have any benefit? Again, it's not clear.
The researchers wrote that some bacterial strains, including Bifidobacterium, seem to adhere to cells in the lining of the gut and strengthen the "intestinal barrier" against harmful bacteria and toxins that may contribute to IBS. And while the heat-treated bacteria are not "living," research suggests they can still latch onto cells in the gut lining.
But both Talley and Ivanina noted that the probiotic in this trial was no home run. The number of people who responded just as well to the placebo -- 19% -- was "significant," Ivanina said.
And the majority of patients in both groups failed to get any notable relief. "The benefit overall is not large," Talley said. "A minority have a good response, at best."
In his practice, he only recommends probiotics as an "adjunct" therapy: Diet changes should be "first line," Talley said.
One diet approach, he noted, is called "low FODMAP" -- which limits fermentable carbohydrates, possibly starving the particular gut bacteria that produce gas.
Examples of those carbs include wheat and rye; fruits such as apples, cherries, mangoes, pears and plums; vegetables like asparagus, cabbage, lentils and onions; and milk and other dairy products.
The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has a primer on irritable bowel syndrome.