With names like "Nature's Bounty," "Healthy Origins" or "Garden of Life," the online marketplace is jammed with so-called "probiotics," pills that claim to restore intestinal bacteria and keep your digestive system healthy and happy. But do we really need these probiotic supplements?
A new study from Denmark casts serious doubts on the marketing claims of what has become a $32-billion worldwide industry.
"Many healthy adults take them because they think there is a health benefit," said Oluf Pedersen, professor of medicine at the University of Copenhagen and director of the Novo Nordisk Foundation Center for Basic Metabolic Research. "But there is no evidence of any effect. There is an enormous mismatch between the market and the science evidence."
Pedersen and colleagues reviewed seven different recent studies of probiotics on human subjects. They did find that they work for patients suffering from irritable bowel syndrome, ulcerative colitis and travelers' diarrhea. In these cases, the variety of normally-occurring "good" bacteria -- called the "microbiotic flora" -- may be disturbed or knocked out of balance.
But for healthy people seeking to stay that way, forget it.
Study participants across the seven original random clinical trials were healthy adults between 19 and 88 years of age. The studies used between 21 to 81 subjects. Probiotic products were administered as biscuits, milk-based drinks, sachets or capsules for 21 to 42 days.
"It's like many people are taking multivitamins because they feel more safe," Pedersen said. "There is a kind of automatism. It's the same with probiotics."
U.S. and European regulatory agencies classify probiotics as a dietary supplement rather than a pharmaceutical, which would require more substantial proof through large-scale clinical trials with one group getting a probiotic and one control group getting nothing.
Proof of a benefit would include a change in gut microbiota in a healthy area, or immune markers that could suggest a healthier immune system.
A recent study out of Japan highlighted some of the weak science behind the pro-probiotic movement. The study found that a small sample of two dozen Japanese medical students who drank probiotic fermented milk product reported less stress hormones than those that did not before a big exam. The sample size was small -- 23 students got the probiotic compared with 24 that drank regular milk. But lead author and 13 others listed on the paper are employed by Yakult, the same company that manufactures the fermented milk. That kind of conflict-of-interest might not pass muster in a bigger study.
Pedersen, whose own review of studies is published today in the open access journal Genome Medicine, said more, bigger and more rigorous studies are needed to find out whether probiotics are a placebo -- or a real, bacterial boon to our upset tummies.