Probiotics are popular, but some questions remain

Probiotics are having a moment. They’re touted as the next big superstar in disease prevention and in treatment for ailments such as irritable bowel syndrome, gestational diabetes, allergies and obesity. Fans claim that these “good” bacteria will nourish your gut microbiome and crowd out the “bad” microbes. As a result, you’ll experience better digestion, a healthier immune system and a sunnier mood.

With this promise of probiotics, consumers are snapping up supplements and bacteria-enhanced beverages and snacks. According to a survey conducted by the National Center for Health Statistics, 3 million more U.S. adults used probiotics or prebiotics (a plant fiber) in 2012 than did so in 2007. The global probiotics market was over $35 billion in 2015, according to research from Global Market Insights.

However, the enthusiasm for these good-for-you bugs may be getting ahead of the research. Scientists are just beginning to understand the complex function of the microbiome, how probiotics work and the potential for targeted treatments.

“The field resembles the Wild West,” says Claire Fraser, director of the Institute of Genome Sciences at the University of Maryland School of Medicine. Although there are some intriguing results pointing to the beneficial effects of probiotics, Fraser says, there needs to be additional studies.

Also, the probiotic supplements on the market now might not be that helpful. It’s not yet clear how to re-create a healthy or fully diverse microbiome, says Lee Kaplan, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital. “It’s unlikely that the probiotics that are currently available will do that,” Kaplan says.

Russian scientist Elie Metchnikoff first observed more than 100 years ago that eating fermented foods may be associated with well-being and longevity. In the past 10 years, research has accelerated as scientists developed tools to study the microbiome in depth. Kaplan says researchers now know the microbiome can affect mood, bowel function, obesity, diabetes and inflammation.

But scientists don’t yet understand how the microorganisms living in our gastrointestinal tract give rise to or affect these conditions, let alone how to fix an unhealthy gut.

Few well-designed human studies offer conclusive evidence that manipulating the gut’s microorganisms can prevent or treat specific diseases, says Purna Kashyap, an assistant professor of medicine at the Mayo Clinic and a member of the scientific advisory board for the American Gastroenterological Association’s Center for Gut Microbiome Research and Education.

So far, evidence supports the use of beneficial bacterial strains as targeted therapy in a few specific cases. For example, probiotics have been found to significantly reduce the incidence of necrotizing enterocolitis, a life-threatening gastrointestinal disease in preterm infants, and diarrhea caused by Clostridium difficile, an infection that may take root following antibiotic use.

Promising research shows that probiotics may help with other conditions, such as acute diarrhea, antibiotics-associated diarrhea in children, Helicobacter pylori infection (a bacterial ailment associated with peptic ulcers) and gastrointestinal disorders including irritable bowel syndrome.

However, additional research and clinical trials are needed to evaluate the efficacy of specific strains of bacteria, or a combination of strains, to “alter both the composition of the microbiome in a given disease state and whether or not clinical symptoms associated with the disease are also relieved,” Fraser says. This will help guide recommendations on dosage and who ultimately may benefit from probiotic treatment.

On the other hand, there’s insufficient evidence that probiotics can help treat Crohn’s disease, eczema, urinary tract infections, periodontal disease or allergies.

Scientists and physicians are optimistic about the future of “good” microbes. Many probiotic and microbial-based compounds are moving to clinical trials. Researchers hope this will illuminate how gut microorganisms interact with specific diseases and medical conditions, yielding more-targeted and therapeutic probiotics.