Concerns raised over prebiotic and probiotic safety

As probiotics and prebiotics grow ever more popular, a new study asks whether we know enough about their potential dangers. After examining the current literature, scientists discover that adverse events are often missed.

The age of gut bacteria is upon us. Almost daily, new studies are being published explaining yet another way in which our microbiome helps or hinders in health or disease.

These are fascinating times for our microbiome.

Health and wellness products are also enjoying a spike in popularity, so microbiome-altering foods and supplements are all the rage.

Two main categories are widely available:

  • probiotics, which are live microorganisms
  • prebiotics, which are designed to alter or encourage the bacteria already in the gut

Also available are synbiotics, which combine both probiotics and prebiotics in one product.

The increased scientific interest in gut bacteria and the prominence of health-based businesses have presented a unique problem. Scientists are now asking whether we know enough about prebiotics' and probiotics' safety.

Benefits and hazards

Because our knowledge of gut bacteria and how they influence our bodies is relatively limited, it is difficult to say with any degree of accuracy whether probiotics and prebiotics might have negative effects.

Recently, researchers based at the Centre of Research in Epidemiology and Statistics at Sorbonne University in Paris, France and Columbia University in New York City, NY, took to the literature to uncover what risks — if any — have been reported during research.

The authors say that the purpose of the study was "[t]o examine how harms-related information is reported in publications of randomized controlled trials of probiotics, prebiotics, and synbiotics."

Their findings were published recently in the journal Annals of Internal Medicine.

They found that most of the 384 randomized controlled trials that they investigated were not adequately recording adverse events; in some cases, they were not reporting harms at all.

In fact, 28 percent of the trials gave no information on hazardous events, and only 2 percent properly recorded harm assessments. As the authors summarize:

"[M]ost studies of probiotics, prebiotics, and synbiotics lack key safety parameters, raising doubts about the confidence we can have in conclusions about the safety of these interventions."

Because of the widespread use of prebiotics and probiotics in products as diverse as baby formula and breakfast cereals, it is important that we gather as much information about the cons as we have about the pros.

The study authors end their paper by explaining, "An international and collective effort is urgently needed."