Sloppy Reporting Undermines Claims of Probiotic Safety

Guest BloggerClinical Corner, Microbiome Environment


First do no harm.

Probiotics appear to be outside the purview of drastic side effects reported for many supplements. No warnings of possible death and dismemberment scroll probiotic labels.

Among manufacturers, researchers and clinicians in the industry, probiotics are considered safe. Theoretical risks  include systemic infections, deleterious metabolic activities, excessive immune stimulation in susceptible individuals, gene transfer and gastrointestinal side effects. Sure, isolated reports of issues pop up from time to time—usually in sick people — but mostly, safety in healthy people is not a huge concern. A long history of safe probiotic use as well as data from clinical trials, and animal and in vitro studies all support the assumption that probiotics are generally safe for most populations.

Assumptions and ommissions regarding safety

Is this an assumption backed by science? One recent analysis shows that lack of proper data could be one cause for complacency.

Aïda Bafeta of Paris Descartes University and colleagues wondered if safety was reported in probiotic intervention experiments: Harms Reporting in Randomized Controlled Trials of Interventions Aimed at Modifying Microbiota: A Systematic Review was published in Annals of Internal Medicine July, 2018.

The researchers gathered randomized control trials (RCTs) from Cochrane Central Register of Controlled Trials, PubMed, EMBASE, and Web of Science from January 1, 2015 to March 20, 2018. To be included the RCT had to assess the safety or efficacy of at least one intervention involving probiotics, prebiotics, or synbiotics alone or in combination with another intervention compared with any control (such as a placebo or an antibiotic) for any clinical condition.

Of 384 trials included, 69% of the trials evaluated probiotics; the others used prebiotics alone or in tandem with probiotics (also called synbiotics).

Results were disturbing:
  • No harms-related data were reported for 106 trials (28%) But even when harms were reported, sloppy metrics (16%) and descriptions (37%) were common.
  • Safety results were not reported for 142 (37%)
  • Number of serious adverse events (SAEs) per study group was not given for 309 (80%)

There’s more:

A full 98% of the trials included did not reveal the number of withdrawals from intervention due to harms.

“Harms reporting in published reports of RCTs assessing probiotics, prebiotics, and synbiotics often is lacking or inadequate. We cannot broadly conclude that these interventions are safe without reporting safety data.”

Are probiotics safe?

Maybe they are, as clinicians no doubt reassure clients. Or perhaps not everyone will find them compatible with their systems. How are we to know with 100% conviction when the harms aren’t tracked consistently?

If the probiotic space wants legitimacy, then researchers must adopt better templates for research. Medical journals too should require stricter standards for what they accept for publication.

No news is good news” is no way to conduct research.

Other reading:

Risk and safety of probiotics

Safety of Probiotics in Pregnancy

Probiotics and Sepsis