A Look into the Safety of Probiotic Supplements

Stephanie Walek, Pharm.D., Allina Health

Probiotic supplements have become a common addition to patients’ medication regimens. Their use is generally associated with preventing C. difficile infections and antibiotic-associated diarrhea. Although probiotics are thought to promote digestive health, they may not be safe for everyone – in particular for those who are immunocompromised because these supplements are live microorganisms. Case reports have described serious adverse events, including fungemia and bacteremia, in such patients. The lack of effective ways to detect post marketing harm from supplements also likely contributes to underreporting of these adverse effects.

The poor quality of regulation surrounding over-the-counter products in the United States is also concerning. Even though the U.S. Food and Drug Administration has established good manufacturing processes for all dietary supplements, not all manufacturers follow them. With low manufacturing compliance, probiotic supplements may contain contaminants and incorrect species of bacteria – something that may be harmful if consumed by an immunocompromised patient.

Another unique risk of probiotic supplements that health professionals need to be aware of is their potential to promote antibiotic resistance. In vitro and rodent models have shown that probiotics signal the presence of a mobile gene that is capable of transferring antibiotic resistance to pathogenic bacteria. Though more research needs to be done with human data, the remote possibility of conferring antibiotic resistance needs to be seriously considered when approaching patients who are on or looking to start probiotic supplements. With the lack of laws and regulations surrounding the manufacturing practices of live microorganisms, it should not be assumed that labeling is accurate. Combining the lack of manufacturing regulation with the possibility of promoting antibiotic resistance, probiotic supplements may not be safe for every patient and need to be carefully considered moving forward.


1. Cohen PA. Probiotic safety – no guarantees [published online September 17, 2018]. JAMAIntern Med. doi:10.1001/jamainternmed.2018.5403