Georgetown University Medical Center, Washington, DC (Dr. Merenstein); International Scientific Association for Probiotics and Prebiotics, Centennial, CO (Dr. Sanders); University of California Davis School of Medicine and Center for Healthcare Policy and Research, Sacramento (Dr. Tancredi) djm23@georgetown.edu
Dr. Merenstein reported no potential conflict of interest relevant to this article.
Dr. Sanders consults with companies engaged in probiotic business, but has no financial stake in any company. She serves on scientific advisory boards for Danone, Yakult Honsha Co., Ltd, Danone North America, and Winclove.
Dr. Tancredi has received statistics educational consulting fees from Pfizer Consumer Health.
Understanding probiotic product labels is a good start. Information shown on the label of a probiotic dietary supplement in the United States should include the genus, species, and strains contained in the product, the dose delivered in CFU (the most common measure of the number of live microbes in a probiotic product) through the end of shelf life, and expected benefits. (For help in deciphering these labels, see the label schematic developed by the International Scientific Association for Probiotics and Prebiotics40 at https://isappscience.org/infographics/probiotic-labelling/.)
Per guidelines from the Food and Agricultural Organization of the United Nations and the World Health Organization, all probiotic products should have this type of information clearly displayed on the product packaging.41 However, some probiotic foods display less information; for example, they may not specify the product’s strains or recommended dosage levels. Product Web sites may or may not disclose details missing from the food label. The absence of such information makes it impossible to make evidence-based recommendations about those products.
Probiotics are generally safe, with caveats
The overall safety of typical probiotics (Lactobacillus species, Bifidobacterium species, and Saccharomycescerevisiae var. boulardii) has been well documented.42,43 Many probiotic strains have been granted Generally Recognized as Safe status for use in foods in the United States.44,45 Many traditional probiotic species have been evaluated by the European Food Safety Authority (similar to FDA, except jurisdiction is only over foods, not drugs) and are considered safe for use in food in the European Union.
Be aware that probiotics delivered in dietary supplements and foods are intended for the general population and not for patient populations. Manufacturers therefore are not required to assure safety in vulnerable populations. Nevertheless, probiotics are often stocked in hospital formularies.46,47 Probiotic usage in vulnerable patient groups has been considered by an expert working group from the standpoint of quality assurance for microbiologic products used to treat and prevent disease, with the experts recommending that health care professionals (including pharmacists and physicians) seek quality information from manufacturers and that manufacturers participate in programs providing third-party (eg, United States Pharmacopeia [USP] or Underwriters Laboratories [UL]) verification of probiotic products to assure products meet applicable purity standards.48,49
Published case studies have reported that probiotics may be a rare cause of sepsis.43 Recently, Lactobacillus rhamnosus GG was linked to bacteremia in 6 critically ill patients, but all cases resolved without complications.50 Further, the death of a premature infant was linked to administration of a probiotic contaminated with an opportunistic pathogenic mold.51 A randomized controlled trial (RCT) of a multispecies probiotic product in critically ill pancreatitis patients showed higher mortality in the group given the multispecies probiotic.52 However, additional examination of the data suggests that the observed higher mortality was due to problems with randomization for disease severity and other concerns, and not to the probiotic.53 Much more frequently, probiotics have been administered orally in at-risk patient groups, including premature infants, cancer patients, and critically ill patients, with no significant increases in adverse events.54-56