This article is part of an ongoing series entitled, Beyond Rx: OTC Corner, which will include topics such as OTC medications, dietary supplements, and other health care approaches that will help nurse practitioners and physician assistants provide patients with tools to manage their health.

Robert D. Sheeler, MD, is guest editor of the series. He is an associate professor of family medicine, Mayo Clinic, in Rochester, Minn. He is board certified in family medicine, integrative medicine, and holistic medicine.

Probiotics are defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”1 This definition necessitates that probiotics must be alive when administered (dead microbes cannot be called probiotic), must be the subject of research documenting health benefits (usually in humans, but probiotics are also used in companion and agriculture animals), and must be microbiologically defined. Mixed cultures (as found in fermented foods) or undefined mixtures (as comprising fecal microbial transplants) are not microbiologically defined to the strain level and do not meet the definition of a probiotic. Some publications have suggested that dead bacteria can have positive physiologic effects, but such products are not probiotics.

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Genus, Species, and Strain Identity

The microbes most often used as probiotics include species of the genera Lactobacillus and Bifidobacterium. Other probiotics include the lactic culture, Streptococcus thermophilus, the yeast, Saccharomyces cerevisiae (biovariant boulardii), and the bacterial sporeformer, Bacilluscoagulans. Each probiotic should be identified using current methods to the species or, if applicable, subspecies level. Furthermore, a strain designation for each strain should be provided. For example, the probiotic “Lactobacillus acidophilus NCFM” (genus, species, and strain, respectively) refers to a specific strain of L acidophilus. Some probiotic benefits are likely a general property of a species, so all strains of that species are expected to impart the benefit. For example, yogurt cultures (L bulgaricus and S thermophilus)—regardless of the strain—seem to aid lactose digestion in situ; however, for most specific, clinical benefits, the strain identity is important because different strains can use different mechanisms of action and ultimately have different physiologic effects. Research should always identify the probiotic to the strain level, and commercial probiotics should disclose the strain designation so that consumers and health care providers can link studies to specific probiotic strains.

Regulatory Categories of Probiotic Products

Probiotics encompass a broad range of product types, including foods, supplements, medical foods, drugs, infant formula, animal foods, nonoral applications, and even devices (such as tampons with probiotics). Although foods and dietary supplements are the most common product types, probiotic drugs are sure to be developed from targeted probiotic research dovetailed with human microbiota findings. Probiotic supplements are typically capsules or powders that often deliver 1 billion bacteria or more per dose. Probiotic drugs (and some devices) require premarket approval of safety and efficacy by the FDA. The remaining categories of products previously listed do not. Claims and safety standards differ depending on the regulatory category. Whereas a drug is intended to cure, treat, prevent, or mitigate disease, and is targeted for a healthy or diseased person, a food or dietary supplement cannot make a drug claim, and is intended for the generally healthy population. 

Probiotic Product Labels 

The following information optimally should be provided on a probiotic product label or accompanying website. Many products on the market do not fully provide this information; missing information makes it difficult for health care providers to best match probiotic products with client needs. 

  • Identification of the genus, species, and strain of each probiotic present in the product

  • The level of each probiotic strain in the product through the end of shelf life; products labeled with a live count “at time of manufacture” are suspect, because it is unclear if an efficacious level will be in the product at time of consumption

  • Indication of the health benefit(s) associated with the product; note that there are regulatory restrictions on what types of information can be communicated for different categories of products

  • Product information website

  • Proper storage conditions

  • Recommended dose based on the level shown to be effective in the published studies