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Labdoor analyzed 37 best-selling probiotic supplements in the United States, measuring amounts of total anaerobic bacteria, genera-specific bacteria, and potential contaminants (mold, yeast, and pathogenic bacteria, including E. coli o157:H7, Salmonella spp., and Staphylococcus aureus).

The U.S. Clinical Guide to Probiotic Products1, Canadian Guide to Probiotic Supplements2 and the WGO Global Guidelines for Probiotics and Prebiotics3 provide suggested effective amounts of specific strains for treating certain health conditions, such as constipation or IBS. All 37 products listed the species of bacteria they contained, but only 14 listed amounts of individual strains. We found that 9 of those 14 products provided beneficial bacteria at effective levels. The Center for Responsible Nutrition recommends4 the industry move toward specifying strains as a best-practice because whether a product works and for what purpose depends on its strains.

Five probiotic supplements recorded measurable amounts of contaminating yeast residues. Typically, probiotics will test positive for yeast if they contain beneficial yeasts (i.e. Saccharomyces bouldarii); however, these products did not claim yeast probiotics in their formulations.



On average, measured amounts of total viable bacteria differed from label claims by -15%.

Label accuracy was an issue for products in this batch. About half of the products (16 of 37) recorded total viable bacteria amounts that were more than 50% off their label claims. Two of those products deviated from their total viable bacteria claims by more than 100%.

Labdoor’s label accuracy score looks at the total amount of tested viable bacteria compared to claimed, amount of specific genera compared to claimed, and whether the label lists the minimum viable numbers for each probiotic strain at the end of shelf-life, per the World Health Organization’s5 labelling recommendations.

Because the effectiveness of probiotics depends on the amounts of specific strains, Labdoor's standard is to heavily penalize products that claim a "proprietary blend" and don't specify strains or respective amounts of each strain.



Four products recorded at least 1000 CFUg of contaminant yeast residues.

33 of 37 passed all purity tests, indicating an absence of harmful contaminant yeast, mold residues and bacteria, including the pathogenic strain of E. coli (E. coli O157:H7), Salmonella spp., and Staphylococcus aureus. The U.S. Pharmacopeia6 recommends a microbial limit of 100 CFUg of combined yeast and mold in dietary supplements and non-detectable limits of E.coli, Salmonella, and Staphylococcus aureus. If a product met these standards, it received a full score.



Due to their tablet or capsule forms, all tested probiotics had insignificant levels of any macronutrients.

Probiotic supplements in this analysis had similar macronutrient profiles; they recorded minimal amounts of calories, fats, carbohydrates, and sugar. Most had so few macronutrients that, according to FDA guidelines7, they were allowed to list them as zero or not at all.



About half of the products (23 of 37) received an Ingredient Safety score of 90 or higher (out of 100).

Probiotics are generally considered safe8 for most healthy people, but may cause gastrointestinal discomfort (abdominal tenderness, pain, gas, andor diarrhea) if intake exceeds individual needs. People with certain health conditions like suppressed immunity or sensitivity to probiotics may experience more severe side effects9. Probiotics can also interact with some medications. Please consult your doctor before starting any new supplement.

In addition to the safety of active ingredients, our ingredient safety score evaluates all inactive ingredients for potential health risks based on scientific literature and the Center for Science in the Public Interest’s10 (CSPI) safety ranking of food additives.



28 of 37 products received a Projected Efficacy score lower than 5 out of 10.

There are currently no established doses set for probiotic intake. The U.S. Clinical Guide to Probiotic Products1, Canadian Guide to Probiotic Supplements2 and the WGO Global Guidelines for Probiotics and Prebiotics3 provide suggested effective amounts of specific strains for treating certain health conditions, such as constipation or IBS.

To factor strain-specific benefits into our efficacy score, we referenced the information in these guides. Products were rewarded for containing strains on these lists. Additionally, measured levels of each strain were compared to what is thought to be effective based on these guides, and scores were scaled accordingly. In cases where products did not list strain-specific amounts, or their listed strains were not included in these guides, total measured CFUs were compared to a general effectiveness threshold of 1 billion CFUs cited by research published in the American Journal of Clinical Nutrition11.



  • 10 CSPI. (2017). Chemical Cuisine.
  • 11 Saavedra JM. (2001). Clinical applications of probiotic agents. American Journal of Clinical Nutrition. 73(6):1147S-1151S.
  • 1 AEP. (2016). Clinical Guide to Probiotic Products - Available in the US: 2017 Edition.
  • 2 AEP. (2016). Clinical Guide to Probiotic Products - Available in Canada: 2017 Edition.
  • 3 WGO. (2017). World Gastroenterology Organisation Global Guidelines Probiotics and Prebiotics.
  • 4 Council for Responsible Nutrition. (2017). Best Practices Guidelines for Probiotics.
  • 5 FAO and WHO. (2002). Guidelines for the Evaluation of Probiotics in Food.
  • 6 USP. (2017) Microbiological Attributes of Nonsterile Nutritional and Dietary Supplements.
  • 7 FDA. (2003). Guides for Industry: A Food Labeling Guide (16. Appendix H: Rounding the Values According to FDA Rounding Rules).
  • 8 NIH. (2016). Probiotics: In Depth.
  • 9 Boyle RJ, et al. (2006). Probiotic use in clinical practice: what are the risks?. American Society for Clinical Nutrition. 83(6):1256-1264.