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What are probiotics?

- Probiotics are characterized live organisms with documented efficacy 

Professional lab technician analyzing probiotics
5 Min read

Probiotics are live microorganisms that are associated with potential health benefits when consumed in adequate amounts. To be characterized as a probiotic, products containing live microorganisms must have demonstrable, strain specific clinical effects at documented CFU levels. Specific probiotic strains have been associated with demonstrable positive health effects  relating to immune function, gastrointestinal health, women’s health and oral health.


Probiotic microorganisms must be consumed alive to perform as intended, but the number of living bacteria in a product decreases over time due to natural cell death - therefore the Colony Forming Unit (CFU) reported on the product should be the potency at ‘end of shelf life’, not on the date of manufacture, as the CFU is likely to decrease between these two dates

Probiotics defined

The World Health Organization defined probiotics as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.1 Many foods and supplements contain live microorganisms, but only characterized strains with a scientifically demonstrated effect on health may correctly be termed ‘probiotics’. By this definition, a probiotic strain must have the characteristics of specificity, potency, and demonstratable clinical efficacy.

Fermented foods such as kimchi and sauerkraut contain microbes and have been associated with health benefits but are not considered probiotics as they have not been characterized, the ‘adequate amount’ (or dose) has not been defined, and their health effects have not been clinically demonstrated.

Scientist analyzing probiotics

Specificity at the strain level

Probiotics are identified through their genus, species, subspecies, and strain. The strain level is important as clinical results of probiotics are directly related to that specific strain.2 For example, the Chr. Hansen probiotic strain Lactobacillus rhamnosus, LGG® is primarily associated with gastrointestinal and immune function,3, 4, 5, 6 while the Lactobacillus rhamnosus, GR-1® strain is predominantly associated with women’s urogenital microflora.7, 8

Probiotic potency

Probiotic products contain millions to billions of live bacteria, each of which can form visible colonies that can be used for enumerating the bacteria; thus, the potency of a product is measured through Colony Forming Units. Probiotic potency at the ‘end of shelf life’, a product's potential expiration date, needs to be within the dosage range of documented clinical results that are specifically associated to that specific probiotic strain.9, 10 The number of viable bacteria will have decreased between manufacturing and purchasing, therefore, the potency at end of shelf life, rather than on the date of manufacture, should be reported on the product.

Microbiome imbalance can lead to health issues

Composition of the human gastrointestinal microbiome fluctuates over a lifetime, with imbalances (dysbiosis) occurring due to age, medications, diet, and disease.11 Additionally, mode of delivery at birth and exposure to antibiotics affects the development of our gut microbiome.12 Some probiotics have been associated with specific effects across a range of diverse health areas, by positively influencing the dysbiotic microbiota.

Probiotics beneficially impact different microbiota

Probiotics have been extensively studied in vitro, in vivo, and in human double-blind clinical trials for decades, and have demonstrated health benefits across different health areas. The suggested mode of action for probiotics involves supporting the integrity of the intestinal epithelial barrier,13, 14 maintaining healthy immune responses,15, 16 promotion of enteroendocrine cell hormone secretion17 and support for production of beneficial metabolites.18, 19 Examples of health areas where certain probiotic strains have been associated with a beneficial effect are listed below.

Gastrointestinal health

Gastrointestinal health is an example of a health area in which probiotic products have demonstrated a beneficial effect. Supplementation with probiotic products containing specific Chr. Hansen strains has been associated with increased defecation frequency in adult populations with infrequent bowel movements,20, 21, 22 and with the management of the symptoms of infant colic23 – an effect that is thought to occur through support for the healthy microbiota structure and function.23

Immune function

In infants and children Chr. Hansen strains have been associated with support for a healthy immune function. Consumption of strain-specific probiotic products have been associated with reduced incidence of respiratory infections,24, 25 respiratory tract infections lasting > 3 days,5 a significantly lower number of days with respiratory symptoms,5 and reduced incidence of acute otitis media.25

Women’s health

Chr. Hansen probiotic strains have been associated with support for healthy urogenital microbiota, with observations of reduced incidence of urinary tract infections,7 vulvovaginal candidiasis,26 and bacterial vaginosis.8, 27, 28

Oral health

Oral health is a fourth example of an area in which probiotic supplementation has demonstrated positive support. In children, consumption of products containing a Chr. Hansen probiotic strain has been associated with a decreased risk of dental caries based on a clinical evaluation and a microbiological analysis, and lower Streptococcus mutans levels from dental plaque and saliva.29, 30

When choosing a probiotic product, it is important to pay attention to the CFU count of the probiotic strain in the product and the potency of the probiotic strain that was investigated in the associated clinical trial.

For more information on our Chr. Hansen strains, click here.

LGG® and GR-1® are registered trademarks of Chr. Hansen A/S.

The article is provided for informational purposes regarding probiotics and is not meant to suggest that any substance referenced in the article is intended to diagnose, cure, mitigate, treat, or prevent any disease.

Pharmacist and customer what are probiotics

References Open Close

1. Hill C, et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11:506. (PubMed)
2. McFarland LV, et al. Strain-Specificity and Disease-Specificity of Probiotic Efficacy: A Systematic Review and Meta-Analysis. Frontiers in medicine. 2018;5:124-. (PubMed)
3. de Vrese M, et al. Probiotic lactobacilli and bifidobacteria in a fermented milk product with added fruit preparation reduce antibiotic associated diarrhea and Helicobacter pylori activity. J Dairy Res. 2011;78(4):396-403. (PubMed)
4. Pärtty A, et al. Effects of Early Prebiotic and Probiotic Supplementation on Development of Gut Microbiota and Fussing and Crying in Preterm Infants: A Randomized, Double-Blind, Placebo-Controlled Trial. The Journal of Pediatrics. 2013;163(5):1272-7.e2. (PubMed)
5. Hojsak I, et al. Lactobacillus GG in the prevention of nosocomial gastrointestinal and respiratory tract infections. Pediatrics. 2010;125(5):e1171-7. (PubMed)
6. Hojsak I, et al. Lactobacillus GG in the prevention of gastrointestinal and respiratory tract infections in children who attend day care centers: a randomized, double-blind, placebo-controlled trial. Clin Nutr. 2010;29(3):312-6. (PubMed)
7. Beerepoot MA, et al. Lactobacilli vs antibiotics to prevent urinary tract infections: a randomized, double-blind, noninferiority trial in postmenopausal women. Arch Intern Med. 2012;172(9):704-12. (PubMed)
8. Petricevic L, et al. Randomized, double-blind, placebo-controlled study of oral lactobacilli to improve the vaginal flora of postmenopausal women. Eur J Obstet Gynecol Reprod Biol. 2008;141(1):54-7. (PubMed)
9. Hoffmann DE, et al. Probiotics: achieving a better regulatory fit. Food Drug Law J. 2014;69(2):237-ii. (PubMed)
10. Jackson SA, et al. Improving End-User Trust in the Quality of Commercial Probiotic Products. Front Microbiol. 2019;10:739. (PubMed)
11. Aleman FDD, Valenzano DR. Microbiome evolution during host aging. PLoS Pathog. 2019;15(7):e1007727. (PubMed)
12. Korpela K, de Vos WM. Early life colonization of the human gut: microbes matter everywhere. Curr Opin Microbiol. 2018;44:70-8. (PubMed)
13. Seth A, et al. Probiotics ameliorate the hydrogen peroxide-induced epithelial barrier disruption by a PKC- and MAP kinase-dependent mechanism. Am J Physiol Gastrointest Liver Physiol. 2008;294(4):G1060-9. (PubMed)
14. Chen L, et al. Lactobacillus rhamnosus GG treatment improves intestinal permeability and modulates microbiota dysbiosis in an experimental model of sepsis. Int J Mol Med. 2019;43(3):1139-48. (PubMed)
15. Claes IJ, et al. Lipoteichoic acid is an important microbe-associated molecular pattern of Lactobacillus rhamnosus GG. Microb Cell Fact. 2012;11:161. (PubMed)
16. Lebeer S, i. Functional analysis of Lactobacillus rhamnosus GG pili in relation to adhesion and immunomodulatory interactions with intestinal epithelial cells. Appl Environ Microbiol. 2012;78(1):185-93. (PubMed)
17. Latvala S, et al. Potentially probiotic bacteria induce efficient maturation but differential cytokine production in human monocyte-derived dendritic cells. World J Gastroenterol. 2008;14(36):5570-82. (PubMed)
18. Kang J-E, et al. A Novel Lactobacillus casei LP1 Producing 1,4-Dihydroxy-2-Naphthoic Acid, a Bifidogenic Growth Stimulator. Prev Nutr Food Sci. 2015;20(1):78-81. (PubMed)
19. Russo M, et al. Lactobacillus fermentum CRL1446 Ameliorates Oxidative and Metabolic Parameters by Increasing Intestinal Feruloyl Esterase Activity and Modulating Microbiota in Caloric-Restricted Mice. Nutrients. 2016;8(7). (PubMed)
20. Eskesen D, et al. Effect of the probiotic strain Bifidobacterium animalis subsp. lactis, BB-12®, on defecation frequency in healthy subjects with low defecation frequency and abdominal discomfort: a randomised, double-blind, placebo-controlled, parallel-group trial. Br J Nutr. 2015;114(10):1638-46. (PubMed)
21. Uchida K, et al. Effect of fermented milk containing Bifidobacterium lactis BB-12 on stool frequency, defecation, fecal microbiota and safety of excessive ingestion in healthy female students. Journal of Nutritional Food. 2005;8:39-51
22. Pitkala KH, et al. Fermented cereal with specific bifidobacteria normalizes bowel movements in elderly nursing home residents. A randomized, controlled trial. J Nutr Health Aging. 2007;11(4):305-11. (PubMed)
23. Nocerino R, et al. The therapeutic efficacy of Bifidobacterium animalis subsp. lactis BB-12® in infant colic: A randomised, double blind, placebo-controlled trial. Aliment Pharmacol Ther. 2019. (PubMed)
24. Taipale T, et al. Bifidobacterium animalis subsp. lactis BB-12 in reducing the risk of infections in infancy. Br J Nutr. 2011;105(3):409-16. (PubMed)
25. Rautava S, et al. Specific probiotics in reducing the risk of acute infections in infancy--a randomised, double-blind, placebo-controlled study. Br J Nutr. 2009;101(11):1722-6. (PubMed)
26. Martinez RC, et al. Improved treatment of vulvovaginal candidiasis with fluconazole plus probiotic Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14. Lett Appl Microbiol. 2009;48(3):269-74. (PubMed)
27. Vujic G, et al. Efficacy of orally applied probiotic capsules for bacterial vaginosis and other vaginal infections: a double-blind, randomized, placebo-controlled study. Eur J Obstet Gynecol Reprod Biol. 2013;168(1):75-9. (PubMed)
28. Anukam K, et al. Augmentation of antimicrobial metronidazole therapy of bacterial vaginosis with oral probiotic Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14: randomized, double-blind, placebo controlled trial. Microbes Infect. 2006;8(6):1450-4. (PubMed)
29. Nase L, et al. Effect of long-term consumption of a probiotic bacterium, Lactobacillus rhamnosus GG, in milk on dental caries and caries risk in children. Caries Res. 2001;35(6):412-20. (PubMed)
30. Glavina D, et al. Effect of LGG yoghurt on Streptococcus mutans and Lactobacillus spp. salivary counts in children. Coll Antropol. 2012;36(1):129-32. (PubMed)

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