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What are probiotics?

- and what are the health benefits?

Professional lab technician analyzing probiotics
5 Min read

Probiotics are live bacteria that are associated with specific health benefits when consumed in the right amounts. To be classified as a probiotic, products must contain live bacteria, they must have health benefits that are supported in human studies, and at a certain amount (CFU) of live bacteria.1 Specific probiotic strains have demonstrated benefits in many areas of health including immune health, digestive health, women’s health and oral health.


The probiotic bacteria must be alive when consumed in order to gain the anticipated health benefits, but the number of living bacteria in a product decreases over time as cells naturally die. Therefore, the number of bacteria reported on the product should be the number that will still be alive at the ‘end of shelf life’, and not the number that were alive on the date of manufacture, as the number will decrease between these two dates. 

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What is the definition of a probiotic?

The World Health Organization has defined probiotics as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.1 That’s us, we are the host. Many foods and supplements contain live bacteria, but only bacterial strains with a scientifically supported health effect may correctly be termed probiotics. 

Fermented foods such as kimchi and sauerkraut contain live bacteria and have been associated with health benefits, but they are not considered probiotics as they have not been the subjects of human clinical studies, and the ‘adequate amount’ that must be consumed to gain the health benefit has not been determined.

Pharmacist and customer what are probiotics

Probiotic bacteria must be alive …

Probiotic products contain millions to billions of live bacteria. However, like any living organism, bacteria naturally die. Therefore, the number of live bacteria in a probiotic product will reduce between the date it was manufactured and the date it is purchased. The number of live bacteria is known as Colony Forming Unit (CFU).

… and the right amount must be consumed

As discussed, to be classified as a probiotic, the health benefits must be supported in human studies. The specific health benefit of each probiotic is then related to the amount (CFU) of live bacteria that was used to show its benefit. As the health effect is only supported at that amount (CFU) of live bacteria, we should consume it at that level to achieve the desired effect.2, 3

So now we know that: 

1) The number of bacteria naturally decreases over time, and 
2) We must consume each probiotic at a specific amount (CFU)

These two points mean that number of bacteria (CFU) on the probiotic product’s potential expiry date (known as ‘end of shelf life’) is more important than the CFU on the date of manufacture.
Read more about what to look for when choosing a probiotic.

Genus, species, strain – does it matter? 

Probiotics are identified through their genus, species, and strain. The strain is important as it is at this level that the probiotics have been studied, not at the more general species level.4

For example, the clinical results associated with the Chr. Hansen probiotic strain Lactobacillus rhamnosus, LGG® (hereafter referred to by use of the trademark LGG®) are primarily connected to digestive and immune health,5, 6, 7, 8 whilst the clinical results of Lactobacillus rhamnosus, GR-1® (hereafter referred to by use of the trademark GR-1®) are primarily linked to women’s vaginal and urinary health.9, 10 Both of these strains are part of the Lactobacillus rhamnosus species, but it is by the specific strain (i.e. the LGG® or GR-1® strain) that has been associated with study results.

Probiotics beneficially affect our health

Probiotics have been extensively studied for decades and have demonstrated benefits across different health areas in human clinical trials. Examples of health areas where certain probiotic strains have been associated with positive health effects are listed below.

Digestive system health 

The digestive system is a health area in which probiotic products have demonstrated a beneficial effect. In several clinical studies, supplementation with probiotic products containing the Chr. Hansen Bifidobacterium, BB-12® (hereafter referred to by use of the trademark BB-12®) strain has been associated with improved regularity of bowel movements in adults with infrequent bowel movements,11, 12, 13 and with reduced incidence of crying and fussing in babies.14 Click to read more about probiotics and excessive crying and fussing in babies.


Immune health

Studies suggest that immune health in babies and children may be impacted following probiotic supplementation with the Chr. Hansen BB-12® and LGG® strains. Some studies have associated these specific probiotic strains with fewer respiratory infections,15, 16 a reduction in the incidence of respiratory infections lasting more than 3 days,7 significantly fewer days with respiratory symptoms,and a reduction in the incidence of ear infections.16

Click to read more about probiotics and respiratory health.


Women’s health

Urogenital health has also been studied following the use of probiotic products. For instance, studies have associated improvements in urinary tract health9 and vaginal health with the Chr. Hansen probiotic blend, UREX (containing Lactobacillus rhamnosus, GR-1® and Lactobacillus reuteri, RC-14®).10, 17, 18, 19 


Oral health 

Probiotic supplementation has also demonstrated positive results relating to oral health. In some studies, the consumption of products containing the Chr. Hansen LGG® probiotic strain by children, has been associated with a reduction in the risk of tooth decay based on clinical and microbiological evaluation, and with a reduction on saliva and dental plaque levels of a specific bacteria that contribute to tooth decay.20, 21

Scientist analyzing probiotics

Key take-aways

When choosing a probiotic product, it must be remembered that: 

  • The documented health benefits of probiotic strains are specific to the probiotic strain and to the amount (CFU) of the probiotic strain that was investigated in the associated human clinical trials.
  • The benefits observed are not generalizable to other health areas or strains.

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

BB-12®, GR-1®, LGG® and UREX 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.

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. Hoffmann DE, et al. Probiotics: achieving a better regulatory fit. Food Drug Law J. 2014;69(2):237-ii. (PubMed)

3. Jackson SA, et al. Improving End-User Trust in the Quality of Commercial Probiotic Products. Front Microbiol. 2019;10:739. (PubMed)

4. 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)

5. 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)

6. 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)

7. Hojsak I, et al. Lactobacillus GG in the prevention of nosocomial gastrointestinal and respiratory tract infections. Pediatrics. 2010;125(5):e1171-7. (PubMed)

8. 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)

9. 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)

10. 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)

11. 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)

12. 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. 

13. 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)

14. 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. 2020. (PubMed)

15. 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)

16. 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)

17. 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)

18. 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)

19. 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)

20. 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)

21. 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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