What are Probiotics?

Probiotics are live microorganisms that, when ingested in adequate amounts, confer health benefits to those who take them.

They act through specific changes in the composition of the microorganisms that are normally present in the intestines — also known as gut microbiota.

Probiotics can be found either in food or supplements containing live active microorganisms similar to the ones present in the body.

Probiotics are often confused with prebiotics, which have the same purpose but work differently. While probiotics are live microbes that form new colonies in the gut, prebiotics are non-digestible dietary substances, usually fibers, that stimulate the growth and/or activity of certain bacterial species already established in the colon.

Probiotics and prebiotics are sometimes combined in the same product — synbiotics.

Food sources of probiotics include the popular and easy-to-find yogurts with added probiotic microorganisms.

However, food sources are not likely to contain sufficient concentrations of probiotics to provide benefits, nor the specific strains that lead to those benefits. As such, probiotic supplements come as a convenient and reliable alternative to supply the body with one or more particular strains of bacteria and adequate dosages of colony-forming units (CFU).

Studies have assessed the potential benefits of Probiotics in the:

  • Maintenance of gut microbiota balance
  • Maintenance of immunologic equilibrium in the gastrointestinal tract
  • Prevention and treatment of acute diarrhea
  • Prevention and treatment of antibiotic-associated diarrhea
  • Relief of symptoms associated with gastrointestinal conditions


Cremon C. et al. Pre- and probiotic overview. Current Opinion in Pharmacology. 2018;43:87-92. doi:10.1016/j.coph.2018.08.010

Guarner F (chair) and Sanders ME (co-chair). WGO Practice Guideline - Probiotics and Prebiotics. World Gastroenterology Organisation. February, 2017.

Sanders ME. Probiotics for human use. Nutrition Bulletin. 2018;43(3):212-225. doi:10.1111/nbu.12334

Tompkins T. et al. The impact of meals on a probiotic during transit through a model of the human upper gastrointestinal tract. Beneficial Microbes. 2011;2(4):295-303. doi:10.3920/bm2011.0022

Witkins T., Sequoia J. Probiotics for Gastrointestinal Conditions: A Summary of the Evidence. American Family Physician. 2017 Aug 1;96(3):170-178. PMID: 28762696

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