Probiotic#Strains

An October 2001 report by the World Health Organization (WHO) defines probiotics as "live microorganisms which when administered in adequate amounts confer a health benefit on the host."{{Cite web |last=Schlundt |first=Jorgen |title=Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live Lactic Acid Bacteria |url=https://www.who.int/foodsafety/publications/fs_management/en/probiotics.pdf |url-status=dead |archive-url=https://web.archive.org/web/20121022161702/http://www.who.int/foodsafety/publications/fs_management/en/probiotics.pdf |archive-date=October 22, 2012 |access-date=17 December 2012 |website=Report of a Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria |publisher=FAO / WHO}}{{Cite book |url=https://www.worldcat.org/oclc/70928765 |title=Probiotics in food : health and nutritional properties and guidelines for evaluation. |date=2006 |publisher=Food and Agriculture Organization of the United Nations |others=Food and Agriculture Organization of the United Nations, World Health Organization |isbn=92-5-105513-0 |location=Rome |oclc=70928765 |access-date=2022-10-31 |archive-date=2023-07-01 |archive-url=https://web.archive.org/web/20230701214654/https://www.worldcat.org/title/70928765 |url-status=live }}{{page needed|date=January 2024}} Following this definition, a working group convened by the Food and Agriculture Organization (FAO)/WHO in May 2002 issued the Guidelines for the Evaluation of Probiotics in Food.{{Cite web |date=1 May 2002 |title=Guidelines for the Evaluation of Probiotics in Food |url=ftp://ftp.fao.org/es/esn/food/wgreport2.pdf |archive-url=https://web.archive.org/web/20170518131130/ftp://ftp.fao.org/es/esn/food/wgreport2.pdf |archive-date=2017-05-18 |url-status=dead |publisher=Joint FAO/WHO Working Group on Drafting Guidelines for the Evaluation of Probiotics in Food, London, Ontario, Canada}} A consensus definition of the term probiotics, based on available information and scientific evidence, was adopted after the aforementioned joint expert consultation between the FAO of the United Nations and the WHO. This effort was accompanied by local governmental and supra-governmental regulatory bodies' requirements to better characterize health claims substantiations.{{citation needed|date=June 2022}}

That first global effort was further developed in 2010; two expert groups of academic scientists and industry representatives made recommendations for the evaluation and validation of probiotic health claims.{{Cite journal |vauthors=Rijkers GT, Bengmark S, Enck P, Haller D, Herz U, Kalliomaki M, Kudo S, Lenoir-Wijnkoop I, Mercenier A, Myllyluoma E, Rabot S, Rafter J, Szajewska H, Watzl B, Wells J, Wolvers D, Antoine JM |year=2010 |title=Guidance for substantiating the evidence for beneficial effects of probiotics: current status and recommendations for future research |journal=J. Nutr. |volume=140 |issue=3 |pages=671S–676S |doi=10.3945/jn.109.113779 |pmid=20130080 |doi-access=free}}{{Cite journal |vauthors=Shane AL, Cabana MD, Vidry S, Merenstein D, Hummelen R, Ellis CL, Heimbach JT, Hempel S, Lynch SV, Sanders ME |year=2010 |title=Guide to designing, conducting, publishing and communicating results of clinical studies involving probiotic applications in human participants |journal=Gut Microbes |volume=1 |issue=4 |pages=243–253 |doi=10.4161/gmic.1.4.12707 |pmc=3023606 |pmid=21327031}} The same principles emerged from those two groups as were expressed in the "Guidelines" of FAO/WHO in 2002. This definition, though widely adopted, is not acceptable to the European Food Safety Authority because it embeds a health claim that is not measurable.

A group of scientific experts assembled in Canada in October 2013 to discuss the scope and appropriate use of the term "probiotic", adjusting the definition to be "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host."{{Cite journal |last1=Hill |first1=C |last2=Guarner |first2=F |last3=Reid |first3=G |last4=Gibson |first4=GR |last5=Merenstein |first5=DJ |last6=Pot |first6=B |last7=Morelli |first7=L |last8=Canani |first8=RB |last9=Flint |first9=HJ |last10=Salminen |first10=S |last11=Calder |first11=PC |last12=Sanders |first12=ME |date=August 2014 |title=Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. |journal=Nature Reviews. Gastroenterology & Hepatology |volume=11 |issue=8 |pages=506–514 |doi=10.1038/nrgastro.2014.66 |pmid=24912386 |doi-access=free|hdl=2164/4189 |hdl-access=free }}

Live probiotic cultures are part of fermented dairy products, other fermented foods, and probiotic-fortified foods.{{Cite journal |last1=Mattila-Sandholm |first1=T. |last2=Myllärinen |first2=P. |last3=Crittenden |first3=R. |last4=Mogensen |first4=G. |last5=Fondén |first5=R. |last6=Saarela |first6=M. |year=2002 |title=Technological challenges for future probiotic foods |url=https://www.sciencedirect.com/science/article/abs/pii/S0958694601000991 |journal=International Dairy Journal |volume=12 |issue=2–3 |pages=173–182 |doi=10.1016/S0958-6946(01)00099-1 |access-date=29 December 2020 |archive-date=16 June 2022 |archive-url=https://web.archive.org/web/20220616074831/http://www.sciencedirect.com/science/article/abs/pii/S0958694601000991 |url-status=live |url-access=subscription }}

Lactic acid bacteria (LAB), which are food fermenting bacteria, have the ability to prevent food spoilage and can improve the nutritive value of the foods they inhabit. Acid fermentation (as well as salting), remains one of the most practical methods of preservation of fresh vegetables, cereal gruels, and milk-cereal mixtures due to its low cost and energy requirements.{{Cite book |url=https://www.ncbi.nlm.nih.gov/books/NBK234703/ |title=Lactic Acid Fermentations |date=1992 |publisher=National Academies Press (US) |language=en |access-date=2021-03-30 |archive-date=2015-04-01 |archive-url=https://web.archive.org/web/20150401052540/https://www.ncbi.nlm.nih.gov/books/NBK234703/ |url-status=live }}

Fermented products that contain lactic acid bacteria include vegetables such as pickled vegetables,{{Cite book |title=Fermented Vegetables; In: Food Microbiology: Fundamentals and Frontiers, 4th Ed |vauthors=Breidt F, McFeeters RF, Perez-Diaz I, Lee CH |publisher=ASM Press |year=2013 |isbn=978-1-55581-626-1 |location=Washington, DC |pages=841–855 |chapter=Fermented Vegetables |doi=10.1128/9781555818463.ch33 |access-date=19 May 2016 |chapter-url=https://fbns.ncsu.edu/USDAARS/Acrobatpubs/P376-400/p380.pdf |archive-date=28 May 2015 |archive-url=https://web.archive.org/web/20150528190455/http://fbns.ncsu.edu/USDAARS/Acrobatpubs/P376-400/p380.pdf |url-status=live }} kimchi,{{Cite journal |vauthors=Oh CK, Oh MC, Kim SH |year=2004 |title=The Depletion of Sodium Nitrite by Lactic Acid Bacteria Isolated from Kimchi |journal=Journal of Medicinal Food |volume=7 |issue=1 |pages=38–44 |doi=10.1089/109662004322984680 |pmid=15117551}} pao cai,{{Cite journal |vauthors=Pederson CS, Niketic G, Albury MN |year=1962 |title=Fermentation of the Yugoslavian pickled cabbage |journal=Applied Microbiology |volume=10 |issue=1 |pages=86–89 |doi=10.1128/AEM.10.1.86-89.1962 |pmc=1057814 |pmid=14484853}} and sauerkraut;{{Cite journal |last1=Friedman |first1=Y |last2=Hugenholtz |first2=Jeroen |last3=De Vos |first3=Willem M. |last4=Smid |first4=Eddy J. |year=2006 |title=Safe use of genetically modified lactic acid bacteria in food. Bridging the gap between consumers, green groups, and industry |url=http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582006000400011&tlng=&lng=en&nrm=iso |url-status=live |journal=Electronic Journal of Biotechnology |volume=9 |issue=4 |pages=E49–55 |doi=10.2225/vol9-issue4-fulltext-12 |doi-broken-date=December 9, 2024 |archive-url=https://web.archive.org/web/20130814122022/http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582006000400011&tlng=&lng=en&nrm=iso |archive-date=14 August 2013 |access-date=7 November 2007 |df=dmy-all}} sourdough bread or bread-like products made without wheat or rye flour, amino acid/peptide meat-flavored sauces and pastes produced by fermentation of cereals and legumes; fermented cereal-fish-shrimp mixtures and fermented meats; soy products such as tempeh,{{Cite journal |vauthors=Moreno MR, Leisner JJ, Tee LK, Ley C, Radu S, Rusul G, Vancanneyt M, De Vuyst L |year=2002 |title=Microbial analysis of Malaysian tempeh, and characterization of two bacteriocins produced by isolates of Enterococcus faecium |journal=Journal of Applied Microbiology |volume=92 |issue=1 |pages=147–157 |doi=10.1046/j.1365-2672.2002.01509.x |pmid=11849339 |doi-access=free |s2cid=20756449}} miso,{{Cite web |last=Ehrlich |first=Steven D. |date=2011-05-24 |title=Lactobacillus acidophilus |url=http://umm.edu/health/medical/altmed/supplement/lactobacillus-acidophilus |url-status=live |archive-url=https://web.archive.org/web/20150911233110/http://umm.edu/health/medical/altmed/supplement/lactobacillus-acidophilus |archive-date=2015-09-11 |access-date=2015-09-17 |publisher=University of Maryland Medical Center (UMMC)}} and soy sauce;{{Cite journal |vauthors=Tanasupawat S, Thongsanit J, Okada S, Komagata K |year=2002 |title=Lactic acid bacteria isolated from soy sauce mash in Thailand |journal=Journal of General and Applied Microbiology |volume=48 |issue=4 |pages=201–209 |doi=10.2323/jgam.48.201 |pmid=12469319 |doi-access=free}} dairy products such as yogurt, kefir,{{Cite journal |vauthors=Plessas S, Alexopoulos A, Voidarou C, Stavropoulou E, Bezirtzoglou E |year=2011 |title=Microbial ecology and quality assurance in food fermentation systems. The case of kefir grains application |journal=Anaerobe |volume=17 |issue=6 |pages=483–485 |doi=10.1016/j.anaerobe.2011.03.014 |pmid=21497663}} buttermilk;{{Cite journal |vauthors=Shiby VK, Mishra HN |year=2013 |title=Fermented milks and milk products as functional foods – a review |journal=Critical Reviews in Food Science and Nutrition |volume=53 |issue=5 |pages=482–496 |doi=10.1080/10408398.2010.547398 |pmid=23391015 |s2cid=3059150}} and non-dairy products such as bee pollen.{{Cite journal |last1=Mohammad |first1=Salma Malihah |last2=Mahmud-Ab-Rashid |first2=Nor-Khaizura |last3=Zawawi |first3=Norhasnida |date=2020-08-25 |title=Probiotic properties of bacteria isolated from bee bread of stingless bee Heterotrigona itama |url=http://psasir.upm.edu.my/id/eprint/87300/1/Probiotic%20properties%20of%20bacteria%20isolated%20from%20bee%20bread.pdf |journal=Journal of Apicultural Research |volume=60 |pages=172–187 |doi=10.1080/00218839.2020.1801152 |issn=0021-8839 |s2cid=225208290 |access-date=2022-04-21 |archive-date=2023-03-27 |archive-url=https://web.archive.org/web/20230327163325/http://psasir.upm.edu.my/id/eprint/87300/1/Probiotic%20properties%20of%20bacteria%20isolated%20from%20bee%20bread.pdf |url-status=live }}

More precisely, sauerkraut contains the bacteria Leuconostoc mesenteroides, Lactobacillus plantarum, Pediococcus pentosaceus, Lactobacillus brevis, Leuconostoc citreum, Leuconostoc argentinum, Lactobacillus paraplantarum, Lactobacillus coryniformis, and Weissella spp.{{Cite journal |last1=Plengvidhya |first1=V. |last2=Breidt |first2=F. Jr. |last3=Lu |first3=Z. |last4=Fleming |first4=H. P. |year=2007 |title=DNA Fingerprinting of Lactic Acid Bacteria in Sauerkraut Fermentations |journal=Applied and Environmental Microbiology |volume=73 |issue=23 |pages=7697–7702 |bibcode=2007ApEnM..73.7697P |doi=10.1128/AEM.01342-07 |pmc=2168044 |pmid=17921264}} Kimchi contains the bacteria Leuconostoc spp., Weissella spp., and Lactobacillus spp. Pao cai contains L. pentosus, L. plantarum , Leuconostoc mesenteroides , L. brevis, L. lactis, and L. fermentum.

A list of many other bacteria found in several Asian fermented fruits and vegetables also is available.{{Cite journal |last1=Swain |first1=Manas Ranjan |last2=Anandharaj |first2=Marimuthu |last3=Ray |first3=Ramesh Chandra |last4=Parveen Rani |first4=Rizwana |year=2014 |title=Fermented Fruits and Vegetables of Asia: A Potential Source of Probiotics |journal=Biotechnology Research International |volume=2014 |pages=1–19 |doi=10.1155/2014/250424 |pmc=4058509 |pmid=25343046 |doi-access=free}}{{Cite journal |title=Table 1: Examples of traditional fermented fruits and vegetables, which are used in various parts of Asian subcontinent |date=2014 |doi=10.1155/2014/250424 |pmid=25343046 |url=https://www.hindawi.com/journals/btri/2014/250424/tab1/ |url-status=live |archive-url=https://web.archive.org/web/20190216153544/https://www.hindawi.com/journals/btri/2014/250424/tab1/ |archive-date=2019-02-16 |access-date=2019-02-16 |journal=Biotechnology Research International |pmc=4058509 | vauthors = Swain MR, Anandharaj M, Ray RC, Parveen Rani R |doi-access=free }} Kefir contains Lactobacillus acidophilus, Bifidobacterium bifidum, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus kefiranofaciens, Lactococcus lactis, and Leuconostoc species.{{Cite journal |vauthors=Guzel-Seydim ZB, Kok-Tas T, Greene AK, Seydim AC |date=March 2011 |title=Review: functional properties of kefir |journal=Crit Rev Food Sci Nutr |volume=51 |issue=3 |pages=261–268 |doi=10.1080/10408390903579029 |pmid=21390946 |s2cid=19963871}}{{Cite journal |last=Farnworth |first=Edward R |date=4 April 2005 |title=Kefir-a complex probiotic |url=http://kefir.it/kefir_probiotic.pdf |url-status=dead |journal=Food Science and Technology Bulletin: Functional Foods |volume=2 |issue=1 |pages=1–17 |citeseerx=10.1.1.583.6014 |doi=10.1616/1476-2137.13938 |archive-url=https://web.archive.org/web/20140514095454/http://www.kefir.it/kefir_probiotic.pdf |archive-date=14 May 2014 |access-date=20 December 2014}} Buttermilk contains either Lactococcus lactis or L. bulgaricus. Other acidic bacteria, said to be probiotic,{{Cite news |last=Bauer |first=Brent |date=July 8, 2017 |title=What is kombucha tea? Does it have any health benefits? |work=Mayo Clinic |url=https://www.mayoclinic.org/healthy-lifestyle/consumer-health/expert-answers/kombucha-tea/faq-20058126 |url-status=live |access-date=2018-09-05 |archive-url=https://web.archive.org/web/20180809045554/https://www.mayoclinic.org/healthy-lifestyle/consumer-health/expert-answers/kombucha-tea/faq-20058126 |archive-date=August 9, 2018 |df=mdy-all}}{{Cite news |last=Wollan |first=Malia |title=Kombucha Tea Attracts a Following and Doubters |newspaper=The New York Times |date=24 March 2010 |url=https://www.nytimes.com/2010/03/25/fashion/25Tea.html |url-status=live |access-date=2018-09-05 |archive-url=https://web.archive.org/web/20180712093540/https://www.nytimes.com/2010/03/25/fashion/25Tea.html |archive-date=2018-07-12}} can be found in kombucha, including Gluconacetobacter xylinus,{{Cite journal |vauthors=Jarrell J, Cal T, Bennett JW |year=2000 |title=The Kombucha Consortia of yeasts and bacteria |journal=Mycologist |volume=14 |issue=4 |pages=166–170 |doi=10.1016/S0269-915X(00)80034-8}}{{Cite journal |last1=Jonas |first1=Rainer |last2=Farah |first2=Luiz F. |year=1998 |title=Production and application of microbial cellulose |journal=Polymer Degradation and Stability |volume=59 |issue=1–3 |pages=101–106 |doi=10.1016/s0141-3910(97)00197-3}} Zygosaccharomyces sp., Acetobacter pasteurianus, Acetobacter aceti, and Gluconobacter oxydans.{{Cite journal |last1=Jayabalan |first1=Rasu |last2=Malbaša |first2=Radomir V. |last3=Lončar |first3=Eva S. |last4=Vitas |first4=Jasmina S. |last5=Sathishkumar |first5=Muthuswamy |year=2014 |title=A Review on Kombucha Tea – Microbiology, Composition, Fermentation, Beneficial Effects, Toxicity, and Tea Fungus |journal=Comprehensive Reviews in Food Science and Food Safety |volume=13 |issue=4 |pages=538–550 |doi=10.1111/1541-4337.12073 |pmid=33412713 |doi-access=free}}

It is incorrect to think that a higher colony forming units (CFU) count corresponds to greater efficacy - rather, probiotic efficacy is strain- and disease specific.{{Cite journal |last1=Guarner |first1=Francisco |last2=Sanders |first2=Mary Ellen |last3=Szajewska |first3=Hania |last4=Cohen |first4=Henry |last5=Eliakim |first5=Rami |last6=Herrera-deGuise |first6=Claudia |last7=Karakan |first7=Tarkan |last8=Merenstein |first8=Dan |last9=Piscoya |first9=Alejandro |last10=Ramakrishna |first10=Balakrishnan |last11=Salminen |first11=Seppo |last12=Melberg |first12=Jim |date=July 2024 |title=World Gastroenterology Organisation Global Guidelines: Probiotics and Prebiotics |url=https://journals.lww.com/jcge/fulltext/2024/07000/world_gastroenterology_organisation_global.2.aspx |journal=Journal of Clinical Gastroenterology |language=en-US |volume=58 |issue=6 |pages=533–553 |doi=10.1097/MCG.0000000000002002 |pmid=38885083 |issn=0192-0790|doi-access=free }}

The manipulation of the gut microbiota is complex and may cause bacteria-host interactions. Though probiotics are considered safe, some have concerns about their safety in certain cases.{{Cite journal |vauthors=Boyle RJ, Robins-Browne RM, Tang ML |year=2006 |title=Probiotic use in clinical practice: what are the risks? |journal=Am J Clin Nutr |type=Review |volume=83 |issue=6 |pages=1256–1264; quiz 1446–1447 |doi=10.1093/ajcn/83.6.1256 |pmid=16762934 |doi-access=free}} Some people, such as those with immunodeficiency, short bowel syndrome, central venous catheters, and cardiac valve disease, and premature infants, may be at higher risk for adverse events. In severely ill people with inflammatory bowel disease, a risk exists for the passage of viable bacteria from the gastrointestinal tract to the internal organs (bacterial translocation) as a consequence of bacteremia, which can cause adverse health consequences. Rarely, consumption of probiotics by children with lowered immune system function or who are already critically ill may result in bacteremia or fungemia (i.e., bacteria or fungi in the blood), which can lead to sepsis, a potentially fatal disease.

Probiotic supplements typically contain between one and ten billion colony-forming units (CFUs) per dose. A higher number of CFUs does not provide additional probiotic effects, but may have unintended consequences of causing digestive discomfort, such as bloating, gas, and diarrhea.{{Cite journal |last1=Aleman |first1=Ricardo S. |last2=Yadav |first2=Ajitesh |date=2023-12-26 |title=Systematic Review of Probiotics and Their Potential for Developing Functional Nondairy Foods |journal=Applied Microbiology |language=en |volume=4 |issue=1 |pages=47–69 |doi=10.3390/applmicrobiol4010004 |doi-access=free |issn=2673-8007}}{{Cite journal |last1=Dore |first1=Maria Pina |last2=Bibbò |first2=Stefano |last3=Fresi |first3=Gianni |last4=Bassotti |first4=Gabrio |last5=Pes |first5=Giovanni Mario |date=2019-12-02 |title=Side Effects Associated with Probiotic Use in Adult Patients with Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials |journal=Nutrients |volume=11 |issue=12 |pages=2913 |doi=10.3390/nu11122913 |doi-access=free |issn=2072-6643 |pmc=6950558 |pmid=31810233}}

Lactobacillus species have been suggested to contribute to obesity in humans, but no evidence of this relationship has been found.{{Cite journal |vauthors=Lahtinen SJ, Davis E, Ouwehand AC |year=2012 |title=Lactobacillus species causing obesity in humans: where is the evidence? |url=https://zenodo.org/record/895849 |journal=Beneficial Microbes |type=Review |volume=3 |issue=3 |pages=171–174 |doi=10.3920/BM2012.0041 |pmid=22968407 |access-date=2020-07-01 |archive-date=2021-06-18 |archive-url=https://web.archive.org/web/20210618204308/https://zenodo.org/record/895849 |url-status=live }}

In 2015, the global retail market value for probiotics was US$41 billion, including sales of probiotic supplements, fermented milk products, and yogurt, which alone accounted for 75% of total consumption.{{Cite web |last=Feldman |first=Monica |date=22 September 2016 |title=The New Market Profile of Probiotics Consumption |url=https://www.naturalproductsinsider.com/digestive-health/new-market-profile-probiotics-consumption |url-status=live |archive-url=https://web.archive.org/web/20180905215114/https://www.naturalproductsinsider.com/digestive-health/new-market-profile-probiotics-consumption |archive-date=5 September 2018 |access-date=5 September 2018 |publisher=Natural Products Insider |df=dmy-all}} Innovation in probiotic products in 2015 was mainly from supplements, which produced US$4 billion and was projected to grow 37% globally by 2020. Consumption of yogurt products in China has increased by 20% per year since 2014.{{Cite news |last=Meiling |first=Chen |date=21 June 2018 |title=Yogurt ferments the dairy segment |work=The Daily Telegraph and China Daily |url=https://www.telegraph.co.uk/news/world/china-watch/business/dairy-industry-in-china/ |url-status=dead |access-date=5 September 2018 |archive-url=https://web.archive.org/web/20180906014116/https://www.telegraph.co.uk/news/world/china-watch/business/dairy-industry-in-china/ |archive-date=6 September 2018 |df=dmy-all}}

{{As of|2019}}, the European Food Safety Authority has rejected all petitions by commercial manufacturers for health claims on probiotic products in Europe due to insufficient evidence for a cause-and-effect mechanism for benefit, thus inconclusive proof of effectiveness. The European Commission placed a ban on putting the word "probiotic" on the packaging of products because such labeling misleads consumers to believe a health benefit is provided by the product when no scientific proof exists to demonstrate that health effect.{{Cite report |url=http://www.ylfa.org/images/file/Probiotics%20generic%20descriptors-2012.pdf |title='Probiotic' As A General Descriptor |publisher=Yogurt & Live Fermented Milks Association (YLFA) |access-date=12 December 2014 |archive-url=https://web.archive.org/web/20141213035214/http://www.ylfa.org/images/file/Probiotics%20generic%20descriptors-2012.pdf |archive-date=13 December 2014 |url-status=live |df=dmy-all}}{{Cite web |date=2014 |title=Probiotic health claims |url=https://www.fsai.ie/faq/probiotic_health_claims.html |url-status=live |archive-url=https://web.archive.org/web/20170710214129/https://www.fsai.ie/faq/probiotic_health_claims.html |archive-date=10 July 2017 |access-date=13 December 2014 |publisher=Food Safety Authority of Ireland, Dublin |df=dmy-all}}{{Cite web |date=2006 |title=Regulation (EC) No 1924/2006 of the European Parliament and of the Council on 20 December 2006 on nutrition and health claims made on foods |url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2006R1924:20080304:EN:PDF |url-status=live |archive-url=https://web.archive.org/web/20160202203417/http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2006R1924:20080304:EN:PDF |archive-date=2 February 2016 |access-date=13 December 2014 |publisher=European Commission, Brussels |df=dmy-all}}

In the United States, the Food and Drug Administration (FDA) and Federal Trade Commission (FTC) have issued warning letters and imposed punishment on various manufacturers of probiotic products whose labels claim to treat a disease or condition.{{Cite web |date=15 December 2010 |title=Dannon Agrees to Drop Exaggerated Health Claims for Activia Yogurt and DanActive Dairy Drink FTC Charges that Evidence Supporting Benefits of Probiotics Falls Short |url=https://www.ftc.gov/news-events/press-releases/2010/12/dannon-agrees-drop-exaggerated-health-claims-activia-yogurt |url-status=live |archive-url=https://web.archive.org/web/20170514073358/https://www.ftc.gov/news-events/press-releases/2010/12/dannon-agrees-drop-exaggerated-health-claims-activia-yogurt |archive-date=14 May 2017 |access-date=9 May 2017 |publisher=Federal Trade Commission, US Government |df=dmy-all}} Food product labeling requires language approved by the FDA, so probiotic manufacturers have received warning letters for making disease or treatment claims.{{Cite web |last=Schmidt |first=Nancy |date=30 July 2014 |title=Warning letter to Plexus Worldwide Inc. |url=https://www.fda.gov/iceci/enforcementactions/warningletters/2014/ucm411287.htm |url-status=dead |archive-url=https://web.archive.org/web/20170508043647/https://www.fda.gov/ICECI/EnforcementActions/WarningLetters/2014/ucm411287.htm |archive-date=8 May 2017 |access-date=9 May 2017 |publisher=Compliance Branch, Inspections, Compliance, Enforcement, and Criminal Investigations, US Food and Drug Administration |df=dmy-all}} The FTC has taken punitive actions, including a US$21 million fine coordinated by 39 different state governments against a major probiotic manufacturer for deceptive advertising and exaggerated claims of health benefits for yogurt and probiotic dairy drink.

In Vietnam, the Vietnam Food Administration (VFA) under the Ministry of Health, in collaboration with other relevant authorities, oversees and addresses violations related to probiotic products. This includes issuing warnings, imposing administrative penalties,{{Cite web |date=2018-07-28 |title=Phạt 257 triệu đồng với 7 cơ sở vi phạm về an toàn thực phẩm |url=https://giaoduc.net.vn/phat-257-trieu-dong-voi-7-co-so-vi-pham-ve-an-toan-thuc-pham-post188367.gd |access-date=2024-09-24 |website=Giáo dục Việt Nam |language=vi}} demanding product recalls{{Cite web |date=2017-01-03 |title=Thu hồi thuốc Men vi sinh sống Biolac |url=https://baochinhphu.vn/thu-hoi-thuoc-men-vi-sinh-song-biolac-102214858.htm |access-date=2024-09-24 |website=baochinhphu.vn |language=vi}}{{Cite web |title=Bioamicus complete |url=https://bioamicus.vn/men-vi-sinh-bioamicus-complete |access-date=2024-09-24 |website=Bioamicus |language=vi}} and coordinating with other agencies.{{Cite web |date=2013-01-01 |title=Siết chặt quản lý thực phẩm chức năng |url=https://nhandan.vn/siet-chat-quan-ly-thuc-pham-chuc-nang-post384951.html |access-date=2024-09-24 |website=Báo Nhân Dân điện tử |language=vi}}{{Cite web |date=2017-01-05 |title=Đình chỉ lưu hành men vi sinh sống Biolac do không đạt chất lượng |url=https://baotainguyenmoitruong.vn/dinh-chi-luu-hanh-men-vi-sinh-song-biolac-do-khong-dat-chat-luong-272047.html |access-date=2024-09-24 |website=baotainguyenmoitruong.vn |language=vi}}

The National Yogurt Association (NYA) of the United States gives a "Live & Active Cultures Seal" to refrigerated yogurt products that contain 100 million cells per gram, or frozen yogurt products that contain 10 million cells per gram at the time of manufacture.{{Cite web |title=Live & Active Culture Yogurt |url=http://aboutyogurt.com/index.asp?bid=5 |url-status=live |archive-url=https://web.archive.org/web/20141208022547/http://www.aboutyogurt.com/index.asp?bid=5 |archive-date=8 December 2014 |access-date=12 December 2014 |publisher=National Yogurt Association |df=dmy-all}} In 2002, the FDA and WHO recommended that "the minimum viable numbers of each probiotic strain at the end of the shelf-life" be reported on labeling,{{Cite report |url=https://www.fda.gov/ohrms/dockets/dockets/95s0316/95s-0316-rpt0282-tab-03-ref-19-joint-faowho-vol219.pdf |title=Guidelines for the Evaluation of Probiotics in Food, Report of a Joint FAO/WHO Working Group on Drafting Guidelines for the Evaluation of Probiotics in Food |date=April 2002 |publisher=Food and Agriculture Organization and World Health Organization |location=London, Ontario, Canada |access-date=12 December 2014 |archive-url=https://web.archive.org/web/20140801074333/https://www.fda.gov/ohrms/dockets/dockets/95s0316/95s-0316-rpt0282-tab-03-ref-19-joint-faowho-vol219.pdf |archive-date=1 August 2014 |url-status=dead |df=dmy-all}} but most companies that give a number report the viable cell count at the date of manufacture, a number that could be much higher than that which exists at consumption.{{Cite journal |last=Sanders |first=ME |date=2000 |title=Considerations for Use of Probiotic Bacteria to Modulate Human Health |journal=The Journal of Nutrition |volume=130 |issue=2S Suppl |pages=384S–390S |doi=10.1093/jn/130.2.384S |pmid=10721912 |doi-access=free |df=dmy-all}} Because of the variability in storage conditions and time before eating, exactly how many active culture cells remain at the time of consumption is difficult to determine. The survival of probiotics was strongly dependent on the storage temperature and remarkable viability loss occurred in room temperature compared to refrigerated storage.{{Cite journal |last1=Ferdousi |first1=Rohollah |last2=Rouhi |first2=Millad |last3=Mohammadi |first3=Reza |last4=Mortazavian |first4=Amir Mohamad |last5=Khosravi-Darani |first5=Kianosh |last6=Rad |first6=Aziz Homayouni |date=Winter 2013 |title=Evaluation of probiotic survivability in yogurt exposed to cold chain interruption |journal=Iranian Journal of Pharmaceutical Research |language=en |volume=12 |issue=Suppl |pages=139–144 |issn=1735-0328 |pmc=3813376 |pmid=24250681}}

Probiotics have received renewed attention in the 21st century from product manufacturers, research studies, and consumers. The history of probiotics dates back to ancient times, with the consumption of fermented foods being a common practice across various civilizations. Different types of fermented milk products were invented in different generations, such as Kefir in 5000 BC and Yeast usage in 5000 BC. Their history can be traced to the first use of cheese and fermented products, which were well-known to the Greeks and Romans who recommended their consumption.{{Cite journal |vauthors=Gismondo MR, Drago L, Lombardi A |year=1999 |title=Review of probiotics available to modify gastrointestinal flora |journal=Int. J. Antimicrob. Agents |volume=12 |issue=4 |pages=287–292 |doi=10.1016/s0924-8579(99)00050-3 |pmid=10493604}} The fermentation of dairy foods represents one of the oldest techniques for food preservation.{{Cite book |last1=Tortora |first1=Gerard J. |url=https://archive.org/details/microbiologyintr00tort_505 |title=Microbiology An Introduction |last2=Funke |first2=Berdell R. |last3=Case |first3=Christine L. |date=2010 |publisher=Pearson Benjamin Cummings |isbn=978-0-321-58202-7 |edition=10th |location=San Francisco, CA |page=[https://archive.org/details/microbiologyintr00tort_505/page/n167 135] |chapter=5 |ref=31 |url-access=limited}}

File:Ilya Ilyich Mechnikov 1913.jpg first suggested the possibility of colonizing the gut with beneficial bacteria in the early 20th century.]]

The original modern hypothesis of the positive role played by certain bacteria was first introduced by Russian scientist and Nobel Prize laureate Élie Metchnikoff, who in 1907 suggested that it would be possible to modify the gut microbiota and to replace harmful microbes with useful microbes.{{Cite book |last=Metchnikoff |first=Elie |url=https://www.worldcat.org/oclc/287028845 |title=The prolongation of life : optimistic studies |date=2004 |publisher=Springer Pub |others=P. Chalmers, Sir Mitchell |isbn=978-0-8261-1877-6 |location=New York |oclc=287028845 |access-date=2022-10-31 |archive-date=2023-07-01 |archive-url=https://web.archive.org/web/20230701214654/https://www.worldcat.org/title/287028845 |url-status=live }}{{page needed|date=January 2024}} Metchnikoff proposed that consumption of fermented milk would "seed" the intestine with harmless lactic-acid bacteria and decrease the intestinal pH, and that this would suppress the growth of proteolytic bacteria.{{Cite journal |last=Vaughan |first=RB |date=July 1965 |title=The romantic rationalist: A study of Elie Metchnikoff |journal=Medical History |volume=9 |issue=3 |pages=201–215 |doi=10.1017/S0025727300030702 |pmc=1033501 |pmid=14321564}}

Bifidobacteria was first isolated from a breastfed infant by Henry Tissier, who also worked at the Pasteur Institute. The isolated bacterium named Bacillus bifidus communisTissier, H. 1900. Recherchers sur la flora intestinale normale et pathologique du nourisson. Thesis, University of Paris, Paris, France. was later renamed to the genus Bifidobacterium.{{Cite journal |title=Probiotic Mechanisms of Action |year=2012 |doi=10.1159/000342079 |pmid=23037511 |url=https://www.karger.com/article/fulltext/342079 |access-date=29 December 2020 |last1=Bermudez-Brito |first1=Miriam |last2=Plaza-Díaz |first2=Julio |last3=Muñoz-Quezada |first3=Sergio |last4=Gómez-Llorente |first4=Carolina |last5=Gil |first5=Angel |journal=Annals of Nutrition and Metabolism |volume=61 |issue=2 |pages=160–174 |s2cid=1295886 |doi-access=free |archive-date=25 May 2021 |archive-url=https://web.archive.org/web/20210525180409/https://www.karger.com/Article/FullText/342079 |url-status=live }} Tissier found that bifidobacteria are dominant in the gut microbiota of breast-fed babies and he observed clinical benefits from treating infant diarrhea with bifidobacteria.

During an outbreak of shigellosis in 1917, German professor Alfred Nissle isolated a strain of Escherichia coli from the feces of a soldier who was not affected by the disease.{{Cite journal |last=Nißle |first=Alfred |year=1918 |title=Die antagonistische Behandlung chronischer Darmstörungen mit Colibakterien |journal=Medizinische Klinik |volume=1918 |issue=2 |pages=29–33}} Methods of treating infectious diseases were needed at that time when antibiotics were not yet available, and Nissle used the E. coli Nissle 1917 strain in acute gastrointestinal infectious salmonellosis and shigellosis.{{Cite journal |last1=Altenhoefer |first1=Artur |last2=Oswald |first2=Sibylle |last3=Sonnenborn |first3=Ulrich |last4=Enders |first4=Corinne |last5=Schulze |first5=Juergen |last6=Hacker |first6=Joerg |last7=Oelschlaeger |first7=Tobias A |date=April 2004 |title=The probiotic Escherichia coli strain Nissle 1917 interferes with invasion of human intestinal epithelial cells by different enteroinvasive bacterial pathogens |journal=FEMS Immunology & Medical Microbiology |language=en |volume=40 |issue=3 |pages=223–229 |doi=10.1016/S0928-8244(03)00368-7 |pmid=15039098 |doi-access=free}}

In 1920, Rettger and Cheplin reported that Metchnikoff's "Bulgarian Bacillus", later called Lactobacillus delbrueckii subsp. bulgaricus, could not live in the human intestine.{{Cite journal |vauthors=Cheplin HA, Rettger LF |date=December 1920 |title=Studies on the Transformation of the Intestinal Flora, with Special Reference to the Implantation of Bacillus Acidophilus: II. Feeding Experiments on Man |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=6 |issue=12 |pages=704–705 |bibcode=1920PNAS....6..704C |doi=10.1073/pnas.6.12.704 |pmc=1084701 |pmid=16576567 |doi-access=free}}{{Primary source inline|date=December 2011}} They conducted experiments involving rats and humans volunteers, feeding them with Lactobacillus acidophilus. They observed the disappearance of the pathogenic protist Balantidium coli as well as of other gas-producing bacteria. Rettger further explored the possibilities of L. acidophilus, and reasoned that bacteria originating from the gut were more likely to produce the desired effect in this environment. In 1935, certain strains of L. acidophilus were found very active when implanted in the human digestive tract.{{Cite book |last=Rettger |first=Frederick Leo |url=http://worldcat.org/oclc/250265817 |title=Lactobacillus acidophilus & its therapeutic application |date=1935 |publisher=Yale Univ. Pr |oclc=250265817 |access-date=2022-10-31 |archive-date=2023-07-01 |archive-url=https://web.archive.org/web/20230701214657/https://worldcat.org/title/250265817 |url-status=live }}{{Primary source inline|date=December 2011}}

Contrasting antibiotics, probiotics were defined as microbially derived factors that stimulate the growth of other microorganisms. In 1989, Roy Fuller suggested a definition of probiotics that have been widely used: "A live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance."{{Cite journal |last=Fuller |first=R |date=May 1989 |title=Probiotics in man and animals |journal=The Journal of Applied Bacteriology |volume=66 |issue=5 |pages=365–378 |doi=10.1111/j.1365-2672.1989.tb05105.x |pmid=2666378 |doi-access=free}} Fuller's definition emphasizes the requirement of viability for probiotics and introduces the aspect of a beneficial effect on the host.

The term "probiotic" originally referred to microorganisms that have effects on other microorganisms.{{Cite journal |vauthors=Lilly DM, Stillwell RH |year=1965 |title=Probiotics: Growth-promoting factors produced by microorganisms |journal=Science |volume=147 |issue=3659 |pages=747–748 |bibcode=1965Sci...147..747L |doi=10.1126/science.147.3659.747 |pmid=14242024 |s2cid=26826201}} The concept of probiotics involved the notion that substances secreted by one microorganism stimulated the growth of another microorganism. The term was used again{{Cite book |last=Sperti |first=G. S. |title=Probiotics |publisher=AVI Publishing Co. |year=1971 |isbn=978-0-87055-099-7 |location=West Point, CT}}{{page needed|date=January 2024}} to describe tissue extracts that stimulated microbial growth. The term probiotics was taken up by Parker,{{Cite journal |last=Parker |first=R. B. |year=1974 |title=Probiotics, the other half of the antibiotic story |journal=Animal Nutrition and Health |volume=29 |pages=4–8}} who defined the concept as, "Organisms and substances that have a beneficial effect on the host animal by contributing to its intestinal microbial balance." Later, the definition was improved by Fuller, whose explanation was similar to the Fuller description of probiotics as a "live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance." He stressed two important claims for probiotics: the viable nature of probiotics and the capacity to help with intestinal balance.

In the following decades, intestinal lactic-acid bacterial species with alleged health-beneficial properties were introduced as probiotics, including Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus johnsonii.{{Cite journal |last=Tannock |first=GW |date=September 2003 |title=Probiotics: time for a dose of realism |journal=Current Issues in Intestinal Microbiology |volume=4 |issue=2 |pages=33–42 |pmid=14503687}}

Some literature gives the word a Greek etymology,{{Cite book |last=Fuller |first=Roy |url=http://worldcat.org/oclc/958540533 |title=Probiotics: the scientific basis. |date=2012 |publisher=Springer Netherlands |isbn=978-94-011-2364-8 |oclc=958540533 |access-date=2022-10-31 |archive-date=2023-07-01 |archive-url=https://web.archive.org/web/20230701214701/https://worldcat.org/title/958540533 |url-status=live }}{{page needed|date=January 2024}}{{Cite journal |vauthors=Alvarez-Olmos MI, Oberhelman RA |year=2001 |title=Probiotic agents and infectious diseases: a modern perspective on a traditional therapy |journal=Clin. Infect. Dis. |volume=32 |issue=11 |pages=1567–1576 |doi=10.1086/320518 |pmid=11340528 |doi-access=free}} but it appears to be a composite of the Latin preposition pro, meaning 'for', and the Greek adjective βιωτικός (biōtikos), meaning 'fit for life, lively',{{Cite book |title=A Greek-English Lexicon |editor-last=Liddell |editor-first=Henry George |chapter=βιωτικός |editor-last2=Scott |editor-first2=Robert |chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dbiwtiko%2Fs |via=Perseus Project |access-date=2021-02-21 |archive-date=2023-04-25 |archive-url=https://web.archive.org/web/20230425182154/https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry%3Dbiwtiko/s |url-status=live }} the latter deriving from the noun βίος (bios), meaning 'life'.{{Cite journal |vauthors=Hamilton-Miller JM, Gibson GR, Bruck W |date=October 2003 |title=Some insights into the derivation and early uses of the word 'probiotic' |journal=Br. J. Nutr. |volume=90 |issue=4 |page=845 |doi=10.1079/BJN2003954 |pmid=14552330 |doi-access=free}}

As food products or dietary supplements, probiotics are under preliminary research to evaluate if they provide any effect on health.{{Cite journal |vauthors=Salminen S, van Loveren H |year=2012 |title=Probiotics and prebiotics: health claim substantiation |journal=Microb Ecol Health Dis |volume=23 |doi=10.3402/mehd.v23i0.18568 |pmc=3747744 |pmid=23990821}} In all cases proposed as health claims to the European Food Safety Authority, the scientific evidence remains insufficient to prove a cause-and-effect relationship between consumption of probiotic products and any health benefit.{{Cite journal |year=2013 |title=Scientific Opinion on the substantiation of a health claim related to a combination of Bifidobacterium longum LA 101, Lactobacillus helveticus LA 102, Lactococcus lactis LA 103 and Streptococcus thermophillus LA 104 and reducing intestinal discomfort pursuant to Article 13(5) of Regulation (EC) No 1924/2006 (example, search EFSA for other opinion reports on probiotics |journal=EFSA Journal |volume=11 |issue=2 |pages=3085 |doi=10.2903/j.efsa.2013.3085 |doi-access=free}} There is no scientific basis for extrapolating an effect from a tested strain to an untested strain.{{Cite web |date=October 2001 |title=Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live Lactic Acid Bacteria |url=https://www.who.int/foodsafety/publications/fs_management/en/probiotics.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120514105145/http://www.who.int/foodsafety/publications/fs_management/en/probiotics.pdf |archive-date=May 14, 2012 |access-date=May 14, 2012 |publisher=Food and Agriculture Organization of the United Nations}}{{Cite journal |vauthors=Rowland I, Capurso L, Collins K, Cummings J, Delzenne N, Goulet O, Guarner F, Marteau P, Meier R |year=2010 |title=Current level of consensus on probiotic science: Report of an expert meeting – London, 23 November 2009 |journal=Gut Microbes |volume=1 |issue=6 |pages=436–439 |doi=10.4161/gmic.1.6.13610 |pmc=3056112 |pmid=21637035}} Improved health through gut flora modulation appears to be directly related to long-term dietary changes.{{Cite journal |last1=Wu |first1=G. D. |last2=Chen |first2=J. |last3=Hoffmann |first3=C. |last4=Bittinger |first4=K. |last5=Chen |first5=Y.-Y. |last6=Keilbaugh |first6=S. A. |last7=Bewtra |first7=M. |last8=Knights |first8=D. |last9=Walters |first9=W. A. |last10=Knight |first10=R. |last11=Sinha |first11=R. |last12=Gilroy |first12=E. |last13=Gupta |first13=K. |last14=Baldassano |first14=R. |last15=Nessel |first15=L. |year=2011 |title=Linking Long-Term Dietary Patterns with Gut Microbial Enterotypes |journal=Science |volume=334 |issue=6052 |pages=1051–1108 |bibcode=2011Sci...334..105W |doi=10.1126/science.1208344 |pmc=3368382 |pmid=21885731 |last16=Li |first16=H. |last17=Bushman |first17=F. D. |last18=Lewis |first18=J. D.}} Claims that some lactobacilli may contribute to weight gain in some humans{{Cite journal |vauthors=Million M, Raoult D |date=February 2013 |title=Species and strain specificity of Lactobacillus probiotics effect on weight regulation |journal=Microbial Pathogenesis |volume=55 |pages=52–54 |doi=10.1016/j.micpath.2012.09.013 |pmid=23332210}}{{Cite journal |vauthors=Million M, Angelakis E, Paul M, Armougom F, Leibovici L, Raoult D |date=August 2012 |title=Comparative meta-analysis of the effect of Lactobacillus species on weight gain in humans and animals |journal=Microbial Pathogenesis |volume=53 |issue=2 |pages=100–108 |doi=10.1016/j.micpath.2012.05.007 |pmid=22634320 |doi-access=free}} remain controversial.{{Cite journal |vauthors=Lahtinen SJ, Davis E, Ouwehand AC |date=September 2012 |title=Lactobacillus species causing obesity in humans: where is the evidence? |url=https://zenodo.org/record/895849 |journal=Beneficial Microbes |volume=3 |issue=3 |pages=171–174 |doi=10.3920/BM2012.0041 |pmid=22968407 |access-date=2020-07-01 |archive-date=2021-06-18 |archive-url=https://web.archive.org/web/20210618204308/https://zenodo.org/record/895849 |url-status=live }}

There is inconsistency in the results of different groups of 3488 children as reported in a Cochrane review.{{Cite journal |last1=Scott |first1=Anna M |last2=Clark |first2=Justin |last3=Julien |first3=Blair |last4=Islam |first4=Farhana |last5=Roos |first5=Kristian |last6=Grimwood |first6=Keith |last7=Little |first7=Paul |last8=Del Mar |first8=Chris B |date=18 June 2019 |title=Probiotics for preventing acute otitis media in children |journal=Cochrane Database of Systematic Reviews |volume=2019 |issue=6 |page=CD012941 |doi=10.1002/14651858.CD012941.pub2 |pmc=6580359 |pmid=31210358}} Also, it shows no significant difference regarding the adverse effects between probiotic and the other comparators.

Only limited, low-quality evidence exists to indicate that probiotics are helpful for treating people with milk allergy.{{Cite journal |vauthors=Qamer S, Deshmukh M, Patole S |date=August 2019 |title=Probiotics for cow's milk protein allergy: a systematic review of randomized controlled trials |journal=Eur. J. Pediatr. |type=Review |volume=178 |issue=8 |pages=1139–1149 |doi=10.1007/s00431-019-03397-6 |pmid=31230196 |s2cid=195259677}} A 2015 review showed low-quality evidence that probiotics given directly to infants with eczema, or in infants whose mothers used probiotics during the last trimester of pregnancy and breastfeeding, had lower risk of eczema.{{Cite journal |last1=Cuello-Garcia |first1=Carlos A. |last2=Brożek |first2=Jan L. |last3=Fiocchi |first3=Alessandro |last4=Pawankar |first4=Ruby |last5=Yepes-Nuñez |first5=Juan José |last6=Terracciano |first6=Luigi |last7=Gandhi |first7=Shreyas |last8=Agarwal |first8=Arnav |last9=Zhang |first9=Yuan |last10=Schünemann |first10=Holger J. |year=2015 |title=Probiotics for the prevention of allergy: A systematic review and meta-analysis of randomized controlled trials |url=https://www.jacionline.org/article/S0091-6749(15)00636-3/fulltext |journal=Journal of Allergy and Clinical Immunology |volume=136 |issue=4 |pages=952–961 |doi=10.1016/j.jaci.2015.04.031 |issn=0091-6749 |pmid=26044853 |access-date=2019-12-12 |archive-date=2022-03-16 |archive-url=https://web.archive.org/web/20220316222456/https://www.jacionline.org/article/S0091-6749(15)00636-3/fulltext |url-status=live |url-access=subscription }}

It is unclear whether probiotic supplementation helps with childhood asthma, as the quality of research evidence is low.{{Cite journal |vauthors=Lin J, Zhang Y, He C, Dai J |date=September 2018 |title=Probiotics supplementation in children with asthma: A systematic review and meta-analysis |journal=J Paediatr Child Health |type=Systematic review |volume=54 |issue=9 |pages=953–961 |doi=10.1111/jpc.14126 |pmid=30051941 |s2cid=51723667}}

Antibiotics are a common treatment for children, with 11% to 40% of antibiotic-treated children developing diarrhea.{{Cite journal |last1=Guo |first1=Qin |last2=Goldenberg |first2=Joshua Z. |last3=Humphrey |first3=Claire |last4=El Dib |first4=Regina |last5=Johnston |first5=Bradley C. |date=30 April 2019 |title=Probiotics for the prevention of pediatric antibiotic-associated diarrhea |journal=The Cochrane Database of Systematic Reviews |volume=4 |issue=4 |pages=CD004827 |doi=10.1002/14651858.CD004827.pub5 |issn=1469-493X |pmc=6490796 |pmid=31039287}} Antibiotic-associated diarrhea (AAD) results from an imbalance in the colonic microbiota caused by antibiotic therapy. These microbial community alterations result in changes in carbohydrate metabolism, with decreased short-chain fatty acid absorption and osmotic diarrhea as a result. A 2015 Cochrane review concluded that a protective effect of some probiotics existed for AAD in children. The known risks of using probiotics for treating Clostridioides difficile outweighs the uncertain benefits.{{Cite journal |vauthors=Su GL, Ko CW, Bercik P, Falck-Ytter Y, Sultan S, Weizman AV, Morgan RL |date=June 2020 |title=AGA Clinical Practice Guidelines on the Role of Probiotics in the Management of Gastrointestinal Disorders |journal=Gastroenterology |type=Clinical guideline |volume=159 |issue=2 |pages=697–705 |doi=10.1053/j.gastro.2020.05.059 |pmid=32531291 |doi-access=free}}

Probiotic treatment might reduce the incidence and severity of AAD as indicated in several meta-analyses.{{Cite journal |last=McFarlandfirst=LV |year=2006 |title=Meta-analysis of probiotics for the prevention of antibiotic-associated diarrhea and the treatment of Clostridium difficile disease |url=https://zenodo.org/record/1230694 |journal=Am. J. Gastroenterol. |volume=101 |issue=4 |pages=812–822 |doi=10.1111/j.1572-0241.2006.00465.x |pmid=16635227 |s2cid=7557917 |access-date=2019-06-30 |archive-date=2020-07-28 |archive-url=https://web.archive.org/web/20200728163339/https://zenodo.org/record/1230694 |url-status=live }}{{Cite journal |vauthors=Szajewska H, Ruszczyński M, Radzikowski A |date=September 2006 |title=Probiotics in the prevention of antibiotic-associated diarrhea in children: a meta-analysis of randomized controlled trials |journal=J Pediatr |volume=149 |issue=3 |pages=367–372 |doi=10.1016/j.jpeds.2006.04.053 |pmid=16939749 |s2cid=28439228}}{{Cite journal |vauthors=Sazawal S, Hiremath G, Dhingra U, Malik P, Deb S, Black RE |date=June 2006 |title=Efficacy of probiotics in prevention of acute diarrhoea: a meta-analysis of masked, randomised, placebo-controlled trials |journal=Lancet Infect Dis |volume=6 |issue=6 |pages=374–382 |doi=10.1016/S1473-3099(06)70495-9 |pmid=16728323}} For example, treatment with probiotic formulations including L. rhamnosus may reduce the risk of AAD, improve stool consistency during antibiotic therapy, and enhance the immune response after vaccination.{{Cite journal |vauthors=Arvola T, Laiho K, Torkkeli S, Mykkänen H, Salminen S, Maunula L, Isolauri E |year=1999 |title=Prophylactic Lactobacillus GG reduces antibiotic-associated diarrhea in children with respiratory infections: A randomized study |journal=Pediatrics |volume=104 |issue=5 |pages=e64 |doi=10.1542/peds.104.5.e64 |pmid=10545590 |doi-access=free}}

The potential efficacy of probiotics to treat AAD depends on the probiotic strains and dosage.{{Cite journal |vauthors=Doron SI, Hibberd PL, Gorbach SL |date=July 2008 |title=Probiotics for prevention of antibiotic-associated diarrhea |journal=J Clin Gastroenterol |volume=42 |issue=Suppl 2 |pages=S58–63 |doi=10.1097/MCG.0b013e3181618ab7 |pmid=18542041 |s2cid=2070623}}{{Cite journal |last=Surawicz |first=CM |date=July 2008 |title=Role of probiotics in antibiotic-associated diarrhea, Clostridium difficile-associated diarrhea, and recurrent Clostridium difficile-associated diarrhea |journal=J Clin Gastroenterol |volume=42 |issue=Suppl 2 |pages=S64–70 |doi=10.1097/MCG.0b013e3181646d09 |pmid=18545161 |s2cid=37993276}} One review recommended for children L. rhamnosus or Saccharomyces boulardii at 5 to 40 billion colony-forming units/day, given the modest number needed to treat and the likelihood that adverse events are very rare. The same review stated that probiotic use should be avoided in pediatric populations at risk for adverse events, such as severely debilitated or immune-compromised children.{{citation needed|date=June 2022}}

Probiotic treatment of bacterial vaginosis is the application or ingestion of bacterial species found in the healthy vagina to cure the infection of bacteria causing bacterial vaginosis. This treatment is based on the observation that 70% of healthy females have a group of bacteria in the genus Lactobacillus that dominate the population of organisms in the vagina. Specific strains of lactobacilli inhibit the growth of bacteria causing BV by producing H₂O₂, lactic acid, and/or bacteriocins, and/or inhibit the adherence of Gardnerella vaginalis to the vaginal epithelium, which prevents the infection from occurring in the vagina.{{Cite journal |last1=Falagas |first1=M.E. |last2=Betsi |first2=G.I. |last3=Athanasiou |first3=S. |date=2007-07-01 |title=Probiotics for the treatment of women with bacterial vaginosis |journal=Clinical Microbiology and Infection |language=en |volume=13 |issue=7 |pages=657–664 |doi=10.1111/j.1469-0691.2007.01688.x |issn=1198-743X |pmid=17633390 |doi-access=free}} Currently, the success of probiotic treatment has been mixed, since the use of probiotics to restore healthy populations of Lactobacillus has not been standardized. Often, standard antibiotic treatment is used at the same time that probiotics are being tested. In addition, some groups of women respond to treatment based upon ethnicity, age, number of sexual partners, pregnancy, and the pathogens causing bacterial vaginosis.{{Cite journal |last1=Petrova |first1=Mariya I. |last2=Lievens |first2=Elke |last3=Malik |first3=Shweta |last4=Imholz |first4=Nicole |last5=Lebeer |first5=Sarah |year=2015 |title=Lactobacillus species as biomarkers and agents that can promote various aspects of vaginal health |journal=Frontiers in Physiology |volume=6 |pages=81 |doi=10.3389/fphys.2015.00081 |issn=1664-042X |pmc=4373506 |pmid=25859220 |doi-access=free}} In 2013, researchers found that administration of hydrogen peroxide-producing strains, such as L. acidophilus and L. rhamnosus, were able to normalize vaginal pH and rebalance the vaginal microbiota, preventing and alleviating bacterial vaginosis.{{Cite journal |vauthors=Borges S, Silva J, Teixeira P |date=March 2014 |title=The role of lactobacilli and probiotics in maintaining vaginal health |journal=Arch. Gynecol. Obstet. |type=Review |volume=289 |issue=3 |pages=479–489 |doi=10.1007/s00404-013-3064-9 |pmid=24170161 |s2cid=23954527}}

{{as of|2017}}, only limited evidence indicated any direct link between high blood pressure and gut microbiota.{{Cite journal |vauthors=Robles-Vera I, Toral M, Romero M, Jiménez R, Sánchez M, Pérez-Vizcaíno F, Duarte J |date=April 2017 |title=Antihypertensive Effects of Probiotics |journal=Curr. Hypertens. Rep. |type=Review |volume=19 |issue=4 |pages=26 |doi=10.1007/s11906-017-0723-4 |pmid=28315049 |s2cid=3834130}}

A 2002 meta-analysis that included five double-blind trials examining the short-term (2–8 weeks) effects of a yogurt with probiotic strains on serum cholesterol levels found little effect of 8.5 mg/dL (0.22 mmol/L) (4% decrease) in total cholesterol concentration, and a decrease of 7.7 mg/dL (0.2 mmol/L) (5% decrease) in serum LDL concentration.{{Cite journal |vauthors=Agerholm-Larsen L, Bell ML, Grunwald GK, Astrup A |year=2002 |title=The effect of a probiotic milk product on plasma cholesterol: a meta-analysis of short term intervention studies |journal=European Journal of Clinical Nutrition |volume=54 |issue=11 |pages=856–860 |doi=10.1038/sj.ejcn.1601104 |pmid=11114681 |doi-access=free}}

A 2019 meta-analysis found low-quality evidence for probiotics having a small improvement in depression and anxiety.{{Cite journal |last1=Liu |first1=Richard T. |last2=Walsh |first2=Rachel F. L. |last3=Sheehan |first3=Ana E. |date=2019-07-01 |title=Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials |journal=Neuroscience and Biobehavioral Reviews |volume=102 |pages=13–23 |doi=10.1016/j.neubiorev.2019.03.023 |issn=1873-7528 |pmc=6584030 |pmid=31004628}} A 2020 review found probiotics might improve depression, but more studies are needed.{{Cite journal |last1=Ansari |first1=Fereshteh |last2=Pourjafar |first2=Hadi |last3=Tabrizi |first3=Aydin |last4=Homayouni |first4=Aziz |date=2020 |title=The effects of probiotics and prebiotics on mental disorders: A review on depression, anxiety, Alzheimer, and autism spectrum disorders |journal=Current Pharmaceutical Biotechnology |volume=21 |issue=7 |pages=555–565 |doi=10.2174/1389201021666200107113812 |issn=1873-4316 |pmid=31914909 |s2cid=210121155}}

Some probiotics are suggested as a possible treatment for various forms of gastroenteritis.{{Cite journal |vauthors=King CK, Glass R, Bresee JS, Duggan C |date=November 2003 |title=Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy |url=https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5216a1.htm |url-status=live |journal=MMWR Recomm Rep |volume=52 |issue=RR–16 |pages=1–16 |pmid=14627948 |archive-url=https://web.archive.org/web/20141028174056/http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5216a1.htm |archive-date=2014-10-28 |access-date=2017-09-08}} As a treatment for infectious diarrhea, probiotics are of no benefit to people who have the condition for more than two days, and there is no evidence they lessen the duration of diarrhea overall.{{Cite journal |vauthors=Collinson S, Deans A, Padua-Zamora A, Gregorio GV, Li C, Dans LF, Allen SJ |date=December 18, 2020 |title=Probiotics for treating acute infectious diarrhea |journal=Cochrane Database Syst Rev |volume=2020 |issue=12 |pages=CD003048 |doi=10.1002/14651858.CD003048.pub4 |pmc=8166250 |pmid=33295643}}

Probiotics are commonly given to breastfeeding mothers and their young children to prevent eczema (dermatitis), but no good evidence shows efficacy for this purpose.{{Cite journal |vauthors=Cuello-Garcia CA, Brożek JL, Fiocchi A, Pawankar R, Yepes-Nuñez JJ, Terracciano L, Gandhi S, Agarwal A, Zhang Y, Schünemann HJ |year=2015 |title=Probiotics for the prevention of allergy: A systematic review and meta-analysis of randomized controlled trials |journal=J. Allergy Clin. Immunol. |type=Systematic review & meta-analysis |volume=136 |issue=4 |pages=952–961 |doi=10.1016/j.jaci.2015.04.031 |pmid=26044853}} There is little evidence to support the use of probiotics to treat atopic dermatitis, and some risk of adverse effects.{{Cite journal |last1=Szeto |first1=Mindy D. |last2=Hassan |first2=Shahzeb |last3=Hamp |first3=Austin |last4=Anderson |first4=Jarett |last5=Sivesind |first5=Torunn E. |last6=Anderson |first6=Jaclyn B. |last7=Laughter |first7=Melissa R. |last8=Makrygeorgou |first8=Areti |last9=Boyle |first9=Robert J. |last10=Dellavalle |first10=Robert P. |date=2021-11-01 |title=From the Cochrane Library: Probiotics for treating eczema |journal=Journal of the American Academy of Dermatology |language=en |volume=86 |issue=3 |pages=e127–e132 |doi=10.1016/j.jaad.2021.10.032 |pmid=34748863 |s2cid=243825695|doi-access=free }} The American Academy of Dermatology stated: "The use of probiotics/prebiotics for the treatment of patients with established atopic dermatitis is not recommended due to inconsistent evidence".{{Cite journal |vauthors=Fenner J, Silverberg NB |date=2018 |title=Oral supplements in atopic dermatitis |journal=Clin. Dermatol. |type=Review |volume=36 |issue=5 |pages=653–658 |doi=10.1016/j.clindermatol.2018.05.010 |pmid=30217278 |s2cid=52278259}}

According to an umbrella review of meta-analyses of randomized controlled trials, probiotics supplementation reduces glucose homeostasis. This can be an effective therapy for lowering high blood sugar levels unless the body becomes hypoglycemic; caution and glucose monitoring are necessary to avoid this.{{Cite journal |title=Role of probiotics/synbiotic supplementation in glycemic control: A critical umbrella review of meta-analyses of randomized controlled trials |year=2022 |doi=10.1080/10408398.2022.2117783|last1=Xu |first1=Dengfeng |last2=Fu |first2=Lingmeng |last3=Pan |first3=Da |last4=Chu |first4=Yifang |last5=Feng |first5=Meiyuan |last6=Lu |first6=Yifei |last7=Yang |first7=Chao |last8=Wang |first8=Yuanyuan |last9=Xia |first9=Jiayue |last10=Sun |first10=Guiju |journal=Critical Reviews in Food Science and Nutrition |volume=64 |issue=6 |pages=1–19 |pmid=36052685 |s2cid=252009294 }}

Some strains of lactic acid bacteria (LAB) may affect Helicobacter pylori infections (which may cause peptic ulcers) in adults when used in combination with standard medical treatments, but no standard in medical practice or regulatory approval exists for such treatment.{{Cite journal |last=Hamilton-Miller |first=JM |date=October 2003 |title=The role of probiotics in the treatment and prevention of Helicobacter pylori infection |journal=International Journal of Antimicrobial Agents |volume=22 |issue=4 |pages=360–366 |doi=10.1016/S0924-8579(03)00153-5 |pmid=14522098}} The only peer-reviewed treatments for H. pylori to date all include various Antibiotic Regimens.{{Cite web |title=H Pylori Facts |url=https://www.cdc.gov/ulcer/files/hpfacts.pdf |url-status=live |archive-url=https://web.archive.org/web/20190112203116/https://www.cdc.gov/ulcer/files/hpfacts.PDF |archive-date=2019-01-12 |website=CDC.gov}}

Some strains of LAB may affect pathogens by means of competitive inhibition (i.e., by competing for growth) and some evidence suggests they may improve immune function by increasing the number of IgA-producing plasma cells and increasing or improving phagocytosis, as well as increasing the proportion of T lymphocytes and natural killer cells.{{Cite journal |vauthors=Reid G, Jass J, Sebulsky MT, McCormick JK |date=October 2003 |title=Potential uses of probiotics in clinical practice |journal=Clin. Microbiol. Rev. |volume=16 |issue=4 |pages=658–672 |doi=10.1128/CMR.16.4.658-672.2003 |pmc=207122 |pmid=14557292}}{{Cite journal |vauthors=Ouwehand AC, Salminen S, Isolauri E |date=August 2002 |title=Probiotics: an overview of beneficial effects |url=https://link.springer.com/article/10.1023/A:1020620607611 |journal=Antonie van Leeuwenhoek |volume=82 |issue=1–4 |pages=279–289 |doi=10.1023/A:1020620607611 |pmid=12369194 |access-date=2022-12-01 |url-access=subscription |s2cid=1870018 |archive-date=2022-12-02 |archive-url=https://web.archive.org/web/20221202022802/https://link.springer.com/article/10.1023/A:1020620607611 |url-status=live }} LAB products might aid in the treatment of acute diarrhea and possibly affect rotavirus infections in children and travelers' diarrhea in adults, but no products are approved for such indications. There are weak evidence probiotics might lower the incidence of acute upper respiratory tract infections in adults, they were better than placebo or no treatment.{{Cite journal |last1=Zhao |first1=Yunli |last2=Dong |first2=Bi Rong |last3=Hao |first3=Qiukui |date=2022-08-24 |title=Probiotics for preventing acute upper respiratory tract infections |journal=The Cochrane Database of Systematic Reviews |volume=2022 |issue=8 |pages=CD006895 |doi=10.1002/14651858.CD006895.pub4 |issn=1469-493X |pmc=9400717 |pmid=36001877}}

Probiotics do not appear to change the risk of infection in older people.{{Cite journal |last1=Wachholz |first1=PA |last2=Nunes |first2=VDS |last3=Polachini do Valle |first3=A |last4=Jacinto |first4=AF |last5=Villas-Boas |first5=PJF |date=3 February 2018 |title=Effectiveness of probiotics on the occurrence of infections in older people: systematic review and meta-analysis. |journal=Age and Ageing |volume=47 |issue=4 |pages=527–536 |doi=10.1093/ageing/afy006 |pmid=29415116 |doi-access=free |hdl=11449/164454|hdl-access=free }}

The use of oral probiotic supplements to modify the composition and behavior of the microbiome has been considered as a possible therapy for both induction and maintenance of remission in people with Crohn's disease and ulcerative colitis. A Cochrane review in 2020 did not find clear evidence of improved remission likelihood, nor lower adverse events, in people with Crohn's disease, following probiotic treatment.{{Cite journal |last1=Limketkai |first1=Berkeley N |last2=Akobeng |first2=Anthony K |last3=Gordon |first3=Morris |last4=Adepoju |first4=Akinlolu Adedayo |date=2020-07-17 |editor-last=Cochrane Gut Group |title=Probiotics for induction of remission in Crohn's disease |journal=Cochrane Database of Systematic Reviews |language=en |volume=2020 |issue=7 |pages=CD006634 |doi=10.1002/14651858.CD006634.pub3 |pmc=7389339 |pmid=32678465}}

For ulcerative colitis, there is low-certainty evidence that probiotic supplements may increase the probability of clinical remission.{{Cite journal |last1=Kaur |first1=Lakhbir |last2=Gordon |first2=Morris |last3=Baines |first3=Patricia Anne |last4=Iheozor-Ejiofor |first4=Zipporah |last5=Sinopoulou |first5=Vasiliki |last6=Akobeng |first6=Anthony K |date=2020-03-04 |editor-last=Cochrane IBD Group |title=Probiotics for induction of remission in ulcerative colitis |journal=Cochrane Database of Systematic Reviews |language=en |volume=3 |issue=3 |pages=CD005573 |doi=10.1002/14651858.CD005573.pub3 |pmc=7059959 |pmid=32128795}} People receiving probiotics were 73% more likely to experience disease remission and over 2x as likely to report improvement in symptoms compared to those receiving a placebo, with no clear difference in minor or serious adverse effects. Although there was no clear evidence of greater remission when probiotic supplements were compared with 5‐aminosalicylic acid treatment as a monotherapy, the likelihood of remission was 22% higher if probiotics were used in combination with 5-aminosalicylic acid therapy. Whereas in people who are already in remission, it is unclear whether probiotics help to prevent future relapse, either as a monotherapy or combination therapy.{{Cite journal |last1=Iheozor-Ejiofor |first1=Zipporah |last2=Kaur |first2=Lakhbir |last3=Gordon |first3=Morris |last4=Baines |first4=Patricia Anne |last5=Sinopoulou |first5=Vasiliki |last6=Akobeng |first6=Anthony K |date=2020-03-04 |editor-last=Cochrane IBD Group |title=Probiotics for maintenance of remission in ulcerative colitis |journal=Cochrane Database of Systematic Reviews |language=en |volume=3 |issue=3 |pages=CD007443 |doi=10.1002/14651858.CD007443.pub3 |pmc=7059960 |pmid=32128794}}

Probiotics are under study for their potential to affect irritable bowel syndrome, although uncertainty remains around which type of probiotic works best, and around the size of possible effect.{{Cite journal |last1=Saez-Lara |first1=Maria Jos |last2=Carolina Gomez-Llorente |last3=Julio Plaza-Diaz |last4=Angel Gil |year=2015 |title=The Role of Probiotic Lactic Acid Bacteria and Bifidobacteria in the Prevention and Treatment of Inflammatory Bowel Disease and Other Related Diseases: A Systematic Review of Randomized Human Clinical Trials |journal=Biomed Res Int |type=Systematic review |volume=2015 |pages=1–15 |doi=10.1155/2015/505878 |pmc=4352483 |pmid=25793197 |doi-access=free}}{{Cite journal |vauthors=Moayyedi P, Ford AC, Talley NJ, Cremonini F, Foxx-Orenstein AE, Brandt LJ, Quigley EM |date=March 2010 |title=The efficacy of probiotics in the treatment of irritable bowel syndrome: a systematic review |journal=Gut |type=Systematic review |volume=59 |issue=3 |pages=3253–3232 |doi=10.1136/gut.2008.167270 |pmid=19091823 |s2cid=18281136}}

Several clinical studies provide evidence for the potential of probiotics to lower the risk of necrotizing enterocolitis and mortality in premature infants. One meta-analysis indicated that probiotics reduce these risks by more than 50% compared with controls but that further, large, high-quality trials were needed to inform policy and practice.{{Cite journal |last1=Sharif |first1=Sahar |last2=Meader |first2=Nicholas |last3=Oddie |first3=Sam J. |last4=Rojas-Reyes |first4=Maria Ximena |last5=McGuire |first5=William |date=October 15, 2020 |title=Probiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants |journal=The Cochrane Database of Systematic Reviews |volume=2020 |issue=10 |pages=CD005496 |doi=10.1002/14651858.CD005496.pub5 |issn=1469-493X |pmc=8094746 |pmid=33058137}}

A Cochrane systematic review found no good evidence that probiotics were of benefit in reducing the risk of gestational diabetes, but good evidence that they increased the risk of pre-eclampsia. For this reason, the use of probiotics in pregnancy was advised against.{{Cite journal |vauthors=Davidson SJ, Barrett HL, Price SA, Callaway LK, Dekker Nitert M |year=2021 |title=Probiotics for preventing gestational diabetes |journal=Cochrane Database of Systematic Reviews |volume=2021 |issue=4 |pages=CD009951 |doi=10.1002/14651858.CD009951.pub3 |issn=1465-1858 |pmc=8094741 |pmid=33870484}}

A 2017 review based on moderate to low-quality evidence suggests that probiotics may be helpful in relieving pain in the short term in children with recurrent abdominal pain, but the proper strain and dosage are not known.{{Cite journal |vauthors=Newlove-Delgado TV, Martin AE, Abbott RA, Bethel A, Thompson-Coon J, Whear R et al. |year=2017 |title=Dietary interventions for recurrent abdominal pain in childhood. |journal=Cochrane Database Syst Rev |volume=2017 |issue=3 |pages=CD010972 |doi=10.1002/14651858.CD010972.pub2 |pmc=6464236 |pmid=28334433 |quote=Overall, there is some evidence to suggest that probiotics may be effective in the treatment of RAP, in terms of improving pain in the shorter term. Clinicians may therefore consider probiotic interventions as part of the management strategy for children with RAP (Recurrent Abdominal Pain). However, we were unable to recommend the optimum strain and dosage of probiotics based on this review. The evidence for the effectiveness of probiotics was based largely on shorter-term outcomes. Further trials are required to assess whether improvements in pain are maintained over the longer term; these trials should also consider the importance of using validated and consistent scales to measure pain and other outcomes.}}

A clinical study investigating the impact of probiotics in relieving the signs and symptoms of dry eye revealed promising results for the ophthalmic formulation of Latilactobacillus sakei, while the oral probiotic demonstrated no discernible benefits.{{cite journal |title=The Effect of Ophthalmic and Systemic Formulations of Latilactobacillus sakei on Clinical and Immunological Outcomes of Patients With Dry Eye Disease: A Factorial, Randomized, Placebo-controlled, and Triple-masking Clinical Trial |journal=Probiotics Antimicrob Proteins |date=2023 |doi=10.1007/s12602-023-10079-1 |pmid=37256485 |url=https://pubmed.ncbi.nlm.nih.gov/37256485/ |last1=Heydari |first1=Mojtaba |last2=Kalani |first2=Mehdi |last3=Ghasemi |first3=Younes |last4=Nejabat |first4=Mahmood |volume=16 |issue=3 |pages=1026–1035 |s2cid=258989191 |access-date=2023-10-06 |archive-date=2023-11-05 |archive-url=https://web.archive.org/web/20231105200101/https://pubmed.ncbi.nlm.nih.gov/37256485/ |url-status=live }}

There is limited evidence indicating probiotics are of benefit in the management of infection or inflammation of the urinary tract.{{Cite book |last=Shortliffe |first=LMD |chapter=Chapter 116: Infection and Inflammation of the Pediatric Genitourinary Tract |title=Campbell-Walsh Urology |publisher=Saunders Elsevier |editor-last=Wein |editor-first=AJ |edition=10th |volume=4 |page=3121 | isbn = 978-1-4160-6911-9 | date=2011}} One literature review found Lactobacillus probiotic supplements appeared to increase vaginal lactobacilli levels, thus reducing the incidence of vaginal infections in otherwise healthy adult women.{{Cite journal |last=Khalesi |first=Saman |date=2019 |title=A review of probiotic supplementation in healthy adults: helpful or hype? |journal=European Journal of Clinical Nutrition |volume=73 |issue=73 |pages=24–37 |doi=10.1038/s41430-018-0135-9 |pmid=29581563 |hdl-access=free |hdl=10072/381737 |s2cid=4362284}}

Supplements such as tablets, capsules, powders, and sachets containing bacteria have been studied. However, probiotics taken orally can be destroyed by the acidic conditions of the stomach. As of 2010, a number of microencapsulation techniques were being developed to address this problem.{{Cite journal |vauthors=Islam MA, Yun CH, Choi YJ, Cho CS |year=2010 |title=Microencapsulation of live probiotic bacteria |url=http://www.jmb.or.kr/submission/Journal/020/JMB020-10-01_FDOC_1.pdf |url-status=live |journal=Journal of Microbiology and Biotechnology |volume=20 |issue=1367–1377 |pages=1367–1377 |doi=10.4014/jmb.1003.03020 |pmid=21030820 |archive-url=https://web.archive.org/web/20110506083823/http://www.jmb.or.kr/submission/Journal/020/JMB020-10-01_FDOC_1.pdf |archive-date=2011-05-06 |access-date=2011-01-28}}

Preliminary research is evaluating the potential physiological effects of multiple probiotic strains, as opposed to a single strain.{{Cite journal |vauthors=Timmerman HM, Koning CJ, Mulder L, Rombouts FM, Beynen AC |date=November 2004 |title=Monostrain, multistrain and multispecies probiotics – A comparison of functionality and efficacy |journal=Int. J. Food Microbiol. |volume=96 |issue=3 |pages=219–233 |doi=10.1016/j.ijfoodmicro.2004.05.012 |pmid=15454313}}{{Cite journal |vauthors=Williams EA, Stimpson J, Wang D, Plummer S, Garaiova I, Barker ME, Corfe BM |date=September 2008 |title=Clinical trial: a multistrain probiotic preparation significantly reduces symptoms of irritable bowel syndrome in a double-blind placebo-controlled study |journal=Aliment. Pharmacol. Ther. |volume=29 |issue=1 |pages=97–103 |doi=10.1111/j.1365-2036.2008.03848.x |pmid=18785988 |doi-access=free |s2cid=12217513}} As the human gut may contain tens of thousands of microbial species, one theory indicates that this diverse environment may benefit from consuming multiple probiotic strains, an effect that remains scientifically unconfirmed.{{citation needed|date=June 2022}}

Only preliminary evidence exists for most probiotic health claims. Even for the most studied probiotic strains, few have been sufficiently developed in basic and clinical research to warrant approval for health claim status by a regulatory agency such as the FDA or EFSA, and {{As of|2010|lc=y}}, no claims had been approved by those two agencies. Some experts are skeptical about the efficacy of different probiotic strains and believe that not all subjects benefit from probiotics.{{Cite news |last=Bee |first=Peta |date=November 10, 2008 |title=Probiotics, not so friendly after all? |work=The Times |location=London |url=http://www.thetimes.co.uk/tto/health/article1788597.ece |url-status=live |access-date=18 June 2010 |archive-url=https://web.archive.org/web/20150511112331/http://www.thetimes.co.uk/tto/health/article1788597.ece |archive-date=11 May 2015 |df=dmy-all}}

Multiple studies have shown that there is a significant difference in the survival rate of Lactobacillus and Bifidobacterium under refrigerated (4 °C) and room temperature (25 °C) storage conditions. At room temperature (25±1 °C), the number of  probiotics decreased by 5 to 6 logarithmic units (down to 1/100,000) after 90 days of storage. In contrast, no significant change in the number of probiotics was observed under refrigerated conditions (4 ± 1 °C).{{Cite journal |last1=Dhewa |first1=T. |last2=Pant |first2=S. |last3=Mishra |first3=Vijendra |date=January 2014 |title=Development of freeze dried synbiotic formulation using a probiotic strain of Lactobacillus plantarum |journal=Journal of Food Science and Technology |language=en |volume=51 |issue=1 |pages=83–89 |doi=10.1007/s13197-011-0457-2 |issn=0022-1155 |pmc=3857416 |pmid=24426051}}

First, probiotics must be alive when administered.{{Cite journal |last=Fuller |first=R |year=1991 |title=Probiotics in human medicine |journal=Gut |volume=32 |issue=4 |pages=439–442 |doi=10.1136/gut.32.4.439 |pmc=1379087 |pmid=1902810}}Fuller R. Probiotics, the Scientific Thesis. London: Chapman & Hall, 1992 {{ISBN?}}{{page needed|date=January 2024}} One of the concerns throughout the scientific literature resides in the viability and reproducibility on a large scale of observed results for specific studies, as well as the viability and stability during use and storage, and finally the ability to survive in stomach acids and then in the intestinal ecosystem.{{Failed verification|date=March 2023|reason=No mention of ability to survive stomach acids, nor of storage stability.}}

Second, probiotics must have undergone controlled evaluation to document health benefits in the target host. Only products that contain live organisms shown in reproducible human studies to confer a health benefit may claim to be probiotic.{{Cite journal |vauthors=Reid G, Gaudier E, Guarner F, Huffnagle GB, Macklaim JM, Munoz AM, Martini M, Ringel-Kulka T, Sartor B, Unal R, Verbeke K, Walter J |year=2010 |title=Responders and non-responders to probiotic interventions: how can we improve the odds? |journal=Gut Microbes |volume=1 |issue=3 |pages=200–204 |doi=10.4161/gmic.1.3.12013 |pmc=3023600 |pmid=21637034}}{{Cite journal |vauthors=O'Hara AM, O'Regan P, Fanning A, O'Mahony C, Macsharry J, Lyons A, Bienenstock J, O'Mahony L, Shanahan F |year=2006 |title=Functional modulation of human intestinal epithelial cell responses by Bifidobacterium infantis and Lactobacillus salivarius |journal=Immunology |volume=118 |issue=2 |pages=202–215 |doi=10.1111/j.1365-2567.2006.02358.x |pmc=1782284 |pmid=16771855}} The correct definition of health benefit, backed with solid scientific evidence, is a strong element for the proper identification and assessment of the effect of a probiotic. This aspect is a challenge for scientific and industrial investigations because several difficulties arise, such as variability in the site for probiotic use (oral, vaginal, intestinal) and mode of application.

Third, the probiotic candidate must be a taxonomically defined microbe or combination of microbes (genus, species, and strain level). It is commonly admitted that most effects of probiotics are strain-specific and cannot be extended to other probiotics of the same genus or species. This calls for precise identification of the strain, i.e. genotypic and phenotypic characterization of the tested microorganism.

Fourth, probiotics must be safe for their intended use. The 2002 FAO/WHO guidelines recommend that, though bacteria may be generally recognized as safe (GRAS), the safety of the potential probiotic be assessed by the minimum required tests:{{Cite journal |last1=Huys |first1=G |last2=Botteldoorn |first2=N |last3=Delvigne |first3=F |last4=Vuyst |first4=L. D. |last5=Heyndrickx |first5=M |last6=Pot |first6=B |last7=Dubois |first7=J. J. |last8=Daube |first8=G |year=2013 |title=Microbial characterization of probiotics – Advisory report of the Working Group "8651 Probiotics" of the Belgian Superior Health Council (SHC) |journal=Molecular Nutrition & Food Research |volume=57 |issue=8 |pages=1479–1504 |doi=10.1002/mnfr.201300065 |pmc=3910143 |pmid=23801655}}

• Assessment of certain metabolic activities (e.g. D-lactate production, bile salt deconjugation)
• Assessment of side effects in human studies
• Determination of antibiotic resistance patterns
• Epidemiological surveillance of adverse incidents in consumers (aftermarket)
• If the strain under evaluation belongs to a species known to produce toxins in mammals, it must be tested for toxin production. One possible scheme for testing toxin production has been recommended by the EU Scientific Committee on Animal Nutrition.{{Cite web |date=December 2001 |title=Commentary by the Scientific Committee on Animal Nutrition on Data Relating to Toxin Production |url=http://ec.europa.eu/food/fs/sc/scan/out73_en.pdf |url-status=live |archive-url=https://web.archive.org/web/20160629162223/http://ec.europa.eu/food/fs/sc/scan/out73_en.pdf |archive-date=29 June 2016 |access-date=5 June 2016 |website=Scientific Opinion |publisher=European Commission, Health & Consumer Protection Directorate-General |df=dmy-all}}
• If the strain under evaluation belongs to a species with known hemolytic potential, determination of hemolytic activity is required.

In Europe, EFSA adopted a premarket system for the safety assessment of microbial species used in food and feed productions to set priorities for the need for risk assessment. The assessment is made for certain microorganisms; if the result is favorable, it leads to "Qualified Presumption of Safety" status.{{Cite journal |year=2007 |title=Introduction of a Qualified Presumption of Safety (QPS) approach for assessment of selected microorganisms referred to EFSA |journal=EFSA Journal |volume=587 |issue=12 |pages=1–16 |doi=10.2903/j.efsa.2007.587 |doi-access=free}}

{{Portal|Food}}

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• Dysbiosis
• Fecal bacteriotherapy
• Functional food
• Microbial food cultures
• Postbiotic
• Probiotics in pediatrics
• Proteobiotics
• Psychobiotic
• Synbiotics

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{{Reflist}}

• {{Skeptoid|id=4801|number=801|title=Probiotics Fact and Fiction: Some people promote probiotics as a miracle cure for just about anything. What can they really do? |date=October 12, 2021}}
• {{Cite journal |title=Probiotics Mechanism of Action on Immune Cells and Beneficial Effects on Human Health |year=2023 |doi=10.3390/cells12010184|journal=Cells |volume=12 |issue=1 |pages=184 |doi-access=free |pmid=36611977 |pmc=9818925 | vauthors = Mazziotta C, Tognon M, Martini F, Torreggiani E, Rotondo JC }}

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Category:Bacteriology

Category:Digestive system

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