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Commercial probiotic products do not always specify the strain of microorganism they contain. When they do, it may be a strain that has never been scientifically studied, or has been studied but no health benefits were identified.

Dozens of microorganisms have been shown to have desirable probiotic qualities, at least in vitro. However, ingested bacteria are normally killed in the stomach. A small number of strains have been shown to colonize the human gastrointestinal(GI) tract in clinical trials(see the definition of an "implantable strain", below). This is thought to be a necessary prerequisite for any health benefits to be conferred. A few strains have shown they both colonize the GI tract and confer specific benefits in human clinical trials. This is the most credible variety of probiotic, and while growing, there are only a small handful. Most are not available commercially in the US market.

For the purposes of this website, I will use the following terms to distinguish the scientific support for different probiotic microorganisms.

Research strain:

Any generally regarded as safe(GRAS) microorganism being studied for probiotic application, but not commercially available in any market.

Commercial strain:

A strain produced on an industrial scale for commercial use, as a fresh product(fermented milk, juice, etc) or nutritional supplement(capsules or sashes).

Probiotic strain:

Any Generally Regarded As Safe(GRAS) microorganism(such as lactobacilli, bifidobacteria, streptococci, sacharomycis, etc) shown in published research to have one or more of the following positive attributes:

1. In vitro adherence to epithilial cells.
2. In vitro antimicrobial activity.
3. In vitro resistance to bile, hydrochloric acid, and pancreatic juice.
4. Anticarcinogenic activity(reduction of carcinogens) in clinical trials.
5. Immune modulation or stimulation in human clinical trials.
6. Reduction of intestinal permeability in human clinical trials.
7. Colonization of the GI tract in human clinical trails.

Implantable strain:

Any microbial strain native to the GI tract of man(i.e. lactobacilli or bifidobacteria) shown to survive passage through the GI tract(appear live in the stool) or persist on biopsies of the GI mucosa after cessation of feeding.

Clinical strain:

An implantable strain which has been shown to have one or more specific health benefits, and therefore have demonstrated clinical usefulness. Some examples of benefits that have been shown are reduced intestinal permeability(LGG), enhancement of immune function(various strains), and treatment of infection.

Table of probiotic strains

There is a short, but growing list of probiotic strains with proven clinical value. The two strains with the most research-proven benefits are probably LGG and Lp299v. Each has a separate page on this site.

1. Lactobacillus GG (ATCC 53103). Identified in 1987 through an in vitro screening process, this is the first bacterium to be proven to colonize the human gastrointestinal tract in vivo⁵. It can relieve some cases of milk allergy by reducing intestinal permeability⁶. It has been shown to improve resistance to candida in immunocompromised mice⁷. Lactobacillus GG is now being sold in the U.S.A. in a product called "Culturelle".
2. Lactobacillus plantarum 299v. Identified through a combination of in vitro and in vivo screening, this bacterium has shown value in surgical recovery where bacterial translocation is a risk. It has also been useful in the treatment of Irritable Bowel Syndrome(IBS), a common and difficult to treat disorder.

Details on other probiotic strains from the table

These may not have been shown to colonize(or implant in) the human intestine, but they still have some proven probiotic attributes.

• Lactobacillus casei strain Shirota, sold by a Japanese company("Yakult") in cultured foods, was recently shown in human trials to be able to implant in the GI tract⁴. Not available in the U.S.
• Lactobacillus rhamnosus VTT E-97800, identified by researchers at VTT(the technical research center of Finland). It has in vitro antimicrobial activity against candida and other pathogens, and can implant in the GI tract.
• Lactobacillus reuteri, manufactured by Biogaia of Sweden. It is effective against rotaviral diarrhea in children³, and produces an antibacterial substance "reuterin". It is an ingredient in "Stoneyfield yogurt" in the USA, as indicated by it's label with the "Reuteri" symbol.
• Lactobacillus acidophilus NCFB 1748, shown in research to appear to reduce candida in the GI tract of human subjects⁸. Sold by "Arla" in their acidophilus milk (not available in the U.S.), I would like a sample of this strain to evaluate but have so far been unable to obtain one.
• Lactobacillus acidophilus Lat 11/83 ("solco lactobacteria", identified in Russia), most research published in Russian with only an abstract in English. There is significant probiotic research being done in Russia, but most is untranslated.
• Lactobacillus rhamnosus 271 (DSMZ 6594), sponsored by Probi AB and sold in "PrimaLiv" and weight watcher's yogurt(in Europe). Not available in the U.S.A.
• The yeast Saccharomyces boulardii, used to reduce antibiotic-associated diarrhea in several studies⁹. This is the only probiotic mentioned on this site that is not a bacterium. It is available in capsules in the USA.

Online resources

Additional information on probiotics

• Probiotics Jump Station, links on probiotics and intestinal microbiology
• ISGNAS Home Page, The International Study Group on New Antimicrobial Strategies(ISGNAS)

Commercial Probiotics Web Sites

• Probi AB, Probi AB, a Swedish probiotic company, produces L.plantarum 299v as well as other probiotics with scientifically supported benefits.
• Biogaia, BioGaia, another Swedish probiotic company, which produces Lactobacillus reuteri
• Living Well with Probiotics, What is Lactobacillus GG? A web site sponsored by an educational grant from CAG Functional Foods (the company with the US rights to market LGG)
• Culturelle's website allows you to purchase it online. This is the only probiotic in the US market that contains LGG.
• Chr Hansen's Biosystems probiotics, Christian Hansen's Biosystems, large food ingredient and diary culture manufacturer.
• Natren, A commercial probiotic company

References

1. Wolf BW, Garleb KA, Ataya BG, CASAS IA "Safety and tolerance of Lactobacillus reuteri in healthy adult male subjects" Microbial Ecology in Health and Disease, 8:41-50, 1995
2. Shornikova AV, Casas IA, Isolauri E, Mykkanen H, Verikari T "Lactobacillus reuteri as a therapeutic agent in acute diarrhea in young children" Journal of Pediatric Gastroenterology and Nutrition 24:399-404 1997
3. Johansson M.L. et al. "Administration of different Lactobacillus strains in fermented oatmeal soup: in vivo colonization of human intestinal mucosa and effect of the indigenous flora" Applied and Environmental Microbiology 59(1):15-20, Jan. 1993
4. "Survival of a probiotic, Lactobacillus casei strain Shirota, in the gastrointestinal tract: selective isolation from faeces and identification using monoclonal antibodies." Int J Food Microbiol 1999 Apr 1;48(1):51-7
5. Goldin BR et al. "Survival of Lactobacillus species (strain GG) in human gastrointestinal tract" Digestive Diseases and Sciences 37(1):121-128
6. Majamaa H. and Isolauri E. "Probiotics: a novel approach in the management of food allergy" J Allergy Clin Immunol (99):179-85, 1997
7. Wagner RD et al. "Biotherapeutic effects of probiotic bacteria on candidiasis in immunodeficient mice" Infection and Immunity 65(10):4165-4172
8. Lidbeck A et al. "Impact of Lactobacillus acidophilus on the normal intestinal microflora after the administration of two antimicrobial agents" Infection 16(6):329-336, 1988
9. McFarland LV, Bernasconi P "Saccaromyces boulardii, a review of an innovative biotherapeutic agent" Microbial Ecology in Health and Disease, 6:1578-171 1993

This page last modified 2023-08-14