Summary of Probiotic Strains

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

This table does not include all strains with probiotic value, just those that are more prominent. I have not necessarily included all the benefits of each strain, but focused on those which are of most interest to people with chronic candida(or a disturbed GI microflora).

Strain Availability Shown to implant Clinical benefits
Saccaromyces boulardii Capsules Yes, as a transient Prevention/treatment of diarrhea
L.casei strain DN-114001 Actimel(Dannon), Phoenix and Denver only -- (Dannon, please send info)
L.reuteri Stoneyfield Yogurt(BioGaia) Yes1 Reduces diarrhea in children2
L.acidophilus NCFB 1748 Arla Acidophilus(Arla), not in USA -- (Arla, please send info)
L.rhamnosus VTT E-97800 Research strain(VTT) Yes Under investigation
L.rhamnosus 271 "PrimaLiv" (Probi AB), not in USA Yes3 (info forthcoming)
L.casei strain Shirota Yakult(Yakult) Yes4 (info forthcoming)
L. Rhamnosus GG "Culturelle" (CAG Functional foods), "Gefilus"(Valio) Yes5 Treat Clostridium difficile infection, reduce intestinal permeability6
L.plantarum 299v "ProViva" (Probi AB) Yes3 treat IBS, prevent translocation in ICU patients (citations forthcoming)

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.

Online resources

Additional information on probiotics

Commercial Probiotics Web Sites


  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