Lactobacillus reuteri
EVIDENCE: MODERATEAlso sold as: L. reuteri, Limosilactobacillus reuteri, DSM 17938, ATCC PTA 5289, Prodentis strain pair
Oral lozenges combining L. reuteri DSM 17938 and ATCC PTA 5289 have randomized trials measuring gingivitis and periodontitis outcomes. The results apply to those strains and preparations. A label saying only L. reuteri does not establish a match.
Compiled by iSupplementReviews editorial team ·Updated 2026-10-13 · 4 sources
- Type
- Probiotic — oral/GI species
- Studied dose
- 4×10⁸ CFU/day (two lozenges of DSM 17938 + ATCC PTA 5289, ~2×10⁸ each)
- Best form
- The Prodentis strain pair (DSM 17938 + ATCC PTA 5289) in a slow-dissolve lozenge — the form every positive oral trial used
- Our rating
- MODERATE — Several human trials — limits in size, duration, or independence
What is Lactobacillus reuteri?
L. reuteri occurs in the gut and mouth and has specific oral-health trials. The main dental research uses DSM 17938 with ATCC PTA 5289 in Prodentis lozenges. DSM 17938 also has a separate infant-colic record in drops, which is a different use.
Other names and forms it’s sold as
- DSM 17938: the colic/gingivitis strain, originally isolated from breast milk
- ATCC PTA 5289: the second Prodentis strain, selected for oral-pathogen antagonism
- Limosilactobacillus reuteri: the 2020 taxonomic rename; same organism, label may use either name
- Generic “L. reuteri”: a species name with no strain ID; the label says nothing about which organism is inside
Where does it come from?
A normal resident of the human mouth, digestive tract, and breast milk. Commercial strains are industrial isolates cultured to pharmaceutical standards; DSM 17938 famously derives from a Peruvian mother’s milk isolate.
How does it work in the body?
The oral mechanism is unusual: reuteri strains produce reuterin, a broad-spectrum antimicrobial compound made from glycerol, that suppresses periodontal pathogens like P. gingivalis. Delivery format is the key distinction: a lozenge dissolving over minutes bathes the gumline in live bacteria; a swallowed capsule doesn’t. It also shows anti-inflammatory signaling (reduced gum-tissue cytokines) in trial measurements.
What is it claimed to do?
Gum health and reduced bleeding, fresher breath via pathogen suppression, sinus/ENT support by extension, and general anti-inflammatory effects. Infant colic is its best-known clinical use (different strain, different form).
What does the research show?
| Claim | Evidence | Dose studied | Verdict |
|---|---|---|---|
| Reduced gum bleeding/inflammation | Several trials, mostly as adjunct to hygiene | ~4×10⁸ CFU/day lozenges | Supported — modest, strain-specific |
| Adjunct benefit in periodontitis | Trials show improved pocket-depth outcomes with deep cleaning | ~4×10⁸ CFU/day | Plausible — adjunct only |
| Fresh breath | Indirect (pathogen suppression) | — | Plausible |
| Sinus/ENT/immune effects | Weak extrapolation from oral data | — | Unproven for these outcomes |
| Whitening teeth | No trials | — | No evidence |
The Prodentis trial line — the evidence that exists
Vivekananda et al. (J Oral Microbiol, 2010, N=30): periodontitis patients taking DSM 17938 + PTA 5289 lozenges (~10⁸ CFU each, twice daily) showed significantly better plaque/gingival/bleeding scores, and the probiotic-plus-cleaning arm cut pocket depth from 5.08mm to 3.78mm. Schlagenhauf et al. (2020, N=72 sailors): the same lozenge pair prevented the gum-health deterioration that placebo sailors showed over a 42-day deployment. Teughels et al. (2020, N=39): adjunctive lozenges after pocket re-instrumentation produced better 24-week pocket depths (2.64 vs 2.92mm) and more pockets converting to shallow.
The findings: real, replicated, modest clinical effects, all on the same two strains, all delivered as lozenges, mostly as an add-on to actual dental care.
What dose was studied?
| Goal | Dose | Form/route | Duration |
|---|---|---|---|
| Gingivitis/periodontal adjunct | ~2×10⁸ CFU per strain per day | oral lozenge, 2×/day | 42 days–1 year |
| Infant colic (separate use) | 10⁸ CFU/day DSM 17938 | drops | weeks |
Side effects
Essentially none at trial doses: the probiotic class’s standard profile of occasional transient digestive adjustment. Rare bloodstream-infection case reports apply to severely immunocompromised or critically ill patients.
Drug interactions
- Antibiotics: space doses several hours apart or take after the course; antibiotics kill the live organisms
- Immunosuppressants: standard class caution for the severely immunocompromised
Who should not take it?
Severely immunocompromised or critically ill patients (class-level caution). Anyone with periodontal disease should treat probiotic lozenges as an adjunct to professional care, not a substitute: the trials worked with deep cleaning, not instead of it.
What the authorities say
ISAPP’s consensus statements set the frame used throughout this page: probiotic benefits are strain-specific; evidence from DSM 17938 + PTA 5289 cannot be assumed for a label that names only the species. The Frontiers in Microbiology review of reuteri’s human-health record maps a broad evidence base while noting the same strain-dependence. No regulator has approved reuteri for any disease claim; all uses remain structure/function territory.
What to know about Lactobacillus reuteri
The oral findings apply to the named strain pair in slow-dissolving lozenges. A label listing only L. reuteri does not establish the same preparation. Check the strain identifiers, count, and delivery method before applying the results.
Frequently asked questions about Lactobacillus reuteri
Does Lactobacillus reuteri help gums?
The named Prodentis strain pair has real human trials: reduced gum bleeding and improved pocket depths as an add-on to cleaning in periodontitis patients, and prevented gum-health decline in sailors unable to brush properly for 42 days. Effects are modest and work as an adjunct to oral hygiene, not a replacement for it.
Is L. reuteri the same as what's in oral probiotics?
Only if the label names the strain. Oral trials used DSM 17938 plus ATCC PTA 5289. Probiotic effects are strain-specific; a label reading just 'L. reuteri' could be a different strain with none of that evidence.
What dose of L. reuteri was studied for oral health?
About 4×10⁸ CFU/day total: two lozenges daily, each carrying ~10⁸ CFU of each of the two strains, dissolved slowly in the mouth. Oral contact time matters; swallowed pills miss the mechanism.
What else is L. reuteri known for?
Infant colic: DSM 17938 drops are the most-studied probiotic for breastfed colicky babies, plus general digestive effects. The colic evidence is separate from the oral-health lozenge evidence and belongs to a different delivery form.
Is L. reuteri safe?
Yes for essentially everyone; decades of food and supplement use. Standard probiotic caution applies to severely immunocompromised or critically ill patients (rare bloodstream-infection case reports across the class).
References
- [1]L. reuteri (Prodentis) lozenges in chronic periodontitis — preliminary RCT (Vivekananda et al., J Oral Microbiol 2010)
- [2]L. reuteri lozenges maintain periodontal health in navy sailors — RCT (J Clin Periodontol 2020)
- [3]Dual-strain L. reuteri improves residual pocket treatment — RCT (Teughels et al., J Clin Periodontol 2020)
- [4]Role of Lactobacillus reuteri in human health and diseases — review (Front Microbiol 2018)
Products we reviewed containing Lactobacillus reuteri
Based on recorded labels or seller-described formulas. Inclusion does not establish a match to the strains, preparations or amounts studied here; check each review's disclosure limits.