Lactobacillus reuteri (DSM 17938)
Also known as: L. reuteri, DSM 17938, ATCC 55730, Limosilactobacillus reuteri, Protectis strain, ATCC PTA 6475, RC-14
Lactobacillus reuteri is a native human gut and breast-milk organism, now classified as Limosilactobacillus reuteri. The strain DSM 17938 is one of the best-documented single strains, with multiple meta-analyses of infant colic trials using 100 million CFU daily in oil drops. Adult products use the same or related strains at higher counts for gut comfort and oral health. Its low effective dose makes it economical in blends, and it is often combined with vitamin D or used in chewables. Strain ATCC PTA 6475 and the vaginal-health strain RC-14 are distinct and not interchangeable.
Research summary
Produces reuterin, an antimicrobial compound; studied for modulation of gut motility and immune signaling.
Dosage
Daily amounts, of compound. CFU shown in billions.
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 0.1 B CFU | 0.1–1 B CFU | — | — |
Amounts are in billions of CFU; the infant colic trials used 0.1 billion (100 million) CFU per day, entered as 0.1. Raw-material weight assumes a 100 billion CFU/g concentrate (10 mg per billion CFU); manufacturers add a 20–50% CFU overage at fill so the label claim holds through shelf life, and the label should state whether CFU are guaranteed at manufacture or at expiry. Adult products commonly use 0.5–1 billion CFU.
Standardization: Strain DSM 17938 designated on CoA; CFU per gram stated
Source material: freeze-dried culture
As supplied: Assumes 100 billion CFU/g concentrate (10 mg per billion CFU); at 0.1–1 billion per serving the raw-material mass is tiny (1–10 mg) and usually requires a carrier for uniform blending.
Forms of Lactobacillus
| Form | Typical dose | Element % | Formats | Price |
|---|---|---|---|---|
| Lactobacillus reuteri (DSM 17938) | 0.1–1 B CFU | — | Capsule, Powder | high |
| Lactobacillus acidophilus | 1–10 B CFU | — | Capsule, Powder | mid |
| Lactobacillus plantarum | 1–10 B CFU | — | Capsule, Powder | mid |
| Lactobacillus casei | 1–10 B CFU | — | Capsule, Powder | mid |
| Lactobacillus gasseri | 1–10 B CFU | — | Capsule, Powder | mid |
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Heat- and moisture-sensitive vegetative cells; capsule or dry powder only. Infant products deliver it in oil drops, which is a licensed format outside this tool's scope.
Formulation notes
Separate from antibiotic dosing by at least two hours. DSM 17938 is licensed by its owner; confirm the supplied strain matches the one cited.
Sources
- NIH ODS — Probiotics Fact Sheet for Health ProfessionalsNIH ODS
- Efficacy of Lactobacillus reuteri DSM 17938 for infantile colic: Systematic review with network meta-analysis. (Gutiérrez-Castrellón 2017)PubMed
- The Efficacy and Safety of the Probiotic Bacterium Lactobacillus reuteri DSM 17938 for Infantile Colic: A Meta-Analysis of Randomized Controlled Trials. (Xu 2015)PubMed
Related ingredients
Probiotic Blend (Multi-Strain)
ProbioticA generic placeholder for a multi-strain probiotic blend, typically combining several Lactobacillus and Bifidobacterium species and sometimes Streptococcus thermophilus or a Bacillus spore.
Typical: 10–50 B CFU
Lactobacillus rhamnosus GG (LGG)
ProbioticLGG (Lactobacillus rhamnosus GG, ATCC 53103) is the single most studied probiotic strain, isolated in 1985 and since reclassified as Lacticaseibacillus rhamnosus.
Typical: 1–10 B CFU
Bifidobacterium lactis
ProbioticBifidobacterium animalis subsp.
Typical: 1–10 B CFU
Saccharomyces boulardii
ProbioticSaccharomyces boulardii is a probiotic yeast rather than a bacterium, originally isolated from lychee and mangosteen skins.
Typical: 5–10 B CFU
L-Glutamine
Amino acidThe most abundant free amino acid in blood and muscle and a primary fuel for intestinal and immune cells.
Typical: 5–10 g