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L. reuteri DSM 17938

Lactobacillus reuteri DSM 17938 · The Infant Colic Probiotic

Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.

The evidence is genuinely strong for one narrow use and weaker for the rest, so a 3 (mixed/moderate RCT) fits the honest picture better than a blanket 4. The best data is the Sung 2018 individual participant data meta-analysis in Pediatrics, which pooled raw patient data from four double-blind RCTs (345 infants) and found that DSM 17938 reduced crying and fussing in BREASTFED colicky infants by roughly 43 to 46 minutes per day at two and three weeks, with breastfed infants about twice as likely to reach treatment success. In formula-fed infants the same analysis found no clear benefit, and the earliest large formula-inclusive trial (Sung 2014, BMJ) was flat or slightly negative. So the honest grade is about 3 to 4 for breastfed infant colic specifically and closer to 1 to 2 for constipation, regurgitation, and antibiotic-associated diarrhea, where trials are smaller and mixed. A large share of the supportive work is BioGaia-funded, which is disclosed and matters. The viral adult longevity and oxytocin claims sit at 0 to 1: they rest on mouse studies from the Erdman and Poutahidis MIT group, not human outcome trials.

FDA
Legal supplement (DSHEA)
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

Very well tolerated in healthy infants, children, and adults; avoid or seek clinician guidance in preterm, immunocompromised, or critically ill patients where rare bloodstream infection is the concern.

Lactobacillus reuteri DSM 17938 is a single probiotic strain owned and licensed by the Swedish company BioGaia, sold to consumers as BioGaia Protectis drops. It descends from a parent strain, ATCC 55730, that was cultured from the breast milk of a mother in the Peruvian Andes; in 2007 two plasmids carrying antibiotic resistance genes were removed to make the daughter strain safer, and that daughter is DSM 17938. Its cleanest evidence is in infant colic, where pooled trial data show it shortens crying time in breastfed babies, with much less benefit in formula-fed ones. It is among the most-studied probiotic strains in pediatrics, though a large fraction of that research is funded by BioGaia. The adult wellness claims now circulating online, longevity and oxytocin and better sleep from homemade L. reuteri yogurt, rest on mouse experiments and personal reports rather than human trials.

The probiotic with the cleanest pediatric infant colic evidence, strain-specific, mother's milk origin.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Reducing crying and fussing in breastfed colicky infants (strongest evidence)
  • Functional constipation in children (mixed, modest)
  • Reducing infant regurgitation and spit-up (modest)
  • Preventing antibiotic-associated diarrhea in children (preliminary)
  • Adjunct to H. pylori eradication to reduce side effects (preliminary)
  • Feeding tolerance in preterm infants under neonatology supervision (investigational)

How it is supposed to work

Lactobacillus reuteri DSM 17938 is a heterofermentative lactic acid bacterium with a uniquely human origin story. The strain derives from L. reuteri ATCC 55730, originally isolated by the Peruvian-American microbiologist Iván Casas from the breast milk of a Peruvian mother in the 1990s. The DSM 17938 designation specifically refers to the cleaned-up commercial strain produced by BioGaia (Sweden) through removal of two plasmids carrying antibiotic resistance genes, a regulatory and safety improvement that maintains the parent strain's probiotic properties while eliminating the antibiotic resistance gene transfer concern. The strain's breast milk origin is mechanistically meaningful: L. reuteri is part of the natural human microbiota, with documented presence in breast milk, oral cavity, and gut of healthy adults and infants. The clinical mechanisms operate through several distinctive pathways. L. reuteri produces reuterin, a broad-spectrum antimicrobial compound formed from glycerol fermentation that inhibits a wide range of gut pathogens (E. coli, Salmonella, Shigella, Helicobacter pylori, Candida species). It modulates gut motility through histamine-related pathways, which is mechanistically why it has the cleanest evidence in the entire probiotic literature for infant colic, a condition fundamentally linked to gut motility and visceral hypersensitivity. It produces TLR2-modulating compounds that shift inflammatory responses toward anti-inflammatory patterns. It adheres to oral and intestinal epithelium through specific surface proteins. The infant colic mechanism (Indrio series, Italy) appears to combine reduced gut inflammation, modified microbiome composition, improved gut motility, and possible direct effects on visceral pain pathways. Unlike many probiotics, L. reuteri has substantial mechanistic evidence rather than purely associative clinical findings.

How it is taken

The pediatric infant colic dose is 5 drops daily (100 million CFU) of BioGaia drops, the dose used in essentially all positive trials. Administered on the breast nipple before feeding, in expressed breast milk, or directly in the infant's mouth. Effects on colic crying time typically observable within 1-2 weeks; full effect over 21 days. The pediatric and adult chewable formulations deliver 100M-1B CFU per dose. The postmenopausal bone health formulation (Osfortis) uses substantially higher doses (5B CFU). Take with or without food, L. reuteri is acid- and bile-tolerant. Refrigeration improves shelf-life potency; the BioGaia drops contain stabilizing oil that supports room-temperature storage during travel. Discontinuation produces gradual return to baseline; no withdrawal effects.

Infant colic
5 drops daily (100M CFU) for 21+ days
Pediatric constipation
100M CFU daily for 4+ weeks
H. pylori adjunct
100M CFU daily during 14-day eradication
Adult chewable
1 tablet daily (100M-1B CFU)
Postmenopausal bone
5B CFU daily (Osfortis)
Administration (infants)
On nipple before feeding, in expressed milk, or directly
Time to effect
1-2 weeks colic; 4+ weeks constipation
Storage
Refrigeration preferred; oil-stabilized for travel

Which form to buy

Not all preparations of the same ingredient are the same thing, and the trials were run on particular ones.

  • BioGaia Drops (DSM 17938 pediatric)

    Rating: gold

    The reference pediatric formulation. 5 drops daily delivers 100 million CFU L. reuteri DSM 17938, the dose used in essentially all positive infant colic trials. Manufactured by BioGaia (Sweden); marketed globally under various country-specific brand names (ProTectis, Gerber Soothe, Nutrigerm). The pediatric clinical standard.

  • BioGaia ProTectis Tablets / Chewables

    Rating: gold

    Adult and child formulation in chewable tablet form. Delivers 100M-1B CFU per tablet. Used in adult constipation, H. pylori adjunct, and functional GI indications. Pleasant strawberry flavor designed for pediatric acceptance.

  • Gerber Soothe (US Pediatric)

    Rating: gold

    US consumer brand of BioGaia DSM 17938 drops. Marketed for infant fussiness and digestive support. Same strain and dosing as ProTectis. Widely available in US pharmacies and infant care sections.

  • BioGaia Osfortis (Bone Health)

    Rating: good

    Higher-dose adult formulation (5 billion CFU) marketed for postmenopausal bone health based on Nilsson 2018 trial showing reduced lumbar spine bone mineral density loss. Distinct indication; same strain.

  • L. reuteri Combinations with Other Strains

    Rating: good

    Multi-strain probiotic formulations including L. reuteri DSM 17938 alongside Bifidobacterium and other Lactobacillus strains. Quality varies, verify DSM 17938 specifically disclosed (not generic L. reuteri).

  • Generic L. reuteri (No Strain ID)

    Rating: caution

    Many mass-market supplements label "Lactobacillus reuteri" without strain identifier. Multiple L. reuteri strains exist with different documented properties. Without DSM 17938 (or related BioGaia strains) specification, the clinical evidence does not transfer.

  • L. reuteri Yogurt / Fermented Milk

    Rating: caution

    Some products market L. reuteri-fermented dairy. CFU and strain identification often poor. Functional foods rather than clinical-grade probiotic delivery.

Who it works for, and who it does not

  • Breastfed infants with colic

    Strength of evidence for this group: strong

    The signature indication. The Savino 2007 and Indrio 2014 NEJM meta-analysis establish L. reuteri DSM 17938 as the most evidence-supported intervention for breastfed infant colic, among the cleanest probiotic-strain-indication pairings in the literature. Effects typically observable within 1-2 weeks.

  • Formula-fed infants with colic

    Strength of evidence for this group: modest

    Less consistent evidence than breastfed infants. Some trials positive, others null. Mechanism may involve interaction with breast milk components that formula does not replicate. Reasonable to try but expectations should be calibrated.

  • Children with functional abdominal pain

    Strength of evidence for this group: modest

    Sung 2018 and several smaller trials support L. reuteri for functional abdominal pain disorders in children. Reasonable adjunct alongside standard pediatric GI care.

  • Pediatric H. pylori eradication adjunct

    Strength of evidence for this group: modest

    Francavilla 2008 and subsequent trials support L. reuteri adjunct to standard eradication therapy. Improves eradication rates and reduces treatment-related side effects. Coordinate with pediatric gastroenterology.

  • Pediatric functional constipation

    Strength of evidence for this group: modest

    Coccorullo 2010 and subsequent trials support modest benefit in children with chronic functional constipation. Effect size smaller than osmotic laxatives but reasonable adjunct.

  • Adults with chronic constipation

    Strength of evidence for this group: cautious

    Less established evidence than pediatric constipation. Adult trials more variable. Reasonable trial as adjunct to standard care.

  • Postmenopausal women for bone health

    Strength of evidence for this group: cautious

    Nilsson 2018 trial showed reduced lumbar spine BMD loss in postmenopausal women with 5B CFU L. reuteri 6390 (a related strain). Preliminary; not yet routine clinical practice. The BioGaia Osfortis product is marketed for this indication.

  • Premature infants

    Strength of evidence for this group: cautious

    Limited safety data in very-low-birth-weight premature infants. Specialist neonatology guidance for any probiotic use in NICU contexts. Some institutions have specific premature infant probiotic protocols using L. reuteri.

Taken with other things

Combinations people actually use. Evidence for one ingredient is not evidence for a pair.

  • H. pylori eradication antibiotics

    Interaction: synergy

    Francavilla 2008 demonstrated improved eradication rates and reduced side effects when L. reuteri is added to standard triple/quadruple therapy. Coordinate with pediatric or adult gastroenterology.

  • Standard antibiotics

    Interaction: caution

    Bacterial probiotic timing applies, separate from antibiotic doses by 2-4 hours. Unlike S. boulardii (yeast), L. reuteri is killed by concurrent antibiotic administration.

  • Other probiotic strains

    Interaction: synergy

    L. reuteri combines well with other Lactobacillus and Bifidobacterium strains in multi-strain formulations. The infant colic indication is generally L. reuteri-specific rather than improved by combination.

  • Breast milk

    Interaction: synergy

    The signature delivery vehicle for infant colic. Breast milk components may support L. reuteri activity. The breastfed-infant colic evidence is stronger than formula-fed-infant evidence.

  • Vitamin D3

    Interaction: synergy

    The Osfortis postmenopausal bone health indication is often co-administered with vitamin D3 in clinical practice. Mechanistically complementary.

  • Anti-acid medications (PPIs, H2 blockers)

    Interaction: neutral

    Reduced stomach acid may improve probiotic survival. Generally well-tolerated combination.

  • Severely immunocompromised patients

    Interaction: caution

    Standard probiotic safety considerations. Theoretical bacteremia risk in immunocompromised users. Specialist guidance reasonable.

  • Active C. difficile infection

    Interaction: neutral

    L. reuteri has not been specifically studied for C. difficile prevention or treatment. S. boulardii and LGG have stronger C. difficile evidence.

What to look for on the label

Look for: DSM 17938 strain explicitly disclosed on the label; BioGaia license disclosed; CFU per dose with shelf-life potency guarantee; pharmaceutical-grade manufacturing standards; reputable pediatric brand recognition (BioGaia ProTectis, Gerber Soothe). Avoid: generic "Lactobacillus reuteri" without strain identifier; products that don't disclose CFU per dose; suspiciously cheap formulations; combination products that obscure individual L. reuteri DSM 17938 dose; products without manufacturer disclosure.

Safety in detail

  • Among the safest probiotics in pediatric populations including infants and newborns. Extensive infant colic trial data with strong safety record.
  • No documented serious adverse events in clinical trials at recommended doses. Mild GI upset (gas, bloating) occasionally reported, typically self-limited.
  • Pediatric safety: among the most-administered probiotics in infant populations globally. The DSM 17938 strain specifically removed antibiotic resistance plasmids from the parent ATCC 55730 strain, eliminating the antibiotic resistance gene transfer concern.
  • Pregnancy and breastfeeding: L. reuteri is naturally present in breast milk. Supplementation during pregnancy and lactation has reassuring safety data. OB-GYN guidance reasonable for routine clinical decisions.
  • Immunocompromised: standard probiotic safety considerations apply. Case reports of L. reuteri bacteremia exist but are rare and typically in severely immunocompromised hosts.
  • Premature infants: limited systematic data in very-low-birth-weight premature infants. Some NICUs have specific protocols using L. reuteri; specialist neonatology guidance for any premature infant use.
  • Drug interactions: minimal documented interactions. Standard probiotic timing apart from antibiotics applies.
  • Allergies: L. reuteri itself is not allergenic; the BioGaia drops use sunflower oil as carrier, sunflower allergy is rare but worth noting.

What people get wrong

  • Often saidAny Lactobacillus reuteri product works for infant colic.

    ActuallyStrain identification matters. DSM 17938 (BioGaia) has the documented clinical evidence. Generic "L. reuteri" without strain identifier may or may not be functionally equivalent. The Indrio NEJM meta-analysis is specifically on DSM 17938.

  • Often saidProbiotics for colic are unproven.

    ActuallyThe L. reuteri DSM 17938 colic evidence is among the cleaner probiotic-indication pairings in the literature. Multiple positive trials, NEJM-published meta-analysis, mainstream pediatric guideline conditional recommendations. The general "probiotics are unproven" framing does not apply to this specific strain-indication pairing.

  • Often saidFormula-fed and breastfed infants respond equally.

    ActuallyBreastfed infants show more consistent response in trials. The mechanism may require breast milk components. Formula-fed infants warrant calibrated expectations.

  • Often saidHigher dose is more effective for colic.

    ActuallyThe 100 million CFU (5 drops daily) dose is what trial evidence supports. Higher doses have not been shown to produce proportionally better outcomes in colic.

  • Often saidL. reuteri eliminates colic completely.

    ActuallyThe trial-level effect is approximately 50% reduction in crying time, meaningful clinical improvement but not complete elimination. Colic is multifactorial and L. reuteri addresses some mechanisms (gut motility, inflammation) but not all underlying causes.

  • Often saidL. reuteri is unsafe for newborns.

    ActuallyAmong the most-studied probiotics in infant populations including newborns from first weeks of life. Extensive safety data. The strain origin from breast milk reinforces the biological appropriateness.

  • Often saidYou should take L. reuteri with antibiotics simultaneously.

    ActuallyBacterial probiotic timing, separate by 2-4 hours from antibiotic doses. Unlike S. boulardii (yeast, antibiotic-resistant), L. reuteri is killed by concurrent antibiotic administration.

Who profits, and who pushes back

  • Sung Australian colic skepticism

    Pushes backTrial methodology calibration

    Our Australian RCT in formula-fed and mixed-fed infant colic did not show the same magnitude of effect as the Italian breastfed-infant trials. The mechanism may require breast milk components for full effect, or the effect may be more modest than the Italian trial inheritance suggests. Practitioners should set expectations accordingly.

  • Mainstream pediatric gastroenterology

    Pushes backEvidence-based pediatric care

    L. reuteri DSM 17938 for breastfed infant colic represents one of the cleaner probiotic strain-indication pairings in the pediatric literature. The evidence supports use as adjunct rather than substitute for standard pediatric evaluation. Persistent colic warrants pediatric evaluation for underlying GI conditions before assuming functional etiology.

  • Critical evidence review

    Pushes backEvidence synthesis methodology

    The L. reuteri infant colic evidence is among the stronger probiotic-indication pairings in the literature, with NEJM-level meta-analytic support. However, the effect size is modest and the cohort specificity (breastfed infants) matters. Formula-fed infant evidence is weaker. The strain-specific evidence does not extend to generic L. reuteri or other strains.

  • BioGaia

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itSwedish manufacturer · strain owner

    Founded 1990 specifically to develop L. reuteri commercially. Substantial industry sponsorship of clinical research over three decades. Disclosed industry source for the bulk of DSM 17938 evidence base while maintaining peer-reviewed publication standards.

  • Flavia Indrio

    Promotes itUniversity of Bari · pediatric gastroenterology

    Career-defining work on pediatric L. reuteri including the NEJM meta-analysis. Independent academic voice with some industry consulting disclosed.

  • Francesco Savino

    Promotes itUniversity of Turin · infant colic research

    Lead author of foundational Italian infant colic trials. Independent academic voice.

  • Pediatric medicine community

    Promotes itAAP, ESPGHAN guidelines

    Multiple pediatric guideline bodies have provided conditional recommendations for L. reuteri DSM 17938 in breastfed infant colic, among the few probiotic strain-specific recommendations in mainstream pediatric guidelines.

  • Gerber / Nestlé

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itUS pediatric brand partner

    Brought BioGaia's DSM 17938 to US pediatric market through Gerber Soothe. Aggressive direct-to-consumer marketing in pediatric care channels.

  • Lactation consultants and pediatric breastfeeding community

    Promotes itClinical practice

    Substantial adoption of L. reuteri for breastfed infant colic in lactation consultant practice. Among the few evidence-based interventions for the condition.

How we got here

The story of L. reuteri DSM 17938 begins with the Peruvian-American microbiologist Iván Casas in the early 1990s. Casas was studying the breast milk microbiome of healthy mothers in Peru when he isolated the original L. reuteri ATCC 55730 strain. The breast milk origin reflects a key insight in the modern probiotic field, that probiotic candidate strains derived from natural human microbiota (breast milk, gut of healthy adults) may have advantages over strains isolated from dairy or environmental sources. BioGaia (Sweden) was founded in 1990 specifically to develop L. reuteri as a commercial probiotic. The company developed the DSM 17938 strain through directed plasmid removal, eliminating two plasmids carrying antibiotic resistance genes from the parent ATCC 55730 strain. This regulatory-driven improvement (responding to concerns about antibiotic resistance gene transfer in food) created the modern commercial strain. The clinical era expanded dramatically through the 2000s-2010s. The Francavilla 2008 H. pylori trial was an early adult application. The Savino 2007 Italian infant colic trial was foundational for what would become the most-evidenced probiotic-indication pairing in pediatrics. The Indrio 2014 NEJM meta-analysis consolidated the evidence and established L. reuteri DSM 17938 as the first-line evidence-supported intervention for breastfed infant colic. The Coccorullo 2010 pediatric constipation trial extended the evidence; the Sung 2018 functional abdominal pain trial extended further. The Nilsson 2018 postmenopausal bone health trial introduced a novel indication. BioGaia has become a substantial commercial probiotic company through DSM 17938 licensing. Gerber Soothe (Nestlé) brought BioGaia's strain to US pediatric audiences through a major brand partnership. The strain is incorporated into multiple country-specific brand names and pediatric formulations globally. Among the clearest examples of strain-specific commercial development built on rigorous clinical trial program.

  1. 1990sCasas isolates parent ATCC 55730 from Peruvian mother's breast milk
  2. 1990BioGaia founded in Sweden to develop L. reuteri commercially
  3. 2000sDSM 17938 developed through plasmid removal from parent strain
  4. 2007Savino infant colic trial, foundational pediatric evidence
  5. 2008Francavilla H. pylori adjunct trial
  6. 2010Savino replication; Coccorullo constipation trial
  7. 2014Indrio NEJM meta-analysis consolidates colic evidence
  8. 2014Indrio regurgitation prevention trial
  9. 2018Nilsson postmenopausal bone health trial; Sung functional pain trial
  10. 2020sBioGaia expansion across multiple licensed brands globally

What we do not know

  • Why formula-fed infant colic response is less consistent than breastfed, whether breast milk components are required cofactors.
  • Whether the postmenopausal bone health (Nilsson 2018, Osfortis) signal will replicate in larger trials and become a standard adjunct.
  • Whether the L. reuteri H. pylori adjunct benefit translates to adult eradication protocols at adult-dose equivalents.
  • Optimal dose-response curve for adult indications, most clinical evidence is at pediatric doses (100M CFU) extrapolated to adults.
  • Whether reuterin production in vivo can be enhanced through dietary glycerol or other substrate provision.
  • Whether L. reuteri pediatric early-life supplementation has long-term effects on microbiome development beyond the acute colic indication.

The market for this

What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.

BioGaia (Sweden) is the sole licensing source for DSM 17938 globally. The strain master is maintained at BioGaia facilities with extensive quality control. Pharmaceutical-grade purity with viability testing through shelf life. Premium brands disclose BioGaia license on the label. Generic "L. reuteri" without DSM 17938 strain designation represents quality uncertainty, multiple L. reuteri strains exist with different documented properties. The BioGaia drops use sunflower oil as a stabilizing carrier; the chewable tablets use proprietary stabilization technology. Cold chain handling preserves CFU through distribution to pediatric and consumer markets.

At a glance

Strain
Lactobacillus reuteri DSM 17938
Manufacturer
BioGaia (Sweden)
Origin
Peruvian mother's breast milk (ATCC 55730 parent)
Discovery
Iván Casas, 1990s
Standard pediatric dose
100M CFU (5 drops) daily
Standard adult dose
100M-1B CFU daily

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about L. reuteri DSM 17938. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.
  • Where we land. We have not taken a position on this yet.

Sources

The studies that matter

  • Casas L. reuteri isolation1990s

    Iván Casas isolated the parent strain ATCC 55730 from breast milk of a healthy Peruvian mother. Foundational identification of the strain that would become commercial DSM 17938.

  • Savino infant colic trial2007

    Italian RCT in breastfed infants with colic: 100 million CFU L. reuteri daily reduced crying time by ~50% versus placebo over 21 days. Foundational infant colic evidence.

  • Savino replication colic trial2010

    Confirmation of the colic findings in a second Italian trial cohort. Reinforced the indication as among the strongest probiotic-specific clinical effects.

  • Indrio NEJM colic meta-analysis2014

    Pooled analysis of multiple L. reuteri colic trials: meaningful reduction in crying time and colic episodes in breastfed infants. The NEJM publication established the strain as evidence-based for infant colic.

  • Coccorullo functional constipation2010

    Pediatric trial in functional constipation: L. reuteri DSM 17938 improved bowel frequency in children with chronic constipation. Replicated subsequent constipation evidence.

  • Francavilla H. pylori adjunct2008

    Trial in pediatric H. pylori-positive patients: L. reuteri added to standard eradication therapy improved eradication rates and reduced treatment-related GI side effects.

  • Indrio regurgitation prevention2014

    Italian trial in newborns: L. reuteri reduced functional regurgitation and infant colic incidence when administered from first week of life.

  • Sung functional abdominal pain2018

    Australian RCT in children with functional abdominal pain disorders: L. reuteri improved pain-related quality of life over 4 weeks.

  • Mu reuterin mechanism review2018

    Comprehensive review of reuterin's antimicrobial mechanism and clinical relevance. Mechanistic foundation supporting L. reuteri's broad-spectrum effects.