What This Strain Does
Lactobacillus reuteri holds a distinguished position among probiotic bacteria as one of the few species that has co-evolved with humans throughout our evolutionary history. Named after German microbiologist Gerhard Reuter who first characterized it, this strain has been reclassified to Limosilactobacillus reuteri under updated bacterial taxonomy, though it remains widely known by its traditional name. Unlike many probiotics that are primarily associated with dairy fermentation, L. reuteri is one of the truly indigenous inhabitants of the human body, naturally colonizing the gastrointestinal tract, oral cavity, skin, and breast milk.
What makes L. reuteri particularly fascinating is its production of reuterin, a potent antimicrobial compound that inhibits a broad spectrum of pathogenic bacteria, yeasts, and fungi without harming beneficial microbes. This unique antimicrobial activity makes L. reuteri especially effective for maintaining microbial balance throughout the body, including in the mouth where it helps control bacteria responsible for dental caries, gum disease, and bad breath.
L. reuteri’s systemic effects extend well beyond the gut. Research has demonstrated its influence on bone metabolism, with studies showing improved bone density and reduced bone loss in certain populations. The strain appears to modulate inflammation throughout the body, potentially through its effects on the gut-immune axis and production of specific metabolites that influence systemic inflammatory pathways.
The strain also shows promise for cardiovascular health. Certain L. reuteri strains can actively break down cholesterol and bile salts, potentially reducing cholesterol absorption and contributing to healthier blood lipid levels. Additionally, research has explored L. reuteri’s benefits during pregnancy for both maternal health and infant development, particularly for reducing colic in breastfed infants.
Research Highlights
L. reuteri has accumulated an impressive body of research across diverse health applications, with some findings that are unique among probiotic strains.
For oral health, a systematic review published in the Journal of Clinical Periodontology examined multiple studies of L. reuteri for gum disease. The analysis found that L. reuteri supplementation significantly reduced markers of periodontal inflammation, including gum bleeding and pocket depth, when used as an adjunct to standard dental care. The strain’s production of reuterin appears to selectively inhibit periodontal pathogens.
Research published in the Journal of Clinical Endocrinology and Metabolism investigated L. reuteri’s effects on bone health in elderly women. The randomized controlled trial found that one year of supplementation with L. reuteri ATCC PTA 6475 significantly reduced bone loss compared to placebo, suggesting a potential role in osteoporosis prevention.
A landmark study published in Pediatrics examined L. reuteri DSM 17938 for infant colic. The probiotic, administered as drops to breastfed infants, significantly reduced crying time compared to placebo, with some infants showing dramatic improvements. This research has led to widespread recommendation of L. reuteri for colicky infants by pediatric organizations.
For cholesterol, research published in the European Journal of Clinical Nutrition demonstrated that L. reuteri NCIMB 30242 (now marketed as Cardioviva) significantly reduced LDL cholesterol, total cholesterol, and certain inflammatory markers in adults with elevated levels. The strain appears to work through novel mechanisms including breakdown of bile salts and potential reduction of cholesterol absorption.
Studies in Gastroenterology Research and Practice examined L. reuteri for acid reflux and functional digestive symptoms. Research showed that supplementation reduced gastric symptoms and may help with conditions involving impaired gastric motility and upper digestive discomfort.
Specific Strains to Look For
L. reuteri strain designations are particularly important, as different strains have been researched for very different applications.
L. reuteri DSM 17938 is the most extensively studied strain for infant colic and general pediatric applications. Derived from L. reuteri ATCC 55730, this strain has accumulated strong evidence for reducing crying time in colicky breastfed infants. It’s available in several commercial infant probiotic products and is one of the few probiotics with pediatric-specific research.
L. reuteri ATCC PTA 6475 has been specifically studied for bone health and immune modulation. Research shows this strain can reduce bone loss in postmenopausal women and may help maintain bone density. It’s often combined with L. reuteri DSM 17938 in products targeting multiple benefits.
L. reuteri NCIMB 30242 (marketed as Cardioviva) has been researched specifically for cardiovascular health and cholesterol management. Studies show significant reductions in LDL cholesterol and inflammatory markers. This strain is available in specific products targeting heart health.
L. reuteri Prodentis (combining strains DSM 17938 and ATCC PTA 5289) has been developed specifically for oral health applications. Research shows this combination reduces periodontal pathogens, gum bleeding, and pocket depth when used as lozenges or chewing gum for direct oral exposure.
What to Look For in Products
Selecting the right L. reuteri product depends heavily on your specific health goals, as different strains target different benefits.
For infant colic, look specifically for L. reuteri DSM 17938 in drop formulations designed for infants. Typical doses in studies are 100 million CFU (10^8) daily, significantly lower than adult probiotic doses. Products should be specifically formulated for infants with appropriate excipients.
For oral health, delivery format matters significantly. L. reuteri Prodentis in lozenges, chewing gum, or oral drops allows the bacteria to colonize the oral cavity directly. Swallowed capsules may provide some benefit through systemic effects but won’t deliver bacteria directly to the mouth where they’re most needed for dental and gum health.
For cholesterol and cardiovascular applications, look for L. reuteri NCIMB 30242 at doses of at least 2 billion CFU daily. The research on this strain used twice-daily dosing with food.
For bone health, L. reuteri ATCC PTA 6475 at approximately 10 billion CFU daily has been studied in clinical trials. Products combining this strain with DSM 17938 may offer additional benefits.
Third-party verification is valuable for confirming strain identity and potency. Given how strain-specific the benefits are for L. reuteri, identity verification through genetic testing is particularly important.
Potential Side Effects
L. reuteri has demonstrated excellent safety across extensive research, including studies in vulnerable populations such as premature infants, pregnant women, and elderly individuals.
In infants, L. reuteri is generally well-tolerated, with studies showing no significant adverse effects compared to placebo. Occasional mild changes in stool consistency may occur but are typically temporary.
In adults, initial supplementation may cause temporary mild gas, bloating, or digestive changes as the microbiome adjusts. These symptoms typically resolve within one to two weeks.
Those who are severely immunocompromised, have central venous catheters, or are critically ill should consult healthcare providers before using L. reuteri or any probiotic due to rare cases of bacteremia in these highly vulnerable populations.
Some L. reuteri strains produce histamine, which may be relevant for individuals with histamine intolerance. Those with histamine sensitivity should start with low doses and monitor their response. Strain-specific information about histamine production may help guide selection.
For pregnancy and breastfeeding, L. reuteri has been studied with good safety outcomes and may provide benefits for both maternal health and infant colic prevention through breast milk. However, pregnant women should consult healthcare providers before starting any supplement.
How to Take
Optimal timing and administration of L. reuteri depends on the target application.
For infant colic, L. reuteri drops should be administered daily, typically with feeding. Studies show best results when started within the first three months of life. The oil-based drop formulation should be shaken well before use to distribute the bacteria evenly.
For oral health, L. reuteri lozenges or chewing gum should be used after brushing and before bed to allow maximum colonization time in the mouth. The probiotic works topically, so swallowing the product immediately reduces effectiveness. Allow lozenges to dissolve slowly in the mouth.
For cardiovascular or bone health benefits, L. reuteri can be taken with or without food. The cholesterol studies used twice-daily dosing with meals. Consistency is important for accumulating benefits, with most studies running eight to twelve weeks.
For acid reflux and upper digestive symptoms, taking L. reuteri before meals may be beneficial, though optimal timing hasn’t been definitively established.
Long-term use appears safe based on available research. For infant colic, treatment typically continues for three to four weeks or until symptoms resolve. For chronic conditions like periodontal disease or osteoporosis prevention, ongoing supplementation may be appropriate.
Key Takeaways
L. reuteri is one of the few probiotics that co-evolved with humans and naturally colonizes multiple body sites including the gut, mouth, and breast milk.
The strain produces reuterin, a unique antimicrobial compound that selectively inhibits pathogens while sparing beneficial bacteria.
For infant colic, L. reuteri DSM 17938 has strong evidence for reducing crying time in breastfed infants and is widely recommended by pediatric organizations.
Research supports strain-specific benefits for oral health (reducing gum disease and dental pathogens), bone health (reducing bone loss), and cholesterol management.
Strain selection is critical with L. reuteri: different strains have very different research support for different conditions.
Available in multiple formats including infant drops, lozenges for oral health, and capsules for systemic benefits, with format matched to application.