Lactobacillus reuteri is a species of lactic acid bacterium studied for its potential health effects in humans and animals. This probiotic microbe is a naturally occurring inhabitant of the human gastrointestinal tract and is also found in breast milk. Although reclassified in 2020 to the genus Limosilactobacillus, it remains commonly referenced by its original name. It is recognized as one of the most researched probiotic species globally, with numerous strains investigated in clinical settings.
Unique Mechanisms of Action
A distinct feature of certain L. reuteri strains is their ability to produce Reuterin, a broad-spectrum antimicrobial compound. Reuterin is primarily composed of 3-hydroxypropionaldehyde (3-HPA), generated through the anaerobic fermentation of glycerol. Reuterin displays antimicrobial activity against a wide range of harmful organisms, including bacteria, fungi, yeast, and protozoa. This production allows L. reuteri to compete effectively within the gastrointestinal tract, suppressing the overgrowth of potential pathogens.
L. reuteri also reinforces the physical integrity of the gut lining. The bacterium contributes to gut health by stimulating the production of mucus, which forms a protective layer over the epithelial cells. This increased mucus layer helps prevent the adhesion and invasion of pathogenic microorganisms. Furthermore, certain strains increase the expression of tight junction proteins, which seal the spaces between intestinal epithelial cells. This action prevents the translocation of undesirable substances from the gut lumen into the bloodstream.
Targeted Digestive Support
The most substantial clinical evidence for L. reuteri focuses on its positive impact on functional gastrointestinal disorders, particularly in infants. Research using the specific strain L. reuteri DSM 17938 has demonstrated its capacity to reduce the duration and severity of infantile colic. Daily administration of 1×10⁸ colony-forming units (CFU) of this strain has been shown to significantly decrease daily crying and fussing times in breastfed infants. The bacterium is thought to improve colic by alleviating intestinal inflammation and influencing gastrointestinal motility, which quickens stomach emptying.
L. reuteri also manages diarrhea, including that associated with antibiotic use. The production of antimicrobial metabolites helps inhibit the growth of pathogens that cause infectious diarrhea. Clinical trials suggest that L. reuteri can reduce the frequency and duration of diarrhea in both children and adults. By strengthening the intestinal barrier and modulating the gut microbiota, the microbe helps restore balance during periods of microbial disruption. The combined effects of antimicrobial action and gut barrier protection improve general intestinal health and function.
Emerging Benefits Beyond the Gut
The influence of L. reuteri extends beyond the digestive system, with applications in oral health. Certain strains help maintain a balanced oral microbiome by inhibiting the growth of bacteria that contribute to dental plaque and gum disease. Studies show that L. reuteri can reduce measures of gum inflammation, such as gingival bleeding and the plaque index. This effect is attributed to its antimicrobial properties and its ability to reduce inflammatory markers.
L. reuteri also modulates the systemic immune response. The bacterium interacts with immune cells in the gut-associated lymphoid tissue (GALT), promoting an anti-inflammatory state. It has been observed to reduce levels of pro-inflammatory mediators while increasing the production of anti-inflammatory cytokines. This immune modulation has systemic implications and suggests a potential influence on the gut-brain axis, linking gut health to neurological functions.
Supplementation and Safety Guidelines
L. reuteri is most commonly accessed via targeted dietary supplements, though it can be consumed through certain fermented foods. When selecting a supplement, look for products that specify the exact strain, such as L. reuteri DSM 17938 or ATCC PTA 5289, as the benefits are strain-specific. Probiotic efficacy is measured in colony-forming units (CFUs), with doses typically ranging from 1×10⁸ to 1×10¹⁰ CFU per serving. The recommended dosage is influenced by the intended use and target population.
Commercial preparations are available as oil suspensions or capsules, requiring specific storage instructions to maintain viability. Stability data often indicate that the product remains stable for several months when stored at refrigerated temperatures. The species is widely recognized as safe for human consumption, with several strains categorized as Generally Recognized as Safe (GRAS). In clinical studies, no serious adverse events have been reported; the most common minor side effects are temporary changes in gas or mild digestive discomfort.