Understanding Limosilactobacillus reuteri(L. reuteri) and Its Health Benefits
- NPSelection
- 9 hours ago
- 6 min read
Among the many beneficial microbes that call our bodies "home", Limosilactobacillus reuteri (formerly Lactobacillus reuteri) stands out for its remarkable journey from nature to laboratories to health-conscious consumers worldwide. This small bacterium, quietly performing its symbiotic duties for millennia, is now at the forefront of gut health research, dental care, and even mood improvement. But where did this microbe come from, and how did we come to appreciate its importance?
The Discovery of L. reuteri
L. reuteri was first isolated in 1962 by German microbiologist Dr. Gerhard Reuter, after whom it was named. Reuter studied the intestinal microbiota of humans and animals, focusing on bacteria that played a role in gut health. From samples of human intestines, he identified a new species of rod-shaped lactic acid bacteria distinct from its relatives in the Lactobacillus genus.
Where in the World is L. reuteri Found?
Geographically, L. reuteri is cosmopolitan. It has been isolated from humans and various animals across the globe, including pigs, chickens, rodents, and even birds. However, one of its most intriguing features is its host-specific strains. That is, L. reuteri strains tend to adapt to specific hosts—what you find in a pig’s gut is genetically distinct from strains colonising humans. In humans, L. reuteri naturally inhabits:- The gastrointestinal tract (especially the stomach and small intestine)
- The oral cavity (tongue, gums, dental biofilm)
- The urogenital tract. It is considered one of the few Lactobacillus species that can stably colonise the human upper gastrointestinal tract, an area hostile to most bacteria due to its acidity.
Natural Habitat & Ecology
In nature, L. reuteri thrives in environments rich in complex carbohydrates and mucosal surfaces. Unlike transient probiotic strains that pass through the gut, L. reuteri forms biofilms, helping it adhere to epithelial cells and outcompete harmful bacteria. Its survival mechanisms are impressive:- It produces reuterin, a potent antimicrobial compound that inhibits pathogens like Escherichia coli, Salmonella, and Candida albicans.- It synthesises exopolysaccharides, enhancing its ability to stick to gut linings and resist bile acids.- It interacts with host immune cells, modulating inflammation and supporting mucosal immunity. These ecological traits made L. reuteri a crucial player in maintaining gut balance long before humans knew it existed.
Evolution and the Human Connection
Interestingly, modern lifestyles may have reduced L. reuteri colonisation in humans. Industrialisation, changes in diet, widespread antibiotic use, and modern hygiene practices have been linked to a decline of ancestral gut microbes. Studies comparing rural populations (e.g., in Africa or South America) with urban dwellers show a higher prevalence of L. reuteri in traditional, agrarian societies. This loss has sparked scientific efforts to reintroduce L. reuteri through probiotics, aiming to restore its beneficial effects.
From Nature to Supplement Shelves
Today, L. reuteri is used in probiotic supplements, yoghurts, infant formulas, and even dental lozenges. Different strains have been studied for:
- Gut health (reducing diarrhoea, constipation, colic)- Oral health (preventing dental caries, gingivitis)
- Skin health (managing atopic dermatitis)
- Bone health (supporting bone density in older women)
- Mental health (modulating stress response and oxytocin release). Each application ties back to its natural role as a guardian of mucosal surfaces.
Curiosity Hook: What Makes L. reuteri Unique?
Lactobacillus reuteri is unique for its ability to produce reuterin, modulate the immune and hormonal systems, and adhere to the gut lining, offering broad health benefits despite being a transient species (it does not colonise the gut for long in some people)
What Can L. reuteri Do for Your Health?
Digestive Health: Studies show L. reuteri can reduce colic in infants and alleviate adult constipation, particularly with the DSM 17938 strain (Sung et al., 2018).
Immune Support: Certain strains of L. reuteri can lower inflammation and encourage the growth of beneficial gut bacteria, helping the immune system function more effectively (Martín et al., 2015).
Mood and Oxytocin: Animal studies suggest L. reuteri might increase oxytocin, the “bonding hormone”, potentially improving mood and social interactions. However, these effects are not yet confirmed in humans (Poutahidis et al., 2013).
Skin Health and Ageing: Probiotics, including L. reuteri, may reduce skin inflammation, but claims of increased collagen production and anti-ageing effects lack robust evidence (Toscano et al., 2017).
Heart Health: Strain NCIMB 30242 has been linked to lower LDL cholesterol levels, suggesting potential cardiovascular benefits, although this is strain-specific (Jones et al., 2012).
L. reuteri has been documented in scientific literature as a species capable of colonising the upper gastrointestinal (GI) tract, particularly the stomach, duodenum, and small intestine. However, its colonisation is host-dependent, which means that it can colonise, but not always persistently, in everyone:
Upper GI tract colonisation:
L. reuteri is one of the few Lactobacilli that naturally colonise the human stomach and upper small intestine.
Its ability to survive in acidic conditions and adhere to mucosal surfaces allows it to colonise these areas temporarily or stably.
Example strains: L. reuteri DSM 17938 and ATCC PTA 6475 are known for upper GI tract colonisation.
Biofilm formation:
L. reuteri produces exopolysaccharides and forms biofilms, which helps it adhere to epithelial cells and maintain colonisation, especially in the oral cavity, gastric mucosa, and small intestine.
But often transient in the lower GI tract (colon):
In the large intestine (colon), L. reuteri is more often a transient inhabitant, unless regularly replenished through diet or supplements.
Modern lifestyles (antibiotics, low-fibre diets) have reduced its prevalence compared to ancestral human populations.
Scientific Support:
Walter et al., 2011: Documented human-specific strains adapted to colonising the upper GI tract.
Valeur et al., 2004 (Microbial Ecology in Health and Disease): Demonstrated successful, though sometimes temporary, colonisation in human volunteers with DSM 17938.
Mu et al., 2018 (Frontiers in Microbiology): Review highlighting L. reuteri's mucosal colonisation abilities and host-specific adaptation.
Dr William Davis and Super Gut: Highlights and Controversy
Dr William Davis, author of Super Gut, has played a significant role in popularising L. reuteri. In his book, he advocates for high-dose L. reuteri through homemade yoghurt, claiming it can improve skin, boost mood, and even enhance muscle growth. While his ideas are intriguing, some claims have drawn criticism:
Homemade Yoghurt: Davis promotes fermenting L. reuteri yoghurt at home to maximise its benefits. While this can be beneficial, improper preparation can lead to contamination and inconsistent doses (Marco et al., 2017).
Exaggerated Claims: Some assertions, such as L. reuteri reversing ageing or significantly enhancing oxytocin levels, rely on animal studies and lack sufficient human research (Poutahidis et al., 2013).
Focus on One Strain: Critics argue that Davis’s emphasis on L. reuteri overlooks the importance of microbial diversity for a healthy gut. A single strain cannot replace the need for a varied and balanced microbiome (Cammarota et al., 2019).
Simplistic Solutions: The suggestion that a single probiotic or yoghurt recipe can address complex health issues like inflammation or ageing is overly simplistic and not aligned with current scientific understanding.
The Importance of Microbiome Diversity
The benefits of L. reuteri depend on each person’s unique microbiome. A healthy gut requires diversity, meaning a wide range of beneficial bacteria.
Relying solely on L. reuteri or any single strain cannot fully support a resilient microbiome. Consuming a fibre-rich diet, whole foods, and fermented products is essential for maintaining microbial diversity and long-term health (Cammarota et al., 2019).
Tips for Using L. reuteri Safely
Seek Professional Advice: Consult a competent professional (dietician, medical person) before making significant dietary changes or trying high-dose probiotics. This person will know you better and also take responsibility for the outcome.
Don’t Overdo It: High doses of probiotics can sometimes disrupt the natural balance of your gut microbiome.
Think Holistically: Incorporate L. reuteri as part of a balanced diet rather than expecting it to be a cure-all.
L. reuteri is a promising probiotic with proven benefits for digestion and immunity. However, its broader claims, such as reversing ageing or drastically improving mood, require more scientific evidence. The key to gut health lies in a diverse microbiome supported by a varied and balanced diet. While L. reuteri can be helpful, it is not a miracle solution.
References
Reuter, G. (2001). "The Lactobacillus and Bifidobacterium microflora of the human intestine: composition and succession." Microbial Ecology in Health and Disease, 13(1), 31-35.
Walter, J., & Ley, R. (2011). "The human gut microbiome: ecology and recent evolutionary changes." Annual Review of Microbiology, 65, 411-429.
Spinler, J. K., et al. (2017). "Human-derived probiotic Lactobacillus reuteri demonstrate antimicrobial activities targeting diverse enteric bacterial pathogens." Anaerobe, 47, 74-83.
Mu, Q., Tavella, V. J., & Luo, X. M. (2018). "Role of Lactobacillus reuteri in human health and diseases." Frontiers in Microbiology, 9, 757.
Sung, V., D’Amico, F., Cabana, M., et al. (2018). Lactobacillus reuteri to Treat Infant Colic: A Meta-analysis. Pediatrics, 141(1), e20171811. https://doi.org/10.1542/peds.2017-1811
Martín, R., Bermúdez-Humarán, L. G., & Langella, P. (2015). Searching for Probiotic Mechanisms in Human Gut Microbiota: From Culturomics to Metagenomics. Frontiers in Microbiology, 6, 354. Frontiers | Phenotypic and transcriptional profiling in Entamoeba histolytica reveal costs to fitness and adaptive responses associated with metronidazole resistance
Poutahidis, T., Kearney, S. M., Levkovich, T., et al. (2013). Microbial Symbionts Accelerate Wound Healing via the Oxytocin Pathway. PLoS ONE, 8(10), e78898. Microbial Symbionts Accelerate Wound Healing via the Neuropeptide Hormone Oxytocin
Marco, M. L., Pavan, S., & Kleerebezem, M. (2017). Towards Understanding Molecular Modes of Probiotic Action. Current Opinion in Biotechnology, 49, 128–135. Redirecting
Jones, M. L., Tomaro-Duchesneau, C., & Prakash, S. (2012). The Gut Microbiome, Probiotics, and Cardiovascular Disease. Applied Microbiology and Biotechnology, 94(5), 1079–1089. https://doi.org/10.1007/s00253-012-4080-0
Cammarota, G., Ianiro, G., Ahern, A., et al. (2019). Gut Microbiome, Fecal Microbiota Transplantation, and Antibiotic-Resistant Infections: A New Frontier in Infectious Diseases. Clinical Microbiology and Infection, 25(12), 1360–1368. Redirecting
Toscano, M., De Grandi, R., Stronati, L., et al. (2017). Effect of Probiotics on the Incidence of
Nosocomial Infections: A Systematic Review and Meta-Analysis. Journal of Clinical Medicine, 6(11), 105. https://doi.org/10.3390/jcm6110105
