Lactobacillus reuteri is a well-studied strain of probiotic bacteria. People are using it as a beauty supplement and to increase vitamin D. Although Lactobacillus reuteri boasts many purported health benefits, the majority still lack proper evidence. Read on for a breakdown of the science.
What is Lactobacillus reuteri?
Lactobacillus reuteri is a strain of lactic acid bacteria that live in the intestines, and occasionally the stomachs, of humans (although not all individuals), other mammals, and birds.
Its name comes from German microbiologist, Gerhard Reuter, who discovered it in samples of human intestine and feces in the 1960s.
Different strains of Lactobacillus reuteri have been shown to have different physiological effects. For example, Lactobacillus reuteri DSMZ 17648, trademarked “Pylopass” is used for H. pylori , while Lactobacillus reuteri NCIMB 30242, trademarked “Cardioviva” is used to address high cholesterol .
Lactobacillus reuteri supplements have not been approved by the FDA for medical use and generally lack solid clinical research. Regulations set manufacturing standards for supplements but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
- People say it promotes beautiful skin and thick, lustrous hair
- May help fight infections
- May reduce inflammation and increase beneficial TREGs
- May improve gut health (possibly decreasing IBS and IBD symptoms)
- May lower cholesterol
- May not be good for those with histamine intolerance
- May cause weight gain in some people
- Large-scale clinical research lacking
- The safety of long-term supplementation is unknown
Purported Benefits of Lactobacillus reuteri
Most of the research on Lactobacillus reuteri was conducted in animals or cells. Clinical studies are sparse, and most of them are low quality, small, or potentially biased. Additionally, the exact strains that were used differ from one study to another.
Therefore, insufficient data support the use of this probiotic strain for any of the below listed purported benefits.
Remember to speak with a doctor before taking Lactobacillus reuteri supplements. L-citrulline should never be used as a replacement for approved medical therapies.
1) Supports Gut Health
Level of Evidence
Solid evidence suggests that L. reuteri (particularly Lactobacillus reuteri ATCC 55730–BioGaia probiotic tablets and drops) seems to reduce antibiotic-associated diarrhea and functional constipation in adults and children.
This probiotic strain also likely helps prevent diarrhea in infants and children.
Additionally, according to clinical research, taking L. reuteri (Probiotic drops, BioGaia AB) for one week can improve infantile colic and symptoms such as crying time in breast-fed infants .
Our gut bacteria need to consume tryptophan in order to make serotonin, which is crucial for proper gut function .
Some theories suggest that when our gut bacteria consume sugar instead of tryptophan, we are more susceptible to Candida and other infections (by not producing AhR ligands). Insufficient evidence backs up this viewpoint, though .
Nonetheless, some researchers believe that Lactobacillus reuteri switches our gut bacteria’s primary food source from sugar to tryptophan, which helps produce serotonin, and protects our gut from infections. According to them, this may lessen susceptibility to gut problems and IBS .
Others suggest that Lactobacillus reuteri helps with constipation, increasing the number of bowel movements people have. People went from having 3.89 bowel movements per week to 5.28 in one study .
Infants also had increased bowel frequency even at a dosage of 100 million cfu (colony forming units) .
Lactobacillus reuteri also decreases the incidence of diarrhea in children, according to one small study .
Yogurt containing Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 increased T regulatory cells in patients with Inflammatory Bowel Disease and decreased inflammation (TNF-alpha and IL-12) .
This probiotic strain likely supports gut health when part of a healthy microbiome. Supplementing may be beneficial in infants, children, and people with specific gut/digestive issues.
2) Skin & Hair
Animal research on a Lactobacillus reuteri strain called ATCC PTA 6475 has shown potential for improving skin quality (thickness and “glow”) and creating thick, lustrous hair .
The probiotic improved skin and hair quality in both sexes, but in female animals caused a dramatic improvement in the level of shine of their hair. The Lactobacillus reuteri caused females to have a more acidic pH, which was found to correlate with hair luster .
However, remember that these alleged beauty benefits are based solely on animal studies. It’s unknown whether this probiotic strain can improve hair and skin health in humans, as clinical studies are lacking.
3) Anti-Inflammatory Effects
Decreased levels of L. reuteri in humans in the past decades is correlated with an increase in the incidences of inflammatory diseases over the same period of time. This, however, does not imply that lower l. reuteri levels directly caused inflammatory diseases, as researchers only looked at associations .
No clinical studies about the effects of L. reuteri on inflammation exist.
Note: Lactobacillus reuteri may not be good for histamine intolerance. Lactobacillus reuteri is able to convert dietary l-histidine into histamine, increasing IL-10, and suppressing TNF-α (by activating the histamine H2 receptor) [19, 20].
In animal models of lupus nephritis, L. reuteri increased Lactobacilli in the gut, improved kidney function, reduced serum autoantibodies, and prolonged survival. Clinical studies are lacking .
4) Stress & Pain
Insufficient evidence supports the use of L. reuteri for stress and pain management.
Scientists think that Lactobacillus reuteri ingestion impacts the nerves in such a way that it may slow gut motility (improving cases of diarrhea) and decrease pain perception. This theory is still unproven, though .
5) May Increase Vitamin D
According to the authors of the study, this is the first time blood levels of vitamin D3 have been increased by oral probiotic supplementation .
Though their findings are promising, this purported benefit remains unproven until additional, large-scale clinical trials are carried out.
6) Vitamin B12 and B9 (Folate) Status
Like many other Lactobacillus spp., scientists believe that several L. reuteri strains are able to produce different types of vitamins, including vitamin B12 (cobalamin) and B9 (folate) .
At least 4 L. reuteri strains with various origins have been found to produce B12. Among these strains, L. reuteri CRL1098 (isolated from sourdough) and L. reuteri JCM1112 are the most studied .
In one study, the administration of L. reuteri CRL1098 together with a diet lacking vitamin B12 was shown to ameliorate pathologies in B12-deficient pregnant female mice and their offspring. It’s unknown if L. reuteri will have similar effects in humans .
Despite the ongoing research efforts, clinical data are lacking to support the use of L. reuteri for improving vitamin B12 and folate levels.
7) Thyroid Health
Evidence is lacking to support the use of this probiotic strain for thyroid health.
In mice, Lactobacillus reuteri increased thyroid size and activity (increasing T4 levels), lessening the fatigue and weight gain associated with aging and causing a more youthful physical appearance .
8) May Lower Cholesterol
Limited clinical evidence supports the benefits of l. reuteri as a complementary strategy for lowering blood cholesterol levels.
In one human study, Lactobacillus reuteri reduced LDL cholesterol by 11.64%, reduced total cholesterol by 9.14%, non-HDL-cholesterol by 11.30% and apoB-100 by 8.41% .
Hs-C-reactive protein and fibrinogen were reduced by 1.05 mg/l and 14.25%, respectively .
Another study used microencapsulated Lactobacillus reuteri NCIMB 30242 yogurt taken twice a day over 6 weeks by adults with high cholesterol. Results included a reduction of LDL by 8.92% and total cholesterol 4.81% over the course of the study .
The Lactobacillus reuteri in that form and delivery method was found to work better than probiotics traditionally used and comparable to other cholesterol-lowering methods .
However, large-scale, multicenter clinical trials using standardized Lactobacillus reuteri formulations are needed to confirm this benefit.
9) Effects on Wound Healing
Overall, evidence is lacking to support this benefit.
Supplementing the rat microbiome with Lactobacillus reuteri in drinking water cuts wound-healing time in half compared to control animals .
According to one theory, Lactobacillus reuteri enhances healing by increasing oxytocin via the vagus nerve. The oxytocin then activates Tregs (CD4+Foxp3+CD25+), which improves the repair of wounds 
Scientists found that L. reuteri can produce antimicrobial molecules, such as alcohol, reuterin, lactic acid, acetic acid, and reutericyclin. Due to its antimicrobial activity, L. reuteri is able to inhibit the colonization of disease-causing microbes .
Of the 8 probiotic strains tested in the lab, Lactobacillus reuteri ATCC 55730 showed the strongest inhibition of Candida albicans in the mouth .
L. reuteri is being researched for its effects against pneumoviruses, circoviruses, rotaviruses, coxsackieviruses, and papillomaviruses .
It has been suggested that L. reuteri ameliorates viral infection by regulating the microbiota and secreting metabolites that have antiviral components. However, studies have yet to confirm this theory .
It has been suggested that L. reuteri works by competing with H. pylori and inhibiting its binding to glycolipid receptors. The competition reduces the bacterial load of H. pylori and decreases the related symptoms .
2-week treatment with L. reuteri DSM17648 significantly reduced H. pylori overgrowth in otherwise healthy adults in one small study .
Additional human studies are needed.
Other Bacterial Infections
Lactobacillus reuteri potently protects against Salmonella, cutting mortality rates in mice, chickens, and turkeys in half .
In chickens, Lactobacillus reuteri was as potent as the antibiotic gentamicin in preventing E. coli-related deaths . The exopolysaccharides synthesized by L. reuteri is able to inhibit E. coli adhesion to pig cells .
An antibiotic produced by Lactobacillus reuteri, called reutericyclin, can kill C. difficile infections .
Human studies are lacking.
11) May Support Oral Health
Scientists are exploring whether Lactobacillus reuteri fights major cavity-producing bacteria .
Chewing gum containing Lactobacillus reuteri decreased plaque and bleeding from the gums in two weeks in one small study .
Lactobacillus reuteri lozenges were shown to fight oral candida in a study of older patients .
Higher-quality clinical trials are needed to explore this purported benefit.
12) Autism Research
There is no evidence to support the use of this probiotic strain in children or adults with autism.
The existing research suggests that future studies may be a good idea.
In an animal model of social deficits in offspring, Lactobacillus reuteri was found to be 9X lower. Supplementing with it significantly improved sociability and preference for social novelty in these offspring .
The main mechanism is by L. reuteri increasing oxytocin, including in the hypothalamus .
13) Sex Drive Research
Some companies market Lactobacillus reuteri‘s to men, claiming that it can strengthen sex drive.
However, it’s currently unknown if L. reuteri affects sex drive in men or women.
14) Fertility Research
Eating probiotic yogurt or purified probiotic bacteria induced more acidic conditions in the skin, mouth, vagina, and rectum of female mice .
An acidic pH in the vagina correlates with the time of peak fertility, estimated to be around age 25. However, the specific benefits of L. reuteri should be researched in more detail .
The microbiota composition varies between lean and obese individuals .
It seems like some strains of L. reuteri may cause weight gain, while other strains can cause weight loss .
A surprisingly high level of Lactobacillus species has been found in the microbiota of obese people, especially L. reuteri. In fact, when individuals had strains of L. reuteri that are resistant to antibiotics (vancomycin), they gained weight after antibiotic (vancomycin) treatment [15, 45].
However, in a randomized, double-blind and placebo-controlled clinical trial, taking L. reuteri JBD301 for 12 weeks significantly reduced body weight in overweight adults .
These results seem conflicting because some L. reuteri strains can cause weight gain, while others cause weight loss .
In a study that tested different strains of L. reuteri, only PTA 4659 efficiently reduced the bodyweight of mice fed with high-fat diet (HFD), whereas L6798-treated mice even gained some weight [15, 46].
L. reuteri GMNL-263 reduces both insulin resistance and fatty liver in rats .