Lactobacillus reuteri is a species of probiotic bacteria that naturally lives in the human body. It has a notable presence in the gastrointestinal tract, and can also be found in the urinary tract and in breast milk. As one of the more extensively researched probiotics, its presence and concentration can vary significantly from one person to another.
The Role of Reuteri in the Body
L. reuteri establishes itself within the gut, where it can survive the acidic conditions of the stomach and temporarily colonize the gastrointestinal tract. One of its activities is the production of antimicrobial substances, including organic acids, ethanol, and a compound called reuterin. These substances can help manage the levels of potentially harmful microbes.
Beyond its antimicrobial effects, L. reuteri plays a part in maintaining the physical structure of the gut. It helps to strengthen the intestinal barrier, the layer of cells that lines the intestines. A strong barrier prevents unwanted substances from passing from the gut into the bloodstream. This function is supported by its ability to promote the production of mucin, a protein that reinforces the gut lining.
This bacterium also has a relationship with the host’s immune system. Some strains of L. reuteri have been observed to modulate immune responses. They can influence the activity of various immune cells, such as promoting the function of regulatory T cells, which help to control inflammation.
Specific Strains and Their Functions
The name Lactobacillus reuteri refers to a species, but within this species are numerous distinct strains, each with specific characteristics and functions. These individual strains are studied in clinical research and featured in supplements. Two of the most well-documented strains are L. reuteri DSM 17938 and L. reuteri ATCC PTA 6475, which have different, though sometimes complementary, actions.
L. reuteri DSM 17938 is one of the most clinically studied probiotic strains, particularly in the area of infant health. Research has investigated its use for managing conditions like infantile colic, where studies have shown it may reduce crying time in breastfed infants. This strain is thought to work in part by producing the antimicrobial substance reuterin and by helping to improve the function of the epithelial barrier in the gut. Studies have also noted its ability to stimulate gastrointestinal motility and increase defecation frequency in children with constipation.
Another highly researched strain, L. reuteri ATCC PTA 6475, is recognized for its effects on the immune system and inflammation. This strain has been shown to modulate the immune response by inhibiting certain pro-inflammatory signaling molecules. Animal studies have suggested it may have benefits for skin quality, bone mass, and hair quality. Some research indicates that certain L. reuteri strains, including ATCC PTA 5289 (a different strain), can help in managing oral ulcers and supporting gum health when used alongside professional dental cleaning.
Often, these two primary strains, DSM 17938 and ATCC PTA 6475, are studied in combination. Research has explored their combined use for conditions like Irritable Bowel Syndrome (IBS), where they have been shown to reduce symptoms and improve stool consistency. They are also investigated for their potential to inhibit the growth of Helicobacter pylori, the bacterium associated with stomach ulcers, and to reduce the side effects of antibiotic treatments.
Natural and Supplemental Sources
Natural food sources of L. reuteri primarily consist of fermented products. Certain yogurts, kefir, and some cheeses like cheddar and Parmigiano Reggiano may contain this bacterium. Other fermented foods such as sauerkraut, miso, and sourdough bread can also be sources. However, the presence and concentration of L. reuteri in these foods can be inconsistent, and the strains in most commercial yogurts often differ from well-researched therapeutic strains.
While food sources provide a variety of microbes, supplements offer a more targeted approach. Probiotic supplements are the most reliable method for obtaining a specific strain, such as L. reuteri DSM 17938 or ATCC PTA 6475, at a documented dosage. Supplements are available in various forms, including capsules, powders, and liquid drops.
It is also possible to encourage the growth of beneficial bacteria like L. reuteri that may already be present in your gut. Consuming prebiotic foods, which are high in fiber, can help nourish these microbes. Foods like garlic, onions, bananas, whole grains, and beans act as fuel for a diverse gut microbiome.
Considerations for Use
When using L. reuteri supplements, the dosage is a consideration and is measured in Colony-Forming Units (CFUs). Research doses typically range from 1 billion to 100 billion CFUs per day, and the effective amount can vary depending on the strain and the intended health purpose. Some studies suggest that dosing every other day can be as effective as daily supplementation. It is recommended to avoid taking probiotics with hot beverages, as heat can damage the live bacteria.
L. reuteri is Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration for most healthy individuals. It has been safely used in studies involving various age groups, from premature infants to adults. Side effects are uncommon and typically mild and temporary, potentially including minor gas or bloating as the digestive system adjusts.
Individuals who are pregnant, nursing, or have a compromised immune system should consult a healthcare professional before beginning any new supplement regimen. Once supplementation stops, the bacterial colonies in the gut will gradually revert to their previous state over a period ranging from a few days to a month.