Lactobacillus rhamnosus (L. rhamnosus) is a beneficial gut microbe sold as a supplement and added to many foods, particularly dairy. It may ease diarrhea and IBS symptoms, support gut health, and help protect teeth from decay.
The human body hosts roughly 10–100 trillion bacteria.
The majority reside in the gastrointestinal tract and are collectively called the gut microbiota. They play a crucial role in overall health.
While a balanced microbiota supports wellness, an imbalance has been associated with many health problems.
One of the most researched beneficial bacteria is L. rhamnosus.
This article summarizes the benefits, possible side effects, and dosing of L. rhamnosus.
What Is Lactobacillus rhamnosus?
L. rhamnosus is a bacterial species commonly found in the intestines.
It belongs to the Lactobacillus genus, bacteria that produce the enzyme lactase. Lactase converts lactose — the sugar in dairy — into lactic acid.
Bacteria from this genus, including L. rhamnosus, are classified as probiotics.
Probiotics are live microorganisms that can confer health advantages when consumed.
Numerous studies have documented benefits associated with L. rhamnosus.
This species is specially adapted to survive both acidic and alkaline environments in the body and can adhere to and colonize the intestinal lining. Those traits improve its odds of surviving and potentially delivering longer-lasting effects.
There are many strains of L. rhamnosus, each with distinct properties.
L. rhamnosus is available as a probiotic supplement and is frequently added to yogurts, cheeses, milks, and other dairy items to enhance probiotic content.
It can also contribute to dairy processing; for example, L. rhamnosus is involved in cheese ripening, enhancing flavor (8).
Note that many products containing L. rhamnosus may not list it explicitly in their ingredient panels.
SummaryL. rhamnosus is a probiotic Lactobacillus species adapted to the gut, which may enable it to provide sustained benefits.
Potential Health Benefits and Uses
L. rhamnosus offers multiple potential benefits for digestion and other aspects of health.
1. May Prevent and Treat Diarrhea
Diarrhea is a frequent issue that can be triggered by bacterial infections.
While often harmless, prolonged diarrhea can lead to fluid loss and dehydration.
Research shows L. rhamnosus may help prevent or treat several forms of diarrhea.
For example, L. rhamnosus may reduce antibiotic-associated diarrhea. Antibiotics can disrupt the microbiota and cause digestive disturbances like diarrhea.
A review of 12 trials involving 1,499 participants reported that supplementation with the L. rhamnosus GG strain lowered the incidence of antibiotic-associated diarrhea from 22.4% to 12.3%.
Taking a probiotic during and after antibiotic therapy can help replenish beneficial gut bacteria that antibiotics often eliminate along with harmful organisms.
Moreover, L. rhamnosus may protect against other diarrhea types, including traveler’s diarrhea, acute watery diarrhea, and diarrhea related to acute gastroenteritis.
2. May Relieve IBS Symptoms
Irritable bowel syndrome (IBS) affects an estimated 9–23% of adults globally.
Although its exact cause is unknown, IBS leads to symptoms like bloating, abdominal pain, and altered bowel habits.
There appears to be an association between IBS and disturbances in the native gut flora.
For example, people with IBS may exhibit reduced Lactobacillus and Bifidobacterium counts and higher levels of potentially harmful Clostridium, Streptococcus, and E. coli.
Human trials indicate that Lactobacillus-rich foods or supplements can ease common IBS symptoms, including abdominal pain.
Animal research suggests certain L. rhamnosus strains may reinforce the gut barrier, potentially helping alleviate IBS complaints.
However, more high-quality human studies are needed before firm recommendations can be made.
3. Supports Gut Health
Like other probiotics, L. rhamnosus benefits digestive health.
As a Lactobacillus, it produces lactic acid, which helps inhibit the survival of harmful bacteria in the gut.
For instance, L. rhamnosus can prevent Candida albicans from colonizing the intestinal lining.
It also promotes the growth of helpful bacteria such as Bacteroides, Clostridia, and bifidobacteria.
Additionally, L. rhamnosus can increase production of short-chain fatty acids (SCFAs) like acetate, propionate, and butyrate.
SCFAs are generated when beneficial gut microbes ferment fiber and serve as fuel for colon cells.
Research links SCFAs with multiple health benefits, including potential protection against colon cancer, support for weight management, and improved blood sugar control.
If you’d like to read more on how gut microbes support digestion and overall wellbeing, see gut health.
4. May Protect Against Cavities
Dental cavities are common, particularly among children.
They result from harmful oral bacteria that produce acids, eroding tooth enamel.
Probiotics such as L. rhamnosus have antimicrobial actions that may help counteract these harmful microbes.
In one study, 594 children received either regular milk or milk supplemented with L. rhamnosus GG five days per week. After seven months, the probiotic group displayed fewer cavities and lower counts of potentially harmful oral bacteria than the control group.
Another trial in 108 adolescents showed that a lozenge containing probiotic strains, including L. rhamnosus GG, significantly reduced bacterial growth and gum inflammation compared with placebo.
Still, further human research is necessary before making definitive recommendations.
5. May Help Prevent UTIs
Urinary tract infections (UTIs) can affect any part of the urinary system, including kidneys, bladder, and urethra.
UTIs are more common in women and are often caused by Escherichia coli and Staphylococcus saprophyticus.
Some evidence suggests certain probiotic strains, including L. rhamnosus, may help prevent UTIs by eliminating harmful bacteria and restoring healthy vaginal flora.
An analysis of five studies with 294 women found several Lactobacillus strains, including L. rhamnosus, were safe and effective for UTI prevention.
Specifically, the L. rhamnosus GR1 strain — administered orally or intravaginally — showed effectiveness against uropathogens.
However, not all L. rhamnosus strains work the same; for example, the GG strain does not adhere well to vaginal tissue and may be less effective.
Although promising, more human trials are needed to confirm these findings.
6–10. Other Possible Benefits
L. rhamnosus has been associated with other potential health advantages, though the supporting evidence is less robust:
- May aid weight loss. Some research suggests L. rhamnosus may curb appetite and food cravings, particularly in women.
- May improve insulin sensitivity. Animal studies indicate several L. rhamnosus strains might enhance insulin sensitivity and glycemic control.
- May lower blood cholesterol. A mouse study found L. rhamnosus reduced cholesterol levels and influenced cholesterol metabolism in a way similar to statin medications.
- May combat allergies. Certain strains of L. rhamnosus could help prevent or ease allergy symptoms by promoting beneficial gut microbes and suppressing harmful ones.
- May assist in treating acne. In a small study of 20 adults, the L. rhamnosus SP1 supplement reduced visible acne.
SummaryL. rhamnosus may enhance digestive health, potentially treating diarrhea, easing IBS, and strengthening gut function. It may also offer protection against dental caries and UTIs. Other purported benefits require more evidence.
Dosage and Recommendations
L. rhamnosus probiotic supplements are available at health stores and online.
Products may contain only L. rhamnosus strains or combine them with other probiotic species.
Probiotics are quantified by colony-forming units (CFU), the count of viable organisms per dose. A typical L. rhamnosus capsule provides about 10 billion CFU.
For general maintenance, one capsule with at least 10 billion live bacteria per day is generally adequate.
To help prevent antibiotic-related diarrhea, take two capsules of L. rhamnosus GG daily providing 10 billion CFU total, or one capsule delivering over 20 billion CFU.
Take the probiotic a few hours after antibiotics and continue for at least one week after finishing the antibiotic course to help reestablish healthy gut flora.
Specific dosing recommendations for other uses are not well established, but a similar daily intake is often suggested.
Remember that L. rhamnosus is frequently added to dairy products — including yogurts and milk — and to cheeses to support ripening, so your diet may already supply some of this bacterium.
SummaryL. rhamnosus is available as a supplement and is commonly included in certain foods, especially dairy, so dietary sources may provide additional intake.
Safety and Side Effects
Products containing L. rhamnosus are typically safe and well tolerated, with few adverse effects.
Some individuals may experience mild bloating or gas.
However, people with weakened immune systems — for example those with HIV, AIDS, or undergoing cancer treatment — should avoid L. rhamnosus and other probiotics (including probiotic-fortified dairy), as these supplements could potentially cause infection.
Similarly, if you take medications that suppress immunity — such as corticosteroids, chemotherapy, or drugs for organ transplantation — probiotics are generally not recommended.
If you meet these criteria or have concerns about side effects, consult your healthcare provider before using probiotic supplements or probiotic-containing foods.
SummaryL. rhamnosus is usually safe with minimal side effects, but those with compromised immunity or on certain medications should either avoid probiotics or discuss them with a medical professional first.
The Bottom Line
L. rhamnosus is a beneficial bacterium naturally present in the gut.
Its possible health effects include easing IBS symptoms, helping treat diarrhea, supporting gut health, and offering some protection against cavities.
L. rhamnosus is available as a supplement and is found in some dairy products.
If you wish to improve digestive health, consider trying L. rhamnosus, and consult a healthcare provider if you have health conditions or are taking medications that could interact with probiotic use.
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