Lactobacillus Rhamnosus: What Human Research Shows, Strain by Strain

Quick answer. Lactobacillus rhamnosus, now formally named Lacticaseibacillus rhamnosus, is a lactic acid bacterium, and human trials have tested specific coded strains of it, not the species as a whole. For L. rhamnosus GG (LGG), a meta-analysis found fewer cases of antibiotic-associated diarrhea in children, but large trials found no benefit in children with acute gastroenteritis, in critically ill adults, or for preventing eczema. Strain HN001 cut eczema by about half in one New Zealand infant trial, and strain GR-1, usually paired with RC-14, has mixed results for vaginal outcomes. Side effects in trials were usually mild, but bloodstream infections have been documented, mostly in seriously ill people, and the FDA has warned that probiotics can cause invasive, potentially fatal disease in preterm infants.

What Lactobacillus rhamnosus is

L. rhamnosus is a species of bacteria. In 2020, taxonomists split the old Lactobacillus genus into 25 genera based on whole-genome data, and L. rhamnosus moved to the new genus Lacticaseibacillus. The NIH Office of Dietary Supplements (ODS) lists LGG as "Lacticaseibacillus (formerly Lactobacillus) rhamnosus GG." This article uses the familiar name.

The strain is what was tested. ODS describes a probiotic by genus, species and strain, and notes that effects can be strain-specific. This article covers three strains:

• LGG (ATCC 53103), a strain of human intestinal origin. It became available as a probiotic in Finland in 1990.
• HN001, tested in pregnancy and infant trials in New Zealand, among others.
• GR-1, selected for urogenital use and usually tested together with RC-14, a strain first reported as L. fermentum and later as L. reuteri.

Other strains, such as R0011, appear in products and trials too. A study of one coded strain does not tell you what an unnamed strain of the same species will do.

Forms in trials. Capsules or capsule contents mixed into liquid, powder through a feeding tube in intensive care, and vaginal capsules. Route matters: a vaginal-capsule result is not evidence for a swallowed capsule.

What human studies have tested

What the findings suggest

LGG and antibiotic-associated diarrhea. In a 2015 meta-analysis, LGG lowered AAD in children (moderate quality of evidence). In adults the result was not statistically significant, except in a small subset taking antibiotics for H. pylori. Strength: moderate in children, low in adults.

LGG for acute gastroenteritis in children. Earlier small trials suggested benefit. The 2018 U.S. trial, with 971 children, found no difference in severity, diarrhea duration or day-care absence. Its authors wrote that their findings call into question recommendations to use LGG for this purpose. Strength: a large, well-run null trial in North American emergency departments.

LGG in critical illness. In PROSPECT, the largest LGG trial we found, LGG did not prevent pneumonia or any of 20 secondary outcomes, and the authors concluded the results "do not support the use of L rhamnosus GG in critically ill patients."

LGG and eczema. The 2001 Finnish trial halved eczema by age 2, but three later trials did not repeat this, and a pooled analysis of five trials found no effect, with high to moderate certainty. Strength: consistent evidence of no benefit.

HN001 and eczema. Giving HN001 to mothers and then to infants for two years halved eczema by age 2 in one trial, and the effect lasted to age 4. A Bifidobacterium strain, HN019, had no effect in the same trial. Giving HN001 to mothers alone did not reduce infant eczema, in the same group's later trial or in an independent Finnish trial that paired it with a Bifidobacterium strain. Strength: one positive trial, not replicated by an independent group.

HN001 in pregnancy. Lower gestational diabetes rates and mood scores were secondary outcomes of a trial designed for infant eczema. The diabetes result was significant by one definition and not the other. Strength: low, exploratory.

GR-1 with RC-14 and the vagina. Results split. Oral trials in Canada, Nigeria and Croatia reported more normal flora or higher BV cure rates. A Chinese trial in women with BV and a UK trial in pregnant women found no effect, and in a third trial in pregnant women, Nugent scores returned to normal in 30% of both the probiotic and placebo groups. One small trial of vaginal capsules found higher cure rates than metronidazole gel at days 6 and 15, but not significantly by day 30. Strength: low and inconsistent. Our review of L. crispatus discusses oral versus vaginal delivery in more detail.

What guidelines say. Guideline positions are strain-specific:

• ESPGHAN (European pediatric gastroenterology society). In 2016 it strongly recommended LGG or S. boulardii, with moderate-quality evidence, when probiotics are considered to prevent AAD in children with risk factors. Its 2020 update gave LGG only a weak recommendation for treating acute gastroenteritis, with very low certainty, and made a strong recommendation against the R0011 and R0052 combination. Its 2023 position paper says clinicians may recommend at least 5 billion CFU a day of LGG or S. boulardii, started with the antibiotic, for children with risk factors for AAD (strong recommendation, moderate certainty).
• AGA (American Gastroenterological Association), 2020. It suggests against probiotics for children with acute infectious gastroenteritis in the U.S. and Canada (conditional, moderate quality). The strains it lists for preventing C. difficile infection during antibiotic use do not include LGG. For preterm, low-birth-weight infants it made conditional suggestions that include L. rhamnosus ATCC 53103; see the FDA warning under Safety.
• World Gastroenterology Organisation. As quoted by ODS, for people with weakened immunity or serious underlying disease it advises "restricting probiotic use to the strains and indications that have proven efficacy."

Where the evidence is limited or conflicting

• Large trials overturned small ones. The LGG findings for gastroenteritis and eczema shifted when larger trials arrived, and PROSPECT did not confirm earlier, smaller probiotic trials in critical care.
• Same outcome, different verdicts. Both 2018 gastroenteritis trials were null, yet ESPGHAN rates the two strains differently (see above).
• Wheezing signals. One eczema trial found more recurrent wheezing with LGG (26% vs 9.1%), and the U.S. gastroenteritis trial reported wheezing in 5 children on LGG and none on placebo. A meta-analysis judged the data too limited and called for more study of this possible harm.
• Who runs the trials. HN001 was made by a dairy company that also randomized the capsules and contributed funds to the pregnancy trial. Reid 2003 and both 2006 Nigerian GR-1 trials, all positive, share two authors; a 2020 trial in pregnant women that found no difference included one of them. The positive Croatian trial and the null Chinese and UK trials came from other groups.
• Colonization. In 10 women using vaginal capsules, GR-1 or RC-14 was found for up to 19 days, LGG for up to 5. In pregnant women taking oral capsules, the strains were rarely found in the vagina.

Safety

In trials. NIH ODS states that probiotics are unlikely to cause harm in healthy people and that side effects are usually minor, such as gas. In the U.S. gastroenteritis trial, no child had an LGG infection outside the gut, and adverse event rates did not differ except for wheezing. In the R0011 combination trial, adverse events were reported by 34.8% vs 38.7% on placebo.

Bloodstream infections. These are documented for LGG. A Finnish review of 89 Lactobacillus bacteremia cases found 11 identical to LGG; 82% of patients had severe or fatal underlying illness, and immune suppression, long hospital stays and surgery were risk factors. A 2005 report described 2 patients who developed Lactobacillus sepsis after taking a probiotic, with blood isolates indistinguishable from the product strain. At a Boston children's hospital, 6 of 522 intensive care patients given LGG (1.1%) developed Lactobacillus bacteremia, compared with 2 of 21,652 who were not, and gene analysis linked the blood isolates to the product. In PROSPECT, L. rhamnosus was found in sterile sites or as the main organism in 1.1% on LGG vs 0.1% on placebo. In Finland, a national review found no rise in Lactobacillus bacteremia as LGG use grew after 1990 (about 0.3 cases per 100,000 people a year in 1995–2000).

Preterm infants. In October 2023, the FDA warned that preterm infants given probiotics "are at risk of invasive, potentially fatal disease," and stated that it has not approved any probiotic for use as a drug or biological product in infants.

Pregnancy. HN001 and GR-1/RC-14 have been given through much of pregnancy in trials. The UK GR-1 trial reported no serious adverse events related to the product, and a 12-week trial in pregnant women reported no adverse issues. These trials were not designed to rule out rare harms. Ask your obstetric clinician before use in pregnancy or breastfeeding.

Medicines. We found no documented drug interactions specific to L. rhamnosus. ODS sets no upper intake level for probiotics and lists no interactions. Because these are live bacteria, people taking immune-suppressing medicines, people with a central line, and anyone seriously ill should ask their doctor first. For antibiotic-associated diarrhea, ODS notes that starting within 2 days of the first antibiotic dose worked better than starting later. Ask a pharmacist about timing.

Regulation. Probiotics sold as dietary supplements in the U.S. have not gone through FDA's premarket review for medical uses, according to ODS. In the EU, a 2012 regulation refused the claim that LGG "helps to maintain defence against intestinal pathogens" after EFSA found that a cause-and-effect relationship had not been established.

What research does not establish

• That L. rhamnosus as a species prevents or treats diarrhea, eczema, BV, UTI or any other condition; results belong to specific strains.
• That LGG shortens acute gastroenteritis in children in the U.S. or Canada.
• That oral GR-1 with RC-14 reliably reaches the vagina or prevents BV, including during pregnancy.
• That HN001's eczema result has been confirmed by an independent group.
• That results for any coded strain apply to a product that names only the species.

How we reviewed the evidence

On November 8, 2026, we searched PubMed for LGG meta-analyses and trials on antibiotic-associated diarrhea (19 records), trials naming GR-1 and RC-14 or GR-1 with vaginal use (59, with overlap), and HN001 trials (51; about 35 titles screened), plus citation lookups and searches on infection case reports, D-lactic acidosis and drug interactions. We searched ClinicalTrials.gov (118 records for "rhamnosus GG") and read the NIH ODS fact sheet, FDA's 2023 preterm-infant warning, EU Regulation 379/2012, the ESPGHAN papers and the AGA 2020 guideline text. We included human trials and meta-analyses and one small colonization study, and excluded lab and animal work and multi-strain products unless a trial named an L. rhamnosus strain. We read full texts where available and abstracts otherwise. None of the cited trials is retracted. Vinatura did not run any trials of L. rhamnosus.

Vinatura Research Perspective

We asked four questions of each study: which coded strain, swallowed or placed in the vagina, in whom, and was the result confirmed in a larger or independent trial. Sorted that way, the species name hides three different evidence records. LGG's record has narrowed over time: an early eczema result and small gastroenteritis trials were followed by larger null trials, leaving antibiotic-associated diarrhea in children as its best-supported use. HN001 has one strong infant eczema result from a single research program, using product from the strain's maker. GR-1 with RC-14 has positive oral trials, three of them sharing two authors, and null results from groups in China and the UK.

Doses also differ by strain. The LGG trials in our table that report a dose gave 10 to 20 billion CFU a day, HN001 trials 6 billion, and GR-1 trials about 1 to 2.5 billion of each strain once or twice a day. A CFU number on a label cannot be compared with these unless the strain is the same.

Our assessment: moderate evidence that LGG reduces antibiotic-associated diarrhea in children, and low evidence in adults; consistent evidence that LGG does not help children with gastroenteritis in North American emergency settings or prevent eczema; limited, single-program evidence for HN001 and eczema; low and conflicting evidence for oral GR-1 and vaginal health. An independent replication of the HN001 infant eczema trial, an adult LGG trial focused on antibiotic-associated diarrhea, and an independently funded trial of oral GR-1 and RC-14 that tracks the strains in non-pregnant women with BV would change this assessment.

Where this ingredient appears in Vinatura products

Women's Probiotic lists Lactobacillus rhamnosus Complex 100 mg (2 billion CFU) per 1 delayed-release capsule, with L. crispatus, L. plantarum, L. reuteri, L. gasseri and L. acidophilus complexes. The label does not name strains. The pages of Vinatura's L. Salivarius Oral Probiotic and Akkermansia Muciniphila do not list L. rhamnosus. The studies above did not test this product.

Frequently asked questions

Is L. rhamnosus GG the same as other L. rhamnosus strains? No. LGG, HN001, GR-1 and R0011 are different strains with different trial records, and guidelines treat them differently.

Does LGG help children with stomach flu? In a U.S. trial of 971 children with acute gastroenteritis, LGG did not reduce severity or diarrhea duration compared with placebo, and the AGA suggests against probiotics for this use in the U.S. and Canada.

Can an oral L. rhamnosus capsule reach the vagina? It depends on the strain, and results are mixed. In pregnant women, oral GR-1 and RC-14 were rarely detected in vaginal samples.

Is L. rhamnosus safe? In trials, side effects were usually mild. Bloodstream infections have occurred, mostly in seriously ill or hospitalized people, and FDA has warned that preterm infants given probiotics are at risk of invasive, potentially fatal disease. Follow your product label and ask a healthcare professional if you are pregnant, immunocompromised or seriously ill.

References

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Editorial note: This article reviews published research for educational purposes. It does not establish the effects or safety of any specific supplement, including Vinatura products, and is not medical advice. Written by Vinatura Editorial Team. Last reviewed November 2026.