L. rhamnosus GG (LGG): The World's Most-Studied Probiotic
Updated June 2026 · 800+ clinical papers · Sources: Szajewska et al. (Aliment Pharmacol Ther), ESPGHAN, NIH ODS
What It Is
Lactobacillus rhamnosus GG (ATCC 53103) was isolated from the intestine of a healthy human in 1983 by Sherwood Gorbach and Barry Goldin at Tufts University. The "GG" designation comes from their surnames. It was the first commercially sold probiotic and remains the most comprehensively studied single probiotic strain, with over 800 published clinical papers as of 2025.
LGG stands out for three biological characteristics: it adheres strongly to intestinal mucus, it survives passage through gastric acid and bile without enteric coating, and it produces pili (hair-like appendages) that allow it to interact with intestinal epithelial cells and stimulate immune signalling. These properties make it one of the few probiotics demonstrably able to transiently colonise the human gut after oral administration.
Culturelle is the principal consumer brand built around LGG. It is sold in over 35 countries and is recommended by multiple national paediatric guidelines. Valio (Finland) also markets LGG dairy products commercially.
What the Evidence Says
Acute Diarrhoea in Children
Strong EvidenceOne of the most studied effects in the probiotic literature. A 2019 meta-analysis (Szajewska et al., Aliment Pharmacol Ther 2019; 15 RCTs, n=3,820) found LGG reduces the duration of acute diarrhoea in children by about 0.85 days (95% CI: -1.15 to -0.56). However, two large 2018 trials (Schnadower et al., NEJM 2018) found no benefit in well-nourished children in high-income settings, so the effect is context-dependent. ESPGHAN still recommends LGG for paediatric acute gastroenteritis, at low certainty of evidence. The effect is strain-specific, not generalisable to all probiotics.
Cite: Szajewska, Kolodziej & Zalewski, Aliment Pharmacol Ther 2019;49(11):1376-84; Schnadower et al., NEJM 2018
Antibiotic-Associated Diarrhoea
Strong EvidenceA 2015 meta-analysis (Szajewska & Kolodziej, Aliment Pharmacol Ther 2015; 12 RCTs, n=1,499) found LGG roughly halved the risk of antibiotic-associated diarrhoea (AAD) overall (RR 0.49, 95% CI 0.29-0.83). The effect was significant in children (RR 0.48) but not in adults overall, except during H. pylori eradication therapy. Clinical practice recommendation: start LGG on day 1 of antibiotic therapy, separate doses by 2-3 hours, and continue for 2-4 weeks after the course ends. Note: S. boulardii (a yeast) has the strongest AAD-prevention evidence; LGG is the best-studied bacterial option.
Cite: Szajewska & Kolodziej, Aliment Pharmacol Ther 2015;42(10):1149-57
Atopic Eczema Prevention
Emerging EvidenceMaternal LGG supplementation in late pregnancy plus postnatal infant supplementation roughly halved the incidence of eczema (atopic dermatitis) in at-risk infants in a landmark Finnish trial (Kalliomaki et al., Lancet 2001: 23% vs 46%, RR 0.51). The benefit persisted at the 4-year follow-up (Kalliomaki et al., Lancet 2003). However, subsequent trials have shown mixed results and the effect is not consistent across settings. Most effective in high-atopic-risk families with a history of eczema or asthma.
Cite: Kalliomaki et al., Lancet 2001;357:1076-79; 4-year follow-up Lancet 2003
IBS
Limited EvidenceUnlike its strong evidence for diarrhoeal disease, LGG alone has limited evidence for IBS. The 2024 network meta-analysis (PMC10490209) did not rank LGG among the top performers for IBS symptom reduction. B. infantis 35624 and L. plantarum 299v have substantially better IBS-specific evidence. Using LGG for IBS is a reasonable and safe approach, but it is not the evidence-preferred choice.
Cite: Ford et al., Am J Gastroenterol 2024; PMC10490209
Dosing
Clinical trials universally use 10 billion CFU per day of LGG. Culturelle's standard formula provides exactly this. The dose should be maintained consistently - LGG does not provide a residual benefit after discontinuation; the effect ends when dosing ends as it is a transient coloniser.
Timing: LGG can be taken with or without food. Unlike some strains, it survives stomach acid without food buffering, though some research suggests slightly better survival when taken with a meal. Refrigeration extends shelf life; the strain is stable at room temperature for limited periods.
Safety
LGG has one of the most extensive safety databases of any probiotic organism. Rare adverse events: case reports of Lactobacillus bacteraemia have been published in immunocompromised patients receiving LGG supplementation (not the majority of cases, and causality is debated in most). The absolute risk for healthy individuals is negligibly low. ESPGHAN, American Academy of Pediatrics, and World Gastroenterology Organisation have all reviewed the safety profile and found LGG appropriate for use in healthy infants, children, and adults.
Products Containing LGG
Affiliate disclosure: links below may be affiliate links.
Culturelle Daily Probiotic (10 billion CFU LGG)
Strong EvidenceThe flagship LGG consumer product. Available in capsule, chewable, and children's formulations. Widely distributed and affordably priced (~$20-28 for 30 days). Good shelf stability.
Culturelle Kids Daily Probiotic (5 billion CFU LGG)
Strong EvidenceChewable tablet for children 1+. Evidence from paediatric trials typically used 10 billion CFU but 5 billion has been used in some paediatric RCTs with effect. Age-appropriate form.
Renew Life Ultimate Flora (multi-strain including LGG)
Emerging EvidenceMulti-strain formulation that includes LGG among multiple Lactobacillus and Bifidobacterium strains. Higher total CFU count.