Cured at 30 days: 88% vs 40%
Anukam 2006, Microbes and Infection · Source
Lactobacillus reuteri
Strain UALre-16 (UAS Labs)
A friendly bacterium of the human gut, also found in breast milk, and one half of the most-studied probiotic pair in women's health.
544women in a vaginal flora trial of a related strain
Breast milkone of the places it's naturally found
10strains in the Daily Probiotic blend
Why we love it
L. reuteri is one of the species that naturally live in the human gut. It is also part of the best-known oral probiotic pairing studied in women, so we wanted it alongside L. rhamnosus in our blend.
What does the research show?
Bacterial vaginosis (BV)
Researchers gave oral RC-14 with GR-1 alongside antibiotics. In a trial of 125 women, 88% were cured at 30 days compared with 40% on antibiotics plus placebo. A trial of 544 women found healthy flora returned in 62% vs 27% on placebo. A later trial of 126 women in China found no added benefit.
Vaginal yeast
In 55 women given one dose of fluconazole, those who also took RC-14 with GR-1 for 4 weeks had less yeast on culture (10% vs 39%).
Urinary tract
In 252 postmenopausal women with repeat UTIs, the pair was less effective than a daily antibiotic over a year, but did not raise antibiotic resistance.
Pregnancy
In 110 pregnant women carrying group B strep, 43% tested negative after taking the pair, compared with 18% on placebo.
Babies and children
The strain DSM 17938 was studied in 345 babies with colic. Breastfed babies cried about 25 minutes less per day by day 21. In 336 children in day care, it was linked with fewer diarrhea episodes and fewer days of respiratory infection.
Bone
In 90 women aged 75 to 80, the strain ATCC PTA 6475 was linked with less bone loss in the shin over a year (0.8% vs 1.9% on placebo).
Studies
Human study tested in people Lab study a starting point, not proof
Studies on other strains of this species
Healthy flora at about 6 weeks: 62% vs 27%
Vujic 2013 · Source
Yeast on culture at 4 weeks: 10% vs 39%
Martinez 2009, Letters in Applied Microbiology · Source
43% tested negative vs 18%
Ho 2016, Taiwanese Journal of Obstetrics and Gynecology · Source
About 25 fewer minutes of crying per day at day 21 in breastfed babies; no clear effect in formula-fed babies
Sung 2018, Pediatrics · Source
99 vs 152 diarrhea episodes; fewer days of respiratory infection
Gutierrez-Castrellon 2014, Pediatrics · Source
Shin bone density fell 0.8% vs 1.9% over 12 months
Nilsson 2018, Journal of Internal Medicine · Source
No added benefit over antibiotics alone
Zhang 2021, Frontiers in Cellular and Infection Microbiology · Source
Less effective than a daily antibiotic; no rise in antibiotic resistance
Beerepoot 2012, Archives of Internal Medicine · Source
Which strain do we use?
Our strain is L. reuteri UALre-16 (UAS Labs). It was also one of 10 strains in a small oral blend study (Martoni 2022), where vaginal pH fell slightly over 28 days. The other studies on this page used other strains of this species, and results belong to the strain tested.
Is L. reuteri safe to take?
The trials above reported no serious side effects, and side effects in the bone study were no different from placebo. Ask a clinician first if you have a weakened immune system, a central line or catheter, a serious illness, or are pregnant or breastfeeding.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed: November 2026.
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Reviewed by the Momotaro Apotheca medical team, including OB-GYNs and naturopathic doctors. Educational information, not medical advice. All ingredient research