Daily gut routine
Jarrow Formulas Saccharomyces Boulardii + MOS
A delayed-release capsule of the probiotic yeast with a prebiotic added, guaranteed at five billion viable cells to the best-by date.
- Format
- Capsule, once a day
- Type
- Probiotic
- Cost
- $0.32 a day
- Customer rating
- 4.6 out of 5 from 5,503 ratings from Amazon
What customers consistently report
- Loose stools and urgency easing over the first few weeks
- No noticeable side effects for most, which reviewers contrast with other probiotics
- Well priced for a three-month supply
Those are the themes that recur across the reviews. High review confidence — 4.6 from 5,503 Amazon ratings on the 90-capsule listing.
Why it might work
Saccharomyces boulardii is a yeast that antibiotics leave alone, which is why the species is taken alongside an antibiotic course and for traveler’s diarrhea; it binds some bacterial toxins, supports the gut lining and settles the inflammatory response to an infection before leaving the gut within days of stopping. Jarrow pairs it with mannan-oligosaccharides, a prebiotic proposed to bind unwanted bacteria and feed beneficial ones, in a delayed-release capsule meant to carry the yeast past stomach acid.
What the research supports
Species-level evidence, strain unnamed. The 21-trial meta-analysis in 4,780 people showing Saccharomyces boulardii cut antibiotic-associated diarrhea used the CNCM I-745 strain (Florastor). A 2026 genomic study found five commercial S. boulardii isolates shared the lineage’s probiotic-relevant traits, which supports the species doing the same kind of thing without proving this product does. MOS, the added prebiotic, has animal-feed evidence and little human data at this dose.
What the label discloses
A minimum of five billion viable cells per capsule is stated under recommended storage through the best-by date, which is the more useful way to state a count. Delayed-release capsule; the added mannan-oligosaccharide (MOS) amount is on the label. Jarrow states the formula is vegan, non-GMO and made without wheat, soy, dairy, egg, fish, shellfish, peanuts or tree nuts. No third-party testing certificate is published.
Who this tends to suit
We match this product to people reporting loose stools, urgency and general abdominal discomfort. It fits someone whose priority is resetting after a course of antibiotics or an upset or day-to-day comfort. Whether it is the best fit for you depends on the rest of your answers — what you have already tried, what format you will take, and anything that has to be ruled out.
Where it may not fit
The label supports vegan, gluten-free, dairy-free and no added sweeteners. A capsule only works if you will take it once a day, every day.
Side effects and what to be aware of
The label does not name the exact strain, so the clinical trials that were run on Florastor’s strain (CNCM I-745) may not apply to this product. Some buyers report stomach pain or diarrhea in the first days, and a few say the capsules arrived inactive, which is a storage question for any live product. As a live yeast, it is not for anyone immune-suppressed, critically ill or with a central line.
Is this the right one for you?
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Others we researched for the same job
These sit in the same role as Jarrow Formulas Saccharomyces Boulardii + MOS — daily gut routine — so they are the sensible things to weigh it against.
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Related reading
Background on how this type of product works, read from the trial evidence.