Daily gut routine
NOW Foods Saccharomyces Boulardii 5 Billion CFU
The same probiotic yeast species as Florastor, without a named strain, at about a fifth of the price.
- Format
- Capsule
- Type
- Probiotic
- Cost
- $0.45 a day
- Customer rating
- 4.6 out of 5 from 4,363 ratings from Amazon
What customers consistently report
- Loose stools and travel-related upset settling, sometimes within a day or two
- Holding up during a course of antibiotics
- Costing a fraction of the branded yeast for the same species
Those are the themes that recur across the reviews. High review confidence — 4.6 from 4,363 Amazon ratings shared across the 60- and 120-capsule listings.
Why it might work
Saccharomyces boulardii is a yeast rather than a bacterium, so antibiotics do not kill it, which is why the species is the usual choice alongside an antibiotic course or for traveler’s diarrhea. It is thought to work by binding some bacterial toxins, supporting the gut lining and dampening the inflammatory response to an infection, and it passes out of the gut within days of stopping. The NOW capsule delivers the species at five billion CFU without naming which isolate it is.
What the research supports
Species-level evidence, strain unnamed. A meta-analysis of 21 randomized trials in 4,780 people found Saccharomyces boulardii cut the risk of antibiotic-associated diarrhea, but those trials used the CNCM I-745 strain sold as Florastor. A 2026 genomic study of five commercial S. boulardii isolates found probiotic-relevant traits — acid tolerance, acetate production, suppression of inflammatory signaling in gut cells — conserved across the lineage, which is the best available argument that an unnamed isolate behaves the same way. It is a laboratory finding, not a trial of this product.
What the label discloses
Five billion CFU per capsule in a cellulose capsule with organic inulin and guar gum. NOW states NPA A-rated GMP certification, and the label prints the strain as Saccharomyces cerevisiae var. boulardii I-3799. Whether the CFU is guaranteed through the best-by date is stated as conditional on refrigeration.
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 as often as the label directs.
Side effects and what to be aware of
The label gives the species and the dose but not the exact strain, so the clinical trials that were run on Florastor’s strain (CNCM I-745) may not apply to this product. The capsules contain inulin, which some people find bloating. NOW says refrigerate on arrival to hold potency to the best-by date. 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 NOW Foods Saccharomyces Boulardii 5 Billion CFU — daily gut routine — so they are the sensible things to weigh it against.
See all the products we have researched →
Related reading
Background on how this type of product works, read from the trial evidence.