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Probiotic strain · 21 human trials behind this page

Saccharomyces boulardii: what the human trials show

Saccharomyces boulardii (S. cerevisiae var. boulardii)

Saccharomyces boulardii is a probiotic yeast with some of the strongest evidence of any probiotic for one job: lowering the chance of diarrhea while you take antibiotics. Pooled trials cut that risk roughly in half, in both children and adults.

The studies, one by one

  1. 2015Meta-analysis of 21 randomized trialsFavored the strain

    4,780 children and adults taking antibiotics

    Antibiotic-associated diarrhea fell from 18.7% to 8.5% with S. boulardii (about half the risk; 10 people treated to prevent one case). The benefit held in children (6 trials) and adults (15 trials). Diarrhea from C. difficile fell significantly only in children.

    Szajewska H, Kołodziej M Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Alimentary Pharmacology & Therapeutics, 2015. PubMed 26216624

  2. 2012Meta-analysis of 63 randomized trials (all probiotic types, including Saccharomyces)Favored the strain

    11,811 people taking antibiotics

    Probiotics as a group lowered antibiotic-associated diarrhea by about 42% (13 people treated to prevent one case). The authors noted that strains were often poorly documented, so this supports the category more than any one product.

    Hempel S, Newberry SJ, Maher AR, et al. Probiotics for the prevention and treatment of antibiotic-associated diarrhea: a systematic review and meta-analysis. JAMA, 2012. PubMed 22570464

What the evidence doesn't show

  • The evidence is for preventing diarrhea during antibiotics, not for weight, blood sugar or general gut health.
  • Preventing diarrhea is not the same as rebuilding your gut bacteria after antibiotics; diet and time do most of that work.
  • The protection against C. difficile diarrhea was significant in children only.

How to find it on a label

Unlike most probiotics, S. boulardii is a yeast, not a bacterium, so antibiotics do not kill it. That is the reason it is taken alongside a course of antibiotics rather than after. A label that names a strain code tells you more than one that names only the species.

Names you may see: Saccharomyces boulardii · S. boulardii · S. cerevisiae var. boulardii

Is it in anything we rank?

None of the products on our metabolic probiotic ranking lists this strain.

Related reading

Questions

Should I take Saccharomyces boulardii with antibiotics?

It is one of the best-supported options for lowering the chance of antibiotic-associated diarrhea: across 21 trials the risk fell from about 19% to 8.5%. Ask your clinician or pharmacist before adding it.

Can I take S. boulardii at the same time as an antibiotic?

It is a yeast, so antibacterial drugs do not kill it, which is why the trials gave it during the antibiotic course. That is different from a bacterial probiotic, which the antibiotic can kill.

Does S. boulardii help weight loss or blood sugar?

Not on the evidence here. Its trials measured diarrhea during antibiotics. For strains with weight or metabolic data, see the strain list linked on this page.

All probiotic strains · Strain-to-evidence lookup · Medical disclaimer

General information, not medical advice. Probiotic effects are strain-specific and modest; talk to a clinician about new, severe or persistent symptoms.