Saccharomyces cerevisiae CNCM I-3856 (probiotic yeast)

Q: Does it help IBS?

Results are mixed. Trials in 179 and 100 adults and a 456-person trial in constipation-type IBS reported less abdominal pain, but a 379-person trial in mixed IBS found no overall benefit. A 2023 meta-analysis of 82 probiotic IBS trials rated the evidence for this strain on abdominal pain as low certainty.

Q: Can it be taken with antifungal medicines?

Antifungals can kill live yeast. Health Canada's probiotics monograph directs that yeast probiotics be taken at least 2–3 hours before or after antifungal medicines.

Q: Is it safe during pregnancy or breastfeeding?

Reliable data are lacking. The IBS trials report no data in pregnant or breastfeeding women; NCCIH gives no pregnancy-specific probiotic safety data and notes many supplements have not been tested in pregnant women or nursing mothers.

Q: Is S. cerevisiae the same as S. boulardii?

Health Canada notes S. boulardii is a subtype within the species S. cerevisiae, but CNCM I-745 (S. boulardii) and CNCM I-3856 are different strains with separate trials. Results for one do not transfer to the other.

Q: Is it the same as baker's or brewer's yeast?

It is the same species, but the trials tested one specific live strain at defined doses. Baking yeast and inactive nutritional yeast were not tested.

Q: Who should not use it?

Health Canada contraindicates probiotics for people with weakened immunity. ODS links S. cerevisiae probiotics to bloodstream yeast infections, mostly in ICU patients or people with central catheters.

Q: Who funded the research?

Lesaffre, which makes the strain, employed authors on four of the five trials and analyses; the 2016 trial was publicly funded, and the Indian trial's authors include staff of a pharmaceutical company.

Also called S. cerevisiae I-3856, CNCM I-3856, probiotic baker's yeast, Saccharomyces cerevisiae probiotic.

Best grade B across 5 graded outcomes Other Last checked Oct 21, 2026

The short answer

From 11 sources

Saccharomyces cerevisiae CNCM I-3856 is a live probiotic yeast strain, distinct from S. boulardii CNCM I-745. In IBS trials it reduced abdominal pain in some studies, including a 456-person trial in constipation-predominant IBS, but a 379-person trial found no overall benefit. Most trials were run or funded by the strain's maker, Lesaffre.

Every graded outcome on this page

5 rows · line = participants

Grade BAbdominal pain in constipation-predominant IBSIBS painn 456
Grade CPooled abdominal pain and bloating in IBSIBS painn 579
Grade CAbdominal pain and discomfort in IBSIBS painn 179
Grade CAbdominal pain and stool consistency as an add-on to standard IBS careIBS painn 100
No effectAbdominal pain and discomfort across IBS subtypesIBS painn 379
2 more graded outcomes, in the evidence chapter

Key facts

IBS with constipation: 45.1% vs 33.9% were abdominal-pain responders after 8 weeks in 456 adults with IBS-C (8 billion CFU/day)¹
Mixed IBS trial: 1,000 mg/day for 12 weeks gave no overall benefit on pain or discomfort in 379 adults with IBS; only the constipation subgroup improved²
Industry role: Lesaffre, which makes the strain, employed authors of four of the five trials and analyses; the 2016 trial itself was publicly funded through a French collaborative program^1,2,3,6
Fungemia risk: ODS counts at least 60 published reports of bloodstream yeast infection with S. cerevisiae probiotics, many in ICU patients or people with central catheters⁷
Health Canada: Lists S. cerevisiae in its probiotics monograph and contraindicates probiotics for people with an immune-compromised condition⁸

What it is

Saccharomyces cerevisiae CNCM I-3856 is a live probiotic strain of baker's yeast studied mainly for irritable bowel syndrome.

How it works

Proposed

As a live yeast, CNCM I-3856 passes through the gut and was recovered in the stool of 90% of women taking it in one study. How it might ease abdominal pain is not established; trial authors propose anti-inflammatory and pain-signalling effects from lab models, which have not been confirmed in people.^5,4

Forms, side by side

2 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.

Saccharomyces cerevisiae CNCM I-3856 (probiotic yeast) forms compared

2 forms

Saccharomyces cerevisiae CNCM I-3856 (probiotic yeast) forms compared: 2 forms by 3 attributes. Empty cells are labelled No data yet, or Not graded in the evidence row.
2 forms	Live S. cerevisiae CNCM I-3856 capsules	S. boulardii CNCM I-745 (different strain)
Absorption in people	Not absorbed; it passes through the gut alive. In 60 healthy women it was found in the stool of 90% and in vaginal samples of 16-21% during supplementation.⁵	No head-to-head human data⁸
GI tolerance	No serious product-related adverse events were reported in the IBS trials of 8-12 weeks.^2,4	Health Canada applies the same probiotic cautions to S. boulardii and S. cerevisiae.⁸
Studied for	Irritable bowel syndrome symptoms	Antibiotic-associated diarrhea risk (see its own page)

Live S. cerevisiae CNCM I-3856 capsules
Absorption in people
Not absorbed; it passes through the gut alive. In 60 healthy women it was found in the stool of 90% and in vaginal samples of 16-21% during supplementation.⁵
GI tolerance
No serious product-related adverse events were reported in the IBS trials of 8-12 weeks.^2,4
Studied for
Irritable bowel syndrome symptoms
S. boulardii CNCM I-745 (different strain)
Absorption in people
No head-to-head human data⁸
GI tolerance
Health Canada applies the same probiotic cautions to S. boulardii and S. cerevisiae.⁸
Studied for
Antibiotic-associated diarrhea risk (see its own page)

What the human research says

Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.

Trial map

5 graded outcomes, largest study first

5 graded outcomes: 3 improved, 1 mixed, 1 no effect. The largest, a 2017 meta-analysis of 579 people on pooled abdominal pain and bloating in IBS, found mixed results.

By sizeTable

1Pooled abdominal pain and bloating in IBS

Mixed · Grade C · Meta-analysis, 579 people, 2017

Individual data from the 2015 and 2016 IBS trials

Dose, result and source

Every graded outcome on this page, largest study first
Outcome	Found	People	Study	Who was studied
Pooled abdominal pain and bloating in IBS	Mixed	579	Grade C · Meta-analysis, 2017	Individual data from the 2015 and 2016 IBS trials
Abdominal pain in constipation-predominant IBS	Improved	456	Grade B · RCT, 2022	Adults with irritable bowel syndrome with predominant constipation (IBS-C)
Abdominal pain and discomfort across IBS subtypes	No effect	379	No-effect grade · RCT, 2016	Adults with IBS of all subtypes
Abdominal pain and discomfort in IBS	Improved	179	Grade C · RCT, 2015	Adults with IBS (Rome III); 84-88% women
Abdominal pain and stool consistency as an add-on to standard IBS care	Improved	100	Grade C · RCT, 2020	Newly diagnosed adults with IBS (diarrhea, constipation and mixed subtypes), Chennai, India

Every graded row

5 rows

Form tested

Showing 5 of 5 outcomes. Human trials only.

Grade BAbdominal pain in constipation-predominant IBSIBS painMore pain respondersRCT
n 456 · 2022

Improved More abdominal-pain responders with the yeast (45.1% vs 33.9%, p = 0.017) and a higher quality-of-life score; the area-under-the-curve pain measure (p = 0.073), stool frequency and stool consistency did not differ.

Design: RCT, n = 456, 2022
Population: Adults with irritable bowel syndrome with predominant constipation (IBS-C)
Form: S. cerevisiae CNCM I-3856 capsules
Dose: 8 × 10^9 CFU/day
Duration: 8 weeks
Source: Reference 1 · PubMed 35979259 (opens PubMed)

Grade CPooled abdominal pain and bloating in IBSIBS painModest, inconsistent benefitMeta-analysis
n 579 · 2017

Mixed Abdominal pain/discomfort was 12.3% lower than placebo during the second month (p = 0.013) and stool consistency improved, but symptom scores did not differ between groups at the end of supplementation.

Design: Meta-analysis, n = 579, 2017
Population: Individual data from the 2015 and 2016 IBS trials
Form: S. cerevisiae CNCM I-3856
Dose: 500-1,000 mg/day
Duration: 8-12 weeks
Source: Reference 6 · PubMed 28127207 (opens PubMed)

Grade CAbdominal pain and discomfort in IBSIBS painMore pain respondersRCT
n 179 · 2015

Improved More abdominal-pain responders in the last 4 weeks (63% vs 47%, p = 0.04; OR 1.88, 95% CI 0.99-3.57). Other symptoms showed only non-significant trends; stool frequency and consistency did not change.

Design: RCT, n = 179, 2015
Population: Adults with IBS (Rome III); 84-88% women
Form: S. cerevisiae (identified as CNCM I-3856 in the later pooled analysis)
Dose: 500 mg/day
Duration: 8 weeks, then 3-week washout
Source: Reference 3 · PubMed 25488056 (opens PubMed)

Grade CAbdominal pain and stool consistency as an add-on to standard IBS careIBS painLess pain vs placeboRCT
n 100 · 2020

Improved Abdominal pain fell more than with placebo, and stool consistency improved in the diarrhea subgroup (p < 0.001), with similar changes in the other subgroups. No serious adverse events.

Design: RCT, n = 100, 2020
Population: Newly diagnosed adults with IBS (diarrhea, constipation and mixed subtypes), Chennai, India
Form: S. cerevisiae CNCM I-3856
Dose: 2 × 10^9 CFU twice daily, added to standard care
Duration: 8 weeks
Source: Reference 4 · PubMed 31807856 (opens PubMed)

No effectAbdominal pain and discomfort across IBS subtypesIBS painNo overall effectRCT
n 379 · 2016

No effect No overall benefit on the primary responder endpoint, symptoms or wellbeing. In the constipation subgroup, abdominal pain and bloating improved vs placebo (subgroup finding needing confirmation).

Design: RCT, n = 379, 2016
Population: Adults with IBS of all subtypes
Form: S. cerevisiae CNCM I-3856
Dose: 1,000 mg/day
Duration: 12 weeks
Source: Reference 2 · PubMed 27403301 (opens PubMed)

What the numbers add up to

Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.

The biggest neutral trial vs the biggest positive one

The 379-person mixed-IBS trial found no overall benefit, while the 456-person trial limited to IBS-C met its pain endpoint. The evidence fits a possible effect in constipation-type IBS, not IBS in general.^1,2

Studied doses

Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.

Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Doses studied in human trials

Doses studied in human trials ranged from 500 mg to 1,000 mg of yeast per day, or 4 to 8 billion CFU per day, for 8 to 12 weeks. These are research doses, not recommendations.^1,2,3,4

Interactions and safety

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

What Saccharomyces cerevisiae CNCM I-3856 meets

1 cited row

Medicines 1

Saccharomyces cerevisiae CNCM I-38561 medicine · 0 supplements

Supplements and foods 0

No supplement rows in our sources.

Drug label or FDA notice

Interactions

1 agent

Published interactions, grouped by kind
Agent	What the source says	Evidence
Medicines1
Antifungal medicines	Antifungals can kill live yeast. Health Canada's probiotics monograph directs that yeast probiotics be taken at least 2-3 hours before or after antifungal medications.⁸	Drug label

Check with what you take

Kept on this device only

Add what you take. We list every interaction our evidence profiles cite between Saccharomyces cerevisiae CNCM I-3856 and your picks, and between your picks.

Add a supplement or medicine

Most cited:

Add a supplement or medicine you take to check it against Saccharomyces cerevisiae CNCM I-3856.

Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.

Who should be careful

5 groups

Weakened immune system: Health Canada contraindicates probiotics, including S. cerevisiae, for people with an immune-compromised condition (for example AIDS, lymphoma or long-term corticosteroid use).⁸
Hospital patients and central lines: ODS reports at least 60 published cases of fungemia linked to S. cerevisiae probiotics, many in ICU patients, people on tube or IV feeding, those with central venous catheters or on broad-spectrum antimicrobials. NCCIH says the risk of harm is greater in seriously ill people.^7,9
Fever or severe digestive symptoms: Health Canada advises asking a health care practitioner before use with fever, vomiting, bloody diarrhea or severe abdominal pain, and stopping if digestive upset worsens or lasts beyond 3 days.⁸
Pregnancy and breastfeeding: None of the IBS trials studied pregnant or breastfeeding women, and the agency probiotic sources give no strain-specific pregnancy data. NCCIH notes many supplements have not been tested in pregnant or nursing women and advises consulting a health care provider before using a probiotic.^9,10
Premature infants: NCCIH notes the FDA has warned that premature infants given probiotics are at risk of severe, potentially fatal infections.⁹

How to read the label

What to check on the Supplement Facts panel.

How to read the label

4 checks

Check the strain number

The IBS trials tested S. cerevisiae CNCM I-3856. S. boulardii CNCM I-745 is a different strain with its own trials, so a label naming only the species does not tell you which evidence applies.^1,2,8

Live probiotic, not baking or nutritional yeast

The trials used one live strain at set doses; baking yeast and inactive nutritional yeast were not tested.^8,1

Milligrams or CFU

Trials stated doses as 500–1,000 mg of yeast a day or 4–8 billion CFU a day. Health Canada counts CFU from all live organisms in a product, so in a blend the S. cerevisiae share can be smaller than the total.^2,3,1,4,8

Spacing from antifungals

Health Canada directs that yeast probiotics be taken at least 2–3 hours before or after antifungal medicines.⁸

Have the bottle? Photograph its Supplement Facts panel and see each line, saccharomyces cerevisiae cncm i-3856 (probiotic yeast) included, beside the doses and forms the trials used in Label X-Ray.

Frequently asked questions

Short answers to common questions; the numbers link to the sources below.

Common questions

7 answers

Does it help IBS?

Results are mixed. Trials in 179 and 100 adults and a 456-person trial in constipation-type IBS reported less abdominal pain, but a 379-person trial in mixed IBS found no overall benefit. A 2023 meta-analysis of 82 probiotic IBS trials rated the evidence for this strain on abdominal pain as low certainty.^1,2,3,4,11

Can it be taken with antifungal medicines?

Antifungals can kill live yeast. Health Canada's probiotics monograph directs that yeast probiotics be taken at least 2–3 hours before or after antifungal medicines.⁸

Is it safe during pregnancy or breastfeeding?

Reliable data are lacking. The IBS trials report no data in pregnant or breastfeeding women; NCCIH gives no pregnancy-specific probiotic safety data and notes many supplements have not been tested in pregnant women or nursing mothers.^9,10

Is S. cerevisiae the same as S. boulardii?

Health Canada notes S. boulardii is a subtype within the species S. cerevisiae, but CNCM I-745 (S. boulardii) and CNCM I-3856 are different strains with separate trials. Results for one do not transfer to the other.⁸

Is it the same as baker's or brewer's yeast?

It is the same species, but the trials tested one specific live strain at defined doses. Baking yeast and inactive nutritional yeast were not tested.^8,1

Who should not use it?

Health Canada contraindicates probiotics for people with weakened immunity. ODS links S. cerevisiae probiotics to bloodstream yeast infections, mostly in ICU patients or people with central catheters.^7,8

Who funded the research?

Lesaffre, which makes the strain, employed authors on four of the five trials and analyses; the 2016 trial was publicly funded, and the Indian trial's authors include staff of a pharmaceutical company.^1,2,3,4,6

Sources

11 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.

Sources cited on this page

11 sources

1Saccharomyces cerevisiae I-3856 in irritable bowel syndrome with predominant constipation.RCT World J Gastroenterol, 2022 · PMID 35979259
2Randomized double blind placebo-controlled trial of Saccharomyces cerevisiae CNCM I-3856 in irritable bowel syndrome: improvement in abdominal pain and bloating in those with predominant constipation.RCT United European Gastroenterol J, 2016 · PMID 27403301
3A randomized clinical trial of Saccharomyces cerevisiae versus placebo in the irritable bowel syndrome.RCT Dig Liver Dis, 2015 · PMID 25488056
4Efficacy of Saccharomyces cerevisiae CNCM I-3856 as an add-on therapy for irritable bowel syndrome.RCT Int J Colorectal Dis, 2020 · PMID 31807856
5Recovery of Saccharomyces cerevisiae CNCM I-3856 in Vaginal Samples of Healthy Women after Oral Administration.RCT Nutrients, 2020 · PMID 32722250
6Saccharomyces cerevisiae CNCM I-3856 in irritable bowel syndrome: An individual subject meta-analysis.Meta-analysis World J Gastroenterol, 2017 · PMID 28127207
7Probiotics: Fact Sheet for Health ProfessionalsFact sheet NIH Office of Dietary Supplements, 2025 · ods.od.nih.gov
8Natural Health Product Monograph: ProbioticsGuideline Health Canada (NNHPD), 2026 · webprod.hc-sc.gc.ca
9Probiotics: Usefulness and SafetyFact sheet National Center for Complementary and Integrative Health (NCCIH), 2019 · nccih.nih.gov
10Using Dietary Supplements WiselyFact sheet National Center for Complementary and Integrative Health (NCCIH), 2019 · nccih.nih.gov
11Efficacy of Probiotics in Irritable Bowel Syndrome: Systematic Review and Meta-analysis.Meta-analysis Gastroenterology, 2023 · PMID 37541528

What changed

Every dated change to this page: what changed, who made it and why.

Change log

2 entries

Dated changes to this page
Date	Change	Who and why
Oct 21, 2026label guide, FAQ	Added a label guide (strain number, live versus nutritional yeast, milligrams versus CFU, antifungal spacing) and FAQs on antifungal medicines and pregnancy; cited a 2023 meta-analysis of 82 probiotic IBS trials (PMID 37541528) that rated evidence for CNCM I-3856 on abdominal pain as low certainty. It is not a table row because its abstract gives no strain-level sample size. PubMed search for 2023–2026 trials of this strain found no newer RCT. Fact-checked against the sources; corrected: the pregnancy answer now says the trials report no data in these groups rather than asserting who they enrolled.	Writer: Kymata Health EditorialTrigger: A–Z page audit
Oct 14, 2026all	Initial editorial evidence review	Writer: Kymata Health EditorialTrigger: new page

Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.

Saccharomyces cerevisiae CNCM I-3856 (probiotic yeast)

Medicines 1

Supplements and foods 0

Antifungal medicines