Compound or practice · Nutrition

Probiotics

Strain-specific or nothing — real benefits for antibiotic-associated diarrhea and some IBS, but 'contains 40 billion CFU' is not a mechanism.

Overall grade: Grade B
Last revised: Jul 10, 2026; 2
graded outcomes: 0
references listed

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A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.

3 at grade B — 3 graded rows

What is known

Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.

Outcome	Grade	Effect size	Agreement
Antibiotic-associated diarrheaSpecific strains	Evidence grade B	Moderate	high
IBS symptomsStrain-dependent	Evidence grade B	Small	mixed

Antibiotic-associated diarrheaEvidence grade B
Specific strains
Moderatehigh
IBS symptomsEvidence grade B
Strain-dependent
Smallmixed

Conditions

How the entry reads its effect on diagnosed conditions: the direction first, then the grade. Never a substitute for the person who treats you.

IBS May improveEvidence grade BStrain-specificGrade B

What is uncertain

Read off the same rows as above. Nothing here is added that the entry does not itself record.

Studies disagree: IBS symptoms (mixed agreement).

Interactions

Documented pairings with supplements and medicines. A medicine on this list is a conversation for whoever prescribes it.

AntibioticsMind the timing
Take 2+ hours from doses; continue 2 weeks after the course.

The evidence in words

What it is

Probiotics are live microorganisms (specific strains of Lactobacillus, Bifidobacterium, Saccharomyces boulardii, etc.) intended to confer a health benefit. Effects are strain- and condition-specific.

How it works

Particular strains compete with pathogens, produce short-chain fatty acids and bacteriocins, and modulate gut immunity and barrier function — but these effects do not generalize across strains.

What the evidence shows

The best evidence is for preventing antibiotic-associated diarrhea (notably S. boulardii and specific Lactobacillus strains) and for some IBS symptoms; benefits in other conditions are strain-dependent and often weak. The category's biggest problem is products marketed on total CFU count rather than the specific strain trialed for your goal.

How to use it

Match the strain to the goal (e.g., S. boulardii around antibiotics), take separated from the antibiotic dose, and continue for a couple of weeks after a course.

Safety & interactions

Safe for most; use caution in the severely immunocompromised or critically ill, where invasive infections have rarely occurred. antibiotics — Take 2+ hours from doses; continue 2 weeks after the course.

Bottom line

Pick the strain trialed for your specific goal, not the biggest CFU number. Best for antibiotic-associated diarrhea and some IBS; skip generic 'gut health' blends.

How it is used

As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.

Standard: Strain matched to goal; separate from antibiotics.

Entries that share this one's tags or conditions.

Probiotics for IBSEvidence grade B — Strain-specificEvidence grade B
Probiotics for Antibiotic-associated diarrheaEvidence grade B — Specific strainsEvidence grade B
Probiotics for IBS symptomsEvidence grade B — Strain-dependentEvidence grade B
Probiotics: dosage and how to take itStrain matched to goal; separate from antibiotics.Evidence grade B

Sources

This entry lists no references of its own.

Last revised Jul 10, 2026. A grade is this entry's reading of the evidence, not medical advice.