Multi-Strain Probiotic

Supplements · Probiotics · Supplement, Typed Supps

Different strains genuinely do different things.

Stage by stage

Intake (Enteric-coated capsule): Must survive stomach acid to reach the intestine alive.
Stomach (Acid barrier): Formulation and strain determine how many bacteria survive this stage.
Gut (Temporary colonization): Surviving bacteria interact with existing gut flora and the gut immune system.
Effect (Interacts with existing flora): Surviving bacteria interact with existing gut flora and the gut immune system — effects depend heavily on which specific strains survive.

What the evidence supports

Reducing antibiotic-associated diarrhoea — strong evidence. One of the best-supported uses, with specific strains — particularly Saccharomyces boulardii and certain lactobacilli.
Shortening infectious diarrhoea — moderate evidence. Reasonable support, again strain-specific.
Relieving IBS symptoms — limited evidence. Some strains help some people. Which strain, which symptom, and which person are all poorly predictable, and trials are inconsistent.
General "gut health" or immunity in healthy people — insufficient evidence. The claim doing most of the marketing work, and the one with least behind it. Effects are strain-specific, and most products are not the strains that were studied.

Typical dose

There is no general dose. What has been studied is a particular strain at a particular amount for a particular problem — for example, 1 to 2 x 10^10 CFU daily in the trials of antibiotic-associated diarrhoea in children. Most products on the shelf supply somewhere between 1 and 10 billion CFU per dose, and some advertise 50 billion or more.

Upper limit: No formal upper limit. Higher CFU counts have not been shown to work better, and most trials ran weeks to a few months rather than years

Timing

Depends on the specific strain and product — varies more than most supplements.

Time to effect

Days: Digestive changes.
Weeks: Any broader claimed effects.

Medication interactions

Immunosuppressants: Live organisms carry a real infection risk in immunocompromised people — there are documented cases of fungaemia and bacteraemia. (high)
Antibiotics: Not a contraindication — this is the best-supported use — but separate doses by a couple of hours so the antibiotic does not simply kill the supplement. (moderate)

Common myth

“All probiotics do the same thing.” In reality: Different strains are studied for very different purposes — they’re not interchangeable.

In the glossary

Gut microbiome