Viable cells
CFU counts at manufacture can exceed counts at expiry. Cold chains matter for some products.
Most ingested strains pass through. A few persist while you keep taking them. They may acidify a niche, compete for sugars or talk to immune cells — mechanisms proposed, not a guarantee.
They are not a tool for engineering your genome and this page gives no culture or modification recipes.
Parts
Strain designation
Genus, species and an alphanumeric strain ID are the minimum honest label.
Matrix (yoghurt vs pill)
Food matrices can buffer acid. A freeze-dried pill is a different journey.
Acid and bile resistance
Selection criteria in papers, not a reason to swallow random soil.
Prebiotic partners
Some products add fibres the strain can eat. Synbiotic is a marketing word until trials exist.
No virulence kit
Commercial strains are chosen to lack known toxin genes. That screening is industry and regulator work.
Life cycle
1Swallow
Stomach acid is the first filter. Food with the dose can change survival.
2Transit
Hours in the intestine. Contact with residents is brief for many strains.
3Transient effect
Measurable changes in stool or symptoms, if any, often fade after stopping.
4No permanent install
Expecting a forever colony from a two-week bottle misunderstands ecology.
If a brand claims to 'rewire DNA', that is advertising, not microbiology class.
Keep exploring
More in Beneficial allies
Gut microbiome
A diverse intestinal community fed by fibre — not a single ideal species list and not a wellness shop.
Familiarity 88Fermentation
Microbes turning food into kimchi, doenjang, yoghurt and other living crafts — chemistry plus culture.
Familiarity 85Skin microbiome
A site-specific living film — oily, moist and dry neighbourhoods, not a sterile wrapper.
Familiarity 62Soil microbes
The hidden workforce of land — decomposers, mycorrhizae and a mostly uncultured majority.
Familiarity 48Nitrogen cycle
How microbes move nitrogen between air, soil, water and food — plus the industrial shortcut that feeds billions.
Familiarity 40