All topics
Gut ecology and biotics
The microbiome is a dynamic ecosystem. Prebiotics, probiotics, synbiotics and postbiotics are distinct concepts. Accurate descriptions require the identity, preparation, target population and evidence of a health benefit.
In-depth articles
All articles →Dietary fiber: solubility, viscosity and fermentability
Use material properties to understand bowel function, fermentation and tolerance rather than treating every fiber as identical.
→The gut microbiome: from buzzwords to testable questions
Understand gut ecology and the biotic categories, then ask who a study actually applies to.
→A map of related concepts; see the entries and sources for detail.
Reference entries
Prebiotic
A substrate selectively used by host microbes with a health benefit. Not every fibre has demonstrated prebiotic effects.
Probiotic
Live microbes that confer benefit at adequate amounts. Genus, species and strain differ; evidence for one strain does not establish benefit for an entire genus.
Postbiotic
Under ISAPP, a beneficial preparation of inanimate microbes and/or their components. A purified metabolite alone does not automatically qualify.
Synbiotic
A beneficial combination of live microbes and selectively used substrates. Listing probiotics and fibre together does not demonstrate synergy.
Short-chain fatty acidsProject inference
Acetate, propionate and butyrate link fermentation to host metabolism. Stool levels reflect production and absorption, not a simple higher-is-better score.
This measurement interpretation does not allow whole-body benefit to be inferred from a stool test alone.
Gut–brain axisProject inference
Neural, immune, endocrine and metabolic signals connect gut and brain. This does not show that any probiotic treats anxiety or improves sleep.
Ecological and geographic contextProject inference
The same substrate may behave differently across microbial communities. New cross-country and community studies support testing relevance in the intended Chinese population.
CFU and cells are not interchangeable
CFU measures colony-forming units; inactivated preparations may use cell counts or mass. Check end-of-shelf-life potency, storage and matching study preparations.
The shared benefit requirement
ISAPP definitions of prebiotics, probiotics, synbiotics and postbiotics all include a health benefit to the host. Not every fermented food meets the probiotic definition; purified metabolites alone do not meet its postbiotic definition.