GLOSSARY

Succinate is a host and microbial intermediate, whose detection alone establishes neither origin nor effect.

Microbial metabolites are products or intermediates of microbial activity, sometimes further modified by the host. Not all are uniquely microbial: hosts also produce lactate and succinate. Location, amount and pathway determine interpretation. A metabolome describes measured chemicals rather than the living community. Detecting a compound without suitable methods does not establish its exact origin or a definite beneficial or harmful effect on the athlete.

Composition identifies detected groups; functional potential concerns genetic capacity, while activity concerns what is actually expressed or produced. Different communities can share functions. A gene's presence does not guarantee a particular metabolite output. Organism names alone therefore establish neither extra usable energy nor improved absorption, strength or recovery. Distinguish taxonomic detection, measured activity and meaningful human outcomes when assessing a microbiome claim.

One microbe's product can feed another; some use lactate or acetate within networks producing other metabolites. Cross-feeding makes community effects more complex than adding individual abundances. Lactate and succinate are not merely useless waste. However, identifying a laboratory pathway does not itself show that supplementing its intermediate or manipulating the community improves athletes. Net output depends on production, consumption and the organisms actually present in context.