GLOSSARY

Butyric Acid is the acid related to butyrate, with ionization changing by environment rather than separate dietary needs.

Acetate, propionate and butyrate are important fermentation products acting as fuels and signals. Butyrate contributes to colonocyte fuel, and much of these acids is absorbed. Their roles do not establish a universal butyrate-supplement requirement or that more of every product is always better. Sports application requires human evidence and tolerance; a changed metabolite alone does not demonstrate improved performance, recovery or a need for concentrated replacement.

Fecal short-chain fatty-acid concentration reflects production, microbial use, absorption and water dilution, not total production rate. Low values have multiple interpretations, and high values are not always better. Define sample and method. Read stool measurements alongside diet and function rather than diagnosing muscle-fuel shortage or prescribing purified acids from one value. Concentration, flux and physiological effect are distinct quantities even when reported for the same compound.

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.

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.

For sports use, do not jump from a mechanism to a definite performance effect; evaluate food, training, tolerance and actual goal-related change together rather than ending assessment at one marker.

Microbes use colonic substrates including carbohydrate and protein products, producing different metabolites. Substrate amount, transit and community composition influence the routes. Protein fermentation does not make every protein meal harmful, and carbohydrate fermentation is not symptom-free at every dose. Sports diets should coordinate adequate protein, plant foods and tolerance rather than judging a whole nutrient solely by one fermentation product or eliminating needed recovery food.

Human enzymes cannot cleave all fiber linkages; some material reaches microbes and is fermented according to type. Products include short-chain fatty acids and gases, with fermentability varying between fibers. Fiber digestion is therefore not the same as starch digestion. Gradual increases and event-specific timing are generally more useful than permanently excluding every source, especially because long-term food variety and short-term gut comfort need coordinated planning.