GLOSSARY

Carbohydrate Fermentation uses carbohydrate reaching microbes, distinct from glucose absorption in the small intestine.

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.

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.