1 · What is HMB · a leucine metabolite
About 5% of dietary leucine converts to , whose primary role is reducing muscle protein breakdown, though it also promotes some synthesis. (β-hydroxy-β-methylbutyrate) is a metabolite of the leucine. About 5% of dietary leucine converts to HMB; the rest goes to muscle protein synthesis or energy.To get 3 g HMB (the clinically effective dose), you'd need ~60 g leucine — roughly 600 g whey protein, which is impractical, hence supplementation.
HMB can also promote some protein synthesis through , but its primary role is anti-catabolic, reducing muscle protein breakdown.