beta-Hydroxy beta-methylbutyric acid
![Human metabolic pathway for HMB and isovaleryl-CoA, relative to leucine.[1] Of the two major pathways, leucine is mostly metabolized into isovaleryl-CoA, while only 5% or so is metabolized into HMB.[1]](/uploads/202501/19/ISSN_HMB_statement_Fig_15107.jpg)
β-Hydroxy β-methylbutyric acid (HMB) and its conjugate base β-hydroxy β-methylbutyrate (hydroxymethylbutyrate, HMB) is a dietary supplement that is marketed as a performance-enhancing agent and that "appears to speed recovery from high-intensity exercise". Based upon a meta-analysis of seven randomized controlled trials, HMB supplementation helps preserve lean muscle mass in older adults and it may be useful for preventing muscle atrophy from bed rest. It does not appear to significantly affect fat mass in older adults. More research is needed to determine the precise effects on muscle strength and function in this age group.