HMB (β-Hydroxy β-Methylbutyrate): What It Actually Does
Educational overview — not medical advice. HMB is not an approved treatment for sarcopenia, cachexia, or any other condition. This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.
HMB has been studied in trials of trained athletes, untrained lifters, and older adults, and results are mixed. Some company-funded trials (Wilson 2014; Lowery 2016) reported large effects, and independent researchers running the same kind of trial in trained athletes reported no meaningful effect (Sanchez-Martinez 2018). Cheap Ca-HMB powder runs about $0.28/day at the standard 3g dose at our last price check. Talk to your clinician before deciding whether HMB is right for you.
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What HMB is
HMB (β-hydroxy β-methylbutyrate) is a metabolite of leucine — about 5% of dietary/muscle leucine is converted to HMB via the enzyme KIC dioxygenase, mostly in the liver. It's sold as Calcium HMB (Ca-HMB), the older, cheaper, slower-absorbing salt form, and HMB free acid (HMB-FA), a newer, faster-absorbing, patented, pricier gel or softgel form. It sits downstream of leucine and adjacent to creatine, BCAAs, and EAAs in the muscle-preservation supplement category — see BCAAs and creatine for the neighboring evidence.
Who funded the trials
Several of the widely quoted HMB trials were funded by, or co-authored with, a company that holds commercial interests in HMB. Wilson et al. 2014 and Lowery et al. 2016 disclose this in their conflict-of-interest statements. Independent groups meta-analyzing trained and competitive athletes reported trivial-to-null effects on strength and body composition (Rowlands & Thomson 2009; Sanchez-Martinez et al. 2018, 6 RCTs, n=193). See the HMB overview.
Other groups studied
HMB has also been studied in untrained lifters and older adults. Deutz et al. 2013 was a 10-day bed-rest trial in 19 healthy older adults using 3g/day Ca-HMB. Wu et al. 2015 was a meta-analysis of 7 RCTs in older adults; the authors note that strength and physical function were not shown to change. Results were small and mixed, and this page makes no claim that HMB treats or prevents any condition. Talk to your clinician.
The one-line takeaway Results for HMB are mixed: company-funded trials in trained athletes reported large effects that independent researchers did not find. See best HMB for cost-per-dose comparisons and the dosage guide for the 3g/day dose.
Frequently asked questions
What does the research say about HMB in trained athletes?
Results are mixed. Some company-funded trials reported large effects that have not been independently replicated. Independent meta-analyses (Rowlands 2009, Sanchez-Martinez 2018) found trivial-to-null effects in trained athletes.
Which groups has HMB been studied in?
HMB has been studied in untrained lifters, older adults, and short bed-rest trials (Deutz 2013, Wu 2015). Results were small and mixed. Talk to your clinician before use.
Is HMB-FA better than HMB-Ca?
HMB-FA absorbs faster and higher (Fuller 2011) but we found no independent trial showing a different outcome. Ca-HMB is the lower-cost form.
What is the standard HMB dose?
3g/day, typically split into three 1g doses, was used in nearly every human trial reviewed.
Related guides
- BCAAs — HMB is a downstream metabolite of leucine, one of the 3 BCAAs
- Creatine — the sports supplement with the far deeper, independently-replicated evidence base
- Protein — whole dietary protein already supplies the leucine HMB is derived from
- Beta-Alanine — fellow amino-acid-derived, honestly-scoped sports-performance supplement
- Betaine (TMG) — another performance supplement, compared on label facts and the research
Sources
- Wilson JM, Lowery RP, Joy JM, et al. "The effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid supplementation on muscle mass, strength, and power in resistance-trained individuals: a randomized, double-blind, placebo-controlled study." Eur J Appl Physiol. 2014. PMID: 24599749
- Lowery RP, Joy JM, Rathmacher JA, et al. "Interaction of Beta-Hydroxy-Beta-Methylbutyrate Free Acid and Adenosine Triphosphate on Muscle Mass, Strength, and Power in Resistance Trained Individuals." J Strength Cond Res. 2016. PMID: 24714541
- Rowlands DS, Thomson JS. "Effects of beta-hydroxy-beta-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men: a meta-analysis." J Strength Cond Res. 2009. PMID: 19387395
- Sanchez-Martinez J, Santos-Lozano A, Garcia-Hermoso A, et al. "Effects of beta-hydroxy-beta-methylbutyrate supplementation on strength and body composition in trained and competitive athletes: A meta-analysis of randomized controlled trials." J Sci Med Sport. 2018. PMID: 29249685
- Deutz NE, Pereira SL, Hays NP, et al. "Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults." Clin Nutr. 2013. PMID: 23514626
- Wu H, Xia Y, Jiang J, et al. "Effect of beta-hydroxy-beta-methylbutyrate supplementation on muscle loss in older adults: a systematic review and meta-analysis." Arch Gerontol Geriatr. 2015. PMID: 26169182
- Fuller JC Jr, Sharp RL, Angus HF, Baier SM, Rathmacher JA. "Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt." Br J Nutr. 2011. PMID: 21134325
- Full product dataset: /hmb/cost-by-brand.json (CC BY 4.0).