What is HMB?
HMB is short for hydroxymethylbutyrate or ꞵ-hydroxy ꞵ-methylbutyrate. It is an active metabolite of the essential amino acid leucine. All of the HMB present in the human body is derived from dietary sources of leucine, with about 5% of all dietary leucine being converted to HMB.[2] HMB is thought to help reduce muscle protein breakdown and may mediate some of the effects of leucine on muscle protein synthesis.
What are HMB’s main benefits?
HMB plays an anticatabolic role in muscle tissue. In other words, HMB prevents muscle protein breakdown and reduces the loss of fat-free mass. These effects seem to be most pronounced during catabolic states, including cancer cachexia,[5] acquired immunodeficiency syndrome (AIDS),[6] and aging.[7][8] HMB seems to be particularly effective for preventing the age-related loss of muscle mass and for preserving strength and body composition in bedridden or sedentary older adults.[7][8]
HMB stimulates muscle protein synthesis, but supplementation fails to increase fat-free mass, improve body composition, or increase measures of strength performance in athletes and trained individuals, and its use in these populations cannot be recommended.[9][10][11] HMB may be effective for reducing exercise-associated muscle damage after high-intensity exercise.[4]
What are HMB’s main drawbacks?
Supplementing with HMB at a dose of 3 grams per day appears to be well tolerated and is not associated with any adverse side effects.[12] This is the dose commonly used in research studies. Higher doses may be equally safe, but very few studies have investigated doses of HMB above 3 grams per day. One study found that 6 grams of HMB per day didn’t cause any concerning changes to cholesterol, blood glucose, red or white blood cells, and liver or kidney function.[13] HMB also appears to be safe when taken with other amino acids (i.e., arginine, lysine, and glutamine) or supplemented alongside creatine.[14][12][4]
How does HMB work?
HMB’s effects on skeletal muscle appear to be due to its actions on both muscle protein synthesis and muscle protein breakdown. HMB promotes muscle protein synthesis by stimulating mammalian target of rapamycin (mTOR), which regulates cell growth and differentiation.[15] HMB may also increase the activity of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis.[16]
HMB reduces protein degradation (protein breakdown) by inhibiting the activity of the body’s ubiquitin-proteasome system and caspases. These two pathways are responsible for breaking down proteins (proteolysis) under catabolic states such as fasting, immobilization, disuse, aging, and disease.[17][18][19] Inhibiting protein breakdown explains why HMB can minimize the loss of lean body mass in certain conditions.
What are other names for HMB
- Hydroxy-MethylButyrate
- beta-hydroxy-beta-methylbutyrate
- Leucine (parent amino acid)
Dosage information
Supplementation of HMB tends to be in the dosage range of 1–3 grams daily for the purpose of reducing muscle mass losses over time (anticatabolic). As HMB is said to be 20-fold more potent than leucine for this purpose, it is seen as equivalent to 20–60g of leucine supplementation.[1]
HMB, a water-soluble metabolite of leucine, is excreted in the urine and is not reabsorbed by the kidneys back into the bloodstream. Studies have shown that approximately half of the supplemented HMB is lost through urine. Since the kidneys don’t reabsorb HMB, dividing the daily HMB dosage into three separate doses throughout the day may help to maintain steadier levels of HMB in the blood and thereby enhance its effectiveness.[2][3]
For the purpose of muscle protein synthesis (MPS), HMB and leucine are fairly equivalent, although the latter (leucine) may be more potent on a per-gram basis. Supplementing with HMB is not advised for inducing muscle protein synthesis, since leucine is likely more effective as well as cheaper.
Supplementation of HMB prior to an exercise session to mitigate exercise-induced muscle damage would require the usage of an HMB free acid rather than a calcium salt, and the above dosage range still holds. For this specific purpose, HMB is to be taken 30–60 minutes before a workout when taking the HMB-FA form, or 60–120 minutes if taking the HMB-Ca form. On the other hand, when HMB is consumed in preparation for a potentially skeletal-muscle-damaging event (e.g., a competition), or prior to a high-intensity training bout for the purpose of reducing muscle damage, it appears to be more effective when taken regularly three times a day starting at least 2 weeks before the training period.[4]
Frequently asked questions
HMB is short for hydroxymethylbutyrate or ꞵ-hydroxy ꞵ-methylbutyrate. It is an active metabolite of the essential amino acid leucine. All of the HMB present in the human body is derived from dietary sources of leucine, with about 5% of all dietary leucine being converted to HMB.[2] HMB is thought to help reduce muscle protein breakdown and may mediate some of the effects of leucine on muscle protein synthesis.
HMB plays an anticatabolic role in muscle tissue. In other words, HMB prevents muscle protein breakdown and reduces the loss of fat-free mass. These effects seem to be most pronounced during catabolic states, including cancer cachexia,[5] acquired immunodeficiency syndrome (AIDS),[6] and aging.[7][8] HMB seems to be particularly effective for preventing the age-related loss of muscle mass and for preserving strength and body composition in bedridden or sedentary older adults.[7][8]
HMB stimulates muscle protein synthesis, but supplementation fails to increase fat-free mass, improve body composition, or increase measures of strength performance in athletes and trained individuals, and its use in these populations cannot be recommended.[9][10][11] HMB may be effective for reducing exercise-associated muscle damage after high-intensity exercise.[4]
Supplementing with HMB at a dose of 3 grams per day appears to be well tolerated and is not associated with any adverse side effects.[12] This is the dose commonly used in research studies. Higher doses may be equally safe, but very few studies have investigated doses of HMB above 3 grams per day. One study found that 6 grams of HMB per day didn’t cause any concerning changes to cholesterol, blood glucose, red or white blood cells, and liver or kidney function.[13] HMB also appears to be safe when taken with other amino acids (i.e., arginine, lysine, and glutamine) or supplemented alongside creatine.[14][12][4]
HMB’s effects on skeletal muscle appear to be due to its actions on both muscle protein synthesis and muscle protein breakdown. HMB promotes muscle protein synthesis by stimulating mammalian target of rapamycin (mTOR), which regulates cell growth and differentiation.[15] HMB may also increase the activity of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis.[16]
HMB reduces protein degradation (protein breakdown) by inhibiting the activity of the body’s ubiquitin-proteasome system and caspases. These two pathways are responsible for breaking down proteins (proteolysis) under catabolic states such as fasting, immobilization, disuse, aging, and disease.[17][18][19] Inhibiting protein breakdown explains why HMB can minimize the loss of lean body mass in certain conditions.
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References
- ^Gabriel J Wilson, Jacob M Wilson, Anssi H ManninenEffects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A reviewNutr Metab (Lond).(2008 Jan 3)
- ^Nissen S, Sharp R, Ray M, Rathmacher JA, Rice D, Fuller JC, Connelly AS, Abumrad NEffect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training.J Appl Physiol (1985).(1996-Nov)
- ^Rahimi MH, Mohammadi H, Eshaghi H, Askari G, Miraghajani MThe Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Recovery Following Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis.J Am Coll Nutr.(2018)
- ^Jacob M Wilson, Peter J Fitschen, Bill Campbell, Gabriel J Wilson, Nelo Zanchi, Lem Taylor, Colin Wilborn, Douglas S Kalman, Jeffrey R Stout, Jay R Hoffman, Tim N Ziegenfuss, Hector L Lopez, Richard B Kreider, Abbie E Smith-Ryan, Jose AntonioInternational Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB)J Int Soc Sports Nutr.(2013 Feb 2)
- ^May PE, Barber A, D'Olimpio JT, Hourihane A, Abumrad NNReversal of cancer-related wasting using oral supplementation with a combination of beta-hydroxy-beta-methylbutyrate, arginine, and glutamine.Am J Surg.(2002-Apr)
- ^Clark RH, Feleke G, Din M, Yasmin T, Singh G, Khan FA, Rathmacher JANutritional treatment for acquired immunodeficiency virus-associated wasting using beta-hydroxy beta-methylbutyrate, glutamine, and arginine: a randomized, double-blind, placebo-controlled studyJPEN J Parenter Enteral Nutr.(2000 May-Jun)
- ^Nicolas de Angelus Costa Riela, Maiara Moeme Alvim Guimarães, Daniela Oliveira de Almeida, Edilene Maria Queiroz AraujoEffects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Elderly Body Composition and Muscle Strength: A Review of Clinical TrialsAnn Nutr Metab.(2021 Mar 12)
- ^Wu H, Xia Y, Jiang J, Du H, Guo X, Liu X, Li C, Huang G, Niu KEffect of beta-hydroxy-beta-methylbutyrate supplementation on muscle loss in older adults: a systematic review and meta-analysis.Arch Gerontol Geriatr.(2015)
- ^Josephine S Jakubowski, Everson A Nunes, Filipe J Teixeira, Victoria Vescio, Robert W Morton, Laura Banfield, Stuart M PhillipsSupplementation with the Leucine Metabolite β-hydroxy-β-methylbutyrate (HMB) does not Improve Resistance Exercise-Induced Changes in Body Composition or Strength in Young Subjects: A Systematic Review and Meta-AnalysisNutrients.(2020 May 23)
- ^Holland BM, Roberts BM, Krieger JW, Schoenfeld BJDoes HMB Enhance Body Composition in Athletes? A Systematic Review and Meta-analysis.J Strength Cond Res.(2022-Feb-01)
- ^Sanchez-Martinez J, Santos-Lozano A, Garcia-Hermoso A, Sadarangani KP, Cristi-Montero CEffects of beta-hydroxy-beta-methylbutyrate supplementation on strength and body composition in trained and competitive athletes: A meta-analysis of randomized controlled trialsJ Sci Med Sport.(2018 Jul)
- ^Rathmacher JA, Nissen S, Panton L, Clark RH, Eubanks May P, Barber AE, D'Olimpio J, Abumrad NNSupplementation with a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine is safe and could improve hematological parameters.JPEN J Parenter Enteral Nutr.(2004)
- ^Gallagher PM, Carrithers JA, Godard MP, Schulze KE, Trappe SWBeta-hydroxy-beta-methylbutyrate ingestion, part II: effects on hematology, hepatic and renal function.Med Sci Sports Exerc.(2000-Dec)
- ^Baier S, Johannsen D, Abumrad N, Rathmacher JA, Nissen S, Flakoll PYear-long changes in protein metabolism in elderly men and women supplemented with a nutrition cocktail of beta-hydroxy-beta-methylbutyrate (HMB), L-arginine, and L-lysine.JPEN J Parenter Enteral Nutr.(2009)
- ^Eley HL, Russell ST, Baxter JH, Mukerji P, Tisdale MJSignaling pathways initiated by beta-hydroxy-beta-methylbutyrate to attenuate the depression of protein synthesis in skeletal muscle in response to cachectic stimuli.Am J Physiol Endocrinol Metab.(2007-Oct)
- ^Gerlinger-Romero F, Guimarães-Ferreira L, Giannocco G, Nunes MTChronic supplementation of beta-hydroxy-beta methylbutyrate (HMβ) increases the activity of the GH/IGF-I axis and induces hyperinsulinemia in rats.Growth Horm IGF Res.(2011-Apr)
- ^Lecker SH, Jagoe RT, Gilbert A, Gomes M, Baracos V, Bailey J, Price SR, Mitch WE, Goldberg ALMultiple types of skeletal muscle atrophy involve a common program of changes in gene expression.FASEB J.(2004-Jan)
- ^Smith HJ, Mukerji P, Tisdale MJAttenuation of proteasome-induced proteolysis in skeletal muscle by {beta}-hydroxy-{beta}-methylbutyrate in cancer-induced muscle loss.Cancer Res.(2005-Jan-01)
- ^Eley HL, Russell ST, Tisdale MJMechanism of attenuation of muscle protein degradation induced by tumor necrosis factor-alpha and angiotensin II by beta-hydroxy-beta-methylbutyrate.Am J Physiol Endocrinol Metab.(2008-Dec)
