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 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?
Note that HMB is also known as:
- Hydroxy-MethylButyrate
- beta-hydroxy-beta-methylbutyrate
HMB should not be confused with:
- 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]
Examine Database: HMB
Research FeedRead all studies
Does HMB affect blood lipids?
Can supplementation with HMB improve muscle strength in older adults with sarcopenia?
Does supplementing with HMB enhance the effects of exercise in older adults?
The effects on skeletal muscle of supplementing with HMB and vitamin D
Frequently asked questions
What is HMB?
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.
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References
Examine Database References
- Low-density lipoprotein (LDL) - Richard B. Kreider, Maria Pontes Ferreira, Michael Greenwood, M. Wilson, Pamela Grindstaff, Steven Plisk, Jeff Reinardy, Edward Cantler, and Anthony L. AmaldaEffects of Calcium β-HMB Supplementation During Training on Markers of Catabolism, Body Composition, Strength and Sprint PerformanceJournal of Exercise Physiology.()
- Low-density lipoprotein (LDL) - Wei Hung, Tsung-Han Liu, Chung-Yu Chen, Chen-Kang ChangEffect of β-hydroxy-β-methylbutyrate Supplementation During Energy Restriction in Female Judo AthletesJournal of Exercise Science & Fitness.()
- Muscle Mass - Vukovich MD, Stubbs NB, Bohlken RMBody composition in 70-year-old adults responds to dietary beta-hydroxy-beta-methylbutyrate similarly to that of young adultsJ Nutr.(2001 Jul)
- Muscle Mass - Portal S, Zadik Z, Rabinowitz J, Pilz-Burstein R, Adler-Portal D, Meckel Y, Cooper DM, Eliakim A, Nemet DThe effect of HMB supplementation on body composition, fitness, hormonal and inflammatory mediators in elite adolescent volleyball players: a prospective randomized, double-blind, placebo-controlled studyEur J Appl Physiol.(2011 Sep)
- Muscle Mass - Slater G, Jenkins D, Logan P, Lee H, Vukovich M, Rathmacher JA, Hahn AGBeta-hydroxy-beta-methylbutyrate (HMB) supplementation does not affect changes in strength or body composition during resistance training in trained menInt J Sport Nutr Exerc Metab.(2001 Sep)
- Muscle Mass - Thomson JS, Watson PE, Rowlands DSEffects of nine weeks of beta-hydroxy-beta- methylbutyrate supplementation on strength and body composition in resistance trained menJ Strength Cond Res.(2009 May)
- Body Fat - 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)
- Muscle Soreness - Hoffman JR, Cooper J, Wendell M, Im J, Kang JEffects of beta-hydroxy beta-methylbutyrate on power performance and indices of muscle damage and stress during high-intensity trainingJ Strength Cond Res.(2004 Nov)
- Liver Enzymes - Kreider RB, Ferreira M, Wilson M, Almada ALEffects of calcium beta-hydroxy-beta-methylbutyrate (HMB) supplementation during resistance-training on markers of catabolism, body composition and strengthInt J Sports Med.(1999 Nov)
- Power Output - Gallagher PM, Carrithers JA, Godard MP, Schulze KE, Trappe SWBeta-hydroxy-beta-methylbutyrate ingestion, Part I: effects on strength and fat free massMed Sci Sports Exerc.(2000 Dec)
- Muscle Damage - 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)
- High-density lipoprotein (HDL) - Sadeghi B, Bahari H, Jozi H, Hasanzadeh MA, Hashemi D, Bideshki MVEffects of β-hydroxy-β-methylbutyrate (HMB) supplementation on lipid profile in adults: a GRADE-assessed systematic review and meta-analysis of randomized controlled trials.Front Nutr.(2024)
- Muscle Soreness - Nunan D, Howatson G, van Someren KAExercise-induced muscle damage is not attenuated by beta-hydroxy-beta-methylbutyrate and alpha-ketoisocaproic acid supplementationJ Strength Cond Res.(2010 Feb)
- Power Output - Wilson JM, Lowery RP, Joy JM, Walters JA, Baier SM, Fuller JC, Stout JR, Norton LE, Sikorski EM, Wilson SM, Duncan NM, Zanchi NE, Rathmacher Jβ-Hydroxy-β-methylbutyrate free acid reduces markers of exercise-induced muscle damage and improves recovery in resistance-trained menBr J Nutr.(2013 Jan 3)
- Body Fat - Su H, Zhou H, Gong Y, Xiang S, Shao W, Zhao X, Ling H, Chen G, Tong P, Li JThe effects of β-hydroxy-β-methylbutyrate or HMB-rich nutritional supplements on sarcopenia patients: a systematic review and meta-analysis.Front Med (Lausanne).(2024 Jul 12)