<h3>(β-Hydroxy-β-Methylbutyrate, Hydroxy-MethylButyrate)</h3> Key actions HMB is a bioactive metabolite of the amino acid leucine. It plays a key role in supporting healthy muscle mass by enhancing muscle protein synthesis and inhibiting protein breakdown pathways.1–4 (See Figure 1). It may also exert antioxidant and anti-inflammatory effects.2 <img src="https://images.contentstack.io/v3/assets/blt948bd74310fc0ad0/blt94b209a4e6084f3a/69f29a9f87ec9707a5802dde/hmb_figure1.jpg" alt="hmb_figure1.jpg" class="embedded-asset" />Figure 1. Anatomical changes associated with muscle loss.<h2> Practice points</h2><h3>Common therapeutic uses</h3><ul><li>Skeletal muscle mass and strength increase in young people, athletes, older adults, and those with sarcopenia.1–3</li><li>Skeletal muscle loss prevention in older adults.1</li><li>Physical rehabilitation support.4</li><li>Exercise-induced muscle damage reduction.3</li><li>Body composition and athletic performance improvement.5</li><li>Muscle mass preservation during caloric restriction and weight loss.6</li></ul><h3>Dosage range</h3><ul><li>3 g per day.1,4,5,7–9</li><li>In divided doses with or without food.2,7</li><li>Beneficial impacts to markers of muscle damage occur after 24 hours.3</li><li>Benefits for muscle mass and body composition are measurable at eight weeks.2</li></ul><h3>Safety issues/mandatory warnings</h3><ul><li>Supplementation at 3 g per day for up to one year is well tolerated and is not associated with adverse side effects.1,7,10–12</li><li>Avoid during pregnancy and breastfeeding due to insufficient reliable information.12</li></ul><h3>Food sources</h3> As a metabolite of leucine,12 HMB is found naturally in small quantities in grapefruit, alfalfa, and catfish. It is also naturally synthesised in the human body in the muscle and liver;12 however, HMB conversion appears to be reduced with age.4 The optimal dose cannot be obtained from a standard diet given the low quantities of HMB available in foods and the low conversion rate of leucine to HMB (~5–10%).4 
<img src="https://images.contentstack.io/v3/assets/blt948bd74310fc0ad0/blt4419f047f1526c50/69f29a9ff44fdf340afd8347/hmb_what-to-look-for-in-a-supplement.jpg" alt="hmb_what-to-look-for-in-a-supplement.jpg" class="embedded-asset" /><h2> Identifying as a need</h2>LookThey may show visible signs of:<ul><li>Frailty</li><li>Advanced age</li><li>Use of walking aids</li><li>Conversely, they may be seeking to improve exercise performance</li></ul>Consider<ul><li>Are they consuming a balanced diet with adequate protein intake?</li><li>Are they taking medications that may increase the risk of muscle loss?</li><li>Are they engaging in regular resistance exercise?</li></ul>AskAre they describing signs of:<ul><li>Poor muscle strength or weakness</li><li>Reduced mobility</li><li>Increased risk of falls</li><li>Rapid weight loss</li><li>Exercise-induced muscle damage or soreness</li></ul>Are they aware if they have:<ul><li>Sarcopenia</li><li>A condition that makes physical activity difficult</li><li>A prolonged period of immobility</li></ul><h2> Risk factors for insufficiency</h2><ul><li>Ageing</li><li>Rapid weight loss-induced muscle loss</li><li>Decreased ability to exercise</li><li>Prolonged periods of immobility</li></ul><h2> Therapeutic uses</h2>Condition-specific dosages for HMB supported by clinical evidence<table><tbody><tr><th>Condition</th><th>Action</th><th>Dose</th></tr><tr><td>Age-related muscle loss and sarcopenia</td><td> <ul><li>Improves lean muscle mass and preserves muscle strength and function in older people with sarcopenia or frailty.8</li><li>Enhances the effects of resistance exercise training on muscle strength, physical performance, and muscle quality in older adults with sarcopenia.2</li><li>Enhances muscle strength and physical functionality in older adults when used in combination with vitamin D3, even if individuals are not engaged in an exercise program.7</li></ul> </td><td>3 g per day.1,4,5,7–9</td></tr><tr><td>Age-related quality of life measures</td><td> <ul><li>Maintenance of strong, healthy muscle mass with age leads to improved health, independence, and functionality.13</li></ul> </td></tr><tr><td>Exercise-induced muscle damage</td><td> <ul><li>Reduces markers of exercise-induced muscle damage (creatine kinase and lactate dehydrogenase) measurable from 24 hours after exercise.3</li><li>Taking HMB in combination with intense resistance exercise prevents increases in markers of muscle damage in trained athletes.9</li></ul> </td></tr><tr><td>Exercise performance</td><td> <ul><li>Promotes advantageous changes in body composition and stimulates an increase in aerobic and anaerobic capacity in trained athletes.5</li></ul> </td></tr><tr><td>Rehabilitation</td><td> <ul><li>Helps recover functional capacity after a fall, prolonged bed rest, or hip fracture in combination with resistance training.4</li></ul> </td></tr></tbody></table><h2> Drug interactions</h2>None known.12<h2> Cautions</h2>Avoid during pregnancy and breastfeeding due to insufficient reliable information12 <img src="https://images.contentstack.io/v3/assets/blt948bd74310fc0ad0/bltb3488d9d6dc5e34c/6aa0cfa62707c5649932b711/BI_CMED_Start_Learning.jpg" alt="BI_CMED_Start_Learning.jpg" class="embedded-asset" /> <h2> References</h2><ol><li>Lin Z, Zhao Y, Chen Q. Effects of Oral Administration of Β-Hydroxy Β-Methylbutyrate on Lean Body Mass in Older Adults: A Systematic Review and Meta-Analysis. European Geriatric Medicine. 2020;12(2):239–51.</li><li>Yang CW, Song Y, Li T, Chen X, Zhou J, Pan Q, et al. Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Older Adults With Sarcopenia: A Randomized, Double-Blind, Placebo-Controlled Study. The Journal of Nutrition Health &amp; Aging. 2023;27(5):329–39.</li><li>Rahimi M, Mohammadi H, Eshaghi H, Askari G, Miraghajani M. The Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Recovery Following Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis. Journal of the American College of Nutrition. 2018;37(7):640–9.</li><li>Courel‐Ibáñez J, Větrovský T, Daďová K, Pallarés JG, Šteffl M. Health Benefits of Β-Hydroxy-Β-Methylbutyrate (HMB) Supplementation in Addition to Physical Exercise in Older Adults: A Systematic Review With Meta-Analysis. Nutrients. 2019;11(9):2082.</li><li>Durkalec–Michalski K, Jeszka J, Podgórski T. The Effect of a 12-Week Beta-Hydroxy-Beta-Methylbutyrate (HMB) Supplementation on Highly-Trained Combat Sports Athletes: A Randomised, Double-Blind, Placebo-Controlled Crossover Study. Nutrients. 2017;9(7):753.</li><li>Chang CK, Kao SY, Wang CY. Beta-Hydroxy-Beta-Methylbutyrate Supplementation Preserves Fat-Free Mass in Collegiate Boxers during Acute Body Mass Loss. Chinese Journal of Physiology. 2023 Nov;66(6):485–93.</li><li>Rathmacher JA, Pitchford LM, Khoo P, Angus HF, Lang J, Lowry KA, et al. Long-Term Effects of Calcium Β-Hydroxy-Β-Methylbutyrate and Vitamin D3 Supplementation on Muscular Function in Older Adults With and Without Resistance Training: A Randomized, Double-Blind, Controlled Study. The Journals of Gerontology Series A. 2020;75(11):2089–97.</li><li>Oktaviana J, Zanker J, Vogrin S, Duque G. The Effect of Β-Hydroxy-Β-Methylbutyrate (HMB) on Sarcopenia and Functional Frailty in Older Persons: A Systematic Review. The Journal of Nutrition Health &amp; Aging. 2019;23(2):145–50.</li><li>Wilson JM, Lowery RP, Joy JM, Walters JA, Baier SM, Fuller JC, et al. Β-Hydroxy-Β-Methylbutyrate Free Acid Reduces Markers of Exercise-Induced Muscle Damage and Improves Recovery in Resistance-Trained Men. British Journal of Nutrition. 2013;110(3):538–44.</li><li>Examine. HMB [Internet]. Examine.com; 2023. Available from: https://examine.com/supplements/hmb/?show_conditions=true</li><li>Prado CM, Orsso CE, Pereira SL, Atherton PJ, Deutz NEP. Effects of Β‐hydroxy Β‐methylbutyrate (HMB) Supplementation on Muscle Mass, Function, and Other Outcomes in Patients With Cancer: A Systematic Review. Journal of Cachexia Sarcopenia and Muscle. 2022;13(3):1623–41.</li><li>Natural Medicines Comprehensive Database. Hydroxymethylbutyrate (HMB) [Internet]. Therapeutic Research Centre (TRC); 2024. Available from: https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs- supplements/professional.aspx?productid=45</li><li>McLeod MK, Breen L, Hamilton DL, Philp A. Live Strong and Prosper: The Importance of Skeletal Muscle Strength for Healthy Ageing. Biogerontology. 2016;17(3):497–510.</li></ol>

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