The Efficacy of Beta-Hydroxy-beta-Methylbutrate (HMB) on Exercise
Monica Hahn
The Ohio State University
Beta-hydroxy-beta-methylbutrate is a natural metabolite of the essential amino acid leucine, attenuating the rate of muscle tissue breakdown in athletes. As an anti-catabolic agent, this supplement maximizes muscle cell integrity and mechanistically decelerates skeletal muscle atrophy by simultaneously increasing the rate of protein synthesis while inhibiting muscle cell proteolysis (Wilson et al., 2013). It is suggested that HMB supplementation mechanistically ensues in the following ways: 1) inhibition of protein degradation; 2) increased protein synthesis; 3) higher availability of cytosolic cholesterol yielding retention of sarcolemma integrity; and, 4) increased myogenesis via expedited proliferation, differentiation, and fusion of satellite muscle cells (Albert, 2015). During a physiological phenomenon called transamination, an intermediate ketoacid called KIC is metabolized from leucine. From KIC, only about five percent of active Beta-Hydroxy-beta-Methylbutrate is procured (“Natural Medicines – Professional,” 2018).
Despite the natural synthetization of HMB, it is recommended that training athletes consume dietary supplements of beta-hydroxy-beta-methylbutrate to enhance its studied effect on muscle maintenance and growth. The purpose of this literature review is to expose the overall efficacy and safety of Beta-hydroxy-beta-methylbutrate in the context of exercise via integrated analyses of peer-reviewed academic journals that are based on clinical research.
According to the Professional Monogram for Beta-hydroxy-beta-methylbutrate, this supplement can be consumed orally in an relatively safe manner should the dosage not exceed three grams daily for up to one year (“Natural Medicines – Professional,” 2018). Lack of generalizable clinical research as well as high-quality evidence coupled with moderate to high data validity, low to moderate research bias, and overall adequate coverage of the product’s adverse effects denote HMB a “Possibly Safe” supplement by the quality rating standards of The Therapeutic Research Center. In conjunction with said standards, insufficient reliable evidence has barred HMB from being attributed a statistically significant rating for its presumed positive effect on muscle strength. The Monogram includes a meta-analysis confirming that daily HMB supplementation at the aforesaid dosage results in notable strength gains and augmented lean mass for non-trained athletes while yielding only trivial benefits for trained athletes engaging in resistance training (Rowlands & Thomson, 2009). Furthermore, Natural Medicine’s official stance on the supplement’s adverse effects and toxicology remain highly discretionary due to lack of reliable data regarding long-term use of HMB.
The British Journal of Sports Medicine features another meta-analysis that supports short-term HMB supplementation by non-trained and trained athletes alike. Nissen and Sharp identified complementary trends with Rowland and Thompson’s meta-analysis, associating increased muscle protein anabolism with the use of exogenous Beta-hydroxy-beta-methylbutrate at three grams daily (Currell et al., 2011). In their study, 41 healthy male subjects were randomly assigned either 0, 1.5, or 3 grams of HMB every day for three weeks. The subjects were weight trained three times per week and upheld strict adherence to a meat-free diet 3/7 days each week. Blood and urine tests were collected on the meat-free diet days and the appropriate biomarkers were analyzed for muscle proteolysis. The group of males who ingested three grams of HMB daily for three weeks showed a fifty-five percent increase in lean body tissue compared to the control group (Currell et al., 2011).
Relatedly, the authors of this journal argue that the difference in magnitude of effect between trained and non-trained athletes can be attributed to HMB’s capacity for reducing protein degradation but inability to provoke protein synthesis compared to leucine (“Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training | Cochrane Library,” 2000). Because suppression of skeletal muscle protein breakdown is already a consequence of adaptations in resistance training, it makes sense that HMB is more effective for preserving the muscle integrity of non-trained athletes experiencing exacerbated exercise-induced muscle protein turnover. Moreover, Nissen and Sharp propose that HMB supplementation would offer more comprehensive utilities for combatting clinically induced muscular atrophy than for inhibiting proteolysis in trained and untrained athletes altogether (Currell et al., 2011).
The International Journal of Sport Nutrition and Exercise Metabolism (Maughan, Burke, Dvorak, & Larson-Meyer, 2018) provides additional insight about the anti-catabolic mechanism of HMB on humans via reference to a physiological study. Again, supplemental HMB yielded reciprocal trends in muscle protein breakdown and muscle protein synthesis (Wilkinson et al., 2013). This means that HMB is a known catalyst for muscle cell retention but does not possess the mechanistic capabilities for stimulating muscle protein synthesis without aid from other chemical synergists.
The National Institute of Health characterizes HMB a supplement for exercise and athletic performance, attesting to the efficacy and safety of the active ingredient. According to the NIH, beta-hydroxy-beta-methylbutrate has been extensively studied on a wide pool of athletes varying in age, fitness level, and oral intake of the supplement. A general baseline for safe ingestion of beta-hydroxy-beta-methybutrate has been conservatively deemed three grams per day for up to eight weeks. No side effects have been noted for adults using HMB in the aforesaid manner. Experts recommend, however, that athletes add this supplement to their diet in moderation by taking three grams per day in equal servings of one gram for a minimum of two weeks to observe its effects (“Office of Dietary Supplements – Dietary Supplements for Exercise and Athletic Performance,” 2018.) Furthermore, the International Society of Sports Medicine suggests that supplementation of calcium infused HMB is more beneficial than the latter, providing four hundred milligrams of calcium for every three grams of beta-hydroxy-beta-methylbutrate.
In terms of the use of HMB by athletes who are engaging in endurance, strength, and power sports, there exist two different formulations of the supplement that permit varying efficacies. The first is HMB-Ca, a calcium salt, and the second is HMB-FA, a free acid. In recent studies, the free acid formulation of HMB has been publicized the superior form of the supplement due to accelerated absorption mechanisms that permit peaked concentrations of the active ingredient in the bloodstream in as little as thirty to sixty minutes following ingestion. The latter form the supplement takes approximately sixty to one hundred-twenty minutes to appear in the blood and is less potent. HMB-FA is likewise the more receptive formulation of the supplement by muscle tissue, subsequently resulting in increased clearance rates (Albert, 2015). Mechanistically, HMB-FA reigns superior to HMB-Ca but the respective efficacies of the aforesaid formulations remain comparable in the practical landscape of high-intensity interval training and resistance training.
The legal but impermissible exogenous supplement, Beta-hydroxy-beta-methylbutrate, appears to demonstrate notable effects on heightened training capacity, the mediation of proteolysis, and conversely the increased catalysis of protein synthesis in athlete populations. Existing already as a byproduct of leucine and KIC, HMB is a natural supplement that can be safely ingested at 1.5-3.0 grams daily. HMB can likewise be acquired via dietary protein. There exists little clinical evidence addressing the long-term toxicity of exogenous HMB, but it has been deemed a non-nugatory supplement that is safe for short-term use nonetheless. Thus, HMB has by and large been regarded “Possibly Safe” by the scientific community. In terms of the collective efficacy rating for supplemental Beta-hydroxy-beta-methybutrate on exercise, a general consensus maintains a notable, but not statistically significant, positive correlation between the use of HMB and muscle damage mitigation. Furthermore, it is highly recommended that calcium infused beta-hydroxy-beta-methylbutrate be considered for a more comprehensive effect on one’s health, although the acid free form offers more potency. Overall, beta-hydroxy-beta-methylbutrate at a steady three grams on a short-term basis appears to elicit favorable ergonomic effects on athletes engaging in strenuous exercise.
References
Albert, F. J. Usefulness of B-hydroxy-b-methylbutrate (HMB) supplementation in different sports: an update and practical implications. (2015). Nutrición hospitalaria: organo oficial de la Sociedad Española de Nutrición Parenteral y Enteral, 32(1), 20-33. | EBSCOhost. https://doi.org/10.3305/nh.2015.32.1.9101
Currell, K., Derave, W., Everaert, I., McNaughton, L., Slater, G., Burke, L. M., … Castell, L. M. (2011). A–Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance–Part 20. British Journal of Sports Medicine, 45(6), 530–532. https://doi.org/10.1136/bjsports-2011-090020
Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training | Cochrane Library. (2018). https://doi.org/10.1002/central/CN-00134219
Maughan, R. J., Burke, L. M., Dvorak, J., & Larson-Meyer, D. E. (2018). IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete, 28(2), 22.
Natural Medicines – Professional. (7/31/2018). Retrieved November 19, 2018, from https://naturalmedicines-therapeuticresearch-com.proxy.lib.ohio-state.edu/databases/food,-herbs-supplements/professional.aspx?productid=45
Office of Dietary Supplements – Dietary Supplements for Exercise and Athletic Performance. (2018). Retrieved November 25, 2018, from https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-Consumer/
Rowlands, D. S., & Thomson, J. S. (2009). 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. Journal of Strength and Conditioning Research, 23(3), 836–846. https://doi.org/10.1519/JSC.0b013e3181a00c80
Wilkinson, D. J., Hossain, T., Hill, D. S., Phillips, B. E., Crossland, H., Williams, J., … Atherton, P. J. (2013). Effects of leucine and its metabolite β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism. The Journal of Physiology, 591(11), 2911–2923. https://doi.org/10.1113/jphysiol.2013.253203
Wilson, J. M., Fitschen, P. J., Campbell, B., Wilson, G. J., Zanchi, N., Taylor, L., … Antonio, J. (2013). International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB). Journal of the International Society of Sports Nutrition, 10(1), 6. https://doi.org/10.1186/1550-2783-10-6