HMB

What does it do? HMB (beta hydroxy-beta-methylbutyrate) is a metabolite of the essential amino acid leucine (one of the branched-chain amino acids). As with other amino acid-related substances, HMB appears to play a role in the synthesis of protein—including the protein that builds new muscle tissue.

Animal research suggests that HMB may improve the growth of lean muscle tissue,¹ but only preliminary and limited research in humans supports the potential link between HMB and enhanced muscle building² or endurance performance³ in athletes. One study involving people involved in a regular weight-lifting program found that supplements of 3 grams per day of HMB, compared with no supplements, contributed to greater gains of muscle mass and strength over the seven-week study.⁴ However, a double-blind, controlled trial found no effect of 3 grams per day of HMB for four weeks on body composition or exercise performance in 41 weight-training football players.⁵ ⁶

Where is it found? Small amounts of HMB are present in many foods of animal and plant origin, especially alfalfa and catfish. The amino acid leucine is metabolized into a compound called alpha-ketoisocaproate (KIC), which is then turned into HMB by the body. Dietary supplements of HMB are also available.

HMB has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating	Health Concerns
	High cholesterol
	HIV support (in combination with glutamine and arginine)
	Athletic performance (for strength and body composition)
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Who is likely to be deficient? HMB is not an essential nutrient. The body creates HMB from leucine, so any diet containing sufficient amounts of leucine (most do) should lead to the adequate production of HMB. Limited evidence indicates that athletes may benefit from supplemental intake of HMB.

References:

1. Nissen SL, Morrical D, Fuller JC. Effects of the leucine catabolite beta-hydroxy-beta-methylbutyrate (HMB) on the growth and health of growing lambs. J Animal Sci 1994;77:243.

2. Nissen S, Panton L, Wilhelm R, et al. Effect of beta-hydroxy-beta-methylbutyrate (HMB) supplementation on strength and body composition of trained and untrained males undergoing intense resistance training. FASEB J 1996;10:A287 [abstract].

3. Vukovich MD, Adams GD. Effect of beta-hydroxy beta-methylbutyrate (HMB) VO2 peak and maximal lactate in endurance trained cyclists. Med Sci Sports Exerc 1997;29:S252 [abstract]

4. Nissen S, Sharp R, Ray M, et al. Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistive-exercise training. J Appl Physiol 1996;81:2095–104.

5. Kreider R, Ferreira M, Wilson M, et al. Effects of calcium beta-HMB supplementation with or without creatine during training on body composition alterations. FASEB J 1997;11:A374 [abstract].

6. Almada A, Kreider R, Ferreira M, et al. Effects of calcium beta-HMB supplementation with or without creatine during training on strength & sprint capacity. FASEB J 1997;11:A374 [abstract].

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2003.