beta-Hydroxy beta-methylbutyric acid
|β-Hydroxy β-methylbutyric acid|
|Jmol-3D images||Image 1|
|Molar mass||118.131 g/mol|
−80 °C, 193 K, -112 °F
88 °C at 1 mmHg
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
β-Hydroxy β-methylbutyric acid (HMB), or β-hydroxy β-methylbutyrate, is a metabolite of the essential amino acid leucine and is synthesized in the human body. It plays a part in protein synthesis and was discovered by Dr. Steven L. Nissen at Iowa State University. It has been used in scientific studies to purportedly increase muscle mass and decrease muscle breakdown. Nissen held the original patent on the metabolite as a nutritional supplement. It was discovered in pigs, and small quantities can also be found in grapefruit, alfalfa, and catfish. As a supplement it is usually sold as a calcium salt.
Research published in the Journal of Applied Physiology has shown that HMB may have an effect on increasing muscle weight and strength. A review in Nutrition & Metabolism provides an in depth and objective analysis of HMB research.  The same study lists as HMB's proposed mechanisms of action the following:
- Increased sarcolemmal integrity via conversion to HMG-CoA
- Enhanced protein synthesis via the mTOR pathway
- Depression of protein degradation through inhibition of the ubiquitin pathway
Three grams of Calcium beta-hydroxy-beta-methylbutyrate per day may help muscles combat protein breakdown, assist in muscle repair and support increased endurance. Studies suggest its benefits may be greater for the untrained. Also, well-controlled scientific studies have found increases in muscle mass and decreases in body fat in 70 year old men. It has helped patients with chronic obstructive pulmonary disease in hospital intensive care units, muscle wasting associated with HIV or AIDS and with cancer, and trauma victims with severe injuries.
The human body produces about 0.2-0.4 grams per day. Standard doses in research studies have been 1.5 to 3.0 grams per day, usually divided into two doses.
Multiple carboxylase disorders
In multiple carboxylase deficiency, individuals have low or non-existent activity in one or more of the enzymes that facilitate recycling of biotin, a nutrient referred to as vitamin B7 or vitamin H. In such individuals, hydroxyisovaleric acid (or hydroxyisovalerate) accumulates as a consequence of incomplete leucine metabolism. The presence of hydroxyisovalerate is therefore a sensitive marker of biotin deficiency and may indicate the presence of a genetic disorder such as biotinidase deficiency or holocarboxylase synthetase deficiency.
- β-Hydroxyisovaleric acid at Sigma-Aldrich
- HMB at gnc.com
- HMB Sport at Blonyx Biosciences
- Nissen S, Sharp R, Ray M, et al. (November 1996). "Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training". J. Appl. Physiol. 81 (5): 2095–104. PMID 8941534.
- Wilson GJ, Wilson JM, Manninen AH. (2008). "Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A review.". Nutrition & Metabolism 5: 1. doi:10.1186/1743-7075-5-1. PMID 18173841.