(10-07-12) Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise Performance and body composition across varying levels of age, sex

Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise Performance and body composition across varying levels of age, sex,and training experience: A review
Gabriel J Wilson*1, Jacob M Wilson2 and Anssi H Manninen3
Address: 1Division of Nutritional Sciences, University of Illinois, Urbana, Illinois, USA, 2Department of Nutrition, Food and Exercise Science,
Florida State University, Tallahassee, Florida, USA and 3Manninen Nutraceuticals Oy, Oulu, Finland
Email: Gabriel J Wilson* - [email protected]; Jacob M Wilson - [email protected];
Anssi H Manninen - [email protected]
* Corresponding author
Abstract
The leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) has been extensively used as an
ergogenic aid; particularly among bodybuilders and strength/power athletes, who use it to promote
exercise performance and skeletal muscle hypertrophy. While numerous studies have supported
the efficacy of HMB in exercise and clinical conditions, there have been a number of conflicting
results. Therefore, the first purpose of this paper will be to provide an in depth and objective
analysis of HMB research. Special care is taken to present critical details of each study in an attempt
to both examine the effectiveness of HMB as well as explain possible reasons for conflicting results
seen in the literature. Within this analysis, moderator variables such as age, training experience,
various states of muscle catabolism, and optimal dosages of HMB are discussed. The validity of
dependent measurements, clustering of data, and a conflict of interest bias will also be analyzed. A
second purpose of this paper is to provide a comprehensive discussion on possible mechanisms,
which HMB may operate through. Currently, the most readily discussed mechanism has been
attributed to HMB as a precursor to the rate limiting enzyme to cholesterol synthesis HMGcoenzyme
A reductase. However, an increase in research has been directed towards possible
proteolytic pathways HMB may operate through. Evidence from cachectic cancer studies suggests
that HMB may inhibit the ubiquitin-proteasome proteolytic pathway responsible for the specific
degradation of intracellular proteins. HMB may also directly stimulate protein synthesis, through
an mTOR dependent mechanism. Finally, special care has been taken to provide future research
implications.


Source: Nutrition & Metabolism 2008, 5:1 doi:10.1186/1743-7075-5-1

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