Supplement research

B-Hydroxy-B-Methylbutyrate (HMB)

What is HMB?

HMB is a metabolite of the amino acid leucine

Proposed Benefits of HMB

HMB is used in order to reduce muscle damage and/or reduce muscle protein breakdown which will result in gains in muscle mass and strength when combined with resistance training.

Mechanism of Action of HMB

HMB is converted to HMG-CoA which is a precursor for cholesterol synthesis. It is suggested that stressed muscles may not be able to make sufficient cholesterol to support cell function. Cholesterol is an integral component of cell membranes which are important for muscle contraction. HMB supplementation may provide the precursors for membrane cholesterol synthesis and thereby improves cell integrity (1).
There is also some suggestion that HMB may directly reduce muscle protein breakdown (2).

Research on HMB

A recent meta-analysis (a study that combines the results of many studies and statistically analyses them) on the effects of dietary supplements on lean mass and strength gains showed that HMB significantly increased net lean muscle gains and increased muscle strength (3). This meta-analysis included 9 studies which supplemented with 3g/day of HMB and resulted in a net increase in lean mass of 0.28% per week. HMB also increased net strength by 1.4% per week.

Rating of Efficacy for HMB 8 /10

References

1.  Nissen S. and Abumrad N.N. Nutritional role of the leucine metabolite B-hydroxy-B-methylbutyrate (HMB). J Nutr Biochem. 8:300-311, 1997.
2.  Clarkson P.M. and Rawson E.S. Nutritional supplements to increase muscle mass. Crit  Rev Food Sci Nutr. 39:317-328, 1999.
3.  Nissen S.L. and Sharp R.L. Effect of dietary supplements on lean mass and strength gains with resistance exercise: a meta-analysis. J Appl Physiol. 94:651-659, 2002.