David Castille, M.S., CSCS
When it comes to competitive athletics, or just reaching goals in the gym, people are always looking for some form of aid or advantage. Beta-hydroxy-beta-methylbutyrate (the only form of HMB), or HMB, may prove to be a potent ergogenic aid for many different kinds of athletes. HMB, discovered by Dr. Steven Nissen, has been around since the early- to mid-90s where it has been used primarily by athletes and bodybuilders. During the past two decades, research has been conducted on HMB in a variety of settings on a variety of populations. While earlier studies were unable to show HMB’s efficacy in highly-trained individuals, it seems that recent research may have opened the door for HMB’s emergence as an effective sports nutrition supplement for everyone
HMB can be synthesized in the body as a metabolite of leucine, the only amino acid thought to directly stimulate muscle protein synthesis. The body is unable to synthesize leucine and must therefore be obtained through the diet. Foods high in leucine content include eggs and meat, especially wild game. ). In supplements, HMB comes in two forms—HMB-FA and HMB-Ca, HMB free acid and calcium HMB, respectively. Calcium HMB, not a significant source of calcium, is the most commercially available. However, only about 5% of leucine in the body gets converted to HMB. This means that to achieve the roughly 3g/day (38mg/kg/day) that is widely used in research, one would need to consume 60 grams of leucine! This also fails to account for the timing factor associated with HMB and performance benefits. Research that has specifically looked at the timing of HMB supplementation has shown that blood plasma levels of HMB peak at 90-120 minutes and 30 minutes after ingestion for HMB-Ca and HMB-FA, respectively. Multiple studies examining the safety of this supplement in animal and human models have conclusively suggested no side effects from its, short-term or chronically.
Several mechanisms are believed to be responsible for HMB’s alleged efficacy. One is that it reduces protein breakdown. The first mechanism of protein breakdown reduction is that HMB is eventually synthesized into cholesterol. Cholesterol is necessary to the body to repair muscle tissue damage, along with other benefits. The second mechanism is inhibition of the ubiquitin pathway. Proteins are constantly recycled in the body. Ubiquitin is a regulatory protein that tags proteins for breakdown and removal. By inhibiting this, HMB may help to reduce the breakdown of protein.
While the research on this supplement has widely varied results, many studies failed to utilize intake timing, to control for diet or to attain high enough exercise intensities to fully explore HMB’s possible benefits. A recent study that did control for all of those factors, however, showed promising effects. Following a 12-week study involving highly resistance trained individuals taking 3g/day of HMB-FA 30 minutes prior to exercise showed significantly greater gains in strength, lean body mass, and improved body composition in comparison to the placebo group. Based on the findings of this and previous studies, it appears there is an interaction between level of training stimulus and the effectiveness of HMB.
While more research needs to be conducted to further examine the effects in highly trained athletes and other populations, it appears that HMB can be an effective supplement.
Wilson JM, Fitschen PJ, Campbell B, Wilson GJ, Zanchi N, Taylor L, Wilborn C, Kalman DS, Stout JR, Hoffman JR, Ziegenfuss TN, Lopez HL, Kreider RB, Smith-Ryan AE, and Antonio J. International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB). Journal of the International Society of Sports Nutrition 10: 6, 2013. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2782876/