HBM: A Dietary Supplement for Building Muscle :: Health Nutrition Papers

HBM: A Dietary Supplement for Building Muscle Three major companies (Twinlab, MetRx, and EAS) currently market the nutritional supplement HMB, or beta-hydroxy beta-methylbutyrate (http://www.sports-nutrition.org/mesomorphosis/3022645.html). HMB has been highly acclaimed since it’s recent market debut by EAS (http://www.eas.com/research/hmb/mindex.html). Many critics have compared it to the wonder-product Creatine Monohydrate. Such a comparison undoubtedly harbors both positive and negative aspects. But nevertheless, HMB products continue to thrive in nutritional stores worldwide. I. What is HMB? "HMB (hydroxy-methylbutraye) is a metabolite of the amino acid Leucine and is produced naturally by the human body. HMB is produced from a metabolite of leucine, called ketoisocaproate (KIC), by the enzyme KIC-dioxygenase. And, at least in the pig, HMB is produced exclusively from leucine"(Nissen p.2095). II. How does HMB work? Steven Nissen and his colleagues have performed the only study to date of HMB on humans. The researchers agree that the mechanism by which HMB impacts muscle proteolysis and function is not currently known. Nevertheless there are a number of postulations. "The high substrate concentration required by the dioxygenase enzyme compared with the liver concentration of KIC suggests that HMB production in the body may be a first-order reaction controlled by enzyme and KIC concentrations. It has been calculated that, under normal conditions, about 5% of leucine oxidation proceeds via this pathway. Therefore, if humans are assumed to have enzyme actions similar to those seen in pigs, a 70-kg human would produce from .2 to .4 g HMB/day depending on the level of dietary leucine. At leucine intakes of 20-50 g/day (which are used therapeutically), the concentrations of leucine and KIC in the liver increase and could result in HMB production reaching gram quantities per day"(Nissen p.2095). Some s tudies involving HMB supplementation to the diet of steers and pigs have been shown to improve caracass quality. Based on these findings, it has been hypothesized that supplementing the diet with HMB may inhibit protein degradation during periods of increased proteolysis such as resistance training. III. What are the Claims? The three companies that currently market the product recommend 1.5-3.0 grams of HMB/day as a dietary supplement. Although the science behind the product’s effectiveness is rather unclear, all three companies show few distinctions between dosages and manufacturing. Most people who have noticed the product often see HMB advertised as a protein breakdown suppressor. Researchers claim that such an advantage actually enhances the gains in muscle strength and lean mass associated with resistance training.