What is it?
HMB is actually a metabolite of the amino acid L-leucine. L-leucine is one of three amino acids known as the branched chain amino acids or BCAA (isoleucine and valine being the other two).
It has been known for a long time that BCAA play a critical role in the turn over of lean body tissues (muscle) and is muscle sparing (i.e. anti-catabolic) in a variety of muscle wasting states. Of the three BCAA, L-leucine appears to be the most important to preserving hard earned muscle mass and intense exercise and certain disease states have been shown to eat up a great deal of L-leucine. So far so good!