What is known about HMB?
HMB Supplement.HMB has been shown to stimulate protein synthesis in cells in vitro. This means that it seems to work in a petri dish. Similarly, some studies have provided evidence for an effect of HMB on protein degradation. The studies in humans on the functional effects (body composition, muscle mass, muscle strength), however, have provided mixed results. Over the last few years several meta-analyses have been performed trying to draw conclusions from all the human studies but even those analyses did not result in convincing conclusions. HMB is available in two different forms as a supplement: HMB that is calcium bound or HMB in a free form (HMB Free acid). There is, however, little evidence that these two forms have different effects.
A new meta-analysis on HMB
Most recently a comprehensive meta-analysis was performed by Jakubowski et al (1) and what I like about this paper is that apart from a thorough meta-analysis, this review also includes a more qualitative point of view and asks critical questions about the results of published studies.
When the authors of this new meta-analysis searched the literature, they initially found 1731 papers and this was narrowed down to 303 for more detailed screening. In the end, 11 double blinded clinical trials were included in the analysis. In these 11 studies, both forms of the available HMB were included. The average study duration was just under 8 weeks. Below are the results of the meta-analysis.