In older men doing strength training, taking HMB-free acid caused a short-term rise in muscle protein synthesis during the first two weeks, but this effect disappeared after that and was not different from taking a placebo. Any muscle growth from this supplement is not due to a lasting increase in protein synthesis.

We analyzed three assertions about HMB-free acid supplementation in older men doing resistance training, and what we’ve found so far suggests it does not meaningfully improve muscle protein synthesis or function beyond training alone. In the first two weeks, some studies observed a short-term rise in muscle protein synthesis with HMB-free acid, but this effect faded and matched what was seen with a placebo afterward [1]. This means any early change in protein building does not last, and it’s not clear it leads to real muscle growth over time [2]. We also found that while HMB-free acid does increase blood levels of HMB in older men, this rise does not translate into better muscle building, changes in gene activity, or improved physical function compared to resistance training by itself [3]. The evidence we’ve reviewed leans toward the idea that HMB-free acid, while absorbed by the body, does not add meaningful benefit to what older men already gain from lifting weights. There is no indication from these studies that the supplement enhances long-term outcomes. Our current analysis shows no consistent or lasting advantage from adding HMB-free acid to a strength training routine in this population. If you’re an older man training regularly, your workouts are doing the work — the supplement doesn’t appear to help more than that.