Beta-hydroxy-betamethylbutyrate (HMB) and sarcopenia

Beta‐hydroxy‐beta‐methylbutyrate (HMB) is an active metabolite of leucine, a branched‐chain essential amino acid entirely derived from food sources, and it has been studied for many decades (Figure 24.1). HMB per se is present in very small amounts of some foods, such as cauliflower, citrus fruit, avocado, and catfish. HMB is synthesized from leucine in two separate steps occurring in liver and muscle cell [1]. At muscle cells level, leucine has an explicit role in controlling and at the same time regulating protein synthesis, and HMB has an important role as a key active metabolite in this process. Nevertheless, only approximately 5% of leucine that we can eat with the usual diet is converted to HMB, which, in a subject weighing 70–80 kg, ends in the production of 0.2–0.4 g of HMB per day [2].