HMB — The Muscle Preserver

HMB (β-hydroxy β-methylbutyrate) is an active metabolite of the essential amino acid leucine. It exerts a dual action on muscle protein turnover by simultaneously stimulating protein synthesis and inhibiting protein degradation. HMB upregulates muscle protein synthesis primarily through the activation of the PI3K/Akt and mTOR (mechanistic target of rapamycin) signaling pathways. Concurrently, it attenuates muscle protein breakdown by inhibiting the ubiquitin-proteasome system and downregulating the expression of atrogenes (muscle-specific ubiquitin ligases) associated with muscle atrophy.

HMB has been extensively studied in older adults and clinical populations for its ability to preserve muscle mass and function. Multiple randomized controlled trials and meta-analyses demonstrate that 3 g/day of HMB improves lean muscle mass, preserves muscle strength, and enhances physical function in older people with sarcopenia or frailty (Oktaviana et al., 2019). It is particularly effective when combined with resistance training or during periods of bed rest and inactivity.

The standard clinical and research dose is 3 g per day, typically divided into two or three doses. It is most commonly administered as calcium HMB (CaHMB) or in a free acid form (FA-HMB). For optimal muscle preservation, it is often combined with resistance training and adequate protein intake.

HMB is generally recognized as safe with a well-established safety profile in both healthy individuals and clinical populations. Side effects are rare and typically limited to mild gastrointestinal discomfort such as bloating or upset stomach. There are no known severe adverse effects or significant drug interactions at standard dosages.

Key Papers