Rathmacher et al. 2024, ISSN position stand on HMB

The International Society of Sports Nutrition position stand on β-hydroxy-β-methylbutyrate (HMB), a consensus review drawn from a scoping analysis of more than 750 articles. HMB is a metabolite of the amino acid leucine, and the stand’s evidence base is weighted towards resistance training and anaerobic performance rather than endurance.

Key points. The standard effective dose is 3 g per day; the stand reports no adverse effects at up to 6 g per day for eight weeks or at 3 g per day chronically for a year, with no impairment of glucose metabolism or insulin sensitivity in humans. Its effect on body composition and strength is real but smaller than that of leucine itself or a high-quality protein intake. On recovery, it cites reduced creatine kinase (a muscle-damage marker) after a 20 km run as one of its better-supported effects. On endurance, the stand records growing interest and reports a potential positive effect on aerobic performance, especially in trained athletes, but calls the evidence preliminary and the mechanism unknown, so any benefit is expected to be small. Moderate evidence for recovery and safety; limited and preliminary for endurance.