Efficacy and Safety of Leucine Supplementation in the Elderly

Leucine supplementation has grown in popularity due to the discovery of its anabolic effects on cell signaling and protein synthesis in muscle. The current recommendation is a minimum intake of 55 mg ⋅ kg^-1. d^-1 Leucine acutely stimulates skeletal muscle anabolism and can overcome the anabolic resistance of aging. The value of chronic leucine ingestion for muscle growth is still unclear. Most of the research into leucine consumption has focused on efficacy. To our knowledge, very few studies have sought to determine the maximum safe level of intake. Limited evidence suggests that intakes of ≤1250 mg ⋅ kg^-1. d^-1 do not appear to have any health consequences other than short-term elevated plasma ammonia concentrations. Similarly, no adverse events have been reported for the leucine metabolite β-hydroxy-β-methylbutyrate (HMB), although no studies have tested HMB toxicity in humans. Therefore, future research is needed to evaluate leucine and HMB toxicity in the elderly and in specific health conditions.