Background: Older adults supplemented for 1 year with β-hydroxy-β-methylbutyrate, arginine, and lysine (HMB/ARG/LYS) were previously shown to have significant gains in fat-free mass (FFM) but not muscular strength.
Objective: Recently, increasing levels of serum vitamin D have been associated with an increase in muscle function, particularly in the elderly. To determine if vitamin D status may have limited strength gain in participants supplemented with HMB/ARG/LYS, the authors performed post hoc analysis of strength based on the participants' vitamin D status.
Methods: Elderly (age 76.0 ± 1.6 years) adults were recruited for a double-blinded, controlled study and were randomly assigned to either an isonitrogenous control (n = 37) or HMB/ARG/LYS (n = 40) for the yearlong study. Participants were further segregated based on their vitamin D status of either <30 or ≥30 ng 25OH-vitD(3)/mL serum, and an analysis was performed on the 4 cohorts.
Results: Regardless of vitamin D status, HMB/ARG/LYS resulted in significantly increased FFM (P < .02), but only in those with vitamin D status ≥30 ng 25OH-vitD(3)/mL was there a significant increase in strength with HMB/ARG/LYS (P < .01). Control-supplemented participants, regardless of vitamin D status, and the HMB/ARG/LYS-supplemented participants with vitamin D status <30 ng 25OH-vitD(3) failed to show improvements in strength.
Conclusions: The nutrient cocktail of HMB/ARG/LYS alone was effective in increasing muscle mass regardless of vitamin D status, but accompanying strength increases were observed only when participants also had adequate vitamin D status indicating a synergistic effect between the HMB/ARG/LYS and vitamin D.