Vitamin D status and supplementation impacts on skeletal muscle function: comparisons between young athletes and older adults.

PURPOSE OF REVIEW: The present narrative review analyzes emerging research implicating vitamin D status and supplementation with skeletal muscle homeostasis and functions in two distinct segments of the adult population: young athletes and older adults. RECENT FINDINGS: Vitamin D deficiency compromises multiple indices of muscle function in young athletes and older adults. A variety of vitamin D3 (cholecalciferol) supplementation regimens may transition young athletes and older adults from deficient or inadequate to adequate vitamin D status. Vitamin D supplementation, used to treat a vitamin D deficiency, but not necessarily an inadequacy, promotes muscle anabolism in older adults. For both young athletes and older adults, vitamin D supplementation, which transitions them from inadequate to adequate vitamin D status, may not beneficially affect measures of muscle strength and power, or physical performance. Also, when vitamin D status is adequate, vitamin D supplementation to further increase serum 25(OH)D concentrations does not seem to confer additional benefits to muscle strength and power and physical performance. SUMMARY: The impacts of vitamin D status and supplementation on skeletal muscle homeostasis and functions seem comparable in young athletes who strive to maximize physical performance and older adults who seek to attenuate muscle mass and physical performance declines.

Effects of oral amino acid supplementation on Multidimensional Prognostic Index in hospitalized older patients: a multicenter randomized, double-blind, placebo-controlled pilot study.

BACKGROUND: It is not known whether amino acid supplementations may influence health status in hospitalized older acutely ill patients. AIM: The aim of this study was to determine whether nutritional supplementation with amino acids (Aminoglutam®) is associated with multidimensional improvement assessed with the Multidimensional Prognostic Index (MPI). METHODS: In this randomized, double-blind, placebo-controlled pilot clinical trial, 126 patients aged ≥65 years were enrolled from 6 Italian geriatric wards. A multidimensional assessment to calculate the MPI was performed at baseline and after 4 weeks of treatment with nutritional supplementation (96 kcal, 12 g amino acids, 0.18 g fat, 11.6 g carbohydrate, and vitamins B1, B6, and C) or placebo administered twice a day. Logistic regression modeling was applied to determine the effect of treatment on the improvement of MPI (vs no-change/worsening), adjusting for gender, age, and MPI at baseline. Treatment's interactions with age, gender, and MPI at baseline were tested adding the appropriate interaction parameter in the regression models. RESULTS: Of the 126 patients included, 117 patients (93%) completed the study. A significant improvement in the MPI score was detected in the overall population (mean difference post-pretreatment: -0.03, p=0.001), with no differences between active and placebo arms. Men in the amino acid supplementation group had a significantly higher rate of improvement in MPI (81%) compared to the placebo group (46%) (Fisher's exact test p=0.03). Adjusting for age, diagnosis, and MPI at baseline, amino acid treatment was shown to be associated with an improvement in MPI in men (OR=4.82, 95% confidence interval [CI]: 0.87-26.7) and not in women (OR=0.70, 95% CI: 0.27-1.81). The interaction effect between active treatment and gender was significant (p=0.04). CONCLUSION: A 4-week amino acid supplementation improved the MPI significantly in hospitalized older male patients but not in female patients. Further studies are needed to confirm the gender effect of amino acid supplementation on MPI in older patients.