Effects of Vitamin D3 Supplementation on Lean Mass, Muscular Strength, and Cardiorespiratory Fitness

Abstract

Low levels of serum 25-hydroxyvitamin D [25(OH)D] are associated with low lean mass, decreased muscle strength, and poor cardiorespiratory fitness. However, the evidence in support of the effect of vitamin D supplementation on lean mass and physical fitness is inconsistent. PURPOSE: To clarify whether there is a direct effect of a 1-year vitamin D3 supplementation on lean mass, muscular strength and cardiorespiratory fitness in healthy adults. METHODS: Ninety-five participants (34 men) randomly received either 420 IU vitamin D3 per day or placebo in a double-blind manner for 1-year. Lean body mass and fat mass were determined by dual energy X-ray absorptiometry (DXA). Hand grip strength (HGS) was measured using a hand grip dynamometer and leg extension power (LEP) was measured using a leg extension power measurement system. Cardiorespiratory fitness (CRF) was assessed by measuring peak oxygen uptake (VO2peak) using bicycle ergometer. Physical activity (PA) was assessed using uniaxial accelerometer and quantified as time spent in moderate- and vigorous physical activity (MVPA). Serum 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations were assessed using commercial ELISA kits. RESULTS: Serum 25(OH)D and 1,25(OH)2D concentrations were significantly increased by approximately 29.5nmol/L and 7.0 pg/mL, respectively, after 1-year vitamin D3 supplementation. After vitamin D3 supplementation, lean body mass was significantly increased from 43.8 kg to 44.3 kg (P<0.05), while the muscle strength and cardiorespiratory fitness were not changed. CONCLUSION: The present study indicates that vitamin D3 supplementation for one year effectively improves lean mass, but not muscle strength and cardiorespiratory fitness in healthy adults. Supported by a Grant-in-Aid for Scientific Research (C), National Natural Science Foundation of China (No. 31571226), and Program for Professors of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (No. TP2014057) to ZBC.