No benefits of prolonged vitamin D3 supplementation for adaptations to resistance training in old adults

Abstract

AbstractBackgroundLifestyle therapy with resistance training is a potent measure to counteract age-related loss in muscle strength and mass. Unfortunately, many individuals fail to respond in the expected manner. This phenomenon is particularly common among older adults and those chronically diseased (e.g. chronic obstructive pulmonary disease, COPD), and may involve endocrine variables such as vitamin D. At present, the effects of vitamin D supplementation on responses to resistance training remain largely unexplored.MethodsNinety-five male and female participants (healthy, n=71; COPD, n=24; age 68 ± 5 years) were randomly assigned to receive either vitamin D3 or placebo supplementation for 28 weeks in a double-blinded manner (latitude 61°N, September-May). Seventy-eight participants completed the RCT, which was initiated by 12 weeks of supplementation-only (in average, 3333 IU.day-1), followed by 13 weeks of combined supplementation (2000 IU.day-1) and supervised whole-body resistance training (twice weekly), interspersed with testing and measurements. Outcome measures included multiple assessments of muscle strength (n=7), endurance performance (n=6), and muscle mass (n=3, legs, primary), as well as muscle quality (legs), muscle biology (m. vastus lateralis; muscle fibre characteristics, transcriptome), and health-related variables (e.g. visceral fat mass and blood lipid profile). For main outcome domains such as muscle strength and muscle mass, weighted combined factors were calculated from the range of singular assessments.ResultsOverall, 13 weeks of resistance training increased muscle strength (13% ± 8%), muscle mass (9% ± 8%) and endurance performance (one-legged, 23% ± 15%; whole-body, 8% ± 7%), assessed as weighted combined factors, and were associated with changes in health variables (e.g. visceral fat, − 6% ± 21%; [LDL]serum, −4% ± 14%) and muscle tissue characteristics such as fibre type proportions (e.g. IIX, −3%-points), myonuclei·fibre-1 (30% ± 65%), total RNA/rRNA abundances (15%/6-19%), and transcriptome profiles (e.g. ∼336 differentially expressed genes). Vitamin D3 supplementation led to robust increases in [25(OH)D]serum (Δ49% vs placebo), but did not affect training-associated changes for any of the main outcome domains, with no interaction being evident with disease status or pre-RCT [25(OH)D]serum. In secondary analyses, vitamin D3 affected expression of gene sets involved in vascular functions in muscle tissue, strength gains in participants with high fat mass, and [cortisol]serum (Δ20%), all of which advocate further study.ConclusionsVitamin D3 supplementation did not affect muscular responses to resistance training in old adults with or without COPD.