Does vitamin-D intake during resistance training improve the skeletal muscle hypertrophic and strength response in young and elderly men? – a randomized controlled trial

Abstract

IntroductionRecent studies have shown that vitamin-D intake can improve skeletal muscle function and strength in frail vitamin-D insufficient individuals. We investigated whether vitamin-D intake can improve the muscular response to resistance training in healthy young and elderly individuals, respectively.MethodsHealthy untrained young (n = 20, age 20–30) and elderly (n = 20, age 60–75) men were randomized to 16 weeks of daily supplementary intake of either 48 μg of vitamin-D + 800 mg calcium (Vitamin-D-group) or 800 mg calcium (Placebo-group) during a period and at a latitude of low sunlight (December-April, 56°N). During the last 12 weeks of the supplementation the subjects underwent progressive resistance training of the quadriceps muscle. Muscle hypertrophy, measured as changes in cross sectional area (CSA), and isometric strength of the quadriceps were determined. Muscle biopsies were analyzed for fiber type morphology changes and mRNA expression of vitamin-D receptor (VDR), cytochrome p450 27B1 (CYP27B1) and Myostatin.ResultsIn the vitamin-D groups, serum 25(OH)D concentration increased significantly and at week 12 was significantly different from placebo in both young men (71.6 vs. 50.4 nmol/L, respectively) and elderly men (111.2 vs. 66.7 nmol/L, respectively). After 12 weeks of resistance training, quadriceps CSA and isometric strength increased compared to baseline in young (CSA p < 0.0001, strength p = 0.005) and elderly (CSA p = 0.001, strength p < 0.0001) with no difference between vitamin-D and placebo groups. Vitamin-D intake and resistance training increased strength/CSA in elderly compared to young (p = 0.008). In the young vitamin-D group, the change in fiber type IIa percentage was greater after 12 weeks training (p = 0.030) and Myostatin mRNA expression lower compared to the placebo group (p = 0.006). Neither resistance training nor vitamin-D intake changed VDR mRNA expression.ConclusionNo additive effect of vitamin-D intake during 12 weeks of resistance training could be detected on either whole muscle hypertrophy or muscle strength, but improved muscle quality in elderly and fiber type morphology in young were observed, indicating an effect of vitamin-D on skeletal muscle remodeling.Trial registrationClinicalTrials with nr. NCT01252381Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0029-y) contains supplementary material, which is available to authorized users.

Vitamin D and Physical Activity

“…Currently, vitamin D has been shown to be a potent modulator of skeletal muscle physiology [5]. Although the expression of the vitamin D receptors in the skeletal muscle tissue was questioned [60], recent data strongly indicate that they are also expressed in the skeletal muscle [61]. As we mentioned earlier, 1,25(OH) 2 D by binding to its nuclear receptor augments the transcription of key muscular proteins [5][6][7].…”

“…A 10-day incubation of muscle cells with 1,25-dihydroxyvitamin D3 induces myosin heavy chain (MHC) type II, a late myogenic marker, while the mean diameter and width of muscular fibers increase compared to parallel controls. Indeed, vitamin D increases the size of MHC type II-positive myotubes [61,64] and the crosssectional area (CSA) of skeletal muscle fibers [65]. Vitamin D signaling has been also reported to alter the expression of C2C12 myotube size [5,61], indicating a direct positive effect on the contractile filaments and thus muscle strength.…”

Muscular effects of vitamin D in young athletes and non-athletes and in the elderly

“…All participants in the study followed a progressive resistance training program of the quadriceps muscles assessed by measurements of muscle hypertrophy, quadriceps isometric strength and muscle biopsies for fiber type morphology, expression of vitamin D receptors and myostatin. 3 Vitamin D supplementation increased the percentage of fiber type IIa and decreased myostatin mRNA compared to parallel controls. Vitamin D supplementation improved the muscular effects of resistance training (muscle strength evaluated by isokinetic dynamometry and percutaneous isometric electromyostimulation) in the older adults but failed to induce any changes in the younger males.…”

“…The effect of vitamin D supplementation on resistance training was examined by Agergaard et al 3 in randomized young and elderly untrained males in a study at latitudes with low sunlight (DecemberApril, 56°N). All participants in the study followed a progressive resistance training program of the quadriceps muscles assessed by measurements of muscle hypertrophy, quadriceps isometric strength and muscle biopsies for fiber type morphology, expression of vitamin D receptors and myostatin.…”

“…2 Muscles are major targets of vitamin D, expressing large numbers of vitamin D receptors. 3 In muscles, vitamin D affects cell proliferation and differentiation and the transport of calcium and phosphate across muscle cell membranes, while it modulates phospholipid metabolism. 4 Vitamin D additionally suppresses the expression of myostatin, a negative regulator of muscle mass, while it up-regulates the expression of follistatin and insulin-like growth factor 2.…”