Association of Vitamin D Supplementation in Cardiorespiratory Fitness and Muscle Strength in Adult Twins: A Randomized Controlled Trial.

Although vitamin D is related to cardiorespiratory fitness and muscle strength, there is no evidence in the literature about the genetic influence of the response to vitamin D supplementation and improvements in these parameters. Therefore, we evaluate the effect of longitudinal supplementation of vitamin D on parameters of physical fitness in monozygotic twins. In total, 74 participants were included, with a mean age of 25 years, divided into two groups, one group received supplementation with cholecalciferol for 60 days and the other group did not. Cardiorespiratory fitness and muscle strength were measured before and after supplementation through maximal treadmill tests and dynamometry, respectively. Wilcoxon tests were used to compare intragroup results and the Mann-Whitney test to examine intergroup differences. There was an increase in the serum concentration of vitamin D in participants who ingested the supplementation. Cardiorespiratory fitness improved after supplementation through increases in the values of maximum oxygen consumption of 28% (p < .001). Muscle strength in left hand grip increased 18% in participants who received the supplement (p = .007). Sixty days of cholecalciferol supplementation improved cardiorespiratory fitness and upper limb muscle strength.

The impact of vitamin D supplementation on VDR gene expression and body composition in monozygotic twins: randomized controlled trial.

Vitamin D supplementation is widely used. However, there is no consensus on the use and dosage of this supplement and the existing recommendations arise from studies based on the benefits that this nutrient can facilitate in bones. In addition, individual genetics can influence the response to supplementation, therefore, research involving monozygotic twins aims to reduce these differences in phenotypic responses. The objective of this randomised controlled study is to examine the effect of vitamin D supplementation on body composition and the expression of the vitamin D receptor (VDR) mRNA. An intervention was performed through supplementation with cholecalciferol at the concentration of 2000 IU in 90 healthy adult monozygotic twins (male or female pairs) for 2 months. The findings showed that serum vitamin D concentration increased by 65% and VDR gene expression sixty times (p = 0.001). Changes in body composition parameters were observed regarding body fat and lean mass. Our results indicate that an increase in serum vitamin D concentration may have potential therapeutic implications.