CONCLUSIONS Vitamin D supplementation positively affected lower limb muscle strength in athletes , but not upper limb muscle strength or muscle power .
Different muscle groups and functions may respond differently to vitamin D supplementation .
BACKGROUND Vitamin D may play a role in skeletal muscle because of the discovery of VDR in skeletal muscle .
However , vitamin D deficiency is a global problem , including athletes .
Studies examining the effect of vitamin D supplementation on muscle function in athletes have inconsistent results .
Therefore , we aim ed to quantitatively summarize the evidence for the effect of vitamin D supplementation on skeletal muscle strength and explosive power of athletes using a meta- analysis .
Monthly High-Dose Vitamin D Treatment for the Prevention of Functional Decline: A Randomized Clinical Trial.
IMPORTANCE Vitamin D deficiency has been associated with poor physical performance . OBJECTIVE To determine the effectiveness of high-dose vitamin D in lowering the risk of functional decline . DESIGN , SETTING , AND PARTICIPANTS One-year , double-blind , r and omized clinical trial conducted in Zurich , Switzerl and . The screening phase was December 1 , 2009 , to May 31 , 2010 , and the last study visit was in May 2011 . The date s of our analysis were June 15 , 2012 , to October 10 , 2015 . Participants were 200 community-dwelling men and women 70 years and older with a prior fall . INTERVENTIONS Three study groups with monthly treatments , including a low-dose control group receiving 24,000 IU of vitamin D3 ( 24,000 IU group ) , a group receiving 60,000 IU of vitamin D3 ( 60,000 IU group ) , and a group receiving 24,000 IU of vitamin D3 plus 300 μg of calcifediol ( 24,000 IU plus calcifediol group ) . MAIN OUTCOMES AND MEASURES The primary end point was improving lower extremity function ( on the Short Physical Performance Battery ) and achieving 25-hydroxyvitamin D levels of at least 30 ng/mL at 6 and 12 months . A secondary end point was monthly reported falls . Analyses were adjusted for age , sex , and body mass index . RESULTS The study cohort comprised 200 participants ( men and women ≥ 70 years with a prior fall ) . Their mean age was 78 years , 67.0 % ( 134 of 200 ) were female , and 58.0 % ( 116 of 200 ) were vitamin D deficient ( < 20 ng/mL ) at baseline . Intent-to-treat analyses showed that , while 60,000 IU and 24,000 IU plus calcifediol were more likely than 24,000 IU to result in 25-hydroxyvitamin D levels of at least 30 ng/mL ( P = .001 ) , they were not more effective in improving lower extremity function , which did not differ among the treatment groups ( P = .26 ) . However , over the 12-month follow-up , the incidence of falls differed significantly among the treatment groups , with higher incidences in the 60,000 IU group ( 66.9 % ; 95 % CI , 54.4 % to 77.5 % ) and the 24,000 IU plus calcifediol group ( 66.1 % ; 95 % CI , 53.5%-76.8 % ) group compared with the 24,000 IU group ( 47.9 % ; 95 % CI , 35.8%-60.3 % ) ( P = .048 ) . Consistent with the incidence of falls , the mean number of falls differed marginally by treatment group . The 60,000 IU group ( mean , 1.47 ) and the 24,000 IU plus calcifediol group ( mean , 1.24 ) had higher mean numbers of falls compared with the 24,000 IU group ( mean , 0.94 ) ( P = .09 ) . CONCLUSIONS AND RELEVANCE Although higher monthly doses of vitamin D were effective in reaching a threshold of at least 30 ng/mL of 25-hydroxyvitamin D , they had no benefit on lower extremity function and were associated with increased risk of falls compared with 24,000 IU . TRIAL REGISTRATION clinical trials.gov Identifier : NCT01017354
CONCLUSIONS Vitamin D supplementation positively affected lower limb muscle strength in athletes , but not upper limb muscle strength or muscle power .
Different muscle groups and functions may respond differently to vitamin D supplementation .
BACKGROUND Vitamin D may play a role in skeletal muscle because of the discovery of VDR in skeletal muscle .
However , vitamin D deficiency is a global problem , including athletes .
Studies examining the effect of vitamin D supplementation on muscle function in athletes have inconsistent results .
Therefore , we aim ed to quantitatively summarize the evidence for the effect of vitamin D supplementation on skeletal muscle strength and explosive power of athletes using a meta- analysis .