The impact of 1-year vitamin D supplementation on vitamin D status in athletes: a dose–response study The effects of vitamin D3 supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose–response study Vitamin D3 Supplementation Does Not Improve Sprint Performance in Professional Rugby Players: A Randomized, Placebo-Controlled, Double-Blind Intervention Study. Vitamin D Supplementation and Physical Performance in Adolescent Swimmers. Vitamin D supplementation and upper respiratory tract infections in adolescent swimmers: a randomized controlled trial. Vitamin D3 supplementation using an oral spray solution resolves deficiency but has no effect on VO2 max in Gaelic footballers: results from a randomised, double-blind, placebo-controlled trial The effects of season-long vitamin D supplementation on collegiate swimmers and divers. A randomized, controlled trial of vitamin D supplementation upon musculoskeletal health in postmenarchal females. A randomized study on the effect of vitamin D₃ supplementation on skeletal muscle morphology and vitamin D receptor concentration in older women. Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial The serum 25-hydroxyvitamin D response to vitamin D supplementation is related to genetic factors, BMI, and baseline levels. Effects of vitamin D supplementation on strength, physical function, and health perception in older, community-dwelling men. Vitamin D supplementation improves neuromuscular function in older people who fall. Effect of vitamin D supplement on depression scores in people with low levels of serum 25-hydroxyvitamin D: nested case-control study and randomised clinical trial. Influence of vitamin D mushroom powder supplementation on exercise-induced muscle damage in vitamin D insufficient high school athletes The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: a controlled study. The role of vitamin D in improving physical performance in the elderly.
Background / Objectives : To assess the prevalence of vitamin D deficiency in Dutch athletes and to define the required dosage of vitamin D3 supplementation to prevent vitamin D deficiency over the course of a year . Subjects/ Methods : Blood sample s were collected from 128 highly trained athletes to assess total 25(OH)D concentration . Of these 128 athletes , 54 male and 48 female athletes ( 18–32 years ) were included in a r and omized , double blind , dose – response study . Athletes with either a deficient ( < 50 nmol/l ) or an insufficient ( 50–75 nmol/l ) 25(OH)D concentration were r and omly assigned to take 400 , 1100 or 2200 IU vitamin D3 per day orally for 1 year . Athletes who had a total 25(OH)D concentration above 75 nmol/l at baseline continued with the study protocol without receiving vitamin D supplements  . Serum total 25(OH)D concentration was assessed every 3 months , as well as  dietary vitamin D intake and sunlight exposure . Results : Nearly 70 % of all athletes showed an insufficient ( 50–75 nmol/l ) or a deficient ( < 50 nmol/l ) 25(OH)D concentration at baseline . After 12 months , serum 25(OH)D concentration had increased more in the 2200 IU/day group ( + 50±27 nmol/l ) than the sufficient group receiving no supplements ( + 4±17 nmol/l ; P<0.01 ) and the 1100 IU/day group ( + 25±23 nmol/l ; P<0.05 ) . Supplementation with 2200 IU/day vitamin D result ed in a sufficient 25(OH)D concentration in 80 % of the athletes after 12 months . Conclusions : Vitamin D deficiency is highly prevalent in athletes . Athletes with a deficient or an insufficient 25(OH)D concentration can achieve a sufficient 25(OH)D concentration within 3 months by taking 2200 IU/day Background Vitamin D deficiency is common in the general public and athletic population s and may impair skeletal muscle function . We therefore assessed the effects of vitamin D3 supplementation on serum 25[OH]D concentrations and physical performance . Methods 30 club-level athletes were block r and omised ( using baseline 25[OH]D concentrations ) into one of three groups receiving either a placebo ( PLB ) , 20 000 or 40 000 IU/week oral vitamin D3 for 12 weeks . Serum 25[OH]D and muscle function ( 1-RM bench press and leg press and vertical jump height ) were measured presupplementation , 6 and 12 weeks postsupplementation . Vitamin D deficiency was defined in accordance with the US Institute of Medicine guideline ( < 50 nmol/l ) . Results 57 % of the subject population were vitamin D deficient at baseline ( mean±SD value 51±24 nmol/l ) . Following 6 and 12 weeks supplementation with 20 000 IU ( 79±14 and 85±10 nmol/l , respectively ) or 40 000 IU vitamin D3 ( 98±14 and 91±24 nmol/l , respectively ) , serum vitamin D concentrations increased in all participants , with every individual achieving concentrations greater than 50 nmol/l . In contrast , vitamin D concentration in the PLB group decreased at 6 and 12 weeks ( 37±18 and 41±22 nmol/l , respectively ) . Increasing serum 25[OH]D had no significant effect on any physical performance parameter ( p>0.05 ) . Conclusions Both 20 000 and 40 000 IU vitamin D3 supplementation over a 6-week period elevates serum 25[OH]D concentrations above 50 nmol/l , but neither dose given for 12 weeks improved our chosen measures of physical performance Vitamin D insufficiency is common in athletes and may lower physical performance . Many cross-sectional studies associate vitamin D status with physical performance in athletes ; however , there have been few prospect i ve r and omized controlled trials with adequate statistical power to test this relationship , and none in the southern hemisphere . Thus , a prospect i ve double-blind , r and omized , placebo-controlled intervention trial was conducted involving 57 professional rugby union players in New Zeal and . Participants were r and omized to receive 50,000 IU of cholecalciferol ( equivalent to 3,570 IU/day ) or placebo once every two weeks over 11 - 12 weeks . Serum 25(OH)D concentrations and physical performance were measured at baseline , weeks 5 - 6 , and weeks 11 - 12 . Mean ( SD ) serum 25(OH)D concentrations for all participants at baseline was 94 ( 18 ) nmol/L , with all players above 50 nmol/L. Vitamin D supplementation significantly increased serum 25(OH)D concentrations compared to placebo , with a 32 nmol/L difference between groups at 11 - 12 weeks ( 95 % CI , 26 - 38 ; p < 0.001 ) . Performance in five of the six tests at study completion , including the primary outcome variable of 30-m sprint time , did not differ between the vitamin D supplemented and placebo groups ( p > 0.05 ) . Performance on the weighted reverse-grip chin up was significantly higher in players receiving vitamin D compared with placebo , by 5.5 kg ( 95 % CI , 2.0 - 8.9 ; p = 0.002 ) . Despite significantly improving vitamin D status in these professional rugby union players , vitamin D supplementation had little impact on physical performance outcomes . Thus , it is unlikely that vitamin D supplementation is an ergogenic aid in this group of athletes It is hypothesized that vitamin D insufficiency in athletes might negatively affect sport performance . The objective of this study was to examine the effect of vitamin D3 supplementation on physical performance of adolescent swimmers with vitamin D insufficiency . Fifty-three adolescent competitive swimmers with vitamin D insufficiency ( serum 25-hydroxyvitamin-D concentrations ( 25(OH)D ) < 30 ng/ml , mean 24.2 ± 4.8 ng/ml ) were r and omized to receive 2,000 IU/day of vitamin D3 or placebo for 12 weeks . Swimming performance at several speeds , arm-grip strength , and one-legged balance , were measured before and after supplementation . The age-adjusted changes in performance variables during the study were compared between groups . 25(OH ) D concentrations at study end were significantly higher in the vitamin group compared with the placebo group ( 29.6 ± 6.5 ng/ml vs. 20.3 ± 4.2 ng/ml , p < .001 ) , yet only 48 % of the vitamin group became vitamin D sufficient with this dosing . No between-group differences were found in the changes of the performance variables tested . No significant differences in performance were found between participants that became vitamin D sufficient , and those who did not . No significant correlation was found between the change in serum 25(OH)D and age-adjusted balance , strength or swimming performance at study end . Vitamin D3 supplementation that raised serum 25(OH)D concentrations by a mean of 9.3 ng/ml above placebo in adolescent swimmers with vitamin D insufficiency , did not improve physical performance more than placebo Observational studies identified associations between vitamin D insufficiency ( serum 25(OH)D < 30ng·ml-1 ) and risk of upper respiratory infection ( URI ) .  Swimmers are highly prone to URIs , which might hinder their performance . The aim of this study was to examine if vitamin D3 supplementation reduces URI burden in vitamin D-insufficient swimmers . Fifty-five competitive adolescent swimmers with vitamin D insufficiency were r and omized to receive vitamin D3 ( 2,000IU·d-1 ) or placebo for 12 winter weeks . A URI symptom question naire was completed weekly . Serum 25(OH)D concentrations were measured by radio-immunoassay before and after supplementation . We used linear regression to examine the relation between the change in 25(OH)D concentrations during the trial , and the duration and severity of URIs . There were no between-group differences in the frequency , severity , or duration of URIs . Exploratory analyses revealed that in the placebo group only , the change in 25(OH)D concentrations during the trial was highly associated with the duration of URIs ( r = -0.90,p < .001 ) , and moderately associated with the severity of URIs ( r = -0.65,p = .043 ) . The between-group differences for duration  were highly significant . Vitamin D3 supplementation in adolescent swimmers with vitamin D insufficiency did not reduce URI burden . However , larger decreases in serum 25(OH)D concentrations were associated with significantly longer and more severe URI episodes Purpose Vitamin D inadequacy is a global health concern in athletes as well as the general population . Whilst the role of vitamin D in skeletal health is well defined , there remains uncertainty over whether vitamin D supplementation has an added benefit beyond bone health . Methods This r and omised placebo-controlled trial in healthy male and female Gaelic footballers ( n = 42 ) investigated the effect of vitamin D3 supplementation [ 3000 IU ( 75 µg ) daily for 12 weeks , via an oral spray solution ] on VO2 max which was the primary outcome measure . Secondary outcomes included skeletal muscle and lung function . Results Supplementation significantly increased total 25-hydroxyvitamin D concentrations compared to the placebo group ( mean ± SD change from baseline , 36.31 ± 32.34 vs. 6.11 ± 23.93 nmol/L , respectively ; P = 0.006 ) . At baseline , 50 and 22 % of footballers presented with vitamin D insufficiency ( 31–49 nmol/L ) and deficiency ( < 30 nmol/L ) , respectively . Total 25-hydroxyvitamin D concentration did not significantly correlate with any measure of physical performance . Analysis of covariance ( ANCOVA ) models demonstrated that vitamin D supplementation over 12 weeks had no significant effect on VO2 max ( P = 0.375 ) , vertical jump height ( P = 0.797 ) , left and right h and grip strength ( P = 0.146 and P = 0.266 , respectively ) , forced vital capacity ( P = 0.573 ) or forced expiratory volume at 1 s ( P = 0.665 ) , after adjusting for confounders . The high prevalence of vitamin D inadequacy observed in this cohort of collegiate Gaelic footballers supports the need for vitamin D supplementation during wintertime to avoid being at risk of poor bone health . Conclusions Twelve-week daily supplementation with 3000 IU ( 75 µg ) vitamin D3 successfully resolved deficiency but did not have any significant effect on VO2 max , skeletal muscle or lung function The purpose of this 6-month r and omized , placebo-controlled trial was to determine the effect of season-long ( September-March ) vitamin D supplementation on changes in vitamin D status , which is measured as 25(OH ) D , body composition , inflammation , and frequency of illness and injury . Forty-five male and female athletes were r and omized to 4,000 IU vitamin D ( n = 23 ) or placebo ( n = 22 ) . Bone turnover markers ( NTx and BSAP ) , 25(OH)D , and inflammatory cytokines ( TNF-alpha , IL-6 , and IL1-β ) were measured at baseline , midpoint , and endpoint . Body composition was assessed by DXA and injury and illness data were collected . All athletes had sufficient 25(OH)D ( > 32 ng/ml ) at baseline ( mean : 57 ng/ml ) . At midpoint and endpoint , 13 % and 16 % of the total sample had 25(OH)D < 32 ng/ml , respectively . 25(OH)D was not positively correlated with bone mineral density ( BMD ) in the total body , proximal dual femur , or lumbar spine . In men , total body ( p = .04 ) and trunk ( p = .04 ) mineral-free lean mass ( MFL ) were positively correlated with 25(OH)D. In women , right femoral neck BMD ( p = .02 ) was positively correlated with 25(OH)D. 25(OH)D did not correlate with changes in bone turnover markers or inflammatory cytokines . Illness ( n = 1 ) and injury ( n = 13 ) were not related to 25(OH)D ; however , 77 % of injuries coincided with decreases in 25(OH)D. Our data suggests that 4,000 IU vitamin D supplementation is an inexpensive intervention that effectively increased 25(OH)D , which was positively correlated to bone measures in the proximal dual femur and MFL . Future studies with larger sample sizes and improved supplement compliance are needed to exp and our underst and ing of the effects of vitamin D supplementation in athletes CONTEXT There has been a resurgence of vitamin D deficiency rickets throughout the developed world , with infants and adolescents being primarily affected . Adolescence is a crucial period for muscle and bone mineral accumulation . OBJECTIVE The aim was to determine the effect of vitamin D supplementation on the adolescent musculoskeletal system . DESIGN AND SETTING We conducted a community-based , double-blind , r and omized controlled trial in a secondary school . PARTICIPANTS Postmenarchal 12- to 14-yr-old females participated in the trial . Ninety-nine were screened , 73 were included in r and omized controlled trial , and 69 completed the trial . There were no adverse events . INTERVENTION Four doses of 150,000 IU vitamin D(2 ) ( ergocalciferol ) were given over 1 yr . MAIN OUTCOME MEASURES Dual-energy x-ray absorptiometry , peripheral quantitative computed tomography , and jumping mechanography were used . RESULTS At follow-up , 25-hydroxyvitamin D [ 25(OH)D ] status was 56.0 ± 8.9 nmol/liter in the intervention group and 15.8 ± 6.6 nmol/liter in controls . There were no effects of supplementation on bone ; however , for muscle function , efficiency of movement improved in the vitamin D-treated group . There was an interaction between baseline 25(OH)D concentration and response to vitamin D supplementation for muscle jump velocity . CONCLUSIONS Despite improvements in 25(OH)D status , treatment with vitamin D(2 ) was not shown to increase mineral accretion , bone geometry or strength , muscle force , or power . There were greater increases in jump velocity in girls with the lowest baseline 25(OH)D concentrations . Lack of effect of intervention after the period of peak mineral and muscle mass accretion suggests that earlier action is required CONTEXT Studies examining whether vitamin D supplementation increases muscle mass or muscle-specific vitamin D receptor ( VDR ) concentration are lacking . OBJECTIVE Our objective was to determine whether vitamin D₃ 4000 IU/d alters muscle fiber cross-sectional area ( FCSA ) and intramyonuclear VDR concentration over 4 months . DESIGN AND SETTING This was a r and omized , double-blind , placebo-controlled study in a single center . PARTICIPANTS Participants were 21 mobility-limited women ( aged ≥ 65 years ) with serum 25-hydroxyvitamin D ( 25OHD ) levels of 22.5 to 60 nmol/L. MAIN OUTCOME MEASURES Baseline and 4-month FCSA and intramyonuclear VDR were measured from vastus lateralis muscle cross-sections probed for muscle fiber type ( I/IIa/IIx ) and VDR using immunofluorescence . RESULTS At baseline , mean ( ±SD ) age was 78 ± 5 years ; body mass index was 27 ± 5 kg/m² , 25OHD was 46.3 ± 9.5 nmol/L , and  a short physical performance battery score was 7.95 ± 1.57 out of 12 . At 4 months , 25OHD level was 52.5 ± 17.1 ( placebo ) vs 80.0 ± 11.5 nmol/L ( vitamin D [ VD ] ; P < .01 ) , and change in 25OHD level was strongly associated with percent change in intramyonuclear VDR concentration-independent of group ( r = 0.87 , P < .001 ) . By treatment group , percent change in intramyonuclear VDR concentration was 7.8 % ± 18.2 % ( placebo ) vs 29.7 % ± 11.7 % ( VD ; P = .03 ) with a more pronounced group difference in type II vs I fibers . Percent change in total ( type I/II ) FCSA was -7.4 % ± 18.9 % ( placebo ) vs 10.6 % ± 20.0 % ( VD ; P = .048 ) . CONCLUSION Vitamin D₃ supplementation  increased intramyonuclear VDR concentration by 30 % and increased muscle fiber size by 10 % in older , mobility-limited , vitamin D-insufficient women . Further work is needed to determine whether the observed effect of vitamin D on fiber size is mediated by the VDR and to identify which signaling pathways are involved Objective : Indoor athletes have been shown to be prone to vitamin D3 deficiency . The aim of the study was to examine the acute effects of vitamin D supplementation on muscle function using isokinetic dynamometry . Design : R and omized placebo-controlled , double-blind study . Setting : Institutional . Participants : Adult male white national level judoka athletes ( n = 22 ) who were involved in full-time training . Exclusion criteria were vitamin supplementation , overseas travel to sunny climes , and /or an injury incurred during the last 3 months before testing . Interventions : Subjects were r and omly allocated to the treatment ( 150 000IU vitamin D3 ) or placebo and given blinded supplements by an independent research er . Participants were tested twice , 8 days apart , on a Monday morning before the start of judo training and after 2 days of rest . A 5 to 7 mL of blood sample was collected followed by isokinetic concentric quadriceps and hamstring muscle function assessment s on the right leg at 30 and 200 ° ·s−1 . Main Outcome Measures : Repeated- measures analysis of variance was used to analyze isokinetic muscle force and serum 25(OH)D3 . Regression to the mean was used to examine changes in 25(OH)D3 levels over the study period . Results : The treatment group demonstrated a significant increase in serum 25(OH)D levels ( 34 % , P ⩽ 0.001 ) and muscle strength ( 13 % , P = 0.01 ) between days 1 and 8 . No significant differences were found for the placebo group for the same period . Conclusions : A single bolus of 150 000IU vitamin D3 had a significant positive effect on serum 25(OH)D levels and muscle function in vitamin D insufficient elite indoor athletes . Clinical Relevance : Serum 25(OH)D3 levels of indoor athletes should be monitored throughout the year and especially during winter months . Beneficial responses , in muscle strength and serum 25(OH)D3 , to 1 dose of vitamin D3 supplementation can be observed within 1 week of ingestion . Muscle strength is linked to serum 25(OH)D levels OBJECTIVE The serum 25-hydroxyvitamin D ( 25(OH)D ) level is not only dependent on vitamin D intake and production in the skin but also dependent on genetic factors . Thus , in large genome-wide association studies , it has been shown that single nucleotide polymorphisms ( SNPs ) in the vitamin D binding protein ( DBP ) , as well as in enzymes related to activation or degradation of vitamin D and its metabolites , are as important for the serum 25(OH)D level as the effect of season . How these SNPs affect the serum 25(OH)D response to vitamin D supplementation is uncertain . DESIGN AND METHODS Data were pooled from three r and omized controlled trials where 40 , 000 IU vitamin D/week was given for 6 months . Serum 25(OH)D was measured before and at the end of the intervention , and the subjects were genotyped for SNPs related to the serum 25(OH)D level . RESULTS Baseline 25(OH)D levels were significantly related to SNPs in the DBP and CYP2R1 genes . Those with SNPs associated with the lowest baseline 25(OH)D levels also had the smallest increase ( delta ) after supplementation . Those with the lowest baseline serum 25(OH)D ( without regard to genotypes ) had the highest increase ( delta ) after supplementation . Subjects with high BMI had lowest baseline 25(OH)D levels and also the smallest increase ( delta ) after supplementation . CONCLUSIONS The serum 25(OH)D response to supplementation depends on genes , baseline level , and BMI . However , whether this is clinical ly important or not depends on the therapeutic window of vitamin D , an issue that is still not settled OBJECTIVES To study the effects of vitamin D supplementation in healthier population s of men . DESIGN : R and omized , controlled trial . SETTING General clinical research center . PARTICIPANTS Sixty-five healthy , community-dwelling men ( mean age+/-st and ard deviation=76+/-4 , range 65 - 87 ) . INTERVENTION Cholecalciferol ( 1,000 IU/d ) or placebo supplementation for 6 months ; all received 500 mg supplemental calcium . MEASUREMENTS Upper and lower extremity muscle strength and power , physical performance and activity , health perception , calcium and vitamin D intake , and biochemical assessment , including 25-hydroxyvitamin D ( 25OHD ) , parathyroid hormone ( PTH ) , and ionized calcium levels . RESULTS The levels of 25OHD increased and PTH decreased in the cholecalciferol group , whereas there were no significant changes in the control group ( P<.001 ) . Baseline 25OHD levels correlated with baseline single-leg stance time and physical activity score . Baseline PTH levels correlated with baseline 8-foot walk time and physical activity score . No significant difference in strength , power , physical performance , or health perception was found between groups . CONCLUSION The 25OHD or PTH levels correlated with physical activity and physical performance in older , community-dwelling men with normal 25OHD status . Vitamin D supplementation increased 25OHD levels and decreased PTH levels but did not increase muscle strength or improve physical performance or health perception in this group of healthy , older men . Further investigations of the effects of vitamin D supplementation should focus on individuals with low levels of vitamin BACKGROUND vitamin D supplementation reduces the incidence of fractures in older adults . This may be partly mediated by effects of vitamin D on neuromuscular function . OBJECTIVE to determine the effects of vitamin D supplementation on aspects of neuromuscular function known to be risk factors for falls and fractures . DESIGN r and omised , double-blind , placebo-controlled study . SETTING falls clinic taking referrals from general practitioners and accident and emergency department . SUBJECTS 139 ambulatory subjects ( > /=65 years ) with a history of falls and 25-hydroxyvitamin D ( 25OHD ) < /=12 microg/l . INTERVENTION patients were r and omised to receive a single intramuscular injection of 600,000 i.u . ergocalciferol or placebo . OUTCOME MEASURES assessment s including biochemistry , postural sway , choice reaction time ( CRT ) , aggregate functional performance time ( AFPT ) , and quadriceps strength were carried out at baseline and 6 months post-intervention . RESULTS baseline characteristics were comparable between both groups . 25OHD in the treatment group increased significantly at 6 months . AFPT deteriorated in the control group and improved in the intervention group , representing a significant difference between groups ( + 6.6 s versus -2.0 s , t = 2.80 , P < 0.05 ) . Similar changes were observed for CRT ( -0.06 s versus + 0.41 s , t = -2.52 , P < 0.01 ) and postural sway ( + 0.0025 versus -0.0138 , t = 2.35 , P < 0.02 ) . There was no significant difference in muscle strength change between groups ( -10 N versus -2 N , t = -1.26 , ns ) . A significant correlation between change in AFPT and change in 25OHD levels was observed ( r = 0.19 , P = 0.03 ) . There was no significant difference in the number of falls ( 0.39 versus 0.24 , t = 1.08 , P = 0.28 ) or fallers ( 14 versus 11 , P = 0.52 ) between two groups . CONCLUSIONS vitamin D supplementation , in fallers with vitamin D insufficiency , has a significant beneficial effect on functional performance , reaction time and balance , but not muscle strength . This suggests that vitamin D supplementation improves neuromuscular or neuroprotective function , which may in part explain the mechanism whereby vitamin D reduces falls and fractures AIMS To compare depressive symptoms in participants with low and high serum 25-hydroxyvitamin D ( 25(OH)D ) levels and to examine whether supplementation with vitamin D(3 ) would improve symptoms in those with low serum 25(OH)D levels . METHOD Participants with low 25(OH)D levels were r and omised to either placebo or 40 000 IU vitamin D(3 ) per week for 6 months . Individuals with high serum 25(OH)D levels were used as nested controls . Depressive symptoms were evaluated with the Beck Depression Inventory , Hospital Anxiety and Depression Scale , Seasonal Pattern Assessment Scale and Montgomery-Åsberg Depression Rating Scale . The study was registered at Clinical Trials.gov ( NCT00960232 ) . RESULTS Participants with low 25(OH)D levels ( n = 230 ) at baseline were more depressed ( P<0.05 ) than participants with high 25(OH)D levels ( n = 114 ) . In the intervention study no significant effect of high-dose vitamin D was found on depressive symptom scores when compared with placebo . CONCLUSIONS Low levels of serum 25(OH)D are associated with depressive symptoms , but no effect was found with vitamin D supplementation Abstract Incidence of vitamin D deficiency is increasing worldwide . The purpose of this study was to determine if supplementation with vitamin D2 from Portobello mushroom powder would enhance skeletal muscle function and attenuate exercise-induced muscle damage in low vitamin D status high school athletes . Participants were r and omised to Portobello mushroom powder ( 600 IU/d vitamin D2 ) or placebo for 6 weeks . Participants then completed a 1.5-h exercise session design ed to induce skeletal muscle damage . Blood sample s and measures of skeletal muscle function were taken pre-supplementation , post-supplementation/pre-exercise and post-exercise . Six weeks supplementation with vitamin D2 increased serum 25(OH)D2 by 9.9-fold and decreased serum 25(OH)D3 by 28 % . Changes in skeletal muscle function and circulating markers of skeletal muscle damage did not differ between groups . In conclusion , 600 IU/d vitamin D2 increased 25(OH)D2 with a concomitant decrease in 25(OD)D3 , with no effect on muscular function or exercise-induced muscle damage in high school athletes OBJECTIVES Athletes who train indoors during the winter months exhibit low serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations due to a lack of sunlight exposure . This has been linked to impaired exercise performance . The purpose of this study was to assess the effects of oral vitamin D₃ supplementation on selected physical fitness and injury parameters in elite ballet dancers . DESIGN Controlled prospect i ve study . METHODS 24 elite classical ballet dancers ( intervention n=17 ; control n=7 ) participated in a controlled 4-month oral supplementation of vitamin D₃ ( 2000 IU per day ) . Isometric muscular strength and vertical jump height were measured pre and post intervention . Injury occurrence during the intervention period was also recorded by the in-house medical team . Repeated measures ANOVA and Mann-Whitney-U statistical tests were used and significance was set at p ≤ 0.05 . RESULTS Significant increases were noted for the intervention group for isometric strength ( 18.7 % , p<0.01 ) and vertical jump ( 7.1 % , p<0.01 ) . The intervention group also sustained significantly less injuries than the controls during the study period ( p<0.01 ) . CONCLUSIONS Oral supplementation of vitamin D₃ during the winter months has beneficial effects on muscular performance and injury occurrence in elite ballet dancers There is an ongoing debate over the role of serum 25(OH ) vitamin D [ 25(OH)D ] levels in maintaining or improving physical performance and muscle strength . Much of the controversy is because of the variability between studies in participants ' characteristics , baseline serum 25(OH)D levels , and baseline physical functioning . The aim of this ancillary study conducted within a r and omized controlled clinical trial was to investigate whether supplementation with 400 or 2000 IU vitamin D3 daily for 6 months would improve measures of physical performance and muscle strength in a community-dwelling elderly population aged 65 to 95 years . Those with the slowest gait speed improved their ability to do chair-st and tests after vitamin D supplementation . This finding remained significant after controlling for potential confounding variables . There was also an inverse correlation between serum 25(OH)D levels and fat mass index ( FMI ) among women , suggesting that higher supplementation with vitamin D is needed as weight increases . The results of this study suggest that supplementation with vitamin D may be most beneficial in older population s who have low baseline physical functioning
Both doses led to sufficiency concentrations during winter months .
Among athletes with baseline vitamin D suggesting sufficiency , serum 25(OH)D sufficiency was maintained from different doses at both latitudes .
Conclusion Despite achieving sufficiency in vitamin D concentrations from ≥3000 IU supplementation , physical performance did not significantly improve .
Background There is currently no systematic review examining the effects of vitamin D supplementation  among athletes .
A rigorous systematic review and meta- analysis is important to provide a balanced view of current knowledge on the effect of vitamin D on serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations and physical performance .
Objectives This systematic review of r and omized controlled trials ( RCTs ) evaluated the effects of oral vitamin D supplementation on serum 25(OH)D concentrations and physical performance in athletes .