title: Calcium and vitamin D supplementation maintains parathyroid hormone and improves bone density during initial military training: a randomized, double-blind, placebo controlled trial. Vitamin D Supplementation and Physical Performance in Adolescent Swimmers. Tibial bone responses to 6-month calcium and vitamin D supplementation in young male jockeys: A randomised 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 Vitamin D2 Supplementation Amplifies Eccentric Exercise-Induced Muscle Damage in NASCAR Pit Crew Athletes Low serum 25-hydroxyvitamin D is associated with increased risk of stress fracture during Royal Marine recruit training Wintertime Vitamin D Deficiency in Male Adolescents: Effect on Parathyroid Function and Response to Vitamin D3 Supplements The Efficacy of Vitamin D Supplementation During a Prolonged Submarine Patrol The effects of season-long vitamin D supplementation on collegiate swimmers and divers. A positive dose-response effect of vitamin D supplementation on site-specific bone mineral augmentation in adolescent girls: a double-blinded randomized placebo-controlled 1-year intervention. The effects of vitamin D3 supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose–response study Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial Vitamin D supplementation and upper respiratory tract infections in adolescent swimmers: a randomized controlled trial. The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: a controlled study. Influence of vitamin D mushroom powder supplementation on exercise-induced muscle damage in vitamin D insufficient high school athletes The impact of 1-year vitamin D supplementation on vitamin D status in athletes: a dose–response study The effect of 14 weeks of vitamin D3 supplementation on antimicrobial peptides and proteins in athletes Calcium and vitamin d supplementation decreases incidence of stress fractures in female navy recruits.
abstract: Calcium and vitamin D are essential nutrients for bone health . Periods of activity with repetitive mechanical loading , such as military training , may result in increases in parathyroid hormone ( PTH ) , a key regulator of Ca metabolism , and may be linked to the development of stress fractures . Previous studies indicate that consumption of a Ca and vitamin D supplement may reduce stress fracture risk in female military personnel during initial military training , but circulating markers of Ca and bone metabolism and measures of bone density and strength have not been determined . This r and omized , double-blind , placebo-controlled trial sought to determine the effects of providing supplemental Ca and vitamin D ( Ca+Vit D , 2000 mg and 1000IU/d , respectively ) , delivered as 2 snack bars per day throughout 9weeks of Army initial military training ( or basic combat training , BCT ) on PTH , vitamin D status , and measures of bone density and strength in personnel undergoing BCT , as well as independent effects of BCT on bone parameters . A total of 156 men and 87 women enrolled in Army BCT ( Fort Sill , OK ; 34.7 ° N latitude ) volunteered for this study . Anthropometric , biochemical , and dietary intake data were collected pre- and post-BCT . In addition , peripheral quantitative computed tomography was utilized to assess tibia bone density and strength in a subset of volunteers ( n=46 ) . Consumption of supplemental Ca+Vit D  increased circulating ionized Ca ( group-by-time , P=0.022 ) , maintained PTH ( group-by-time , P=0.032 ) , and increased the osteoprotegerin : RANKL ratio ( group-by-time , P=0.006 ) . Consistent with the biochemical markers , Ca+Vit D  improved vBMD ( group-by-time , P=0.024 ) at the 4 % site and cortical BMC ( group-by-time , P=0.028 ) and thickness ( group-by-time , P=0.013 ) at the 14 % site compared to placebo . These data demonstrate the benefit of supplemental Ca and vitamin D for maintaining bone health during periods of elevated bone turnover , such as initial military training . This trial was registered with ClincialTrials.gov , NCT01617109 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 Young male jockeys compromise bone health by engaging in caloric restriction and high volumes of physical activity during periods of musculoskeletal growth and development . The aim of this r and omised , double-blinded , placebo-controlled trial was to establish whether calcium and vitamin D supplementation would improve bone properties of young male jockeys . We conducted a 6-month trial with two groups of weight- , height- and age-matched apprentice male jockeys ( age=20.2 ± 3.2 yrs ) . Participants were supplemented with 800 mg of calcium and 400 IU of vitamin D ( S , n=8 ) or a placebo ( cellulose ) ( P , n=9 ) daily for 6-months . Baseline calcium intake was ( 669.7 ± 274.3 ( S ) vs 790.4 ± 423.9 ( P ) and vitamin D 64.6 ± 19.5 ( S ) vs 81.2 ± 24.4 ( P ) with no statistical differences . Peripheral quantitative computed tomography ( pQCT ) measured ultra-distal ( 4 % ) and proximal ( 66 % ) tibial bone properties at baseline and 6 months . Blood-borne markers of bone turnover , P1NP and CTX and vitamin D concentration were assessed . After co-varying for height , weight and baseline bone measurements , the supplemented group displayed greater post-intervention bone properties at the 66 % proximal site with cortical content ( mgmm ) 6.6 % greater ( p<0.001 ) , cortical area ( mm(2 ) ) 5.9 % larger ( p<0.001 ) , cortical density ( mgcm(2 ) ) 1.3 % greater ( p=0.001 ) , and total area ( mm(2 ) ) 4 % larger ( p=0.003 ) . No other between group differences in bone variables were observed . Blood analysis indicated higher vitamin D levels ( 18.1 % , p=0.014 ) and lower CTx ( ng/L ) ( -24.8 % , p=0.011 ) in the supplemented group with no differences observed in P1NP . This is the first r and omised controlled trial to examine the efficacy of calcium and vitamin D supplementation in improving bone properties in a highly vulnerable , young athletic , weight-restricted population . Results using pQCT indicate beneficial effects of supplementation on bone properties in as little as six months . Although the study size is small , this intervention appears promising as a strategy for improving bone health in young athletes in weight-restricted sports 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 This study determined if 6-weeks vitamin D2 supplementation ( vitD2 , 3800 IU/day ) had an influence on muscle function , eccentric exercise-induced muscle damage ( EIMD ) , and delayed onset of muscle soreness ( DOMS ) in National Association for Stock Car Auto Racing ( NASCAR ) NASCAR pit crew athletes . Subjects were r and omized to vitD2 ( n = 13 ) and placebo ( n = 15 ) , and ingested supplements ( double-blind ) for six weeks . Blood sample s were collected and muscle function tests conducted pre- and post- study ( leg-back and h and grip dynamometer strength tests , body weight bench press to exhaustion , vertical jump , 30-s Wingate test ) . Post- study , subjects engaged in 90 min eccentric-based exercise , with blood sample s and DOMS ratings obtained immediately after and 1- and 2-days post-exercise . Six weeks vitD2 increased serum 25(OH)D2 456 % and decreased 25(OH)D3 21 % versus placebo ( p < 0.001 , p = 0.036 , respectively ) , with no influence on muscle function test scores . The post- study eccentric exercise bout induced EIMD and DOMS , with higher muscle damage biomarkers measured in vitD2 compared to placebo ( myoglobin 252 % , 122 % increase , respectively , p = 0.001 ; creatine phosphokinase 24 h post-exercise , 169 % , 32 % , p < 0.001 ) , with no differences for DOMS . In summary , 6-weeks vitD2 ( 3800 IU/day ) significantly increased 25(OH)D2 and decreased 25(OH)D3 , had no effect on muscle function tests , and amplified muscle damage markers in NASCAR pit crew athletes following eccentric exercise Summary The aim of this study was to investigate vitamin D status and stress fracture risk during Royal Marine military training . Poor vitamin D status was associated with an increased risk of stress fracture .  Vitamin D supplementation may help to reduce stress fracture risk in male military recruits with low vitamin D status . Introduction Stress fracture is a common overuse injury in military recruits , including Royal Marine ( RM ) training in the UK . RM training is recognised as one of the most arduous basic training programmes in the world . Associations have been reported between serum 25-hydroxyvitamin D ( 25(OH)D ) and risk of stress fracture , but the threshold of 25(OH)D for this effect remains unclear . We aim ed to determine if serum 25(OH)D concentrations were associated with stress fracture risk during RM training . Methods We prospect ively followed 1082 RM recruits ( males aged 16–32 years ) through the 32-week RM training programme . Troops started training between September and July . Height , body weight and aerobic fitness were assessed at week 1 . Venous blood sample s were drawn at weeks 1 , 15 and 32 . Serum sample s were analysed for 25(OH)D and parathyroid hormone ( PTH ) . Results Seventy-eight recruits ( 7.2 % ) suffered a total of 92 stress fractures . Recruits with a baseline serum 25(OH)D concentration below 50 nmol L−1 had a higher incidence of stress fracture than recruits with 25(OH)D concentration above this threshold ( χ2(1 ) = 3.564 , p = 0.042 ; odds ratio 1.6 ( 95 % confidence interval ( CI ) 1.0–2.6 ) ) . Baseline serum 25(OH)D varied from 47.0 ± 23.7 nmol L−1 in February , to 97.3 ± 24.6 nmol L−1 in July ( overall mean 69.2 ± 29.2 nmol L−1 , n = 1016 ) . There were weak inverse correlations between serum 25(OH)D and PTH concentrations at week 15 ( r = −0.209 , p < 0.001 ) and week 32 ( r = −0.214 , p < 0.001 ) , but not at baseline . Conclusion Baseline serum 25(OH)D concentration below 50 nmol L−1 was associated with an increased risk of stress fracture . Further studies into the effects of vitamin D supplementation on stress fracture risk are certainly warranted Abstract : The first part of this study consisted of an 18 month follow-up of the vitamin D status and parathyroid function in a group of 54 French male adolescents , aged from 13 to 16 years old and all pupils of a jockey training school . During the 18 month period four samplings were made , one every 6 months . The first was during September of the first year , the second and third during March and October of the second year , and the last in March of the third year . Therefore we had two main periods : summer and winter . The summer 25-hydroxyvitamin D ( 25(OH)D ) concentrations were higher ( 71.6 ± 19.9 and 52.4 ± 16.5 nmol/l ) than the winter ones ( 20.4 ± 6.9 and 21.4 ± 6.1 nmol/l ) . Conversely , the winter intact parathyroid hormone ( iPTH ) serum levels ( 4.18 ± 1.18 and 4.11 ± 1.35 pmol/l ) were higher than the summer ones ( 2.44 ± 0.82 and 2.71 ± 0.71 pmol/l ) . At the two winter time points the 25(OH)D concentrations were lower than 25 nmol/l ( 10 ng/ml ) in 72 % ( 2nd year ) and 68 % ( 3rd year ) of the adolescents . In the second part of the study we tried a vitamin D3 supplementation procedure design ed to maintain the 25(OH)D and iPTH postsummer serum levels throughout the winter . Pairs of male adolescents matched for height , weight and Tanner pubertal stage were r and omly assigned to either vitamin D3 supplementation ( 2.5 mg , i.e. , 100 000 IU ) administered orally at three specific periods ( end of September , November and January ) or no vitamin D3 treatment ( control subjects ) . Blood was collected just before the first intake of vitamin D3 and 2 months after the last intake ( March ) . The control subjects had blood drawn at the same time points . In the vitamin D3-treated subjects , the concentrations of 25 (OH)D ( 55.3 ± 11.5 nmol/l ) and of iPTH ( 3.09 ± 1.16 pmol/l ) in March and September ( 53.8 ± 12.3 nmol/l and 2.75 ± 1.26 pmol/l ) were not significantly different . In the control subjects , March 25(OH)D levels ( 21.0 ± nmol/l were low , with values below 25 nmol/l in 78 % of subjects , and iPTH concentrations ( 3.97 ± 1.08 pmol/l ) were significantly ( p<0.001 ) higher than in September ( 2.91 ± 0.81 pmol/l ) . The constant vitamin D wintertime deficiency and wintertime rise in iPTH in adolescent French males throughout puberty has been demonstrated . In adolescents with low dairy calcium intakes , the vitamin D3 treatment was sufficient to maintain 25(OH)D concentrations at their summer levels throughout winter and to prevent an excessive wintertime rise in iPTH levels Submariners spend prolonged periods submerged without sunlight exposure and may benefit from vitamin D supplementation to maintain vitamin D status . The primary objective of this study was to determine the efficacy of daily vitamin D supplementation on maintenance of 25-hydroxyvitamin D ( 25(OH)D ) during a 3-month submarine patrol . Submariners were r and omly divided into three groups : placebo ( n = 16 ) , 1,000 IU/day ( n = 20 ) , or 2,000 IU/day ( n = 17 ) . Anthropometrics , self-reported dietary calcium and vitamin D intake , serum markers of vitamin D and bone metabolism , and peripheral quantitative computed tomography ( pQCT ) parameters of the tibia were determined before and after the patrol . Prior to departure , 49 % of the subjects were vitamin D insufficient ( < 50 nmol/L ) . Following the patrol , 25(OH)D increased in all groups ( p < 0.001 ) : 3.3 ± 13.1 ( placebo ) , 4.6 ± 11.3 ( 1,000 IU/day ) , and 13 ± 14 nmol/L ( 2,000 IU/day ) . The changes in 25(OH)D levels were dependent upon the baseline concentration of 25(OH)D and body mass ( p < 0.001 ) . Osteocalcin increased by 38 % ( p < 0.01 ) , and pQCT analyses revealed small , yet significant increases in indices of tibial structure and strength ( p < 0.05 ) that were independent of supplementation . These data suggest that vitamin D status was low prior to the patrol , and the subsequent changes in vitamin D status were dependent on the baseline 25(OH)D levels and body mass . Furthermore , short-term skeletal health does not appear to be negatively affected by 3 months of submergence in spite of a suboptimal response to vitamin D supplementation 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 UNLABELLED The effect of vitamin D supplementation on bone mineral augmentation in 212 adolescent girls with adequate calcium intake was studied in a r and omized placebo-controlled setting . Bone mineral augmentation determined by DXA increased with supplementation both in the femur and the lumbar vertebrae in a dose-responsive manner . Supplementation decreased the urinary excretion of resorption markers , but had no impact on formation markers . INTRODUCTION Adequate vitamin D intake protects the elderly against osteoporosis , but there exists no indisputable evidence that vitamin D supplementation would benefit bone mineral augmentation . The aim of this 1-year study was to determine in a r and omized double-blinded trial the effect of 5 and 10 microg vitamin D3 supplementation on bone mineral augmentation in adolescent girls with adequate dietary calcium intake . MATERIAL S AND METHODS Altogether , 228 girls ( mean age , 11.4 + /- 0.4 years ) participated . Their BMC was measured by DXA from the femur and lumbar spine . Serum 25-hydroxyvitamin D [ S-25(OH)D ] , intact PTH ( S-iPTH ) , osteocalcin ( S-OC ) , and urinary pyridinoline ( U-Pyr ) and deoxypyridinoline ( U-Dpyr ) were measured . Statistical analysis was performed both with the intention-to-treat ( IT ) and compliance-based ( CB ) method . RESULTS In the CB analysis , vitamin D supplementation increased femoral BMC augmentation by 14.3 % with 5 microg and by 17.2 % with 10 microg compared with the placebo group ( ANCOVA , p = 0.012 ) . A dose-response effect was observed in the vertebrae ( ANCOVA , p = 0.039 ) , although only with the highest dose . The mean concentration of S-25(OH)D increased ( p < 0.001 ) in the 5-microg group by 5.7 + /- 15.7 nM and in the 10-microg group by 12.4 + /- 13.7 nM , whereas it decreased by 6.7 + /- 11.3 nM in the placebo group . Supplementation had no effect on S-iPTH or S-OC , but it decreased U-DPyr ( p = 0.042 ) . CONCLUSIONS Bone mineral augmentation in the femur was 14.3 % and 17.2 % higher in the groups receiving 5 and 10 microg of vitamin D , respectively , compared with the placebo group , but only 10 mug increased lumbar spine BMC augmentation significantly . Vitamin D supplementation decreased the concentration of bone resorption markers , but had no impact on bone formation markers , thus explaining increased bone mineral augmentation . However , the positive effects were noted with the CB method but not with IT 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 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 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 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 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 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 Abstract Heavy training is associated with increased respiratory infection risk and antimicrobial proteins are important in defence against oral and respiratory tract infections . We examined the effect of 14 weeks of vitamin D3 supplementation ( 5000 IU/day ) on the resting plasma cathelicidin concentration and the salivary secretion rates of secretory immunoglobulin A ( SIgA ) , cathelicidin , lactoferrin and lysozyme in athletes during a winter training period .  Blood and saliva were obtained at the start of the study from 39 healthy men who were r and omly allocated to vitamin D3 supplement or placebo .  Blood sample s were also collected at the end of the study ; saliva sample s were collected after 7 and 14 weeks . Plasma total 25(OH)D concentration increased by 130 % in the vitamin D3 group and decreased by 43 % in the placebo group ( both P = 0.001 ) . The percentage change of plasma cathelicidin concentration in the vitamin D3 group was higher than in the placebo group ( P = 0.025 ) . Only in the vitamin D3 group , the saliva SIgA and cathelicidin secretion rates increased over time ( both P = 0.03 ) . A daily 5000 IU vitamin D3 supplement has a beneficial effect in up-regulating the expression of SIgA and cathelicidin in athletes during a winter training period , which could improve resistance to respiratory infections INTRODUCTION Stress fractures ( SFx ) are one of the most common and debilitating overuse injuries seen in military recruits , and they are also problematic for nonmilitary athletic population s. The goal of this r and omized double-blind , placebo-controlled study was to determine whether a calcium and vitamin D intervention could reduce the incidence of SFx in female recruits during basic training . MATERIAL S AND METHODS We recruited 5201 female Navy recruit volunteers and r and omized them to 2000 mg calcium and 800 IU vitamin D/d or placebo .  SFx were ascertained when recruits reported to the Great Lakes clinic with symptoms . All SFx were confirmed with radiography or technetium scan according to the usual Navy protocol . RESULTS A total of 309 subjects were diagnosed with a SFx result ing in an incidence of 5.9 % per 8 wk . Using intention-to-treat analysis by including all enrolled subjects , we found that the calcium and vitamin D group had a 20 % lower incidence of SFx than the control group ( 5.3 % versus 6.6 % , respectively , p = 0.0026 for Fisher 's exact test ) . The per protocol analysis , including only the 3700 recruits who completed the study , found a 21 % lower incidence of fractures in the supplemented versus the control group ( 6.8 % versus 8.6 % , respectively , p = 0.02 for Fisher 's exact test ) . CONCLUSIONS Generalizing the findings to the population of 14,416 women who entered basic training at the Great Lakes during the 24 mo of recruitment , calcium and vitamin D supplementation for the entire cohort would have prevented approximately 187 persons from fracturing . Such a decrease in SFx would be associated with a significant decrease in morbidity and financial costs
target: 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: 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 .