title: Tibial bone responses to 6-month calcium and vitamin D supplementation in young male jockeys: A randomised controlled trial. Vitamin D3 Supplementation Does Not Improve Sprint Performance in Professional Rugby Players: A Randomized, Placebo-Controlled, Double-Blind Intervention Study. Evidence that vitamin D3 increases serum 25-hydroxyvitamin D more efficiently than does vitamin D2. Vitamin D2 Supplementation Amplifies Eccentric Exercise-Induced Muscle Damage in NASCAR Pit Crew Athletes Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Wintertime Vitamin D Deficiency in Male Adolescents: Effect on Parathyroid Function and Response to Vitamin D3 Supplements The effects of season-long vitamin D supplementation on collegiate swimmers and divers. Low vitamin D and high parathyroid hormone levels as determinants of loss of muscle strength and muscle mass (sarcopenia): the Longitudinal Aging Study Amsterdam. Ergocalciferol from mushrooms or supplements consumed with a standard meal increases 25-hydroxyergocalciferol but decreases 25-hydroxycholecalciferol in the serum of healthy adults. Improving the vitamin D status of vitamin D deficient adults is associated with improved mitochondrial oxidative function in skeletal muscle. Correcting Vitamin D Insufficiency Improves Some But Not All Aspects of Physical Performance During Winter Training in Taekwondo Athletes. Vitamin D and health in pregnancy, infants, children and adolescents in Australia and New Zealand: a position statement. Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial 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
abstract: 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 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 In all species tested , except humans , biological differences between vitamins D2 and D3 are accepted as fact . To test the presumption of equivalence in humans , we compared the ability of equal molar quantities of vitamin D2 or D3 to increase serum 25-hydroxyvitamin D [ 25(OH)D ] , the measure of vitamin D nutrition .  Subjects took 260 nmol ( approximately 4000 IU ) vitamin D2  ( n=17 ) or vitamin D3  ( n=55 ) daily for 14 d. 25(OH)D was assayed with a method that detects both the vitamin D2 and D3 forms . With vitamin D3 , mean ( + /-SD ) serum 25(OH)D increased from 41.3+/-17.7 nmol/L before to 64.6+/-17.2 nmol/L after treatment . With vitamin D2 , the 25(OH)D concentration went from 43.7+/-17.7 nmol/L before to 57.4+/-13.0 nmol/L after . The increase in 25(OH)D with vitamin D3  was 23.3+/-15.7 nmol/L , or 1.7 times the increase obtained with vitamin D2 ( 13.7+/-11.4 nmol/L ; P=0.03 ) . There was an inverse relation between the increase in 25(OH)D and the initial 25(OH)D concentration . The lowest 2 tertiles for basal 25(OH)D showed larger increases in 25(OH)D : 30.6 and 25.5 nmol/L , respectively , for the first and second tertiles . In the highest tertile [ 25(OH)D > 49 nmol/L ] the mean increase in 25(OH)D was 13.3 nmol/L ( P < 0.03 for comparison with each lower tertile ) . Although the 1.7-times greater efficacy for vitamin D3 shown here may seem small , it is more than what others have shown for 25(OH)D increases when comparing 2-fold differences in vitamin D3 dose . The assumption that vitamins D2 and D3 have equal nutritional value is probably wrong and should be reconsidered 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 Public health recommendations do not distinguish between vitamin D2 and vitamin D3 , yet disagreement exists on whether these two forms should be considered equivalent . The objective of the present study was to evaluate the effect of a daily physiological dose of vitamin D2 or vitamin D3 on 25-hydroxyvitamin D ( 25(OH)D ) status over the winter months in healthy adults living in Dunedin , New Zeal and ( latitude 46 ° S ) . Participants aged 18 - 50 years were r and omly assigned to 25 μg ( 1000 IU ) vitamin D3 ( n 32 ) , 25 μg ( 1000 IU ) vitamin D2 ( n 31 ) or placebo ( n 32 ) daily for 25 weeks beginning at the end of summer . A per- protocol approach , which included ≥ 90 % supplement compliance , was used for all analyses . Serum 25-hydroxyvitamin D3 ( 25(OH)D3 ) , 25-hydroxyvitamin D2 ( 25(OH)D2 ) and parathyroid hormone ( PTH ) were measured at baseline and at 4 , 8 , 13 and 25 weeks . Geometric mean total serum 25(OH)D concentrations ( sum of 25(OH)D2 and 25(OH)D3 ) at baseline was 80 nmol/l . After 25 weeks , participants r and omised to D2 and placebo had a significant reduction in serum 25(OH)D3 concentrations over the winter months compared with vitamin D3-supplemented participants ( both P < 0.001 ) . Supplementation with vitamin D2  increased serum 25(OH)D2 but produced a 9 ( 95 % CI 1 , 17 ) nmol/l greater decline in the 25(OH)D3 metabolite compared with placebo ( P < 0.036 ) . Overall , total serum 25(OH)D concentrations were 21 ( 95 % CI 14 , 30 ) nmol/l lower in participants receiving vitamin D2 compared with those receiving D3 ( P < 0.001 ) , among whom total serum 25(OH)D concentrations remained unchanged . No intervention-related changes in PTH were observed . Daily supplementation of vitamin D3 was more effective than D2 ; however , the functional consequence of the differing metabolic response warrants further investigation 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 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 The age-related change in hormone concentrations has been hypothesized to play a role in the loss of muscle mass and muscle strength with aging , also called sarcopenia . The aim of this prospect i ve study was to investigate whether low serum 25-hydroxyvitamin D ( 25-OHD ) and high serum PTH concentration were associated with sarcopenia . In men and women aged 65 yr and older , participants of the Longitudinal Aging Study Amsterdam , grip strength ( n = 1008 ) and appendicular skeletal muscle mass ( n = 331 , using dual-energy x-ray absorptiometry ) were measured in 1995 - 1996 and after a 3-yr follow-up . Sarcopenia was defined as the lowest sex-specific 15th percentile of the cohort , translating into a loss of grip strength greater than 40 % or a loss of muscle mass greater than 3 % . After adjustment for physical activity level , season of data collection , serum creatinine concentration , chronic disease , smoking , and body mass index , persons with low ( < 25 nmol/liter ) baseline 25-OHD levels were 2.57 ( 95 % confidence interval 1.40 - 4.70 , based on grip strength ) and 2.14 ( 0.73 - 6.33 , based on muscle mass ) times more likely to experience sarcopenia , compared with those with high ( > 50 nmol/liter ) levels . High PTH levels ( > or=4.0 pmol/liter ) were associated with an increased risk of sarcopenia , compared with low PTH ( < 3.0 pmol/liter ) : odds ratio = 1.71 ( 1.07 - 2.73 ) based on grip strength , odds ratio = 2.35 ( 1.05 - 5.28 ) based on muscle mass . The associations were similar in men and women . The results of this prospect i ve , population -based study show that lower  25-OHD  and higher  PTH levels increase the risk of sarcopenia in older men and women Few foods contain ergocalciferol or cholecalciferol . Treatment of mushrooms with UV light increases ergocalciferol content and could provide a dietary source of vitamin D. We evaluated the impact of consuming UV-treated white button mushrooms ( Agaricus bisporus ) on the vitamin D status of healthy adults . Thirty-eight volunteers were r and omized to 4 treatments consumed with a st and ard meal for 6 wk : the control ( C ) group received untreated mushrooms providing 0.85 μg/d ergocalciferol ( n = 10 ) ; groups M1 and M2 received UV-treated mushrooms providing 8.8 ( n = 10 ) and 17.1 μg/d ( n = 9 ) , respectively ; and the supplement ( S ) group received purified ergocalciferol plus untreated mushrooms , providing a total of 28.2 μg/d ( n = 9 ) . Serum total 25-hydroxyvitamin D [ 25(OH)D ] and 25-hydroxyergocalciferol [ 25(OH)D2 ] were 83 ± 38 and 2.4 ± 2.0 nmol/L , respectively , at baseline ( mean ± SD ) . At wk 6 , 25(OH)D2 had increased and was higher in all treatment groups than in the C group , whereas 25-hydroxycholecalciferol [ 25(OH)D3 ] had decreased and was lower in the M2 and S groups than in the C group . Increases in 25(OH)D2 for groups C , M1 , M2 , and S were 1.2 ± 5.2 , 13.8 ± 7.3 , 12.7 ± 3.7 , and 32.8 ± 3.3 nmol/L and decreases in 25(OH)D3 were -3.9 ± 16.3 , -10.4 ± 6.4 , -20.6 ± 14.6 , and -29.5 ± 15.9 nmol/L , respectively . Concentrations did not change in group C. In summary , ergocalciferol was absorbed and metabolized to 25(OH)D2 but did not affect vitamin D status , because 25(OH)D3 decreased proportionally OBJECTIVE Suboptimal mitochondrial function has been implicated in several disorders in which fatigue is a prominent feature . Vitamin D deficiency is a well-recognized cause of fatigue and myopathy . The aim of this study was to examine the effects of cholecalciferol therapy on skeletal mitochondrial oxidative function in symptomatic , vitamin D-deficient individuals . DESIGN This longitudinal study assessed mitochondrial oxidative phosphorylation in the gastrosoleus compartment using phosphorus-31 magnetic resonance spectroscopy measurements of phosphocreatine recovery kinetics in 12 symptomatic , severely vitamin D-deficient subjects before and after treatment with cholecalciferol .  All subjects had serum assays before and after cholecalciferol therapy to document serum 25-hydroxyvitamin D ( 25OHD ) and bone profiles . Fifteen healthy controls also underwent (31)P-magnetic resonance spectroscopy and serum 25OHD assessment . RESULTS The phosphocreatine recovery half-time ( τ1/2PCr ) was significantly reduced after cholecalciferol therapy in the subjects indicating an improvement in maximal oxidative phosphorylation ( 34.44 ± 8.18 sec to 27.84 ± 9.54 sec , P < .001 ) . This was associated with an improvement in mean serum 25OHD levels ( 8.8 ± 4.2 nmol/L to 113.8 ± 51.5 nmol/L , P < .001 ) . There was no difference in phosphate metabolites at rest . A linear regression model showed that decreasing serum 25OHD levels was associated with increasing τ1/2PCr ( r = -0.41 , P = .009 ) . All patients reported an improvement in fatigue  after cholecalciferol therapy . CONCLUSIONS Cholecalciferol therapy augments muscle mitochondrial maximal oxidative phosphorylation after exercise in symptomatic , vitamin D-deficient individuals . This finding suggests that changes in mitochondrial oxidative phosphorylation in skeletal muscle could at least be partly responsible for the fatigue experienced by these patients . For the first time , we demonstrate a link between vitamin D and the mitochondria in human skeletal muscle We investigated the effects of vitamin D3 supplementation on physical performance during winter training in vitamin D insufficient taekwondo athletes . Thirty-five collegiate male and female taekwondo athletes , aged 19 - 22 years with low serum 25(OH)D concentration ( 28.8 ± 1.10 nmol/L ) , were r and omly assigned to a vitamin D group ( n = 20 ) or a placebo group ( n = 15 ) . Subjects received either a vitamin D3 capsule ( 5,000 IU/day ) or a placebo during 4 weeks of winter training . Blood sample s were collected for analyzing serum 25(OH)D concentration . Physical performance tests included Wingate anaerobic test , isokinetic muscle strength and endurance , a countermovement jump test , sit-ups , agility test , and 20-m pacer . Serum 25(OH)D concentrations increased significantly in the vitamin D group ( 96.0 ± 3.77 nmol/L ) after 4 weeks of supplementation , but no changes were found in the placebo group ( F = 242.44 , p = .000 ) . There were significant interaction effects for anaerobic peak power ( F = 7.49 , p = .010 ) and isokinetic knee extension at 180 deg/s ( F = 6.08 , p = .019 ) . Changes in serum 25(OH)D concentration were positively associated with changes in peak power and isokinetic knee extension at 180 deg/s . However , no significant interaction effects were observed in other performance variables . This study suggests that 4 weeks of vitamin D supplementation elevates serum 25(OH)D concentration to sufficient levels . Correcting vitamin D insufficiency improves some but not all aspects of performance . Thus , efficacy of vitamin D supplementation to enhance performance remains unclear • The recommended level for serum 25-hydroxyvitamin D ( 25(OH)D ) in infants , children , adolescents and during pregnancy and lactation is ≥ 50 nmol/L. This level may need to be 10 - 20 nmol/L higher at the end of summer to maintain levels ≥ 50 nmol/L over winter and spring . • Sunlight is the most important source of vitamin D. The US recommended dietary allowance for vitamin D is 600 IU daily in children aged over 12 months and during pregnancy and lactation , assuming minimal sun exposure . • Risk factors for low vitamin D are : lack of skin exposure to sunlight , dark skin , southerly latitude , conditions affecting vitamin D metabolism and storage ( including obesity ) and , for infants , being born to a mother with low vitamin D and exclusive breastfeeding combined with at least one other risk factor . • Targeted measurement of 25(OH)D levels is recommended for infants , children and adolescents with at least one risk factor for low vitamin D and for pregnant women with at least one risk factor for low vitamin D at the first antenatal visit . • Vitamin D deficiency can be treated with daily low-dose vitamin D supplements , although barriers to adherence have been identified . High-dose intermittent vitamin D can be used in children and adolescents . Treatment should be paired with health education and advice about sensible sun exposure . Infants at risk of low vitamin D should be supplemented with 400 IU vitamin D₃ daily for at least the first year of life . • There is increasing evidence of an association between low vitamin D and a range of non-bone health outcomes , however there is a lack of data from robust r and omised controlled trials of vitamin D supplementation 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 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
target: Conclusion Although , serum 25(OH)D concentrations after supplementation reached sufficiency was observed , muscle strength did not significantly improve at this point of current meta- analysis .
background: Background The purpose of this systematic review and meta- analysis is to investigate the effects of vitamin D3 supplementation on skeletal muscle strength in athletes .
  Vitamin D3 supplements or vitamin D3 fortified foods always have cl aims for bringing people health benefits including bone and muscle health .
  An up-to- date rigorous systematic review and meta- analysis is important to better underst and the effect of vitamin D3 supplementation on muscle strength .