Vitamin D Supplementation and Physical Performance in Adolescent Swimmers. Effect of vitamin D supplementation on inflammation: protocol for a systematic review The effects of vitamin D3 supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose–response study Correcting Vitamin D Insufficiency Improves Some But Not All Aspects of Physical Performance During Winter Training in Taekwondo Athletes. Vitamin D3 Supplementation Does Not Improve Sprint Performance in Professional Rugby Players: A Randomized, Placebo-Controlled, Double-Blind Intervention Study. Efficacy of vitamin D supplementation in depression in adults: a systematic review protocol The impact of 1-year vitamin D supplementation on vitamin D status in athletes: a dose–response study The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: a controlled study. A systematic review protocol examining the effect of vitamin D supplementation on endothelial function Serum 25-Hydroxyvitamin D Concentrations and Risk for Hip Fractures Calcium Absorption Varies within the Reference Range for Serum 25-Hydroxyvitamin D Vitamin A to prevent bronchopulmonary dysplasia in very-low-birth-weight infants: has the dose been too low? The NICHD Neonatal Research Network. Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial Vitamin D: do we get enough? Serum Vitamin D levels and Vitamin D supplementation do not correlate with the severity of chronic eczema in children. Association Between Vitamin D Supplementation During Pregnancy and Offspring Growth, Morbidity, and Mortality Vitamin D intake is low and hypovitaminosis D common in healthy 9− to 15-year-old Finnish girls 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
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 Introduction The extraskeletal role of vitamin D is being increasingly recognised . This has important clinical implication s , as vitamin D deficiency has reached epidemic proportions worldwide . Vitamin D has proposed anti-inflammatory properties , yet the role of vitamin D supplementation in reducing inflammation remains largely unknown . The purpose of this review is to investigate the impact of vitamin D supplementation on inflammation , and to identify relevant knowledge gaps in the field . Methods and analysis Medline , CINAHL , EMBASE and All EBM will be systematic ally search ed for r and omised controlled trials ( RCTs ) and systematic review s of RCTs , comparing vitamin D supplementation with placebo , usual care or other pharmacological or non-pharmacological interventions . One review er will assess articles for eligibility according to prespecified selection criteria , after which 2 independent review ers will perform data extraction and quality appraisal . Meta-analyses will be conducted where appropriate . Ethics and dissemination Formal ethical approval is not required as no primary data is collected . This systematic review will identify potential clinical implication s of vitamin D deficiency and supplementation , and will be disseminated through a peer- review ed publication and at conference meetings , to inform future research on the efficacy of vitamin D supplementation for inflammation and inflammatory diseases . PROSPERO registration number CRD42016037104 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 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 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 Background The role of vitamin D in management of depression is unclear . Results from observational and emerging r and omized controlled trials ( RCTs ) investigating the efficacy of vitamin D in depression lack consistency - with some suggesting a positive association while others show a negative or inconclusive association . Methods / Design The primary aim of this study is to conduct a systematic review of RCTs to assess the effect of oral vitamin D supplementation versus placebo on depression symptoms measured by scales and the proportion of patients with symptomatic improvement according to the authors ’ original definition . Secondary aims include assessing the change in quality of life , adverse events and treatment discontinuation . We will conduct the systematic review and meta- analysis according to the recommendations of the Cochrane H and book for Systematic Review s of Interventions . We will search the Cochrane Central Register of Controlled Trials ( CENTRAL ) , MEDLINE ( 1966 to present ) , EMBASE ( 1980 to present ) , CINAHL ( 1982 to present ) , PsychINFO ( 1967 to present ) and Clinical Trials.gov . Unpublished work will be identified by search ing two major conferences : the International Vitamin Conference , the Anxiety Disorders and Depression Conference , while grey literature will be acquired by contacting authors of included studies . We will use the r and om-effects meta- analysis to synthesize the data by pooling the results of included studies . Discussion The results of this systematic review will be helpful in clarifying the efficacy of vitamin D supplementation and providing evidence to establish guidelines for implementation of vitamin D for depression in general practice and other relevant setting s. Study registration Unique identifier : CRD42013003849 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 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 Introduction Vitamin D has potential benefits for extraskeletal health . These could include an anti-inflammatory effect as well as a reduction in endothelial dysfunction . We aim to provide quality evidence for the hypothesis that supplementation with vitamin D will improve endothelial function ( EF ) , possibly through the abrogation of systemic inflammation . Methods and analysis We will conduct a systematic review of all r and omised controlled trials on  vitamin D supplementation and EF lasting 12 weeks or more . The search will cover the period 2000–2015 and include studies that describe direct measures of EF  , markers of endothelial cell ( EC ) activation  and if concurrently reported , indicators of systemic inflammation  . Study selection will follow the Preferred Reporting Items for Systematic Review s and Meta-Analyses ( PRISMA ) guidelines and study quality will be assessed by the Jadad score in addition to an evaluation of allocation concealment and data analysis . If sufficient data are available , a meta- analysis will be conducted . The effect sizes will be generated using Hedges ’ g score , for both fixed and r and om effect models . I2 statistics and Galbraith plots will be used to assess heterogeneity and identify their potential sources . Potential publication and small sample size bias will be assessed by visual inspections of funnel plots and also Egger 's test . Meta-regression analysis ( if feasible ) will be conducted with restricted maximum likelihood ( REML ) estimation method , controlling for potential confounders ( demographics , study methods , location , etc ) . A backward elimination process will be applied in the regression modelling procedure . Subgroup analysis , conditional on number of studies retrieved and their sample size , will be stratified on participant disease category , total dose administered , degree of 25(OH)D change and type of supplement used . Ethics and dissemination Formal ethical approval is not required as primary data will not be collected . The results will be disseminated through a peer- review ed publication , conference presentation and the popular press . Trial registration number International Prospect i ve Register for Systematic Review s ( PROSPERO ) number CRD42014013523 Context Vitamin D supplementation may help prevent fractures , but the relationship between blood vitamin D concentrations and fracture risk is unclear . Contribution These authors observed an increased risk for hip fracture among women with lower serum 25-hydroxyvitamin D [ 25(OH ) vitamin D ] concentrations that was independent of measures of frailty , body mass index , physical function , and falls . Caution The authors did not measure bone mineral density ( BMD ) , so they could not determine whether 25(OH ) vitamin D concentrations give different information about fracture risk than that offered by BMD . Implication Low serum 25(OH ) vitamin D concentrations seem to be associated with a higher hip fracture risk . The Editors Vitamin  D deficiency is common in older adults , especially during the winter ( 1 ) and in homebound population s ( 2 ) , general medical in patients ( 3 ) , and community-dwelling women admitted to the hospital with acute hip fracture ( 4 ) . A recently published evidence -based report on vitamin D and bone health ( 5 ) found the level of evidence for an association between serum 25-hydroxyvitamin D [ 25(OH ) vitamin D ] concentrations and fracture risk to be inconsistent ( 5 ) . Since publication of that review , 1 prospect i ve study ( 6 ) reported no relationship between serum 25(OH ) vitamin D concentrations and fractures , whereas another ( 7 ) reported a significantly lower risk for hip fracture with 25(OH ) vitamin D concentrations greater than 60 nmol/L. Vitamin D concentration could be associated with fractures in several ways . It could influence muscle strength and balance , both of which contribute to falls and disability ( 810 ) . The association between 25(OH ) vitamin D concentrations and fracture may also be influenced by renal function , because renal insufficiency has been linked to fracture ( 11 ) and to vitamin D deficiency ( 12 ) . Several interactions between vitamin D and estrogen receptors have been described ( 13 ) ; hormone therapy has been shown to reverse abnormalities in vitamin D metabolism ( 14 ) , and low vitamin D concentrations have also been linked to higher bone turnover ( 15 , 16 ) . Thus , sex-steroid hormones and bone turnover could contribute to the association between 25(OH ) vitamin D concentration and fractures . We conducted a nested casecontrol study within the WHI-OS ( Women 's Health Initiative Observational Study ) among 400 case- patients with adjudicated incident hip fracture and 400 control participants . We tested whether low serum 25(OH ) vitamin D concentrations are associated with a higher risk for hip fractures in community-dwelling women and whether this relationship may be mediated by poor physical functioning , frailty , falls , sex-steroid hormones , renal function , or bone turnover . Methods Study Population Our study population came from the WHI-OS , a prospect i ve cohort study that enrolled 93676 women between 1994 and 1998 at 40 U.S. clinical centers ( age range , 50 to 79 years ) . Study methods are described in detail elsewhere ( 17 ) . In brief , women were eligible if they were postmenopausal , were unlikely to move or die within 3 years , were not enrolled in the WHI clinical trials , and were not currently participating in any other clinical trial . The human subjects review committees from each participating institution approved the study . Follow-up and Outcome Ascertainment We sent women question naires annually to report any hospitalization and other outcomes , including fractures . As of August 2004 , median follow-up duration was 7.1 years ( range , 0.7 to 9.3 years ) . At that time , 3.7 % of participants had withdrawn or were lost to follow-up and 5.3 % had died . We review ed medical records to verify cases of hip fracture , and blinded central adjudicators confirmed the cases ( 18 ) . We excluded patients with pathologic hip fractures . Nested CaseControl Study Design The present study is a casecontrol study nested within the prospect i ve design of WHI-OS . We excluded women who had a history of hip fracture ; were receiving hormone therapy up to 1 year before enrollment ; or were currently receiving and rogens , selective estrogen receptor modulators , antiestrogens , or other osteoporosis treatments ( bisphosphonates , calcitonin , or parathyroid hormone ) . We also excluded women with insufficient serum stored or of unknown ethnicity , leaving 39793 eligible participants . Of these , 404 women had a hip fracture . We r and omly selected 400 of these women to form the incident hip fracture group . For each case-patient , we selected 1 control participant who was within 1 year of the case-patient 's age at screening , was of matching race or ethnicity , and had their blood drawn within 120 days of the case-patient 's blood draw date ; 99 % of case- patients and control participants were matched within 30 days . Baseline Clinical Variables We divided clinical centers into 3 geographic regions on the basis of latitude : northern ( > 40 N ) , middle ( 35 to 40 N ) , and southern ( < 35 N ) . We ascertained all covariates at baseline . Clinic interviewers recorded current use of prescription medications by direct inspection of medicine containers . We entered prescription names into the WHI data base and assigned drug codes by using Medispan software ( First Data Bank , San Bruno , California ) . Average amounts of elemental calcium and vitamin D preparations were entered directly from supplement containers . Dietary intakes of calcium and vitamin D were assessed by using a semiquantitative food-frequency question naire ( 19 ) . Total calcium and vitamin D intake was defined as the sum of diet and supplements . We used question naires to ascertain date of birth , race or ethnicity , age at menopause , history of any fracture after age 55 years , smoking , parental history of hip fracture , self-rated health status , and alcohol consumption . We classfied physical activity on the basis of frequency and duration of walking and mild , moderate , and strenuous activities in the previous week . We calculated kilocalories of energy expended in 1 week as the metabolic equivalent ( kcal hours/week per kg ) ( 20 ) . We measured physical function by using the R AND Short Form-36 physical function scale , which comprises 10 items measuring whether health now limits physical function in moderate or vigorous activity ( 2 items ) ; strength to lift , carry , stoop , bend , or stair climb ( 4 items ) ; ability to walk various distances without difficulty ( 3 items ) ; and self-care ( 1 item ) ( 21 ) . The scale is scored from 0 to 100 , with higher scores indicating better physical function . We compared women with a score greater than 90 versus those with a score less than or equal to 90 , a cutoff value corresponding to the median score . We computed a frailty score , which included self-reported muscle weakness and impaired walking speed ( R AND Short Form-36 physical function scale score < 75 ) , exhaustion ( R AND Short Form-36 vitality scale score < 55 ) , low physical activity ( lowest quartile of physical activity ) , and unintended weight loss between baseline and 3 years of follow-up ( 22 ) . A woman was considered frail if she reported 3 or more of these indicators . Weight was measured on a balance-beam scale with the participant dressed in indoor clothing without shoes . Height was measured by using a wall-mounted stadiometer . Body mass index was calculated as weight ( in kg ) divided by height ( in m2 ) . Laboratory Procedures Laboratory personnel blinded to casecontrol status obtained a 12-hour fasting blood sample at the baseline visit , which was processed and stored at 80C according to strict quality control procedures ( 23 ) . Serum 25(OH ) vitamin D concentrations and sex-steroid hormone levels were measured at the Reproductive Endocrine Research Laboratory at the University of Southern California .  25-Hydroxyvitamin vitamin D was measured by using a radioimmunoassay with DiaSorin reagents ( DiaSorin , Stillwater , Minnesota ) . The sensitivity of the assay was 3.75 nmol/L. The interassay coefficients of variation were 11.7 % , 10.5 % , 8.6 % , and 12.5 % at 14.0 , 56.8 , 82.5 , and 122.5 nmol/L , respectively . Estradiol and testosterone concentrations were quantified by using sensitive and specific radioimmunoassays after organic solvent extraction and celite column partition chromatography ( 2427 ) . The intra- and interassay coefficients of variation were 7.9 % and 8 % to 12 % , respectively , for estradiol and 6 % and 10 % to 12 % , respectively , for testosterone . We calculated bioavailable hormone concentrations by using mass action equations ( 2830 ) . We measured sex hormonebinding globulin by using a solid-phase , 2-site chemiluminescent immunoassay . The intra- and interassay coefficients of variation were 4.1 % to 7.7 % and 5.8 % to 13 % , respectively . Serum cystatin C , a marker of renal function that is independent of age and weight , was measured at Medical Research Laboratories International , Highl and Heights , Kentucky , by using the Dade Behring BN-II nephelometer and Dade Behring reagents ( Dade Behring , Ramsey , Minnesota ) in a particle-enhanced immunonepholometric assay . Serum C-terminal telopeptide of type I collagen and aminoterminal procollagen extensions propeptide were measured by immunoassay ( Synarc , Lyon , France ) . Statistical Analysis We used chi-square and t tests to compare baseline characteristics between case- patients with hip fracture and matched control participants . We assigned 25(OH ) vitamin D concentrations to quartile categories defined on the basis of the distribution in the control participants . To further assess confounding , we compared baseline characteristics across quartiles of 25(OH ) vitamin D concentrations in case- patients and control participants combined . We calculated the P values for trend by using logistic regression and coding the variable of interest as a continuous variable . We assessed the association between serum 25(OH ) vitamin D concentrations and incident hip fracture in conditional logistic regression models that retained the matched casecontrol design . We first examined the unadjusted associations and then adjusted for age , Background : Calcium absorption is generally considered to be impaired under conditions of vitamin D deficiency , but the vitamin D status that fully normalizes absorption is not known for humans . Objective : To quantify calcium absorption at two levels of vitamin D repletion , using pharmacokinetic methods and commercially marketed calcium supplements . Design : Two experiments performed in the spring of the year , one year apart . In the first , in which participants were pretreated with 25-hydroxyvitamin D ( 25OHD )  , mean serum 25OHD concentration was 86.5 nmol/L ; and in the other , with no pretreatment , mean serum concentration was 50.2 nmol/L. Participants received 500 mg oral calcium loads as a part of a st and ard low calcium breakfast . A low calcium lunch was provided at mid-day . Blood was obtained fasting and at frequent intervals for 10 to 12 hours thereafter . Methods : Relative calcium absorption at the two 25OHD concentrations was estimated from the area under the curve ( AUC ) for the load-induced increment in serum total calcium . Results : AUC9 ( ± SEM ) , was 3.63 mg hr/dL ± 0.234 in participants pretreated with 25OHD  and 2.20 ± 0.240 in those not pretreated ( P < 0.001 ) . In brief , absorption was 65 % higher at serum 25OHD levels averaging 86.5 nmol/L than at levels averaging 50 nmol/L ( both values within the nominal reference range for this analyte ) . Conclusions : Despite the fact that the mean serum 25OHD level in the experiment without supplementation was within the current reference ranges , calcium absorptive performance at 50 nmol/L was significantly reduced relative to that at a mean 25OHD level of 86 nmol/L. Thus , individuals with serum 25-hydroxyvitamin D levels at the low end of the current reference ranges may not be getting the full benefit from their calcium intake . We conclude that the lower end of the current reference range is set too low OBJECTIVE Inconsistent effects of vitamin A supplementation on prevention of  bronchopulmonary dysplasia  have been reported . Meta- analysis of these reports result ed in a relative risk of 0.69 - 1.02 for death or bronchopulmonary dysplasia associated with vitamin A supplementation . Effective dosage regimens or serum retinol concentrations have not been determined in previous reports . The purpose of this pilot study was to define a vitamin A regimen that produces serum retinol concentrations of 25 - 55 micrograms/dl . STUDY DESIGN In this three-phase study , 91 infants ( mean birth weight 799 - 864 g ) were enrolled .  Vitamin A was administered three times/week for 4 weeks at an average daily dose of 986 - 2143 IU/day . Physical examinations were performed and serum retinol specimens were collected weekly to assess clinical signs of toxicity . RESULTS The majority of serum retinol concentrations remained < 25 micrograms/dl until an intramuscular vitamin A dose of 5000 IU/dose three times/week was used . No clinical signs of toxicity were associated with the higher dosage and higher serum concentrations of vitamin A. CONCLUSION A large clinical trial of vitamin A supplementation with 5000 IU/dose three times/week ( 25 - 114 % more than the dose used in the three published clinical trials ) is needed to assess whether vitamin A supplementation  safely reduces the risk of bronchopulmonary dysplasia  in very-low-birth-weight infants 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 Summary On September 29 , 2011 , acknowledged experts in the field of vitamin D , mainly European , were brought together in order to discuss the recent scientific advances in relation to vitamin D : the current requirements and associations with various health outcomes . In this article , the discussion s result ing from the meeting are summarized . Introduction Several groups at risk for developing vitamin D insufficiency have been identified . Accordingly , review s indicate that a significant percentage of the population worldwide have serum 25-hydroxyvitamin D levels below 50 nmol/l . In addition to the role of vitamin D in bone health , recent studies suggest that it may play a pivotal role in other systems , e.g. , the cardiovascular system , pancreas , muscle , immune system and brain . Most evidence , however , is obtained from observational studies and yet inconclusive . Methods To exchange and broaden knowledge on the requirements for vitamin D and its effect on various health outcomes , a workshop entitled “ Vitamin D Expert Meeting : Do we get enough ? ” , was organized . Results Despite low vitamin D levels worldwide , consensus on the definition of deficiency is not yet reached . In order to define cut-off points for vitamin D whilst taking into account extraskeletal health effects , r and omized controlled trials in these fields are warranted . The experts do emphasize that there is evidence to suggest an important role for vitamin D in the maintenance of optimal bone health at all ages and that vitamin D supplementation , in most studies co-administered with calcium , reduces fracture risk in the senior population . Conclusion To reach a serum 25-hydroxyvitamin D level of 50 nmol/l older adults aged ≥65 years are therefore recommended to meet a mean daily vitamin D intake of 20 μg ( 800 IU ) , which is best achieved with a supplement BACKGROUND Eczema is one of the most common chronic inflammatory skin diseases , affecting about 20 % of children . The pathogenic mechanisms of eczema are still not fully understood , and current treatment of moderate-severe eczema is often difficult . Recently , it has been suggested that Vitamin D plays a key role in this disease , even if mechanisms are only partially known . OBJECTIVE The purpose of our study was to assess the  25-Hydroxyvitamin D serum levels in a pediatric population suffering from chronic eczema ( IgE-mediated and non-IgE-mediated ) , and to correlate these phenotypes with the SCORAD severity and selected clinical and biological parameters . Moreover , we aim ed to evaluate whether a supplementation of Vitamin D3 could affect the same clinical and laboratory parameters . METHODS 89 children with chronic eczema were enrolled in the study . Severity of eczema was assessed with the SCORAD index . Past and present history was taken , and patients were divided into two groups according to the state of sensitization . According to a r and omization schedule , the enrolled children were assigned to the following groups : supplementation group , which received a daily oral Vitamin D3 supplementation ( 2000 IUs ) for 3 months ; control group which received no supplementation . RESULTS  Vitamin D concentrations in patients with moderate and severe eczema were not statistically different from Vitamin D concentration detected in the serum of patients with mild eczema . Furthermore , we did not find any correlation between Vitamin D levels , total IgEs and SCORAD index , both in the Sensitized and in the Not-Sensitized group . The Vitamin D3 supplementation did not influence the SCORAD severity or the total IgEs concentration . CONCLUSION To our knowledge , our study is the first one that shows no correlation between serum levels of Vitamin D , eczema severity and IgE sensitization in a pediatric population suffering from chronic eczema Importance Whether vitamin D supplementation during pregnancy is beneficial and safe for offspring is unclear . Objective To systematic ally review studies of the effects of vitamin D supplementation during pregnancy on offspring growth , morbidity  , and mortality . Data Sources Search es of Medline , Embase , and the Cochrane Data base of Systematic Review s were conducted up to October 31 , 2017 . Key search terms were vitamin D , pregnancy , r and omized controlled trials , and offspring outcomes . Study Selection R and omized clinical trials of vitamin D supplementation during pregnancy and offspring outcomes . Data Extraction and Synthesis Two authors independently extracted data , and the quality of the studies was assessed . Summary risk ratio ( RR ) , risk difference ( RD ) or mean difference ( MD ) , and 95 % CI were calculated using fixed-effects or r and om-effects meta- analysis . Main Outcomes and Measures Main outcomes were fetal or neonatal mortality , small for gestational age ( SGA ) , congenital malformation , admission to a neonatal intensive care unit , birth weight , Apgar scores , neonatal 25-hydroxyvitamin D ( 25[OH]D ) and calcium concentrations , gestational age , preterm birth , infant anthropometry , and respiratory morbidity during childhood . Results Twenty-four clinical trials involving 5405 participants met inclusion criteria . Vitamin D supplementation during pregnancy was associated with a lower risk of SGA ( RR , 0.72 ; 95 % CI , 0.52 to 0.99 ; RD , −5.60 % ; 95 % CI , −0.86 % to −10.34 % ) without risk of fetal or neonatal mortality ( RR , 0.72 ; 95 % CI , 0.47 to 1.11 ) or congenital abnormality ( RR , 0.94 ; 95 % CI , 0.61 to 1.43 ) . Neonates with prenatal vitamin D supplementation had higher 25(OH)D levels ( MD , 13.50 ng/mL ; 95 % CI , 10.12 to 16.87 ng/mL ) , calcium levels ( MD , 0.19 mg/dL ; 95 % CI , 0.003 to 0.38 mg/dL ) , and weight at birth ( MD , 75.38 g ; 95 % CI , 22.88 to 127.88 g ) , 3 months ( MD , 0.21 kg ; 95 % CI , 0.13 to 0.28 kg ) , 6 months ( MD , 0.46 kg ; 95 % CI , 0.33 to 0.58 kg ) , 9 months ( MD , 0.50 kg ; 95 % CI , 0.01 to 0.99 kg ) , and 12 months ( MD , 0.32 kg ; 95 % CI , 0.12 to 0.52 kg ) . Subgroup analysis by doses showed that low-dose vitamin D supplementation ( ⩽2000 IU/d ) was associated with a reduced risk of fetal or neonatal mortality ( RR , 0.35 ; 95 % CI , 0.15 to 0.80 ) , but higher doses ( > 2000 IU/d ) did not reduce this risk ( RR , 0.95 ; 95 % CI , 0.59 to 1.54 ) . Conclusions and Relevance Vitamin D supplementation during pregnancy is associated with a reduced risk of SGA and improved infant growth without risk of fetal or neonatal mortality or congenital abnormality . Vitamin D supplementation with doses of 2000 IU/d or lower during pregnancy may reduce the risk of fetal or neonatal mortality Objectives : To study the prevalence of hypovitaminosis D , the effect of vitamin D supplementation on serum 25-hydroxyvitamin D [ S-25(OH)D ] , and the intakes of vitamin D and calcium in Finnish 9− to 15-year-old athletic and nonathletic girls . Design : 1-year follow-up study ( February 1997-March 1998 ) with three months of vitamin D supplementation ( 10 μg/d ) from October to January . Setting : Turku University Central Hospital , Finl and .Subjects : 191 female volunteers aged 9–15 y ( 131 athletes and 60 controls ) . Methods :  Vitamin D and calcium intakes were estimated by a four-day food recording and a semi-quantitative food frequency question naire ( FFQ ) . S-25(OH)D was followed by radioimmunoassay ( RIA ) . Results : At baseline the mean S-25(OH)D concentration was 33.9 nmol/l among all girls . In winter severe hypovitaminosis D ( S-25(OH)D<20 nmol/l ) occurred in 13.4 % of the participants and in 67.7 % S-25(OH)D was below 37.5 nmol/l . By the next summer the mean S-25(OH)D concentration was 62.9 nmol/l and in 1.6 % of the subjects it was below 37.5 nmol/l . The prevalence of severe hypovitaminosis D was not significantly reduced by three months of vitamin D ( 10 μg/d ) supplementation . At baseline , the mean intake of vitamin  D was 2.9 μg/d by food recording and 4.3 μg/d by FFQ . The mean calcium intake was 1256 mg/d and 1580 mg/d , respectively . The intakes of vitamin D and calcium remained unchanged during the follow-up period . The athletes consumed more calcium than nonathletic controls , whereas the intake of vitamin D was quite similar among both groups . The vitamin D intake by FFQ correlated with the S-25(OH)D concentration in wintertime ( r=0.28 , P<0.01 ) . Conclusion : Hypovitaminosis D is fairly common in growing Finnish girls in the wintertime , and three months of vitamin D supplementation with 10 μg/d was insufficient in preventing hypovitaminosis D. The daily dietary vitamin D intake was insufficient ( < 5 μg/d ) in the majority of participants , while the calcium intake was usually sufficient . Sponsorship : Supported by the Yrjö Jahnsson Foundation , The Turku University Foundation , and the Medical Research Foundation of the Turku University Central Hospital 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
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 .