Vitamin D, muscle function, and exercise performance

Thoroughbred Racehorses in Hong Kong Require Vitamin D Supplementation to Mitigate the Risk of Low Vitamin D Status

There is a paucity of data relating to the vitamin D status of racehorses. We hypothesised that the management of racehorses in Hong Kong (HK) predisposes to low vitamin D status unless they receive dietary supplementation. Serum concentrations of 25-hydroxyvitamin D₂ (25OHD₂), 25-hydroxyvitamin D₃ (25OHD₃) and total 25-hydroxyvitamin D (total 25OHD) for 79 non-grazing HK racehorses were compared with those for 22 racehorses training in the United Kingdom (UK) that grazed for ≥1 h/d, and for which published data exists. A nested group of 41 HK horses was sampled twice to determine the effect of the duration in HK on vitamin D status. The HK horses had significantly lower serum concentrations of total 25OHD and 25OHD₂ than the UK horses; 25OHD₂ was undetectable in 15/79 HK sera and serum concentrations of 25OHD₂ declined with the duration in HK. The main determinants of vitamin D status were assessed using linear regression; the retained variables were the 25OHD₃ concentration and the duration in HK. The inverse relationship between the serum concentrations of 25OHD₂ and 25OHD₃, previously identified in humans, was observed for the first time in horses. In conclusion, HK racehorses have low serum 25OHD₂ and total 25OHD concentrations and rely on D₃ supplementation to maintain adequate vitamin D status. Further study is required to determine the optimal form of dietary vitamin D supplementation for Thoroughbred racehorses.

Vitamin D, exercise, and immune health in athletes: A narrative review

Vitamin D exerts important extra-skeletal effects, exhibiting an exquisite immune regulatory ability, affecting both innate and adaptive immune responses through the modulation of immunocyte function and signaling. Remarkably, the immune function of working skeletal muscle, which is fully recognized to behave as a secretory organ with immune capacity, is under the tight control of vitamin D as well. Vitamin D status, meaning hormone sufficiency or insufficiency, can push toward strengthening/stabilization or decline of immune surveillance, with important consequences for health. This aspect is particularly relevant when considering the athletic population: while exercising is, nowadays, the recommended approach to maintain health and counteract inflammatory processes, “too much” exercise, often experienced by athletes, can increase inflammation, decrease immune surveillance, and expose them to a higher risk of diseases. When overexercise intersects with hypovitaminosis D, the overall effects on the immune system might converge into immune depression and higher vulnerability to diseases. This paper aims to provide an overview of how vitamin D shapes human immune responses, acting on the immune system and skeletal muscle cells; some aspects of exercise-related immune modifications are addressed, focusing on athletes. The crossroad where vitamin D and exercise meet can profile whole-body immune response and health.

Changes of 25(OH)D Concentration, Bone Resorption Markers and Physical Performance as an Effect of Sun Exposure, Supplementation of Vitamin D and Lockdown among Young Soccer Players during a One-Year Training Season

The main purpose of this research was to demonstrate the changes in 25(OH)D concentration, bone resorption markers, and physical fitness along the one-year training season in young soccer players. A total of 24 young soccer players (age: 17.2 ± 1.16 years, mass: 70.2 ± 5.84, height: 179.1 ± 4.26 cm) were tested at four different time points across one year (T1—September 2019; T2—December 2019; T3—May 2020; T4—August 2020). After T2 (during COVID-19 lockdown), players were divided into a supplemented (GS) group and a placebo group (GP). Variables such as 25(OH)D, calcium (Ca), phosphorus (P), parathyroid hormone (PTH), aerobic capacity, speed, and explosive power were measured. Analyses performed for all participants indicated significant changes in all selected blood markers and running speed. The highest values in 25(OH)D were noted during summertime in T1 and T4. After individuals were split into two groups, a two-factorial ANOVA demonstrated a significant time interaction for 25(OH)D, Ca, P, PTH, 30 m sprint, and counter-movement jump. Significant time x group effect was calculated for aerobic capacity. This study confirmed that 25(OH)D concentration varies between four seasons, with the greatest decreases in the low sunlight periods. Vitamin D supplementation did not cause a preventive and long-lasting effect of increasing the 25(OH)D concentration in the young soccer players.

Dietary Supplementation for Para-Athletes: A Systematic Review

The use of dietary supplements is high among athletes and non-athletes alike, as well as able-bodied individuals and those with impairments. However, evidence is lacking in the use of dietary supplements for sport performance in a para-athlete population (e.g., those training for the Paralympics or similar competition). Our objective was to examine the literature regarding evidence for various sport supplements in a para-athlete population. A comprehensive literature search was conducted using PubMed, SPORTDiscus, MedLine, and Rehabilitation and Sports Medicine Source. Fifteen studies met our inclusion criteria and were included in our review. Seven varieties of supplements were investigated in the studies reviewed, including caffeine, creatine, buffering agents, fish oil, leucine, and vitamin D. The evidence for each of these supplements remains inconclusive, with varying results between studies. Limitations of research in this area include the heterogeneity of the subjects within the population regarding functionality and impairment. Very few studies included individuals with impairments other than spinal cord injury. Overall, more research is needed to strengthen the evidence for or against supplement use in para-athletes. Future research is also recommended on performance in para-athlete populations with classifiable impairments other than spinal cord injuries.

Vitamin D Status in Spanish Elite Team Sport Players

Low vitamin D is usual; however, data are limited for elite team players. The aim was to investigate the vitamin D levels in Football Club Barcelona (FCB) first division players of six sport modalities. Ninety-five elite male players (27.3 ± 4.6 y) belonging to FCB provided data for vitamin D throughout a season. In this study, 25(OH)D was measured in serum by chemiluminescent immunoassay. Outdoor/indoor training and supplementation were also considered. Total mean 25(OH)D concentrations were 91.9 ± 23.1 nmol/L in all players, with higher mean levels among supplemented players (94.7 ± 24.3 nmol/L). Around 25% of the team players were below optimal levels (<75 nmol/L), but none were below 50 nmol/L. Caucasian, supplemented football and handball players had the highest mean vitamin D concentrations over the whole year, whereas basketball players (indoor training) had the lowest ones. The highest rate of vitamin D insufficiency was found in spring (40%). A positive significant effect was observed for the interaction between indoor/outdoor training and supplementation with 25(OH)D concentrations (p < 0.05). Those team players training outdoors with supplementation had higher total vitamin D concentrations than those with indoors training and/or supplementation. A positive interaction of outdoor training with supplementation exists to determine 25(OH)D concentrations in team players.

Performance demands in the endurance rider

Endurance is one of the fastest growing equestrian disciplines worldwide. Races are long distance competitions (40-160 km), organised into loops, over variable terrain usually within one day. Horse and rider combinations in endurance races have to complete the course in good condition whilst also aiming to win. Horse welfare is paramount within the sport and horses are required to ‘pass’ a veterinary check prior to racing, after each loop of the course and at the end of the race. Despite the health, fitness and welfare of both athletes within the horse-rider dyad being essential to achieve success, few equivalent measures assessing the wellbeing of the endurance rider are implemented. This review considers evidence from ultra-endurance sports and rider performance in other equestrian disciplines, to consider physiological and psychological strategies the endurance rider could use to enhance their competition performance. Successful endurance riding requires an effective partnership to be established between horse and rider. Within this partnership, adequate rider health and fitness are key to optimal decision-making to manage the horse effectively during training and competition, but just as importantly riders should manage themselves as an athlete. Targeted management for superior rider performance can underpin more effective decision-making promoting ethical equitation practices and optimising competition performance. Therefore, the responsible and competitive endurance rider needs to consider how they prepare themselves adequately for participation in the sport. This should include engaging in appropriate physiological training for fitness and musculoskeletal strength and conditioning. Alongside planning nutritional strategies to support rider performance in training and within the pre-, peri- and post-competition periods to promote superior physical and cognitive performance, and prevent injury. By applying an evidence informed approach to self-management, the endurance athlete will support the horse and rider partnership to achieve to their optimal capacity, whilst maximising both parties physical and psychological wellbeing.

Seasonal Changes in 25(OH)D Concentration in Young Soccer Players-Implication for Bone Resorption Markers and Physical Performance

Searching for potential relations between changes in 25(OH)D concentration and in physical fitness is an interesting scientific topic. Thus, the main purpose of this study was to investigate the changes in serum concentrations of 25(OH)D in young football players in conjunction with indicators determining bone resorption and physical fitness. A total of 35 young soccer players were tested during the autumn competition period. Biochemical analysis of blood, aerobic capacity, running speed and power tests (Wingate test, squat jump, counter movement jump) were carried out at the beginning and at the end of the competition period. Significant decrements in concentration of 25(OH)D from 33.9 ± 5.87 to 23.7 ± 5.58 ng/mL were noted after the analyzed competition period. There were no significant changes in aerobic capacity along the competition period. Significant improvements were observed in 10 m sprint, 30 m sprint (p < 0.001), maximal power (p = 0.011) and total work capacity (p = 0.024). We found that the effect of changes in the players' physical fitness does not occur in relation to 25 OH(D) concentration but occurs when these changes are analyzed as a function of the duration of the observation period. Changes in physical fitness of soccer players are determined by other factors then 25(OH)D concentration.

Seasonal variability of the vitamin D effect on physical fitness in adolescents

Studies investigating the relationship between vitamin D and physical fitness in youth have provided inconsistent findings. Recent evidence indicates that the expression of receptors and vitamin D-modulated genes in young subjects has a seasonal profile. Therefore, we investigated the role of vitamin D on physical fitness across seasons in a total of 977 male adolescents. Anthropometrics, lifestyle, dietary habits, biochemical profiles and physical fitness were studied. Multiple linear regression models, including pairwise interaction terms involving total 25-OH-vitamin D, were fitted. The interacting effect of season and total 25-OH-vitamin D had a significant influence on physical fitness performance (spring and total 25-OH-vitamin D: ß 0.19, SE 0.07, p = 0.007; summer and total 25-OH-vitamin D: ß 0.10, SE 0.06, p = 0.11; autumn and total 25-OH-vitamin D: ß 0.18, SE 0.07, p = 0.01), whereas the main effect of total 25-OH-vitamin D alone was not significant (p = 0.30). Body fat percentage, recreational physical activity level, time spent per day gaming/TV-watching, smoking, and hemoglobin levels were also related to the physical fitness performance score. Future studies should further explore the role of seasonal-dependent effects of vitamin D on health.

Vitamin D Supplementation Improves Health-Related Quality of Life and Physical Performance in Children with Sickle Cell Disease and in Healthy Children

INTRODUCTION

No study determined if vitamin D supplementation improves health-related quality of life (HRQL) using pediatric Patient-Reported Outcomes Measurement Information System or physical functioning in type SS sickle cell disease (HbSS).

METHOD

Subjects with HbSS (n = 21) and healthy subjects (n = 23) were randomized to daily oral doses (4,000 vs. 7,000 IU) of cholecalciferol (vitamin D3) and evaluated at 6 and 12 weeks for changes in serum 25 hydroxyvitamin D (25(OH)D), HRQL, and physical functioning.

RESULTS

In subjects with HbSS, significant reductions in pain, fatigue, and depressive symptoms and improved upper-extremity function were observed. In healthy subjects, significant reductions in fatigue and improved upper-extremity function were observed. Significant improvements in peak power and dorsiflexion isometric maximal voluntary contraction torques were observed in both groups. In subjects with HbSS, improved plantar flexion isometric maximal voluntary contraction torques were observed. Both groups saw significant improvement in their total Bruininks-Oseretsky Test of Motor Proficiency score.

DISCUSSION

Daily high-dose vitamin D supplementation for African American children with and without HbSS improved HRQL and physical performance.

Athlete's Passport: Prevention of Infections, Inflammations, Injuries and Cardiovascular Diseases

Laboratory medicine in sports medicine is taking on an ever-greater role in the assessment and monitoring of an athlete's health condition. The acute or intense exercise practiced by elite athletes can lead to the appearance of infections, inflammations, muscle injuries or cardiovascular disorders, whose diagnosis is not always rapid and efficient, as there is no continuous monitoring of the athlete. The absence of such monitoring can have serious consequences in terms of recovery of the professional athlete. These imbalances can induce metabolic adaptations which translate into alterations of specific parameters in terms of concentration and activity. The aim of this study was to follow the variation of specific biochemical biomarkers in a basketball team participating to the maximum championship during different phases of the agonistic season. The evaluation of serum biomarkers can help doctors to safeguard the athlete's health and sports trainers to adapt workouts, thus avoiding the appearance of diseases and injuries that in some cases can be underestimated by becoming irreversible ailments that do not allow the athlete to return to a healthy state. This information can be useful to create athlete biologic passports.

Vitamin D protects against immobilization-induced muscle atrophy via neural crest-derived cells in mice

Vitamin D deficiency is a recognized risk factor for sarcopenia development, but mechanisms underlying this outcome are unclear. Here, we show that low vitamin D status worsens immobilization-induced muscle atrophy in mice. Mice globally lacking vitamin D receptor (VDR) exhibited more severe muscle atrophy following limb immobilization than controls. Moreover, immobilization-induced muscle atrophy was worse in neural crest-specific than in skeletal muscle-specific VDR-deficient mice. Tnfα expression was significantly higher in immobilized muscle of VDR-deficient relative to control mice, and was significantly elevated in neural crest-specific but not muscle-specific VDR-deficient mice. Furthermore, muscle atrophy induced by limb immobilization in low vitamin D mice was significantly inhibited in Tnfα-deficient mice. We conclude that vitamin D antagonizes immobilization-induced muscle atrophy via VDR expressed in neural crest-derived cells.

The Effect of Vitamin D3 Supplementation on Physical Capacity among Active College-Aged Males

Vitamin D₃ supplementation can affect strength and power; however, the effect on both aerobic and anaerobic performance remains unclear. Here, we investigate the effects of eight weeks of a high dose of vitamin D₃ supplementation and its impact on circulating 25-hydroxyvitamin D (25-OH-D₃) concentrations and selected indicators of physical capacity. Subjects (n = 28, age 21.1 ± 1.6) were divided into two groups: supplemented (SUP), which was given 6000 IU of vitamin D₃ daily for eight weeks; and placebo group (PLA). Serum 25-OH-D₃ concentrations were determined in pre- and post-intervention. Aerobic (V.O_2max test) and anaerobic (Wingate Anaerobic Test) capacity were determined before and after the supplementation. The mean baseline concentration of 25-OH-D₃ was recognized as deficient (20 ng/mL) and significantly increased over time in the supplemented group (p < 0.01, η² = 0.86), whilst it remained unchanged in the placebo group. Moreover, the supplementation caused a significant improvement in maximal aerobic (p < 0.05, η² = 0.27) and anaerobic power (p < 0.01, η² = 0.51) whereas no changes were observed in PLA group. The V.O_2max differences were also significant in the supplemented group (p < 0.05). In summary, the changes in aerobic and anaerobic capacity observed in this study were associated with a serum concentration of 25-OH-D₃. Our data imply that vitamin D₃ supplementation with a dose of 6000 IU daily for eight weeks is sufficient to improve physical capacity and vitamin D₃ status.

Vitamin D Status Differs by Sex, Sport-Season, and Skin Pigmentation among Elite Collegiate Basketball Players

Vitamin D plays a key role in bone health, musculoskeletal function, and sport performance. Collegiate athletes competing in indoor sports may be at greater risk of vitamin D deficiency due to limited outdoor time. Therefore, the purpose was to assess 25-hydroxyvitamin D (25(OH)D) concentrations among collegiate men and women basketball (MBB, WBB) athletes. National Collegiate Athletic Association Division I men (MBB, n = 11) and women (WBB, n = 9) were tested during the off-season (T1; July) and pre-season (T2; October). Measurements included serum 25(OH)D; skin pigmentation, bone mineral density, and daily sun exposure (self-reported). Paired t-tests determined changes in 25(OH)D by sport-season and sex. Pearson correlations examined relationships between outcome variables. MBB athletes (mean ± SD; 19.6 ± 1.3 years) showed a reduction in 25(OH)D (T1: 64.53 nmol·L⁻¹ ± 11.96) (T2: 56.11 nmol·L⁻¹ ± 7.90) (p = 0.001). WBB (20.1 ± 1.1 years) had no change in 25(OH)D (T1: 99.07 nmol·L⁻¹ ± 49.94. T2: 97.56 nmol·L⁻¹ ± 36.47, p = 0.848). A positive association between 25(OH)D and skin pigmentation was observed (r = 0.47, p = 0.038). 25(OH)D was inversely correlated with lean body mass (LBM), body mass (BM), and bone mineral density (BMD), while a positive association was seen between 25(OH)D and skin pigmentation. In summary, 25(OH)D insufficiency was prevalent amongst male collegiate basketball athletes, with 25(OH)D levels being lower in the pre-season (October) than the off-season (July). Furthermore, darker skin pigmentation significantly correlated with 25(OH)D, indicating that individuals with darker skin tones may be at a greater risk of insufficiency/deficiency. More research is needed to examine the relationships between 25(OH)D and bone health in athletes.

A single mega dose of vitamin D3 improves selected physical variables in vitamin D-deficient young amateur soccer players: a randomized controlled trial

This randomized controlled trial aimed to test whether vitamin D (VD) supplementation affects measures of physical performance in VD-deficient, mildly trained children. Thirty-six recreationally soccer player boys were randomly assigned to single dose (200 000 IU) of VD3 (n = 19) or placebo (n = 17). Plasma 25-hydroxyvitamin D (25-OHD) was assessed and measures of physical performance (i.e., vertical and standing broad jumps, triple hop, 10-m and 30-m sprints, shuttle run) were performed before and 12 weeks after the loading dose. Mixed ANCOVA models were performed and effect size was estimated by partial eta squared (η_p²). Baseline 25-OHD and physical variables were equivalent in the 2 groups. Twelve weeks after VD loading, plasma 25-OHD increased and physical variables improved only in the VD group. There was a significant interaction effects for group by time for vertical jump (F = 14.9, p = 0.001, η_p² = 0.394), triple hop jump (F = 24.2, p < 0.001, η_p² = 0.513), 10-m (F = 4.46, p = 0.046, η_p² = 0.162) and 30-m (F = 6.56, p = 0.017, η_p² = 0.222) sprints, and shuttle run (F = 13.4, p = 0.001, η_p² = 0.369). In conclusion, a single bolus of VD3 resulted in significant improvements in jumping ability, agility, and running speed in mildly trained children that are deficient in VD. The findings suggest that correcting VD deficit might be beneficial for physical performance. Novelty A mega dose of VD3 improves jumping ability, agility, and running speed in VD-deficient, mildly trained children. Effect of VD on measures of physical performance is noticeable 3 months after the loading dose.

Physical performance is not improved with vitamin D repletion: a randomized trial

BACKGROUND

Studies enrolling physically active participants have used various vitamin D dosing strategies which can result in diverse post supplementation vitamin D status due to individual body weight and initial vitamin D status. Emerging evidence suggests serum 25(OH)D levels of 100-120 nmol/L are optimal for peak performance, however, studies generally administer the same dose for all participants regardless of initial 25(OH)D status and body weight. This approach will not likely get all participants to the optimal 25(OH)D level proposed for optimal physical performance. Therefore, it's important to enroll vitamin D insufficient/deficient participants to observe the effects of vitamin D supplementation on physical performance. We assessed vitamin D repletion on markers of anaerobic performance in physically active adults by replenishing insufficient/deficient vitamin D to the target of 100-120 nmol/L suggested for optimal physical performance.

METHODS

We conducted a double-blind randomized control trial in 42 physically active participants, 18-42 years of age in the winter months. Physically active participants with insufficient/deficient 25(OH)D status (<75 nmol/L) were supplemented with an individualized dosing strategy to achieve 25(OH)D of 120 nmol/L with eight weeks of supplementation using the following formula: Dose (IU)=40•[Target 25(OH)D3 - Initial 25(OH)D3]•Body Weight (kg). A modified Wingate test, 10m and 40m sprints, vertical jump, hand grip strength, pushups, and isokinetic knee flexion and extension were assessed before and after repletion of 25(OH)D.

RESULTS

Thirty-nine out of 42 participants completed the study. Twenty-seven participants in the vitamin D group significantly increased 25(OH)D from 61 nmol/L to 123 nmol/L (P<0.001). 12 participants in the Placebo group had a significant decrease in 25(OH)D from 98 nmol/L to 83 nmol/L (P=0.02). Despite these changes in 25(OH)D status in each group, no significant changes in anaerobic performance markers were found.

CONCLUSIONS

These findings indicate that vitamin D repletion to levels sufficient for optimal physical performance does not improve anaerobic physical performance.

Effect of vitamin D supplementation on upper and lower limb muscle strength and muscle power in athletes: A meta-analysis

BACKGROUND

Vitamin D may play a role in skeletal muscle because of the discovery of VDR in skeletal muscle. However, vitamin D deficiency is a global problem, including athletes. Studies examining the effect of vitamin D supplementation on muscle function in athletes have inconsistent results. Therefore, we aimed to quantitatively summarize the evidence for the effect of vitamin D supplementation on skeletal muscle strength and explosive power of athletes using a meta-analysis.

METHODS

PubMed, EMBASE, Cochrane Library, and Web of Science were searched for studies to identify randomized controlled trials or controlled trials meeting the inclusion criteria. By a meta-analysis, effect sizes (standardized mean differences, SMD) with 95% confidence intervals (CI) was calculated to compare reported outcomes across studies, I2 index was used to assessing heterogeneity, and heterogeneity factors were identified by regression analysis. The potential publication and sensitivity analyses were also assessed.

RESULTS

Eight RCTs involving 284 athletes were included. The protocols used to evaluate the muscle strength of athletes were inconsistent across the included studies, and muscle explosive power was assessed via vertical jump tests. The results indicated that vitamin D supplementation had no impact on overall muscle strength outcomes (SMD 0.05, 95% CI: -0.39 to 0.48, p = 0.84). In subgroup analysis, vitamin D supplementation had an effect on lower-limb muscle strength (SMD 0.55, 95% CI:0.12 to 0.98, p = 0.01) but not upper-limb muscle strength (SMD -0.19, 95% CI:-0.73 to 0.36, p = 0.50) or muscle explosive power (SMD 0.05, 95% CI:-0.24 to 0.34, p = 0.73). Vitamin D supplementation was more effective for athletes trained indoors (SMD 0.48, 95% CI:0.06 to 0.90, p = 0.02).

CONCLUSIONS

Vitamin D supplementation positively affected lower limb muscle strength in athletes, but not upper limb muscle strength or muscle power. Different muscle groups and functions may respond differently to vitamin D supplementation. Additional studies should focus on determining the appropriate vitamin D supplementation methods and optimal serum 25(OH)D levels for athletes.

REGISTRATION

The protocol for our study is registered in the international prospective register of systematic reviews (PROSPERO registration number CRD42016045872).

The Prevalence of Dysphonia and Dysphagia in Patients with Vitamin D Deficiency

OBJECTIVE

To investigate the prevalence of phonatory and swallowing symptoms in patients with hypovitaminosis D.

METHODS/DESIGN

All patients presenting to the endocrinology clinic and investigated for vitamin D deficiency between January 2018 and April 2018 were asked to participate in this study. Demographic data included age, gender, allergy, and history of smoking. Patients filled Voice handicap Index (VHI-10) and Eating Assessment Tool (EAT-10).

RESULTS

A total of 136 consecutive subjects presenting to the endocrinology clinic for vitamin D testing were included: 60 with hypovitaminosis D and 76 with no hypovitaminosis D. The mean vitamin D level in the study group and controls was 13.25 ng/mL and 31.91 ng/mL, respectively. There was no significant difference in the mean score of VHI-10, nor in the mean score of EAT-10 in patients with hypovitaminosis D versus those with no hypovitaminosis D (P value >0.05).

CONCLUSION

There was no significant difference in the prevalence of phonatory and dysphagia symptoms using VHI-10 and EAT-10 questionnaires between subjects with hypovitaminosis D and those with normal serum vitamin D levels.

The effects of indoor and outdoor sports participation and seasonal changes on vitamin D levels in athletes

OBJECTIVE

Nowadays, people tend to spend more time in the closed areas and benefit less from sunlight. In this study, we examined the results of vitamin D measurements of athletes from different disciplines in different months and aimed to determine if the synthesis of vitamin D decreases or not according to exercise environment and month.

METHODS

The study was conducted in participants aged 5-52 years. A total of 555 elite-level sportsmen who were admitted to our Sports Medicine Clinic in the study participated in this study. Indoor and outdoor environmental and seasonal effects on the measurements in different months were statistically evaluated. Independent-samples test and definitive statistics were used for statistical analyses and a p-value less than 0.05 has been considered significant.

RESULTS

The study group consisted of 229 male and 326 female athletes. The serum 25-hydroxyvitamin D concentration was observed; 120 (21.6%) athletes have severe serum vitamin D deficiency (<11-20 ng/mL). Vitamin D levels were not significantly different from outdoor athletes (393; 70.8%). Winter measurements of vitamin D levels were significantly lower than those measured in autumn (p = 0.000).

CONCLUSION

Increasing vitamin D levels are very important especially in participating athletes and additional supplements are recommended whenever necessary. Gender and indoor/outdoor sports participation showed no statistically significant outcomes on vitamin D levels. However, winter season had a negative effect on vitamin D levels. Therefore, adequate precautions should be taken to increase vitamin D, especially during winter, to maintain the best performance of the athletes.

Perioperative Serum 25-Hydroxyvitamin D Levels Affect Revision Surgery Rates After Arthroscopic Rotator Cuff Repair

PURPOSE

To examine any association between perioperative serum 25-hydroxyvitamin D levels and failure of arthroscopic rotator cuff repair (RCR) requiring revision surgery.

METHODS

Using a private-payer national insurance database, patients who underwent arthroscopic RCR with perioperative serum 25-hydroxyvitamin D levels recorded were included. Patients were stratified into groups of (1) serum 25-hydroxyvitamin D deficiency (<20 ng/mL), (2) insufficiency (20-30 ng/mL), or (3) sufficient (>30-<150 ng/mL). The primary outcome measure was ipsilateral revision rotator cuff surgery, including revision repair, debridement, or reverse shoulder arthroplasty. A multivariable logistic regression analysis was used to control for patient demographics and comorbidities during comparisons.

RESULTS

A total of 982 patients were included in the study. The rate of revision rotator cuff surgery was significantly higher in patients in the serum 25-hydroxyvitamin D-deficient group (5.88%) compared with the serum 25-hydroxyvitamin D-sufficient control group (3.7%) (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.6-5.8; P = .007). Patients with serum 25-hydroxyvitamin D deficiency (5.88%) also had a significantly higher incidence of revision surgery compared with patients with serum 25-hydroxyvitamin D insufficiency (OR, 2.4; 95% CI, 1.5-3.9; P = .011). There was no significant difference in the incidence of revision surgery in the serum 25-hydroxyvitamin D-insufficient group (4.97%) compared with the serum 25-hydroxyvitamin D-sufficient control group (3.7%) (OR, 1.4; 95% CI, 0.8-2.3; P = .250). The absolute risk reduction of revision surgery for 25-hydroxyvitamin D-deficient patients compared with controls was 2.2%, corresponding to a number needed to treat to avoid 1 revision surgery of 46 patients, relative risk reduction = 0.59.

CONCLUSIONS

Although the present study found a significant statistical association between serum 25-hydroxyvitamin D deficiency and insufficiency and the rate of revision rotator cuff surgery after primary arthroscopic RCR, the absolute differences of these revision rates are minimal and are accompanied with overlapping confidence intervals limiting the clinical significance of these findings.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

25-Hydroxyvitamin D levels and its relation to muscle strength, maximal oxygen consumption, and body mass index in young and middle adulthood women

Introduction

Vitamin D is a potent secosteroid hormone that provides many health benefits. The ubiquitous nature of vitamin D receptor (VDR) suggests widespread effect.

Purpose

The purpose of this study was to investigate the relationship between 25-hydroxyvitamin D (25OHD) levels and muscle strength, maximal oxygen consumption (VO₂max), and body mass index (BMI) in Iranian young and middle adulthood women.

Participants and methods

A cross-sectional descriptive study was conducted in 182 healthy Iranian women within the age range of 26–60 years. Body weight and height were measured, and BMI was calculated. VO₂max was determined by the Rockport test. Muscle strength was determined by the chest press, leg press, and hand grip test. Also, circulating levels of 25OHD were evaluated.

Results

Results showed a significant relationship between 25OHD levels and BMI, VO₂max, and muscle strength (chest press, leg press, hand grip dominant hand [HGDH], and hand grip nondominant hand [HGNDH]) in young and middle adulthood women (BMI in young and middle adulthood: r=−0.48, P<0.001 and r=−0.27, P=0.01, respectively; VO₂max in young and middle adulthood women: r=0.69, P<0.001 and r=0.57, P<0.001, respectively; chest press, leg press, HGDH, and HGNDH in young adulthood: r=0.58, r=0.59, r=0.65, and r=0.42, respectively, P<0.001; and in middle adulthood: r=0.73, r=0.34, r=0.66, and r=0.55, respectively, P≤0.001). Multiple linear regression analysis showed that higher levels of VO₂max, HGDH, and chest press predicted higher 25OHD levels in the young adulthood women (R²=0.75; β=0.39, β=0.35, and β=0.30, respectively; P<0.001). Moreover, VO₂max and HGDH were the strongest predictor of 25OHD levels in the middle adulthood women (R²=0.71; β=0.35, β=0.40, respectively; P<0.001).

Conclusion

Based on the results, it could be concluded that VO₂max and strength are useful indirect marker for 25OHD levels in the young and middle adulthood women. It also seems that VO₂max and HGDH strength had stronger associations with 25OHD levels in the young adulthood women, and chest press and HGDH had stronger associations with 25OHD levels in the middle adulthood women.

Effect of Vitamin D on Muscle Function and Injury in Elite Adolescent Dancers: A Randomized Double-Blind Study

PURPOSE

A number of studies have noted low levels of vitamin D in dancers, and this has been associated with increased risk of injuries and decreased muscle-strength indices. The aim of the present study was to examine whether vitamin D supplementation over a 4-mo period can improve muscle function and injury incidence.

METHODS

A total of 84 participants volunteered; exclusion criteria and dropout (19%) reduced the cohort to 67 participants (females = 29 and males = 38; 17-19 y). Participants were randomly assigned to either an intervention or placebo group (2∶1 ratio). All provided a venous blood sample before and after the 4-mo study period. The intervention group received 120,000 IU vitamin D to be taken over a 1-wk period, and the placebo group received the same number of inert pills. Participants completed a series of muscle function tests before and after the monitoring period. Injury incidence was recorded by the independent health team at the school.

RESULTS

Preintervention, 6% of the cohort were vitamin D deficient, 81% were insufficient, and 13% had sufficient levels; postintervention, 53% were insufficient and 47% were sufficient. The intervention group reported a significant increase in serum 25(OH)D3 (57%; P < .00) and isometric strength (7.8%; P = .022) but not muscle power. There was a significant association between traumatic injury occurrence for the intervention and control groups (10.9% vs 31.8%; P < .02).

CONCLUSION

Vitamin D supplementation decreased the numbers of deficient and insufficient participants in this cohort. The intervention group reported a small significant increase in muscle strength that was negatively associated with traumatic injury occurrence.

ISSN exercise & sports nutrition review update: research & recommendations

Background

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult.

Methods

This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.

Conclusions

This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

Prevalence of Vitamin D Deficiency in Children (6-18 years) Residing in Kullu and Kangra Districts of Himachal Pradesh, India

OBJECTIVE

To assess the prevalence of Vitamin D deficiency (VDD) and associated risk factors amongst children in the age group of 6-18 y residing at an altitude of 1000 mts and above.

METHODS

A community based cross-sectional study was conducted in the year 2015-2016. Two districts (namely: Kangra and Kullu) of Himachal Pradesh state, India was selected for the present study. In each district thirty clusters/schools were identified using Population Proportionate to Size (PPS) sampling methodology. In the identified school, all the children in schools were enlisted. Twenty children per school were selected by using random number tables. A total of 1222 children (Kangra: 610; Kullu: 612) in the age group of 6-18 y were enrolled. The data on socio economic status, physical activity and sunlight exposure was collected. The blood samples were collected and serum 25-hydroxyvitamin D, intact parathyroid hormone, serum calcium, phosphorous, albumin and alkaline phosphate were assessed using standard procedures.

RESULTS

Eighty one percent (Kangra) and 80.0% (Kullu) of school age children were found Vitamin D deficient as per serum 25(OH) D levels (less than 20 ng/ml).

CONCLUSIONS

A high prevalence of VDD was found in children residing in 2 districts located at high altitude regions of Himachal Pradesh, India.

The Association of Vitamin D Status in Lower Extremity Muscle Strains and Core Muscle Injuries at the National Football League Combine

PURPOSE

To evaluate the association between serum vitamin D level and the prevalence of lower extremity muscle strains and core muscle injuries in elite level athletes at the National Football League (NFL) combine.

METHODS

During the 2015 NFL combine, all athletes with available serum vitamin D levels were included for study. Baseline data were collected, including age, race, body mass index, position, injury history specific to lower extremity muscle strain or core muscle injury, and Functional Movement Screen scores. Serum 25-hydroxyvitamin D was collected and defined as normal (≥32 ng/mL), insufficient (20-31 ng/mL), and deficient (<20 ng/mL). Univariate regression analysis was used to examine the association of vitamin D level and injury history. Subsequent multivariate regression analysis was used to examine this relation with adjustment for collected baseline data variables.

RESULTS

The study population included 214 athletes, including 78% African American athletes and 51% skilled position players. Inadequate vitamin D was present in 59%, including 10% with deficient levels. Lower extremity muscle strain or core muscle injury was present in 50% of athletes, which was associated with lower vitamin D levels (P = .03). Athletes with a positive injury history also showed significantly lower vitamin D levels as compared with uninjured athletes (P = .03). African American/black race (P < .001) and injury history (P < .001) was associated with lower vitamin D. Vitamin D groups showed no differences in age (P = .9), body mass index (P = .9), or Functional Movement Screen testing (P = .2). Univariate analysis of inadequate vitamin D levels showed a 1.86 higher odds of lower extremity strain or core muscle injury (P = .03), and 3.61 higher odds of hamstring injury (P < .001). Multivariate analysis did not reach an independent association of low vitamin D with injury history (P = .07).

CONCLUSIONS

Inadequate vitamin D levels are a widespread finding in athletes at the NFL combine. Players with a history of lower extremity muscle strain and core muscle injury had a higher prevalence of inadequate vitamin D.

LEVEL OF EVIDENCE

Level IV, retrospective study-case series.

Prevalence of Vitamin D Deficiency in Pediatric Patients With Scoliosis Preparing for Spinal Surgery

BACKGROUND

Establishing prevalence of vitamin D deficiency in elective scoliosis surgery may impact clinical outcomes. The objectives of this study were to document vitamin D status of patients with scoliosis preparing for surgical intervention in order to establish frequency of deficiency and determine characteristics influencing levels.

METHODS

Records were queried for patients with scoliosis diagnosis who underwent posterior spinal fusion or initial growing rod placement and had serum vitamin 25 hydroxyvitamin D (D25) recorded in the preoperative period. Demographic data (gender, age, body mass index [BMI], race, scoliosis type, spine surgery procedure, and season of the year) were extracted. Chi-square analysis and multivariate modeling were used to evaluate deficiency status among various demographic categories and determine the demographic factors impacting D25.

RESULTS

A total of 217 patients with a mean age of 13.6 ± 3.6 years had vitamin D levels drawn a mean of 38.7 ± 20.6 days prior to surgery. The majority of the sample presented with a diagnosis of idiopathic scoliosis (n = 126), and most patients were scheduled for spinal fusion surgery (n = 192). Nearly 75% of the study population (n = 162) demonstrated D25 values below normal. African Americans presented with greater risk of deficiency (p < .0002) compared to Caucasians, as did patients preparing for spinal fusion versus growing rod placement (p < .03). Severe hypovitaminosis D was more common in winter than any other season (p < .005). Patients with neuromuscular scoliosis demonstrated significantly higher D25 levels over the idiopathic diagnosis type (p < .0002). Gender, BMI, and age did not impact D25.

CONCLUSION

Low D25 levels are reported in pediatric patients with scoliosis preparing for corrective spinal surgery. Population subsets most at risk for deficiency in this limited study include African American children, those presenting for spinal fusion surgery, and patients admitted in winter season.

Effect of Vitamin D Deficiency on Voice

PURPOSE

The purpose of this article was to investigate the relationship between low level of vitamin D, phonatory symptoms, and acoustic findings.

METHOD

A total of 38 subjects presenting to the endocrinology clinic were enrolled in 2 groups: 19 with vitamin D deficiency who were not on treatment, and 19 with normal vitamin D level who were on treatment. Demographic data included age, gender, and history of smoking. All patients were asked about the presence or absence of dysphonia, degree of phonatory effort, and vocal fatigue. Acoustic analysis and perceptual evaluation using the grade, roughness, breathiness, asthenia, and strain scale were performed on all subjects.

RESULTS

The mean age of the total group was 47.29 ± 13.52 years. The difference in the mean and frequency of phonatory effort, vocal fatigue, and dysphonia, and in the mean of the acoustic variables, perceptual parameters, and the score of the Voice Handicap Index-10 was not statistically significant between patients with low vitamin D levels compared with controls.

CONCLUSION

The results of this study revealed no significant difference in the prevalence of phonatory symptoms in patients with vitamin D deficiency compared with patients with no vitamin D deficiency. A larger study is needed to substantiate the difference in the prevalence of phonatory systems between the 2 groups.

Association of Vitamin D Receptor Gene Polymorphism in Adults With Type 2 Diabetes in the Kashmir Valley

OBJECTIVES

Approx 1 billion people across various ethnic and age groups have vitamin D deficiency. The high prevalence of such a deficiency is an imperative public health issue because hypovitaminosis D is an autonomous risk factor for mortality in the general population. Beyond bone integrity and calcium homeostasis, it is involved in numerous physiologic and pathologic processes. The role of vitamin D in the pathogenesis and prevention of type 2 diabetes mellitus has sparked universal interest.

METHODS

This hospital-based case-control study was designed to study the association between 25-hydroxy vitamin D (25[OH]D) levels and the vitamin D receptor (VDR) gene polymorphism with diabetes and to evaluate their roles as risk factors for diabetes. 100 cases and controls were taken. 25(OH)D levels were analyzed by the chemilumenescence method using a Siemens ADVIA Centaur analyzer. Genomic DNA was extracted and Taq-1 and Bsm-1 genotyping in the VDR gene was done by using the polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP).

RESULTS

25(OH)D levels of patients with diabetes were significantly lower than those of controls (19.26±0.95 ng/mL vs. 25.49±1.02 ng/mL; p=0.001). 25(OH)D levels were found to be inversely associated with glycated hemoglobin percentages in cases (r²=0.74). The results suggested that the single nucleotide polymorphisms Taq-1 t(T) allele and b (G allele) in Bsm-1 might be a susceptibility allele for diabetes in the Kashmiri population.

CONCLUSIONS

VDR gene polymorphisms appear to be an important genetic determinant in the progression of diabetes. Considering the important predisposition risk factor, we observed that Taq-1 and Bsm-1 were strongly associated with diabetes in northern Indians. But requires further study as a probable genetic risk marker for diabetes.

Effect of vitamin D deficiency on the laryngo-pharyngeal tract

OBJECTIVE

To investigate the effect of vitamin D deficiency on the laryngopharyngeal tract.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary care center.

SUBJECTS AND METHODS

A total of 38 human subjects were prospectively recruited, equally divided into two groups. The Vitamin D deficiency group defined as 25-OH<25ng/dl and the control subjects with normal vitamin D level defined as 25-OH>25ng/dl. The presence and severity of vocal tract symptoms was assessed using the Vocal Tract Discomfort score.

RESULTS

There was no significant difference in vocal tract discomfort score for frequency and severity between patients with Vitamin D deficiency and patients with no vitamin D deficiency (p value 0.272). However there was a significant difference in the mean frequency of burning, aching, soreness and lump sensation (p value<0.05) in patients with vitamin D deficiency compared to those with no vitamin D deficiency. There was also a significant difference in the means of vocal tract severity symptoms, namely for burning and aching between patients with vitamin D deficiency compared to patients with no vitamin D deficiency (p value<0.05).

CONCLUSION

Subjects with vitamin D deficiency do not have a higher vocal tract discomfort score than subjects with no vitamin D deficiency. However the frequency and severity of certain vocal tract discomfort symptoms was higher and can be based hypothetically on the similarity in structure between the laryngopharyngeal complex and the musculoskeletal system.

Interventions to prevent and treat corticosteroid-induced osteoporosis and prevent osteoporotic fractures in Duchenne muscular dystrophy

BACKGROUND

Corticosteroid treatment is considered the 'gold standard' for Duchenne muscular dystrophy (DMD); however, it is also known to induce osteoporosis and thus increase the risk of vertebral fragility fractures. Good practice in the care of those with DMD requires prevention of these adverse effects. Treatments to increase bone mineral density include bisphosphonates and vitamin D and calcium supplements, and in adolescents with pubertal delay, testosterone. Bone health management is an important part of lifelong care for patients with DMD.

OBJECTIVES

To assess the effects of interventions to prevent or treat osteoporosis in children and adults with DMD taking long-term corticosteroids; to assess the effects of these interventions on the frequency of vertebral fragility fractures and long-bone fractures, and on quality of life; and to assess adverse events.

SEARCH METHODS

On 12 September 2016, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL Plus to identify potentially eligible trials. We also searched the Web of Science ISI Proceedings (2001 to September 2016) and three clinical trials registries to identify unpublished studies and ongoing trials. We contacted correspondence authors of the included studies in the review to obtain information on unpublished studies or work in progress.

SELECTION CRITERIA

We considered for inclusion in the review randomised controlled trials (RCTs) and quasi-RCTs involving any bone health intervention for corticosteroid-induced osteoporosis and fragility fractures in children, adolescents, and adults with a confirmed diagnosis of DMD. The interventions might have included oral and intravenous bisphosphonates, vitamin D supplements, calcium supplements, dietary calcium, testosterone, and weight-bearing activity.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed reports and selected potential studies for inclusion, following standard Cochrane methodology. We contacted study authors to obtain further information for clarification on published work, unpublished studies, and work in progress.

MAIN RESULTS

We identified 18 potential studies, of which two, currently reported only as abstracts, met the inclusion criteria for this review. Too little information was available for us to present full results or adequately assess risk of bias. The participants were children aged five to 15 years with DMD, ambulant and non-ambulant. The interventions were risedronate versus no treatment in one trial (13 participants) and whole-body vibration versus a placebo device in the second (21 participants). Both studies reported improved bone mineral density with the active treatments, with no improvement in the control groups, but the abstracts did not compare treatment and control conditions. All children tolerated whole-body vibration treatment. No study provided information on adverse events. Two studies are ongoing: one investigating whole-body vibration, the other investigating zoledronic acid.

AUTHORS' CONCLUSIONS

We know of no high-quality evidence from RCTs to guide use of treatments to prevent or treat corticosteroid-induced osteoporosis and reduce the risk of fragility fractures in children and adults with DMD; only limited results from two trials reported in abstracts were available. We await formal trial reports. Findings from two ongoing relevant studies and two trials, for which only abstracts are available, will be important in future updates of this review.

Bone Health in Athletes

CONTEXT

The health of the skeletal system is important for athletes young and old. From the early benefits of exercise on bones to the importance of osteoporosis prevention and treatment, bone health affects the ability to be active throughout life.

EVIDENCE ACQUISITION

PubMed articles dating from 1986 to 2016 were used for the review. Relevant terms such as keywords and section titles of the article were searched and articles identified were reviewed for relevance to this article.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Levels 1 through 4 evidence included.

RESULTS

There is strong evidence that exercise benefits bone health at every age and is a critical factor in osteoporosis prevention and treatment. Vitamin D, calcium, and hormones play vital roles in ensuring optimal bone health. When there is an imbalance between exercise and nutrition, as seen in the female athlete triad, bone health is compromised and can lead to bone stress injuries and early osteoporosis. Both of these can lead to morbidity and lost time from training and competition. Thus, early recognition and appropriate treatment of the female athlete triad and other stress fracture risk factors are vital to preventing long-term bone health problems.

CONCLUSION

To optimize bone health, adequate nutrition, appropriate weightbearing exercise, strength training, and adequate calcium and vitamin D are necessary throughout life.

Association of plasma 25-hydroxyvitamin D with physical performance in physically active children

Vitamin D is thought to regulate skeletal muscle function and boost physical performance. The aim of this study was to assess the relationship between vitamin D and physical performance in physically active children. This cross-sectional study included 125 children who practice football as a leisure activity. Plasma 25-hydroxyvitamin D (25-OHD) was assessed using a chemiluminescence immunoassay method. Vitamin D inadequacy was defined as 25-OHD < 20 ng/mL. Physical performance testing included measurements of muscle strength (maximal isometric contraction), jumping ability (vertical jump, standing broad jump, triple hop test), linear sprint (10 m and 20 m), and agility (9 × 4-m shuttle run). Plasma 25-OHD concentrations were positively correlated with muscle strength (r = 0.539; p < 0.001), vertical jump (r = 0.528; p < 0.001), and standing broad jump (r = 0.492; p < 0.001) but inversely correlated with sprint performance (r = -0.539; p < 0.001). In multivariate analysis models, plasma 25-OHD concentrations were associated with each physical performance parameter independently of age, maturity status, body mass index, fat mass, and protein and calcium intakes. In conclusion, a low plasma 25-OHD level was associated with decreased muscle strength, agility, and jumping and sprinting abilities in physically active children. Vitamin D inadequacy may limit exercise performance. Further research should verify whether correction of vitamin D deficiency enhances physical performance.

Vitamin D Deficiency Among Professional Basketball Players

Background:

Vitamin D plays an important role in several systems of the human body. Various studies have linked vitamin D deficiency to stress and insufficiency fractures, muscle recovery and function, and athletic performance. The prevalence of vitamin D deficiency in the elite athletic population has not been extensively studied, and very few reports exist among professional athletes.

Hypothesis:

There is a high prevalence of vitamin D deficiency or insufficiency among players attending the National Basketball Association (NBA) Combine.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

This is a retrospective review of data previously collected as part of the routine medical evaluation of players in the NBA Combines from 2009 through 2013. Player parameters evaluated were height, weight, body mass index (BMI), and vitamin D level. Statistical analysis using t tests and analysis of variance was used to detect any correlation between the player parameters and vitamin D level. Vitamin D levels were categorized as deficient (<20 ng/mL), insufficient (20-32 ng/mL), and sufficient (>32 ng/mL).

Results:

After institutional review board approval was submitted to the NBA, the NBA released deidentified data on 279 players who participated in the combines from 2009 through 2013. There were 90 players (32.3%) who were deficient, 131 players (47.0%) who were insufficient, and 58 players (20.8%) who were sufficient. A total of 221 players (79.3%) were either vitamin D deficient or insufficient. Among all players included, the average vitamin D level was 25.6 ± 10.2 ng/mL. Among the players who were deficient, insufficient, and sufficient, the average vitamin D levels were 16.1 ± 2.1 ng/mL, 25.0 ± 3.4 ng/mL, and 41.6 ± 8.6 ng/mL, respectively. Player height and weight were significantly increased in vitamin D–sufficient players compared with players who were not sufficient (P = .0008 and .009, respectively). Player age and BMI did not significantly differ depending on vitamin D status (P = .15 and .77, respectively).

Conclusion:

There is a high prevalence of vitamin D deficiency or insufficiency among participants in the NBA Combines. As a result, there should be a high suspicion for this metabolic abnormality among elite basketball players.

Clinical Relevance:

Vitamin D level has been linked to bone health, muscle recovery and function, and athletic performance. Because of the high prevalence of vitamin D deficiency in the NBA Combines, clinicians should maintain a high suspicion for vitamin D abnormalities among elite basketball players.

Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial

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

Randomized 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 randomly allocated to the treatment (150 000IU vitamin D3) or placebo and given blinded supplements by an independent researcher. 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 assessments on the right leg at 30 and 200°·s.

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.

Vitamin D and the immunomodulation of rotator cuff injury

Tendon-to-bone healing after rotator cuff repair surgery has a failure rate of 20%–94%. There has been a recent interest to determine the factors that act as determinants between successful and unsuccessful rotator cuff repair. Vitamin D level in patients is one of the factors that have been linked to bone and muscle proliferation and healing, and it may have an effect on tendon-to-bone healing. The purpose of this article is to critically review relevant published research that relates to the effect of vitamin D on rotator cuff tears and subsequent healing. A review of the literature was conducted to identify all studies that investigate the relationship between vitamin D and tendon healing, in addition to its mechanism of action. The data were then analyzed in order to summarize what is currently known about vitamin D, rotator cuff pathology, and tendon-to-bone healing. The activated metabolite of vitamin D, 1α,25-dihydroxyvitamin D₃, affects osteoblast proliferation and differentiation. Likewise, vitamin D plays a significant role in the tendon-to-bone healing process by increasing the bone mineral density and strengthening the skeletal muscles. The 1α,25-dihydroxyvitamin D₃ binds to vitamin D receptors on myocytes to stimulate growth and proliferation. The form of vitamin D produced by the liver, calcifediol, is a key initiator of the myocyte healing process by moving phosphate into myocytes, which improves function and metabolism. Investigation into the effect of vitamin D on tendons has been sparse, but limited studies have been promising. Matrix metalloproteinases play an active role in remodeling the extracellular matrix (ECM) of tendons, particularly deleterious remodeling of the collagen fibers. Also, the levels of transforming growth factor-β3 positively influence the success of the surgery for rotator cuff repair. In the tendon-to-bone healing process, vitamin D has been shown to successfully influence bone and muscle healing, but more research is needed to delve into the mechanisms of vitamin D as a factor in skeletal tendon health and healing.

Vitamin D deficiency in Swiss elite wheelchair athletes

STUDY DESIGN

This is a retrospective analysis of total serum 25-hydroxyvitamin D (25[OH]D) in Swiss elite wheelchair athletes.

OBJECTIVES

The aim was to investigate the occurrence of vitamin D deficiency in Swiss elite wheelchair athletes over the whole year and to detect differences between winter and summer months, and between indoor and outdoor athletes.

SETTING

This study was conducted in Switzerland.

METHODS

A total of 164 blood samples from 72 Swiss elite wheelchair athletes (mean±s.d.: age 32±13 years) were analyzed for total serum 25[OH]D. All participants were members of the national team in their discipline. The following disciplines have been included: rugby, athletics, cycling, tennis, ski alpine, curling and basketball. According to general guidelines, insufficient vitamin D status was defined between 50 and 75 nmol l^-1, deficiency below 50 nmol l^-1 and severe deficiency below 27.5 nmol l^-1.

RESULTS

In all, 73.2% of all samples showed an insufficiency/deficiency in vitamin D status. Total serum 25[OH]D was significantly higher during summer compared with winter months (69.5±21.4 nmol l^-1 vs 51.5±21.9 nmol l^-1; P<0.001). Indoor sports showed a higher amount of vitamin D insufficiency/deficiency (80.9%) than outdoor sports (70.1%), with a significantly higher 25[OH]D concentration in outdoor sports (P=0.042).

CONCLUSION

A high percentage of vitamin D deficiency was found among Swiss elite wheelchair athletes. Conclusively, we recommend supplementation with vitamin D-especially during winter-to prevent a deficiency and an impairment of performance.

Vitamin D status and V[combining dot above]O2peak during a skate treadmill graded exercise test in competitive ice hockey players

Vitamin D status has been associated with cardiorespiratory fitness (CRF) in cross-sectional investigations in the general population. Data characterizing the association between 25-hydroxyvitamin D (25(OH)D) concentration and CRF in athletes are lacking. Junior and collegiate ice hockey players were recruited from the Minneapolis, MN (44.9° N), area during the off-season period (May 16-June 28). The purpose of this study was to examine the cross-sectional association between 25(OH)D concentration and CRF in a sample population of competitive ice hockey players. Circulating 25(OH)D level was assessed from a capillary blood sample analyzed using liquid chromatography-tandem mass spectrometry. V[Combining Dot Above]O2peak during a skate treadmill graded exercise test (GXT) was used to assess CRF. Data on both 25(OH)D concentration and V[Combining Dot Above]O2peak were available for 52 athletes. Insufficient 25(OH)D concentrations were found in 37.7% of the athletes (<32 ng·ml). Vitamin D status was not significantly associated with any physiological or physical parameter during the skate treadmill GXT.

Functional Improvement in Geriatric Hip Fractures: Does Vitamin D Deficiency Affect the Functional Outcome of Patients With Surgically Treated Intertrochanteric Hip Fractures

Introduction:

The “Integrated Care Pathway” for geriatric intertrochanteric (IT) fractures in Singapore’s Tan Tock Seng Hospital has shown significant functional recovery in patients’ activities of daily living. However, the influence of preoperative vitamin D on functional recovery remains equivocal. This retrospective study therefore aims to determine whether patients with preoperative vitamin D deficiency have poorer functional outcomes.

Method:

A total of 171 patients who had surgical treatment for IT fractures were recruited in the study. They were categorized into group A (vitamin D deficient) and group B (normal vitamin D). Charlson Comorbidity Index (CCI) score and nutritional parameters including hemoglobin, albumin, and adjusted calcium levels on admission were recorded. The Modified Barthel Index (MBI) score was used to measure functional recovery at the following time intervals: at pre-fall, at discharge after surgery, at 6 months, and at 1-year follow-up.

Results:

The mean age of both the groups (A: 79.7 years, n = 45; B: 83.0 years, n = 126) was statistically different (P < .05). However, the mean CCI (A: 9.42 and B: 10.13), hemoglobin (A: 12.4 and B 11.1), adjusted calcium (A: 2.39 and B: 2.38), and mean albumin (A: 33.6 and B: 33.0) of the groups were not significantly different. Furthermore, the MBI scores were not significantly different for both groups at preinjury (A: 91.5 and B: 89.4), at discharge (A: 55.2 and B: 58.9), at 6 months (A: 70.9 and B: 75.1), and at 1 year (A: 75.8 and B: 79.4).

Conclusion:

In our cohort, patients with vitamin D deficiency were younger. However, vitamin D deficiency at time of injury had no significant influence on functional recovery in patients with surgically treated hip fracture in our Integrated Care Pathway. In addition, patients who had a normal vitamin D levels had similar functional scores and improvement postoperatively and at 1 year (A: 82.8% and B: 88.9%).

Effects of vitamin D and quercetin, alone and in combination, on cardiorespiratory fitness and muscle function in physically active male adults

Introduction

Vitamin D and the antioxidant quercetin, are promising agents for improving physical performance because of their possible beneficial effects on muscular strength and cardiorespiratory fitness.

Purpose

The purpose of this study was to determine the effects of increased intakes of vitamin D, quercetin, and their combination on antioxidant status, the steroid hormone regulators of muscle function, and measures of physical performance in apparently healthy male adults engaged in moderate-to-vigorous-intensity exercise training.

Methods

A total of 40 adult male participants were randomized to either 4,000 IU vitamin D/d, 1,000 mg/d quercetin, vitamin D plus quercetin, or placebo for 8 weeks. Measures of cardiorespiratory fitness and muscle function, blood markers for antioxidant and vitamin D status, and hormones 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) and testosterone were measured pre- and postsupplementation.

Results

At enrollment, 88.6% of participants were vitamin D sufficient (serum 25-hydroxyvitamin D >50 nmol/L) and had normal serum testosterone levels. Supplementation with vitamin D significantly increased serum 25(OH)D concentration (by 87.3% in the vitamin D group, P<0.001) and was associated with an increasing trend of testosterone concentration. There were no changes in concentration of 1,25(OH)₂D₃ and markers of antioxidant status associated with vitamin D or quercetin supplementation. No improvements in physical performance measures associated with vitamin D and quercetin supplementation were found.

Conclusion

The findings obtained demonstrate that long-term vitamin D and quercetin supplementation, alone or in combination, does not improve physical performance in male adults with adequate vitamin D, testosterone, and antioxidant status.

Vitamin D receptor gene polymorphisms and musculoskeletal injuries in professional football players

The aim of the present study was to investigate the association between vitamin D receptor (VDR) gene polymorphisms and musculoskeletal injury (MI) in elite football players. In total, 54 male professional football players were recruited from an official Italian professional championship team between 2009 and 2013. The cohort was genotyped for the ApaI, BsmI and FokI polymorphisms and MI data were collected over four football seasons. No significant differences were identified among the genotypes in the incidence rates or severity of MI (P=0.254). In addition, no significant associations were observed between VDR polymorphisms and MI phenotypes (P=0.460). However, the results of the casewise multiple regression analysis indicated that the ApaI genotypes accounted for 18% of injury severity (P=0.002). Therefore, while the BsmI and FokI polymorphisms did not appear to be associated with the severity or incidence of MI, the ApaI genotypes may have influenced the severity of muscle injury in top-level football players.

Vitamin D status, body composition, and fitness measures in college-aged students

Low vitamin D, commonly assessed as serum 25-hydroxyvitamin D (25OHD), is associated with the development of many age-related chronic diseases. A positive relationship exists between elevated 25OHD and muscle synthesis, strength, power, and decreased body fat in elderly individuals. However, these findings have not been consistently reported in younger healthy populations. The purpose of this study was to investigate the relationship between 25OHD and measures of body size, composition, metabolism, and physical fitness in a young physically active population. Thirty-nine subjects (20 men, 19 women; aged 23 ± 0.7 years) reported 6 times for testing. Blood was collected to determine 25OHD. Primary outcomes included the following: body mass index (BMI) and percent body fat (dual x-ray absorptiometry); resting metabolic rate; maximal oxygen uptake (V[Combining Dot Above]O2max); power output (Wingate); and muscular strength (8 repetition maximum for bench press, upright row, and leg extension and flexion exercises). Our analysis included all participants, and subgroup analyses for individuals with suboptimal 25OHD concentration below 35 ng·mL ("low"; n = 20, 25.97 ± 1.97 ng·mL) or equal to and above 35 ng·mL ("high"; n = 19, 44.15 ± 2.17 ng·mL). Twenty subjects in this study had serum levels of 25OHD below 35 ng·mL. There was a significant positive relationship between V[Combining Dot Above]O2max and serum 25OHD and a negative relationship between BMI and serum 25OHD. These data suggest that vitamin D deficiency is prevalent even in a young physically active population in the southern United States and that there was a positive relationship between a measure of cardiovascular fitness and serum 25OHD, and a negative relationship between serum 25OHD and BMI.

Effects of vitamin D supplementation on upper and lower body muscle strength levels in healthy individuals. A systematic review with meta-analysis

OBJECTIVES

To investigate the effects of vitamin D supplementation on muscle strength in healthy individuals.

DESIGN

A systematic review with meta-analysis.

METHODS

In October 2013 a computerised literature search of three databases (PubMed, Web of Knowledge and Scopus) was performed. Included in the review were controlled and randomised controlled trials, published in English, which measured muscle strength and serum vitamin D concentration in participants 18-40 years old. References of identified articles were then cross-checked and citations scanned for additional articles. Quality was assessed using the PEDro scale. Muscle strength and vitamin D levels were extracted for a meta-analysis on upper and lower limb strength with standardised mean differences calculated to analyse effect.

RESULTS

Six randomised controlled trials and one controlled trial were identified and quality assessment showed all seven trials were of 'good quality'. Data was extracted from 310 adults, 67% female, with mean ages ranging from 21.5 to 31.5 years. Trials lasted from 4 weeks to 6 months and dosages differed from 4000 IU per day to 60,000 IU per week. Upper and lower limb muscle strength had a standardised mean difference of 0.32 (95% CI=0.10, 0.54) and 0.32 (95% CI=0.01, 0.63) respectively, suggesting vitamin D supplementation significantly increased muscle strength in the experimental group for upper (P=0.005) and lower limbs (P=0.04).

CONCLUSIONS

Vitamin D supplementation increases upper and lower limb strength. Further research should focus on its effect on muscle power, endurance and maximal strength.

Prevalence of Abnormal Vitamin D Levels Among Division I NCAA Athletes

Background:

Up to 1 billion people have insufficient or deficient vitamin D levels. Despite the well-documented, widespread prevalence of low vitamin D levels and the importance of vitamin D for athletes, there is a paucity of research investigating the prevalence of vitamin D deficiency in athletes.

Hypothesis:

We investigated the prevalence of abnormal vitamin D levels in National Collegiate Athletic Association (NCAA) Division I college athletes at a single institution. We hypothesized that vitamin D insufficiency is prevalent among our cohort.

Study Design:

Cohort study.

Level of Evidence:

Level 1.

Methods:

We measured serum 25-hydroxyvitamin D (25(OH)D) levels of 223 NCAA Division I athletes between June 2012 and August 2012. The prevalence of normal (≥32 ng/mL), insufficient (20 to <32 ng/mL), and deficient (<20 ng/mL) vitamin D levels was determined. Logistic regression was utilized to analyze risk factors for abnormal vitamin D levels.

Results:

The mean serum 25(OH)D level for the 223 members of this study was 40.1 ± 14.9 ng/mL. Overall, 148 (66.4%) participants had sufficient 25(OH)D levels, and 75 (33.6%) had abnormal levels. Univariate analysis revealed the following significant predictors of abnormal vitamin D levels: male sex (odds ratio [OR] = 2.83; P = 0.0006), Hispanic race (OR = 6.07; P = 0.0063), black race (OR = 19.1; P < 0.0001), and dark skin tone (OR = 15.2; P < 0.0001). Only dark skin tone remained a significant predictor of abnormal vitamin D levels after multivariate analysis (adjusted OR = 15.2; P < 0.0001).

Conclusion:

In a large cohort of NCAA athletes, more than one third had abnormal vitamin D levels. Races with dark skin tones are at much higher risk than white athletes. Male athletes are more likely than female athletes to be vitamin D deficient. Our study demonstrates a high prevalence of vitamin D deficiency among healthy NCAA athletes.

Clinical Relevance:

Many studies indicate a significant prevalence of vitamin-D insufficiency across various populations. Recent studies have demonstrated a direct relationship between serum 25(OH)D levels and muscle power, force, velocity, and optimal bone mass. In fact, studies examining muscle biopsies from patients with low vitamin D levels have demonstrated atrophic changes in type II muscle fibers, which are crucial to most athletes. Furthermore, insufficient 25(OH)D levels can result in secondary hyperparathyroidism, increased bone turnover, bone loss, and increased risk of low trauma fractures and muscle injuries. Despite this well-documented relationship between vitamin D and athletic performance, the prevalence of vitamin D deficiency in NCAA athletes has not been well studied.

Sports health benefits of vitamin d

CONTEXT

Vitamin D is a potent secosteroid hormone that provides many skeletal and extraskeletal health benefits. Musculoskeletal injury prevention and recovery are potentially affected by sufficient circulating levels of the storage form of vitamin D: 25-hydroxyvitamin D3, or 25(OH)D. Vitamin D deficiency can exist among young, active, and healthy people, which may put them at increased risk for injury and prolonged recovery.

EVIDENCE AQUISITION

PubMed was searched using vitamin D and skeletal muscle, vitamin D and athletic performance, and vitamin D review articles. Studies from the 1930s to 2012 were used for the review.

RESULTS

There is strong correlation between vitamin D sufficiency and optimal muscle function. Increasing levels of vitamin D reduce inflammation, pain, and myopathy while increasing muscle protein synthesis, ATP concentration, strength, jump height, jump velocity, jump power, exercise capacity, and physical performance. 25(OH)D levels above 40 ng/mL are required for fracture prevention, including stress fractures. Optimal musculoskeletal benefits occur at 25(OH)D levels above the current definition of sufficiency (> 30 ng/mL) with no reported sports health benefits above 50 ng/mL.

CONCLUSIONS

Vitamin D deficiency is common in athletes. For athletes presenting with stress fractures, musculoskeletal pain, and frequent illness, one should have a heightened awareness of the additional likely diagnosis of vitamin D deficiency. Correction of this deficiency is completed by standardized and supervised oral supplementation protocols producing significant musculoskeletal sports health benefits.

Triennial Growth Symposium--Novel roles for vitamin D in animal immunity and health

Recent years have seen significant advances in the generation, validation, and implementation of nutritional supplements for food production animals. Examination of their impact on animal performance and health requires collaboration among animal scientists, nutritionists, biochemists, immunologists, veterinarians, and others. Each provides a unique perspective on the mechanisms of action, short and long-term impacts, and most effective strategies for implementation into continuously evolving industrial practices. In this review we provide a comparative immunology perspective on the impact of vitamin D on animal performance and health, describe the differential contributions of vitamin D3 and of a commercial hydroxylated version of vitamin D3, 25-hydroxyvitamin D3 (25(OH)D3 or HyD) to swine immunity, and highlight recent advances in the technologies that can be used to dissect the cellular and molecular mechanisms that impact production animal immunity and health. Among others, we pay particular attention to how these novel approaches help decrease the variability often observed in immune-associated datasets. From a practical perspective, this is critical for evaluation of in vivo effects for this nutritional supplement as small but meaningful changes to specific immune responses are typical under normal physiological conditions. Furthermore, as the range of reagents and technologies expands for comparative animal models, it is imperative that continued efforts are placed on the capacity to compare results across different experimental platforms.