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Kelly Pritchett, Robert C. Pritchett, Lauren Stark, Elizabeth Broad and Melissa LaCroix

The National Health and Nutrition Examination Survey III determined that vitamin D insufficiency (<75 nmol/L) affects over 77% of the population. According to the World Health Organization and the Endocrine Society serum 25(OH) vitamin D (25(OH)D) standards, vitamin D deficiency is defined as <50

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Amanda Zaleski, Beth Taylor, Braden Armstrong, Michael Puglisi, Priscilla Clarkson, Stuart Chipkin, Charles Michael White, Paul D. Thompson and Linda S. Pescatello

 al., 2018 ; Whelton et al., 2018 ) and is strongly associated with all cause and CVD mortality ( Whelton et al., 2018 ). In addition, blood serum 25-hydroxyvitamin D [25(OH)D] insufficiency (i.e., 25(OH)D <75 nmol/L or <30 ng/ml) is a major public health problem, affecting 42% of Americans ( Forrest

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Jenna E. Heller, Joi J. Thomas, Bruce W. Hollis and D. Enette Larson-Meyer

Excess body fat or obesity is known to increase risk of poor vitamin D status in nonathletes but it is not known if this is the case in athletes. Furthermore, the reason for this association is not understood, but is thought to be due to either sequestration of the fat-soluble vitamin within adipose tissue or the effect of volume dilution related to obese individuals’ larger body size. Forty two US college athletes (24 men 18 women, 20.7 ± 1.6 years, 85.0 ± 28.7 kg, BMI = 25.7 ± 6.1 kg/m2) provided blood samples during the fall and underwent measurement of body composition via dual energy X-ray absorptiometry. Serum samples were evaluated for 25-hydroxyvitamin D (25(OH)D) concentration to assess vitamin D status using Diasorin 25(OH)D radioiodine assay. Serum 25(OH)D concentration was negatively associated with height (r = -0.45), total body mass (r = -0.57), BMI (r = -0.57), body fat percentage (r = -0.45), fat mass (r = -0.60) and fat-free mass (r = -0.51) (p < .05). These associations did not change after controlling for sex. In a linear regression mixed model, fat mass (coefficient -0.47, p = .01), but not fat-free mass (coefficient -0.18, p = .32) significantly predicted vitamin D status and explained approximately 36% of the variation in serum 25(OH)D concentration. These results suggest that athletes with a large body size and/or excess adiposity may be at higher risk for vitamin D insufficiency and deficiency. In addition, the significant association between serum 25(OH)D concentration and fat mass in the mixed model, which remained after controlling for sex, is in support of vitamin D sequestration rather than volume dilution as an explanation for such association.

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Blair Crewther, Christian Cook, John Fitzgerald, Michal Starczewski, Michal Gorski and Joanna Orysiak

The steroid 25-hydroxyvitamin D, or 25(OH)D, plays an important role in regulating calcium homeostasis and bone health ( 19 , 29 ). Thus, considerable scientific and societal attention has been placed on identifying and alleviating population deficiencies in 25(OH)D ( 19 , 29 , 35 ). Skeletal

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Xiaomin Sun, Zhen-Bo Cao, Kumpei Tanisawa, Satomi Oshima and Mitsuru Higuchi

in heavier weight-class professional athletes ( Guo et al., 2013 ). Recent studies indicate that low circulating vitamin D concentrations, measured as 25-hydroxyvitamin D [25(OH)D], are associated with a higher risk of poor cardiovascular outcome and physical fitness ( Girgis et al., 2014 ; Parker

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Hyun Chul Jung, Myong Won Seo, Sukho Lee, Sung Woo Jung and Jong Kook Song

prevalence of vitamin D deficiency in TKD athletes has not been systematically examined, our pilot study revealed that collegiate TKD athletes were vitamin D insufficient —serum 25(OH)D concentration, male: 28.7 ± 1.22 nmol/L and female: 27.3 ± 1.81 nmol/L, unpublished data (pilot-test result; March, 2015

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Michelle S. Rockwell, Madlyn I. Frisard, Janet W. Rankin, Jennifer S. Zabinsky, Ryan P. Mcmillan, Wen You, Kevin P. Davy and Matthew W. Hulver

protein synthesis, improved calcium availability during muscle crossbridge cycling, and action upon anabolic steroid hormones ( Owens, Allison, & Close, 2018 ; Todd et al., 2015 ). Serum 25-hydroxyvitamin D [25(OH)D], the common biomarker for vitamin D status, has been positively correlated with muscular

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Kirsty A. Fairbairn, Ingrid J.M. Ceelen, C. Murray Skeaff, Claire M. Cameron and Tracy L. Perry

people with serum 25-hydroxyvitamin D (25(OH)D) concentrations below 50 nmol/L improves muscle strength, power, and performance ( Glerup et al., 2000 ; Gupta et al., 2010 ). A meta-analysis of nonathletic participants with low vitamin D status reported that vitamin D supplementation improved muscle

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Gal Dubnov-Raz, Netachen Livne, Raanan Raz, Daniel Rogel, Avner H. Cohen and Naama W. Constantini

Serum vitamin D concentrations (25[OH]D) are associated with physical performance in the general population, but few studies have been published in athletes. 80 competitive adolescent swimmers from both sexes were tested for serum 25(OH)D concentrations, grip strength, balance and swimming performance at several speeds. Spearman’s correlations were used to examine the associations between 25(OH)D concentrations and age-adjusted measures of performance. Performance parameters were also compared between vitamin D sufficient (n = 27), insufficient (25[OH]D ranging 20−29.9 ng/ml, n = 42), and deficient (25[OH]D < 20 ng/ml, n = 11) participants. No significant associations were found between serum 25(OH)D concentrations and any of the performance measures, with no significant differences found between vitamin D sufficient, insufficient and deficient participants. In competitive adolescent swimmers, serum vitamin D concentrations were not associated with strength, balance or swimming performance. Vitamin D insufficient/deficient swimmers did not have reduced performance.

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Regina M. Lewis, Maja Redzic and D. Travis Thomas

The purpose of this 6-month randomized, placebo-controlled trial was to determine the effect of season-long (September–March) vitamin D supplementation on changes in vitamin D status, which is measured as 25(OH) D, body composition, inflammation, and frequency of illness and injury. Forty-five male and female athletes were randomized to 4,000 IU vitamin D (n = 23) or placebo (n = 22). Bone turnover markers (NTx and BSAP), 25(OH)D, and inflammatory cytokines (TNF-alpha, IL-6, and IL1-β) were measured at baseline, midpoint, and endpoint. Body composition was assessed by DXA and injury and illness data were collected. All athletes had sufficient 25(OH)D (> 32 ng/ml) at baseline (mean: 57 ng/ml). At midpoint and endpoint, 13% and 16% of the total sample had 25(OH)D < 32 ng/ml, respectively. 25(OH)D was not positively correlated with bone mineral density (BMD) in the total body, proximal dual femur, or lumbar spine. In men, total body (p = .04) and trunk (p = .04) mineral-free lean mass (MFL) were positively correlated with 25(OH)D. In women, right femoral neck BMD (p = .02) was positively correlated with 25(OH)D. 25(OH)D did not correlate with changes in bone turnover markers or inflammatory cytokines. Illness (n = 1) and injury (n = 13) were not related to 25(OH)D; however, 77% of injuries coincided with decreases in 25(OH)D. Our data suggests that 4,000 IU vitamin D supplementation is an inexpensive intervention that effectively increased 25(OH)D, which was positively correlated to bone measures in the proximal dual femur and MFL. Future studies with larger sample sizes and improved supplement compliance are needed to expand our understanding of the effects of vitamin D supplementation in athletes.