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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.

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

or those participating in sports that require uniforms that minimize skin exposure ( Constantini et al., 2010 ). Given the strong evidence suggesting that vitamin D levels may be lower for certain sports during the winter months, recent research has examined the effects of vitamin D supplementation

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Leslie N. Silk, David A. Greene, and Michael K. Baker

Research examining the preventative effects of calcium and vitamin D supplementation has focused on children and females, leaving the effects on male bone mineral density (BMD) largely unexplored. Thus, the aim of this systematic review and meta-analysis is to examine the efficacy of calcium supplementation, with or without vitamin D for improving BMD in healthy males. Medline, EMBASE, SPORTDiscus, Academic Search Complete, CINHAHL Plus and PubMed databases were searched for studies including healthy males which provided participants calcium supplementation with or without vitamin D and used changes to BMD as the primary outcome measure. Between trial standardized mean differences of percentage change from baseline in BMD of femoral neck, lumbar spine, total body and total hip sites were calculated. Nine studies were included in the systematic review with six references totaling 867 participants contributing to the meta-analysis. Significant pooled effects size (ES) for comparison between supplementation and control groups were found at all sites included in the meta-analysis. The largest effect was found in total body (ES = 0.644; 95% CI = 0.406–0.883; p < .001), followed by total hip (ES = 0.483, 95% CI= 0.255–0.711, p < .001), femoral neck (ES = 0.402, 95% CI = 0.233–0.570, p = .000) and lumbar spine (ES = 0.306, 95% CI = 0.173–0.440, p < .001). Limited evidence appears to support the use of calcium and vitamin D supplementation for improving BMD in older males. There is a need for high quality randomized controlled trials, especially in younger and middle-aged male cohorts and athletic populations to determine whether supplementation provides a preventative benefit.

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

and function ( Barker et al., 2013 ), increased rates of stress fractures ( Ruohola et al., 2006 ), and even poor athletic performance ( Koundourakis et al., 2014 ). Vitamin D supplementation has been proposed for facilitating the number of processes that are important for optimal physical performance

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

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)<30ng/ml, mean 24.2 ± 4.8ng/ml) were randomized to receive 2,000IU/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 ± 6.5ng/ml vs. 20.3 ± 4.2ng/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 ageadjusted balance, strength or swimming performance at study end. Vitamin D3 supplementation that raised serum 25(OH)D concentrations by a mean of 9.3ng/ml above placebo in adolescent swimmers with vitamin D insufficiency, did not improve physical performance more than placebo.

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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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Matthew A. Wyon, Roger Wolman, Nicolas Kolokythas, Karen Sheriff, Shaun Galloway, and Adam Mattiussi

48%). 6 Low serum 25(OH)D has been linked to reduced muscle strength and power which are fundamental to athletic performance 6 , 7 ; this has further been associated with an increased incidence of injury. 8 , 9 Vitamin D supplementation has become recommended practice in a number of sports including

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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

; Jastrzebska et al., 2016 ), interventional studies suggest that vitamin D supplementation increases strength and power in athletes (dancers, taekwondo, and judoka athletes), particularly lower-extremity strength ( Zhang et al., 2019 ). Of note, improved strength and power has primarily been observed as a

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Richard D. Lewis and Christopher M. Modlesky

Calcium and vitamin D can significantly impact bone mineral and fracture risk in women. Unfortunately, calcium intakes in women are low and many elderly have poor vitamin D status. Supplementation with calcium (~1000 mg) can reduce bone loss in premenopausal and late postmenopausal women, especially at sites that have a high cortical bone composition. Vitamin D supplementation slows bone loss and reduces fracture rates in late postmenopausal women. While an excess of nutrients such as sodium and protein potentially affect bone mineral through increased calcium excretion, phytoestrogens in soy foods may attenuate bone loss ihrough eslrogenlike activity. Weight-bearing physical activity may reduce the risk of osteoporosis in women by augmenting bone mineral during the early aduli years and reducing the loss of bone following menopause. High-load activities, such as resistance training, appear to provide the best stimulus for enhancing bone mineral; however, repetitive activities, such as walking, may have a positive impact on bone mineral when performed at higher intensities. Irrespective of changes in bone mineral, physical activities that improve muscular strength, endurance, and balance may reduce fracture risk by reducing the risk of falling. The combined effect of physical activity and calcium supplementation on bone mineral needs further investigation.

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Pamela J. Magee, L. Kirsty Pourshahidi, Julie M. W. Wallace, John Cleary, Joe Conway, Edward Harney, and Sharon M. Madigan

Background:

A high prevalence of vitamin D insufficiency/deficiency, which may impact on health and training ability, is evident among athletes worldwide. This observational study investigated the vitamin D status of elite Irish athletes and determined the effect of wintertime supplementation on status.

Methods:

Serum 25-hydroxyvitamin D [25(OH)D], calcium, and plasma parathyroid hormone were analyzed in elite athletes in November 2010 (17 boxers, 33 paralympians) or March 2011 (34 Gaelic Athletic Association [GAA] players). A subset of boxers and paralympians (n = 27) were supplemented during the winter months with either 5,000 IU vitamin D3/d for 10–12 weeks or 50,000 IU on one or two occasions. Biochemical analysis was repeated following supplementation.

Results:

Median 25(OH)D of all athletes at baseline was 48.4 nmol/L. Vitamin D insufficiency/deficiency (serum 25(OH)D <50 nmol/L) was particularly evident among GAA players (94%) due to month of sampling. Wintertime supplementation (all doses) significantly increased 25(OH)D (median 62.8 nmol/L at baseline vs. 71.1 nmol/L in April or May; p = .001) and corrected any insufficiencies/deficiencies in this subset of athletes. In contrast, 25(OH)D significantly decreased in those that did not receive a vitamin D supplement, with 74% of athletes classed as vitamin D insufficient/deficient after winter, compared with only 35% at baseline.

Conclusions:

This study has highlighted a high prevalence of vitamin D insufficiency/deficiency among elite Irish athletes and demonstrated that wintertime vitamin D3 supplementation is an appropriate regimen to ensure vitamin D sufficiency in athletes during winter and early spring.