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      Vitamin D 3 supplementation using an oral spray solution resolves deficiency but has no effect on VO 2 max in Gaelic footballers: results from a randomised, double-blind, placebo-controlled trial

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          Abstract

          Purpose

          Vitamin D inadequacy is a global health concern in athletes as well as the general population. Whilst the role of vitamin D in skeletal health is well defined, there remains uncertainty over whether vitamin D supplementation has an added benefit beyond bone health.

          Methods

          This randomised placebo-controlled trial in healthy male and female Gaelic footballers ( n = 42) investigated the effect of vitamin D 3 supplementation [3000 IU (75 µg) daily for 12 weeks, via an oral spray solution] on VO 2 max which was the primary outcome measure. Secondary outcomes included skeletal muscle and lung function.

          Results

          Supplementation significantly increased total 25-hydroxyvitamin D concentrations compared to the placebo group (mean ± SD change from baseline, 36.31 ± 32.34 vs. 6.11 ± 23.93 nmol/L, respectively; P = 0.006). At baseline, 50 and 22 % of footballers presented with vitamin D insufficiency (31–49 nmol/L) and deficiency (<30 nmol/L), respectively. Total 25-hydroxyvitamin D concentration did not significantly correlate with any measure of physical performance. Analysis of covariance (ANCOVA) models demonstrated that vitamin D supplementation over 12 weeks had no significant effect on VO 2 max ( P = 0.375), vertical jump height ( P = 0.797), left and right handgrip strength ( P = 0.146 and P = 0.266, respectively), forced vital capacity ( P = 0.573) or forced expiratory volume at 1 s ( P = 0.665), after adjusting for confounders. The high prevalence of vitamin D inadequacy observed in this cohort of collegiate Gaelic footballers supports the need for vitamin D supplementation during wintertime to avoid being at risk of poor bone health.

          Conclusions

          Twelve-week daily supplementation with 3000 IU (75 µg) vitamin D 3 successfully resolved deficiency but did not have any significant effect on VO 2 max, skeletal muscle or lung function.

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          Most cited references58

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          Aerobic endurance training improves soccer performance.

          The aim of the present study was to study the effects of aerobic training on performance during soccer match and soccer specific tests. Nineteen male elite junior soccer players, age 18.1 +/- 0.8 yr, randomly assigned to the training group (N = 9) and the control group (N = 10) participated in the study. The specific aerobic training consisted of interval training, four times 4 min at 90-95% of maximal heart rate, with a 3-min jog in between, twice per week for 8 wk. Players were monitored by video during two matches, one before and one after training. In the training group: a) maximal oxygen uptake (VO2max) increased from 58.1 +/- 4.5 mL x kg(-1) x min(-1) to 64.3 +/- 3.9 mL x kg(-1) x min(-1) (P < 0.01); b) lactate threshold improved from 47.8 +/- 5.3 mL x kg(-1) x min(-1) to 55.4 +/- 4.1 mL x kg(-1) x min(-1) (P < 0.01); c) running economy was also improved by 6.7% (P < 0.05); d) distance covered during a match increased by 20% in the training group (P < 0.01); e) number of sprints increased by 100% (P < 0.01); f) number of involvements with the ball increased by 24% (P < 0.05); g) the average work intensity during a soccer match, measured as percent of maximal heart rate, was enhanced from 82.7 +/- 3.4% to 85.6 +/- 3.1% (P < 0.05); and h) no changes were found in maximal vertical jumping height, strength, speed, kicking velocity, kicking precision, or quality of passes after the training period. The control group showed no changes in any of the tested parameters. Enhanced aerobic endurance in soccer players improved soccer performance by increasing the distance covered, enhancing work intensity, and increasing the number of sprints and involvements with the ball during a match.
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            Regulation of iron metabolism by hepcidin.

            Hepcidin, a peptide hormone made in the liver, is the principal regulator of systemic iron homeostasis. Hepcidin controls plasma iron concentration and tissue distribution of iron by inhibiting intestinal iron absorption, iron recycling by macrophages, and iron mobilization from hepatic stores. Hepcidin acts by inhibiting cellular iron efflux through binding to and inducing the degradation of ferroportin, the sole known cellular iron exporter. Synthesis of hepcidin is homeostatically increased by iron loading and decreased by anemia and hypoxia. Hepcidin is also elevated during infections and inflammation, causing a decrease in serum iron levels and contributing to the development of anemia of inflammation, probably as a host defense mechanism to limit the availability of iron to invading microorganisms. At the opposite side of the spectrum, hepcidin deficiency appears to be the ultimate cause of most forms of hemochromatosis, either due to mutations in the hepcidin gene itself or due to mutations in the regulators of hepcidin synthesis. The emergence of hepcidin as the pathogenic factor in most systemic iron disorders should provide important opportunities for improving their diagnosis and treatment.
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              Relationship between serum 25-hydroxyvitamin d and pulmonary function in the third national health and nutrition examination survey.

              Age, gender, height, ethnicity, and smoking are important determinants of lung function but do not explain all of the variation between individuals. Low concentrations of vitamin D have been associated with a number of diseases, including osteoporosis, hypertension, and type I diabetes. It is possible that serum concentrations of vitamin D might also influence pulmonary function. To determine the relationship between serum concentrations of 25-hydroxy vitamin D and pulmonary function. The analysis was conducted using data from the Third National Health and Nutrition Examination Survey, which was a cross-sectional survey of the US civilian population that was conducted from 1988 to 1994. The analyses were restricted to 14,091 people who > or = 20 years of age, were interviewed at mobile examination centers, and had undergone spirometry, and in whom serum 25-hydroxy vitamin D levels had been measured. After adjustment for age, gender, height, body mass index, ethnicity, and smoking history, the mean FEV1 was 126 mL (SE, 22 mL), and the mean FVC was 172 mL (SE, 26 mL) greater for the highest quintile of serum 25-hydroxy vitamin D level (> or = 85.7 nmol/L) compared with the lowest quintile (< or = 40.4 nmol/L; p < 0.0001). With further adjustment for physical activity, the intake of vitamin D supplements, milk intake, and the level of serum antioxidants, the mean difference between the highest and lowest quintiles of 25-hydroxy vitamin D was 106 mL (SE, 24 mL) for FEV1, and 142 mL (SE, 29 mL) for FVC (p < 0.0001). There is a strong relationship between serum concentrations of 25-hydroxy vitamin D, FEV1, and FVC. Further studies are necessary to determine whether supplementation with vitamin D is of any benefit in patients with respiratory disease.
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                Author and article information

                Contributors
                +44 28 70124360 , pj.magee@ulster.ac.uk
                Journal
                Eur J Nutr
                Eur J Nutr
                European Journal of Nutrition
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                1436-6207
                1436-6215
                25 March 2016
                25 March 2016
                2017
                : 56
                : 4
                : 1577-1587
                Affiliations
                [1 ]ISNI 0000000105519715, GRID grid.12641.30, Northern Ireland Centre for Food and Health, , University of Ulster, ; Coleraine, UK
                [2 ]Irish Institute of Sport, Sports Campus Ireland, Abbotstown, Dublin 15, UK
                [3 ]ISNI 0000000121885934, GRID grid.5335.0, Institute of Molecular Medicine, , Trinity College, ; Dublin, UK
                [4 ]Department of Medicine, Trinity Centre for Health Science St. James’s Hospital, Dublin, UK
                Article
                1202
                10.1007/s00394-016-1202-4
                5486642
                27015912
                82fe652b-48bd-43d2-ab9f-f31198e3c2a7
                © The Author(s) 2016

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                History
                : 19 November 2015
                : 7 March 2016
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/100008303, Department for Employment and Learning, Northern Ireland;
                Categories
                Original Contribution
                Custom metadata
                © Springer-Verlag Berlin Heidelberg 2017

                Nutrition & Dietetics
                vitamin d,vo2 max,athletes,randomised controlled trial,football
                Nutrition & Dietetics
                vitamin d, vo2 max, athletes, randomised controlled trial, football

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