Vitamin D Status and Supplementation in Elite Irish Athletes

Authors: Pamela J. Magee¹, L. Kirsty Pourshahidi¹, Julie M.W. Wallace¹, John Cleary^{2, 3}, Joe Conway⁴, Edward Harney⁵ and Sharon M. Madigan^{2, 3}

Affiliations: ¹Northern Ireland Centre for Food and Health, University of Ulster, Coleraine, Northern Ireland, ²High Performance Unit, National Boxing Stadium, Dublin,Ireland, ³Irish Institute of Sport, Sports Campus Ireland, Abbottstown, Dublin Ireland, ⁴Paralympics Ireland, Sport HQ, Clondalkin, Dublin 12 and ⁵Down County Board, Castlewellan, Northern Ireland.

Acceptance Date: March 12, 2013

ABSTRACT
Background A high prevalence of vitamin D insufficiency/deficiency is evident among athletes worldwide, which may impact on health and training ability. 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 (17 boxers, 33 paralympians and 34 Gaelic Athletic Association (GAA) players) in November 2010 (boxers and paralympians) or March 2011 (GAA players). A sub-set of boxers and paralympians (n=27) were supplemented with vitamin D₃ during the winter months with either 5000 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/May; p = 0.001) and corrected any insufficiencies/deficiencies in this sub-set 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 to 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 regime to ensure vitamin D sufficiency in athletes during winter and early spring.

Link to paper: http://journals.humankinetics.com/ijsnem-in-press/ijsnem-in-press/vitamin-d-status-and-supplementation-in-elite-irish-athletes