Recent evidence suggests that vitamin D insufficiency is associated with an increased risk of stress fracture, total body inflammation, infectious illness and impaired muscle function⁽ Reference Willis, Peterson and Larson-Meyer ^{1 ,} Reference Larson-Mayer and Willis ^{2 )} and is thus likely to impair the training ability of athletes in addition to affecting their overall health. Though not widely studied, vitamin D deficiency and insufficiency have been reported among athletes, irrespective of geographic location⁽ Reference Holick ^{3 )}. The aim of the current study was to assess vitamin D status in two groups of elite Irish athletes sampled in different months of the year.

Non-fasting blood samples were taken from consenting volunteers (n 66) and total serum 25-hydroxyvitamin D (25(OH)D) was quantified by enzymeimmunoassay (IDS Limited, Boldon, UK). Serum calcium and plasma parathyroid hormone (PTH) concentration were also assessed (using the I-lab 650 Clinical Chemistry analyser and ARCHITECT i1000SR integrated system, respectively).

* Significant difference between athletic groups (P<0.05, independent t-test). Significance remained after controlling for age and gender (P<0.001, ANCOVA); †mean daily intakes estimated from a validated food frequency questionnaire⁽ Reference Collins ^{4 )} (n 25); 25(OH)D, 25-hydroxyvitamin D; PTH, parathyroid hormone.

Vitamin D status was significantly lower in the gaelic athletes compared to the paralympians. Moreover, a greater proportion of gaelic athletes had a 25(OH)D<50 nmol/L compared to the paralympians (94% vs. 28%); a level most experts use to define 25(OH)D deficiency⁽ Reference Holick ^{3 )}. Among the paralympians, the serum 25(OH)D and calcium concentrations of wheelchair-bound athletes were significantly lower compared to that of their able-bodied counterparts (P=0.013 and P=0.001, respectively), without significantly affecting PTH concentrations (P=0.676). There were no significant differences in mean daily vitamin D (P=0.903) or calcium (P=0.210) intakes between the two groups of paralympians. Mean daily vitamin D and calcium intake were significantly correlated after controlling for age and gender (r=0.464, P=0.030), however were not associated with circulating 25(OH)D, PTH or calcium concentrations.

This study highlights a high prevalence of vitamin D deficiency among elite Irish athletes, particularly at the end of winter. Inadequate sun exposure, rather than diet, is the likely cause of lower 25(OH)D concentrations observed in the wheelchair athletes. A serum 25(OH)D concentration ≥80 nmol/L has recently been postulated as desirable for athletes⁽ Reference Larson-Mayer and Willis ^{2 )} however, the majority of athletes sampled in this study failed to reach this level. Vitamin D supplementation should therefore be considered for these athletic groups.