1. HYPOVITAMINOSIS D IN YOUNG ATHLETES FROM THE MIDDLE EAST AND SEASONAL VARIATIONS
Nikolovski Z1, Cardinale M1, Varamenti E1, Elzain Elgingo M1, Douglas AR1, Cable TN1
1 Aspire Academy, Doha, Qatar

2. Introduction
The most important source of Vitamin D is skin synthesis upon exposure to ultraviolet B radiation (UVB) and to a lesser extent, diet. The cut-off to define vitamin D deficiency has been a matter of debate; some consider levels >75 nmol/L to define sufficiency (Dawson-Hughes et al., 2005) while others consider 50 nmol/L an adequate cut-off level (Lips, 2007). The aim of this study was to assess Vitamin D levels in young athletes of Qatar in 3 different periods of their training and competition season.
Methods
52 elite male youth athletes (age 12 to 18) were assessed for Vitamin D status in September, January and May. Serum Vitamin D level was determined in serum using 25-OH Vitamin D ELISA kit (Euroimmun, Luebeck, Germany). Anthropometric measures were performed for the determination of peak height velocity (PHV; Mirwald et al., 2002).

3. Results Mean PHV of the subjects was 14.1 + 0.8 years.
Figure 3. Serum vitamin D concentration expressed
relative to PHV.
1 = pre PHV
2 = post PHV (mean + S.D.).
Serum levels of Vitamin D were lower than the 50 nmol/L cut-off value (dotted line). Maturation status was shown to affect Vitamin D metabolism with pre PHV presenting lower Vit D levels than post PHV in athletes. There is significant difference between PHV categories (p <0.0001).
Figure 1. Serum vitamin D concentration during school year. Figure 1 shows vitamin D concentration (means + S.D.) change during school year (p <0.05) on different screening points (1-September, 2-January, 3-May). Serum levels of Vitamin D were consistently lower than the 50 nmol/L cut-off (dotted line) in each period ( nmol/L; nmol/L;
nmol/L). Vitamin D concentration in May was significantly higher than in September (P<0.05).
Figure 2. The percentage of athletes with vitamin D levels above the 50nmol/L cut-off .
Figure 2 shows improvement of the percentage of the athletes whose vitamin D concentration was above the 50 nmol/l cut-off threshold from September to May (18% above threshold in September as compared to 42% in May). Anyhow, still more than 50 % of the athletes in this cohort in May has vitamin D concentration below 50 nmol/l.

4. Discussion and conclusions
Our data show that young athletes from the Middle-East region present Vitamin D deficiency.
However, since a statistical improvement was observed in May, it seems that more outdoor training sessions and activities during winter months from January to May, have a positive impact on Vitamin D levels.
Furthermore, our data suggest an influence of vitamin D metabolism on growth and maturation.
Increase of Vitamin D concentration lagging after PHV, can explain the fact that normally peak bone mineral content velocity (PBMCV) is achieved 0.7 year after PHV.
References
Dawson-Hughes, B. et al. Estimates of optimal vitamin D status. Osteoporos. Int. 16, 713–716 (2005).
Lips, P. vitamin D status and nutrition in Europe and Asia. J. Steroid Biochem. Mol. Biol. 103, 620–625 (2007).
Mirwald, R.L, et al. (2002), Med Sci Sports Exerc. 34(4):
Bailey DA, et al. (1999 ), J Bone Miner Res.; 14: