Vitamin D Status of Elite Athletes in Singapore and Its Associations With Muscle Function and Bone Health

Abstract

Purpose

The primary aim of this study is to determine the prevalence of vitamin D deficiency and insufficiency among Asian athletes participating in indoor and outdoor sports in equatorial Singapore. Secondary aims are to examine the relationship between vitamin D status and skeletal muscle strength and performance, and bone density.

Methods

Serum 25(OH)D concentrations were determined in 95 indoor and outdoor athletes across various sports. Skeletal muscle strength and performance were assessed using the isometric mid-thigh pull (IMTP), drop jump test and 30 m sprint test. Bone Mineral Density (BMD) was measured using Dual-energy X-ray Absorptiometry (DXA).

Results

Mean serum 25(OH)D concentrations were 28.6 ± 8.9 ng/mL among indoor, and 39.2 ± 13.2 ng/mL among outdoor sport athletes respectively (P < 0.05). More indoor sport athletes (62%) had insufficient vitamin D compared to outdoor sport athletes (30%) (P < 0.05). Outdoor sport athletes exhibited significantly greater peak force generation than indoor sport athletes (2079 ± 470 N vs. 1869 ± 546 N, P = 0.027). Other markers of muscle function were not significantly different between groups. Indoor and outdoor sport athletes did not have significantly different BMDs although none of the athletes studied presented with poor BMD. Athletes who were deficient in vitamin D had significantly lower BMD compared to athletes with sufficient vitamin D (P = 0.01).

Conclusion

Forty-seven percent of Singaporean athletes studied had suboptimal vitamin D status. Routine monitoring of vitamin D levels among indoor sport athletes should be in place to ensure optimal health and performance.