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Biomed Rep. 2016 Jul;5(1):113-117. Epub 2016 May 6.

Seasonal variations in vitamin D status in indoor and outdoor female athletes.

Author information

1
Department of Health and Sports Science, Juntendo University, Inzai, Chiba 270-1695, Japan; Department of Host Defense and Biochemical Research, School of Medicine, Juntendo University, Bunkyo-ku, Tokyo 113-8421, Japan.
2
Graduate School of Health and Sports Science, Juntendo University, Inzai, Chiba 270-1695, Japan.

Abstract

Vitamin D (VD) insufficiency is a concern, particularly among young females. The VD status shows seasonal variations, since it correlates with duration of sunlight exposure. VD insufficiency in indoor athletes is therefore suggested in winter. The aim of the present study was to determine seasonal variations in VD and bone status among indoor and outdoor female athletes. The prospective study was conducted in participants aged 20-22 years old. The participants comprised of 15 indoor and 15 outdoor athletes. The biochemical markers and bone parameters were measured in March, June, September and December. The serum 25-hydroxyvitamin D (25-OH-VD) concentration showed a seasonal oscillation, with a nadir in March (indoor, 19±4.0 ng/ml; outdoor, 32±2.7 ng/ml) and a peak in September (indoor, 32±6.6 ng/ml; outdoor, 39±5.7 ng/ml). The amplitude of oscillation was greater in the indoor compared to the outdoor athletes. Seasonal variations in serum calcium exhibited a similar pattern, while the parathyroid hormone showed an inverse pattern to serum 25-OH-VD. The nadir in bone mass, measured as speed of sound, occurred in June after peaking in December among the indoor and outdoor athletes. The pattern followed 3 months after the changes in 25-OH-VD. Indoor sports athletes are more susceptible to VD insufficiency compared to outdoor sports athletes. Insufficiency is most likely to arise in winter, and could affect bone mineralization observed 3 months after.

KEYWORDS:

female athletes; indoor; outdoor; seasonal change; vitamin D insufficiency

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