Vitamin D status among female handball and football elite athletes in Norway at latitude 60°N Kristin Lundanes Jonvik Master thesis in Clinical Nutrition

Department of Nutrition School of Medicine

UNIVERSITY OF OSLO April 2011

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Acknowledgement The master project was initiated by the Department of Sports Nutrition at the Norwegian Olympic Sports Center, Olympiatoppen in cooperation with the Department of Nutrition, University of Oslo. The study can be considered a pilot study on the vitamin D status (implying serum 25(OH)D levels being insufficient or sufficient) of female elite athletes in Norway, and is not primarily a dietary survey. The study was planned in spring 2010 and was conducted from autumn 2010 to spring 2011. To all the athletes who participated in the study, thank you so much for devoting your time and being so dedicated with the records and questionnaires. I would like to thank my supervisors, Christine Helle, Cand. scient in nutrition and head of the Nutrition Dept. at Olympiatoppen, and Prof. Lene Frost Andersen, Dept. of Nutrition at the University of Oslo, for valuable advice and guidance during the project period. To Christine and Olympiatoppen, I am grateful for the opportunity to be a part of your work environment and increase my knowledge in the field of sports nutrition. To Lene, thank you for sharing your great knowledge and experiences in nutritional methodology and research with me. I would also like to thank University lecturer Elin Bjørge Løken, Dept. of Nutrition at the University of Oslo, for the help concerning KBS and food data coding, and Prof. Marit Veierød, Dept. of Biostatistics/Dept. of Nutrition at the University of Oslo, for the help with statistical matters. Last, but definitely not least, I want give the deepest thanks to my mom for all the help with language, questions about metabolism and lay out of the thesis, and to my family and Kevin for all the patience and help when I was writing in the Netherlands. I could not have done it without you.

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Abstract Background: An unexpectedly high prevalence of vitamin D insufficiency has recently been reported worldwide, but little is known about the level in athletes. Vitamin D has known skeletal functions with high impact on bone health. The vitamin also has muscle and immune functions and low levels have been linked to decreased muscle strength in elderly and chronic diseases. If these functions can affect an athlete‟s health status and performance are yet to be established. Purpose: To measure serum vitamin D concentrations, as 25-hydroxyvitamin D (25(OH)D), in female elite athletes in handball and football in the south eastern parts of Norway, at latitude 60ºN. We also wanted to address possible exposure factors of the 25(OH)D level in this group, by investigating dietary intake, supplement use and sun behavior. Methods: Serum 25(OH)D concentrations were measured in 48 female elite athletes (26 handball/22 football) in October/November 2010. Insufficiency was defined as serum 25(OH)D concentration