Vitamin D and Exercise Performance
Vitamin D is a unique vitamin with hormone actions. Synthesized cutaneously from UVB light or derived from the diet, vitamin D is essential for maintaining bone health and calcium homeostasis. Vitamin D is transported in the circulation bound to vitamin D
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Vitamin D and Exercise Performance Joi J. Thomas, MS and D. Enette Larson-Meyer, PHD CONTENTS Introduction Physiology of Vitamin D Vitamin D, Calcium Regulation, and Bone Health Additional Roles of Vitamin D Vitamin D Synthesis and Metabolism Cutaneous Synthesis Dietary Intake of Vitamin D Vitamin D-Binding Protein Vitamin D Receptor Methods of Measurement and Optimal Concentrations Vitamin D and Immunity Hypovitaminosis D Vitamin D Receptor and Skeletal Muscle Vitamin D and Sarcopenia Vitamin D and Exercise Performance Summary References
INTRODUCTION In 1645, Daniel Whistler first described the physical manifestation that came to be known as rickets in the equivalent of a PhD dissertation. Francis Glisson, an English physician, reported similar observations 5 years later in one of the first pediatric texts published in London (1). In this text, A Treatise of the Rickets: Being a Disease Common to Children, he gave a complete description of rickets and also differentiated between rickets and infantile scurvy. He did not, however, note the importance of diet or the origin of the disease in his clinical description. As early as 1822, however, Sniadecki From: Endocrinology of Physical Activity and Sport: Second Edition Edited by: N. Constantini and A.C. Hackney, DOI 10.1007/978-1-62703-314-5_18 © Springer Science+Business Media New York 2013 339
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published observations that children in Warsaw, Poland, had a higher incidence of rickets while children living in rural areas outside of the city had a much lower prevalence of the disease (2). He hypothesized that the development of rickets was due to a lack of adequate sun exposure. Rickets was also observed with a high prevalence in the UK and India in children of the very rich who were kept from the sunlight. It was also seen in children living in highly industrialized areas like London and New York City. Close to the beginning of the twentieth century there were three major discoveries regarding vitamin D. The first, from both UK and US researchers, was that vitamin D was a dietary compound (2). McCollum and Davis conducted extensive investigations with development and growth in rats fed a variety of diets (3). They noted that diets consisting simply of purified proteins, carbohydrates, and fats were insufficient to promote growth in young rats. These studies led the way for the work of Sir Edward Mellanby. Mellanby induced rickets in dogs through their diet to show that McCollum and Davis were working with a compound other than vitamin A, as previously thought (4). Mellanby noted that some of the fastest growing dogs in his experiments were fed diets low in vitamin A. He was also one of the first investigators to note the antirachitic effects of cod liver oil which is rich in vitamin A. McCollum was later able to eliminate vitamin A and correctly identify a previously unidentified compound, referred to as “calcium-depositing vitamin” in earlier journal articles, which he named vitamin D (5). McCollum focused on the antirachitic propertie
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