VITAMIN D AND ATHLETES PERFORMANCE

Vitamin D and Athletes Performance

Vitamin D and Athletes Performance

Introduction

The previous decade has been marked with the discovery of many new physiological functions of vitamin D as well as the documentation of epidemic vitamin D deficiency and insufficiency among adults and children worldwide. While less is known about vitamin D status in athletes, emerging evidence is suggesting that vitamin D plays an important role in an athlete's health, training and performance. Specifically, it is now recognized that vitamin D is imperative for bone health, immune function, and inflammatory modulation and it may even be necessary for optimal muscle function and performance. In addition, vitamin D deficiency is linked to an increased risk for chronic and autoimmune disorders - including hypertension, cardiovascular disease, rheumatoid arthritis, osteoarthritis, inflammatory bowel disease, depression, and certain types of cancer - many of which occur even in the trained athlete. This paper will provide an update on the importance of this vitamin in athletes and how it can improve the performance of employees.

Vitamin D Sources and Synthesis

For meeting the physiological sufficiency of a body of athlete, Vitamin D has proved its effectiveness in doing so. Previtamin D3 then undergoes thermal isomerization to vitamin D3 (cholecalciferol) over a period of 2 to 3 d. Vitamin D3 then migrates into the dermal capillary bed and into circulation with the assistance of vitamin D binding protein (VDBP) and is subsequently hydroxylated in the liver by enzymes of the cytochrome P-450 system to 25(OH)D (Edelman, Gurnick, Kaminsky, Meyers, Udell & Lattorulo 2011, pp. 32-34). Further hydroxylation in kidney tubules to the hormonally-active form, 1,25 (OH)2D, is driven by parathyroid hormone (PTH) when serum calcium and phosphate concentrations fall below the physiological range. In addition, many extra-renal cells (and tissues), including macrophages, brain, colon, breast, and others, have the enzymatic machinery (1-[alpha]-hydroxylase) to produce 1,25(OH)2D locally. Cutaneous production of vitamin D, however, is variable and dependent on environmental and individual factors, including time of day, season, cloud cover, smog, latitude, skin pigmentation, age, and sunscreen use (Asp 2009, p. 36). In addition, vitamin D cannot be synthesized in winter months at latitudes greater than 35° to 37° degrees because the zenith angle of the sun prevents sufficient UVB photons from reaching the earth's surface (Nielsen, Skjønsberg & Lyberg 2008, pp. 526-533).

There are various sources from which Vitamin D can be obtained like margarine, cereals, sun-dried mushrooms, egg yolks, fortified milk and fatty fish. Vitamin D for diet includes both D2 (ergocalciferol) and D3 (animal form, cholecalciferol) that is gained from UVB exposure of precursor fungi and yeast ergosterols. Both D3 and D2 are absorbed into intestinal mucosal cells from micelles in association with lipid (and the aid of bile salts) where they are incorporated into chylomicrons and enter circulation via the lymphatic system. Both are readily absorbed (~50% bioavailable) except in individuals with malabsorption syndromes. Following absorption, dietetic vitamin D is carried to the liver & metabolized similarly to endogenous vitamin D3 (Phillips 2005, pp. 132-167).

Vitamin D Intake and Status of Athletes

Although numerous studies have documented ...