In this article the following topics will be covered:
- What is Vitamin D?
- How common is Vitamin D deficiency?
- Can Vitamin D be used as a performance enhancer?
- Can Vitamin D make you stronger?
- Can Vitamin D prevent injuries?
- The diseases Vitamin D deficiency is related with
- Vitamin D and the immune system
What is Vitamin D?
It's a fat solubole Vitamin D secosteriod responsible for enhancing intestinal absorption of calcium, iron, magnesium, phosphate and zinc. The body produces Vitamin D from sunlight, which is how most people get their fix. Now we've covered the basics, let's get into the nitty-gritty.
How common is Vitamin D deficiency?
Vitamin D deficiency is far more common than people think. In the world today, an estimated 1 billion people have a vitamin D deficiency which can be found in all ethnicities and age groups. [1-3] The fact is that most people don't even know they are deficient. Well I'm here to bring awareness to that. If you live in a area that doesn't get much sunlight during the winter, chances are you're going to be deficient in Vitamin D, especially if you're working the routine hours indoors when sunlight is present most i.e. the 9-5 office job. Even in summer some people can still have deficiencies if they don't get enough sunlight. A insufficiency can be classed as levels of 20-30 ng/ml 25 OH-Vitamin D. While levels below 20 and 10 ng/ml represent deficiency and severe deficiency.  The thing is that Vitamin D is very important and can have huge benefits for your health and sport performance.
Can Vitamin D be used as a performance enhancer?
Short answer is yes! As much as a deficiency can be a potenetial performance limiting factor - meaning that you might not perform as well if you are deficient. It has been long thought that Vitamin D can hold secret performance powers that can give you the edge.  Vitamin D can:
- Increase oxygen uptake 
- Prevent injuries 
- Improve muscle strength 
- Reduce muscle fatique 
- Prevent bone related injuries 
I'm sure many of you, ranging from fitness enthusiasts to weekend warriors will find some of those benefits intriguing. So I'll explain them in a bit more detail. An experiment measuring how much oxygen adults were taking up while exercising on a treadmill while taking Vitamin D compared to those who were not supplementing with it showed that their maximal aerobic exercise capacity was higher.  Muscle injury prevention and recovery are potentially affect While measuring effects of Vitamin D supplementation on upper and lower body muscle strength levels in healthy individuals, scientists found that people who were supplementing with Vitamin D surprisingly had higher strenght levels.  Vitamin D can also reduce muscle fatique as scientists found that people who were deficient had higher muscle fatique than those who had higher levels of the vitamin.  There numerous studies that indicate that Vitamin d can prevent bone fractures, stress fractures shin splints and related injuries. [10,11] As you can see, the lower your levels of Vitamin D, the higher the risk of getting a stress fracture[/caption] In fact, the benefits of Vitamin D is so useful in sports performance now that olympic athletes are becoming more interested in supplementing with it.  Scientists even found out that 5000iu's of Vitamin D helped professional UK athletes during the winter.  The American Orthopaedic Society for Sports Medicine’s (AOSSM) discovered that there were more muscle injuries in NFL football players if they were deficient in Vitamin D.  Researches found that athletes who perform indoors are more likely to be deficient than those who perform outdoors. [15-17] Maybe that's enough to make you change your cardio routine from the treadmill to the pavement.
The diseases Vitamin D is related with
I could write an huge lift of all the diseases that are related with it but it could become quite boring so instead here is an pie chart showing you: Map of 137 vitamin D related outcomes: percentage of outcomes per outcome category for all study designs[/caption] As you can see Vitamin D is related to a lot of nasty outcomes. I think the "better safe than sorry" rule applies here when it comes to Vitamin D supplementation. Although do not take too much of it as it may have some side effects according to the NHS. The NHS website reccomends 2500iu's a day. 
Vitamin D and the immune system
Vitamin D has shown to have great benefits in terms of immune function. Research suggests that children who have vitamin D-deficiency rickets are more likely to get respiratory infections, while children who are exposed to sunlight appear to have fewer respiratory infections.  Also adults who have low vitamin D levels are more likely to report having had a recent cough, cold, or upper respiratory tract infection.  A recent trial in Japanese school children tested whether taking daily vitamin D supplements would prevent seasonal flu. The results were that the school children who were taking the Vitamin D supplements 40% lower rates of flu compared to those on a placebo. 
So as you can see, Vitamin D is a very interesting supplement that holds a huge array of benefits that range from everything from sport performance to general health. If you aren't supplementing with it we have a product that will keep you healthy and happy during the winter months, PurePharma Vitamin D3. Elgan Mathias References 1. Holick MF. Vitamin D deficiency. N Engl J Med. 2007; 357:266-81. 2. Gordon CM, DePeter KC, Feldman HA, Grace E, Emans SJ. Prevalence of vitamin D deficiency among healthy adolescents. Arch Pediatr Adolesc Med. 2004; 158:531-7. 3. Lips P. Worldwide status of vitamin D nutrition. J Steroid Biochem Mol Biol. 2010; 121:297-300. 4. Holick M. Vitamin D deficiency. New Engl J Med. 2007;357:266–81. [PubMed] 5. Cannell J, Hollis B, Sorenson M, et al. Athletic performance and vitamin D. Med Sci Sports Exerc. 2009;41:1102–10. [PubMed] 6. Am J Cardiol. 2011 Apr 15;107(8):1246-9. Epub 2011 Feb 23. 7. Franklin D. Shuler et al. Sports Health. Nov 2012; 4(6): 496–501. 8. Peter B. Tomlinson, Corey Joseph, Manuela Angioi. Journal of Science and Medicine in Sport, Available online 11 August 2014 9. Akash Sinha, Kieren G. Hollingsworth, et al. The Journal of Clinical Endocrinology & Metabolism March 1, 2013 vol. 98 no. 3 E509-E513 10. Tenforde AS, Sayres LC, Sainani KL, Fredericson M. PM R. 2010 Oct;2(10):945-9. 11. Bischoff-Ferrari HA. Endocrinol Metab Clin North Am. 2010 Jun;39(2):347-53, table of contents. 12. John Cannell, MD. Dr. Cannell will be speaking at the American College of Sports Medicine in Seattle May 27, 2009. 13. Close GL, Russell J, Cobley JN et al. J Sports Sci. 2012 Oct 22. 14. American Orthopaedic Society for Sports Medicine. San Diego, CA (PRWEB) July 09, 2011 15. Tervo T, Nordström P, Nordström A. Bone. 2010 Sep;47(3):666-72. Epub 2010 Jun 25. 16. Ducher, Gaele 1; Kukuljan, S. 2; Hill, B. 2; Garnham, A.P. 2; Nowson, C.A. 2; Kimlin, M.G. 3; Cook, J. 2 Journal of Dance Medicine & Science, Volume 15, Number 3, September 2011 , pp. 99-107(9) 17. Diego Villacis, MD†, Anthony Yi et al. Sports Health: A Multidisciplinary Approach February 25, 2014 1941738114524517 18. NHS website on Vitamin D - http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Vitamin-D.aspx 19. Cannell JJ, Vieth R, Umhau JC, et al. Epidemic influenza and vitamin D. Epidemiol Infect. 2006; 134:1129-40. 20. Ginde AA, Mansbach JM, Camargo CA, Jr. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009; 169:384-90. 21. Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 91:1255-60. Epub 2010 Mar 10.