Elite athletes are revered for their ability to repetitively perform feats that push the human body to its physical and physiological limits. In the eyes of many they are superhuman. If we consider fictional superheroes many demonstrate the same abilities, albeit exaggerated, that we admire in athletes such as strength, speed and agility. Sports scientists are constantly looking for ways to achieve and maintain peak performance with the latest growing interest being in supplementation of vitamin D.
Vitamin D is a naturally synthesised hormone historically associated with calcium homeostasis, muscle and bone health. Apart from bone disease and muscle weakness, deficiency in vitamin D is associated with an increased risk of developing all cancers[i].
The effect of circulating vitamin D [25(OH)D3] on muscle activity has been demonstrated in several studies. Most recently a positive relationship was shown between 25(OH)D3 levels and jump height, velocity, power as well as fitness levels in adolescent girls [ii]. In a separate study Ardestani et al showed with each standard deviation increase in 25(OH)D3 VO2 max increased by 2.6ml/kg/min (p=0.0001) for individuals with low levels of physical activity and 1.6ml/kg/min (p<0.0004) for moderately active people.[iii]
Athletes are susceptible to infections either due to the immuno-suppressed state that accompanies their level of training or the close proximity surrounding team sports. Protective antimicrobial proteins lining epithelial surfaces are directly regulated by Vitamin D and deficiency is associated with increase incidence of infections[iv]. In a large epidemiological study Juzienne and Moan suggest that seasonal nadir in vitamin D levels may be a controlling factor in influenza epidemics.
Rapid recovery following injury is vital for any athlete and 25(OH)D3 levels, through its direct regulation of insulin-like growth factor (IGF-1), has been shown to increase the healing speed of skeletal muscles[v].
The primary source of Vitamin D is ultraviolet-B rays from sunlight with dietary sources accounting for very little. For anyone living above the 43-degree parallel north sun exposure is only effective at generating vitamin D between the months of April and September. What this means is that irrespective of outdoor training and games players of seasonal sports such as Rugby Union, Football, or NFL, whose season falls outside of these months, may require supplementation. Ultraviolet radiation treatment is not a new concept: in 1938 Russian researchers reported a 7.4% improvement in 100m dash times of collegiate sprinters following UV treatment compared to 1.7% improvement of the control group’s times[vi].
Vitamin D deficiency is a public health issue that goes beyond the boundaries of sports and exercise medicine. By correcting the deficiency Sports Physicians look to give their athletes an advantage over others that would otherwise be affected by seasonal variation. Should health-governing bodies look to address the problem through public health initiatives, such as increased fortification of food products, perhaps this advantage would be negated. Till then I will continue to take my daily supplement and hope to be stronger, faster and aspire to leap large puddles in a single bound.
MBBS, MRCS (Eng), Dip SEM (GB & I), BSc (Hons)
Registrar in Sports and Exercise Medicine
Dr James Thing coordinates the UK SEM Registrars Guest Blogs. Dr Thing is a Sport and Exercise Medicine Trainee and General Practitioner in London, England
[i] Lappe JM et al. Vitamin D and Calcium Supplementation reduces cancer risk: results of a randomized trail. Am J Clin Nutr. 2007 Jun;85(6): 1586-91.
[ii] Stockton KA et al. Osteoporos Int 2010 Oct 6
[iii] Alderstani et al. Relation of Vitamin D level to maximal oxygen uptake in adults. Am J Car (2011) Apr 15;107(8):1246-9.
[iv] Sabetta JR, DePetrillo P, Cipriani RJ, Smardin J, Burns LA et al (2010) Serum 25-Hydroxyvitamin D and the Incidence of Acute Viral Respiratory Tract Infections in Healthy Adults. PLoS ONE 5(6): e11088. Doi:10.1371/journal.pone.0011088.
[v] Bogazzi et al 2010
[vi] Journal of Physiologiy of the USSR 1938; 25:695-701 (In Russian)
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