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Vitamin D and the Athlete

It is a bit of a misnomer to call Vitamin D a vitamin at all. “Vitamin” implies that adequate amounts of it can be obtained naturally through the diet. Vitamin D is not actually a vitamin, but is a pre-prohormone [15]. As a species, we evolved a photosynthetic mechanism which produces large amounts of vitamin D3 in the skin, thus making it the “sunshine vitamin.” By and large, vitamin D does not occur naturally in our food supply, but the production of Vitamin D [cholecalciferol] in the skin is astonishingly rapid: a light-skinned person sunbathing for 30 minutes midday (enough to produce slight redness) in the summer releases as much Vitamin D as individuals ingesting 10,000 to 25,000 IU of vitamin D2 - 17-41 times the RDA [12].

If we evolved to produce this hormone via sun exposure how do we obtain adequate amounts in the absence of sun exposure? At latitudes above 40o [e.g. New York City] there is insufficient sunlight intensity to produce adequate vitamin in the winter months, no matter how much of the body is exposed [17]. Anything that blocks UVB light will block vitamin D production, including darker skin pigmentation; sunscreens with a sun protection of 15 reduce the skin’s ability to manufacture Vitamin D by 99% [20].

Furthermore, body fat absorbs vitamin D putting some populations at especially high risk, such as obese African-American individuals . In fact, Yanoff LB [32] found that nearly 60% of obese African Americans were deficient. Africans living near the equator, however, do not exhibit a high prevalence of vitamin D deficiency [30], underscoring the role of sun exposure.



Most cells in the human body have Vitamin D receptors and hundreds, if not thousands, of genes may be affected by vitamin D. These genes enhance immune function, insulin function and glucose handling, and maximize bone mineralization, among many other functions [12]. The emerging data regarding vitamin D’s role in health prompted a recent reevaluation of vitamin D guidelines by the Institute of Medicine [IOM]. They tripled the amount of recommended dietary vitamin D from 200 to 600 IU daily, with an upper tolerable limit of 4000 IU daily [26]. It is generally accepted that the toxicity threshold is between 10,000 – 40,000 IU daily, or serum values consistently >500 nmol/L [16]

Many experts agree that − in the absence of adequate sun exposure – most children and adults require 800- 1000 IU/day [31] from dietary sources. We know that a minimum blood level of 34 ng/ml is needed to optimize calcium absorption, thus affecting bone health [11] but a level of 52 ng/ml is required to reduce breast cancer risk [8]. People working outside in the summer, as we evolved to do, have blood levels of about 50 ng/ml [1]. Based on these and similar findings many experts recommend serum Vitamin D levels to be at the high end of the natural range, 40-70 ng/ml [2].

It has been suggested that the de-pigmentation of skin in far northern latitudes was a necessary evolutionary adaptation which allowed adequate Vitamin D synthesis [6]. While much attention has been focused on the reduction of skin cancers by reducing sun exposure, little consideration has been given to the positive effects of UV radiation [25]. Since 90% of our Vitamin D requirements are typically met with sun exposure, it is unsurprising that sun avoidance results in Vitamin D deficiency [19]. This data has led dermatologists to recommend “sensible” sun exposure, in addition to Vitamin D supplementation [25]. Excessive UV exposure should be avoided, particularly sun burns in childhood, and avoidance of excessive sun exposure during the summer months [25]. It should be noted that even in summer months, the sun’s rays are oblique during the early morning and late afternoon, and are therefore almost entirely absorbed by the ozone layer. Thus, skin exposure during those hours results in very little or no Vitamin D production [13].

How much sun exposure is needed to maintain adequate serum Vitamin D levels depends upon a person’s skin pigmentation, the latitude, weather and time of year. Holick states that a Caucasian at a latitude similar to Boston, MA , in June, will produce adequate amounts of Vitamin D by exposing their skin to mid-day sun for 5 – 15 minutes, a few times per week. After that amount of time, application of sunscreen with a protection factor of 15 or greater is recommended to uncovered skin [13].


In Athletes

Athletes, even those who train outside, are also vulnerable to vitamin D insufficiency. In a study of 41 athletes training at high altitude - which ought to increase their exposure to UVB - 25% had sub-optimal Vitamin D status in the summer [<40 ng/ml] but 60% had insufficient vitamin D levels in the winter [10]. American professional football players were also found to have widespread Vitamin D insufficiency in the spring. Eighty percent had Vitamin D levels below 32 ng/ml [28]. Unsurprisingly, Vitamin D status of athletes involved in indoor sports such as dancers is especially poor. Even in sun-drenched Israel, Constantini et al. reported that 73% of young athletes were found to have vitamin D insufficiency [serum levels < 30 ng/ml]: 94% of dancers, and 67% of martial artists were Vitamin D insufficient, vs. 48% of those engaged in outdoor sports [3].

Low Vitamin D levels are associated with many disease states, such as osteoporosis, cancers, cardio-vascular disease [4], type 2 diabetes [7], auto-immune diseases such as multiple sclerosis, and infections [14,21, 24]. Vitamin D supplementation of 1200 IUM daily has been shown to reduce the risk of influenza by 42%, and adults with Vitamin D levels > 38 ng/ml had two-fold less risk of acute respiratory infections, and less sick days taken, compared to those with insufficient [<38 ng/ml] vitamin D levels [21].

Several epidemiologic reports suggest that heavily training athletes are at increased risk of illness [5,29] : athletes in heavy training are especially prone to upper respiratory infections [9]. Impaired immune function has been noted for a few days following a bout of heavy exertion [22]. Vitamin D monitoring and supplementation with Vitamin D3, therefore, should be considered by all athletes and especially by those such as marathoners, who are often in a state of over-training and thus at risk of infection.

1. Barger-Lux MJ, Heaney RP. Effects of above average summer sun exposure on serum

    25-hydroxyvitamin D and calcium absorption. J Clin Endocrinol Metab. 2002


2. Cannell JJ, Hollis BW. Use of Vitamin D in Clincial Practice. Alt Med Review. 13[1]: 2008,


3. Constantini NW, Arieli R, Chodick G, Dubnov-Raz G. High prevalence of vitamin D

    insufficiency in athletes and dancers. Clin J Sport Med. 2010 Sep;20(5):368-71.

4. Dong Y, Stallmann-Jorgensen IS, Pollock NK, Harris RA, Keeton D, Huang Y, Li K, Bassali R,

    Guo DH, Thomas J, Pierce GL, White J, Holick MF, Zhu H. 16-week randomized clinical trial

    of 2000 international units daily vitamin D3 supplementation in black youth: 25

    hydroxyvitamin D, adiposity, and arterial stiffness. J Clin Endocrinol Metab. 2010


5. Fitzgerald L. Overtraining increases the susceptibility to infection. Int J Sports Med. 1991

    Jun;12 Suppl 1:S5-8.

6. Freemon FR, Loomis WF. Vitamin D and skin pigments. Science. 1967 Nov 3;158(801)

    :579-80. N

7. Ganji V, Zhang X, Shaikh N, Tangpricha V. Serum 25-hydroxyvitamin D concentrations are

    associated with prevalence of metabolic syndrome and various cardiometabolic risk

    factors in US children and adolescents based on assay-adjusted serum 25-hydroxyvitamin

    D data from NHANES 2001-2006. Am J Clin Nutr. 2011 Jul;94(1):225-33.

8. Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci EL, Lipkin M, Newmark H, Holick

    MF, Garland FC. Vitamin D and prevention of breast cancer: pooled analysis.J Steroid

    Biochem Mol Biol. 2007 Mar;103(3-5):708-11.

9. Gleeson M. J Immune function in sport and exercise. Appl Physiol. 2007 Aug;103(2):


10. Halliday TM, Peterson NJ, Thomas JJ, Kleppinger K, Hollis BW, Larson-Meyer DE. Vitamin

      D status relative to diet, lifestyle, injury, and illness in college athletes. Med Sci Sports

      Exerc. 2011 Feb;43(2):335-43.

11. Heaney RP, Dowell MS, Hale CA, Bendich A. Calcium absorption varies within the

      reference range for serum 25-hydroxyvitamin D. J Am Coll Nutr. 2003 Apr;22(2):142-6.

12. Holick MF, Chen TC, Lu Z, Sauter E. Vitamin D and skin physiology: a D-lightful story. J

      Bone Miner Res. 2007 Dec;22 Suppl 2:V28-33.

13. Holick MF. How Much Sunlight Do We Need? In Sunlight, UV Radiation, Vitamin D and Skin

      Cancer. Reichrath J. ed. Springer Science Business Media LLC and Landes Bioscience.


14. Holick MF. The IOM D-lemma. Public Health Nutr. 2011 May;14(5):939-41.

15. Hollis BW. Circulating 25-Hydroxyviamin D Levels Indicative of Vitamin D Sufficiency:

      Implications for Establishing a New Effective Dietary Intake Recommendation for Vitamin

      D. J Nutr. 2005 Feb;135(2):317-22. Review.

16. Jones G. Pharmacokinetics of vitamin D toxicity. Am J Clin Nutr. 2008 Aug;88(2):

      582S-586S. Review.

17. Kimlin MG. Geographic location and vitamin D synthesis. Mol Aspects Med. 2008

      Dec;29(6):453-61.. Review.

18. Lee JH, O'Keefe JH, Bell D, Hensrud DD, Holick MF. Vitamin D deficiency an important,

      common, and easily treatable cardiovascular risk factor? J Am Coll Cardiol. 2008 Dec


19. McGrathJJ, Kimlin MG, Saha S, Eyels DW, Parisi AV. Vitamin D insuffieciency in south-east

      Queensland. Med J Aust 2001; 86:1212-21.

20. Matsuoka LY, Ide L, Wortsman J, MacLaughlin JA, Holick MF. Sunscreens suppress

      cutaneous vitamin D3 synthesis. J Clin Endocrinol Metab. 1987 Jun;64(6):1165-8.

21. Melamed ML, Muntner P, Michos ED, Uribarri J, Weber C, Sharma J, Raggi P. Serum

      25-hydroxyvitamin D levels and the prevalence of peripheral arterial disease: results

      from NHANES 2001 to 2004. Arterioscler Thromb Vasc Biol. 2008 Jun;28(6):1179-85.

22. Müns G. Effect of long-distance running on polymorphonuclear neutrophil phagocytic

      function of the upper airways. Int J Sports Med. 1994 Feb;15(2):96-9.

23. Nieman DC. Risk of upper respiratory tract infection in athletes: an epidemiologic and

      immunologic perspective. J Athl Train. 1997 Oct;32(4):344-9.

24. Peterlik M, Cross HS.Dysfunction of the vitamin D endocrine system as common cause

      for multiple malignant and other chronic diseases. Anticancer Res. 2006 Jul-Aug;

      26(4A):2581-8. Review.

25. Reichrath J. The challenge resulting from positive and negative effects of sunlight: how

      much solar UV exposure is appropriate to balance between risks of vitamin D deficiency

      and skin cancer? Prog Biophys Mol Biol. 2006 Sep;92(1):9-16.

26. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK et al. The 2011

      Report on Dietary Reference Intakes for vitamin D and calcium from the Institute of

      Medicine: What clinicians need to know. J Clin Endocrinol Metab 2011;96(1):53-8.

27. Sabetta JR, DePetrillo P, Cipriani RJ, Smardin J, Burns LA, Landry ML. Serum 25-

      hydroxyvitamin d and the incidence of acute viral respiratory tract infections in healthy

      adults. PLoS One. 2010 Jun 14;5(6):e11088.

28. Shindle MK, Voos JE, Gulotta L, Weiss L, Rodeo SA, Kelly B, Lane J, Barnes R, Warren R.

      Vitamin D Status in a Professional American Football Team. AOSSM 2011 Abstract 46-


29. Spence L, Brown WJ, Pyne DB, Nissen MD, Sloots TP, McCormack JG, Locke AS, Fricker

      PA. Incidence, etiology, and symptomatology of upper respiratory illness in elite athletes.

      Med Sci Sports Exerc. 2007 Apr;39(4):577-86.

30. Thacher TD, Fischer PR, Strand MA, Pettifor JM.Nutritional rickets around the world:   

      causes and future directions. Ann Trop Paediatr. 2006 Mar;26(1):1-16. Review.

31. Vieth R, Bischoff-Ferrari H, Boucher BJ, Dawson-Hughes B, Garland CF, Heaney RP,

      Holick MF, Hollis BW, Lamberg-Allardt C, McGrath JJ, Norman AW, Scragg R, Whiting SJ,

      Willett WC, Zittermann A. The urgent need to recommend an intake of vitamin D that is

      effective. Am J Clin Nutr. 2007 Mar;85(3):649-50.

32. Yanoff LB, Parikh SJ, Spitalnik A, Denkinger B, Sebring NG, Slaughter P, McHugh T,

      Remaley AT, Yanovski JA. The prevalence of hypovitaminosis D and secondary

      hyperparathyroidism in obese Black Americans. Clin Endocrinol (Oxf). 2006