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The Effects of Vitamin D Deficiency in Athletes
Michael E. Angeline, Albert O. Gee, Michael Shindle, Russell F. Warren and Scott A. Rodeo The online version of this article can be found at: can be found at:
The American Journal of Sports Medicine
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Michael E. Angeline,* MD, Albert O. Gee,* MD, Michael Shindle,y MD,Russell F. Warren,* MD, and Scott A. Rodeo,*z MDInvestigation performed at the Hospital for Special Surgery, New York, New York Vitamin D acts to maintain calcium and phosphate homeostasis within the body. It is now estimated that 1 billion people world-wide are vitamin D deficient. This problem is particularly important to athletes of all ages, as vitamin D plays a significant role inbone health, immune function, and physical performance. In the deficient state, the athlete may be at an increased risk for poten-tial problems such as stress fractures, respiratory infections, and muscle injuries. The purpose of this article is to examine vitaminD deficiency and review its relationship to the athlete.
Keywords: vitamin D deficiency; athletic performance; nutritional physiology Vitamin D deficiency is a common but underrecognized meniscectomy, were vitamin D insufficient, and one-third problem within the global population. Although there is of these patients had deficient levels.
no consensus on optimal serum levels of 25-hydroxyvitamin This high prevalence of vitamin D deficiency also extends D3 (25(OH)D3), vitamin D deficiency is defined by most to the elite athlete population. A recent study from the Hos- experts as a total 25-hydroxyvitamin D level of less than pital for Special Surgery in New York examined the vitamin 20 ng/mL. Vitamin D insufficiency is defined as a level of D levels from 89 players on a single National Football 20 to 31 ng/mL, and a level of 32 ng/mL or greater is indic- League team and found that 30% of the players were defi- ative of sufficient levels. Vitamin D intoxication is observed cient while 51% had insufficient levels (Shindle, unpub- when serum levels of 25-hydroxyvitamin D are greater than lished data, 2011). The players with muscle injuries were 150 ng/mL.10,11 The effects of vitamin D deficiency and found to have significantly lower vitamin D levels than insufficiency involve skeletal health regarding bone and were uninjured players. A similar study examined 18 elite muscle function; deficiency can also relate to chronic ill- Australian gymnasts and found that 15 had insufficient lev- nesses such as cancer, infectious diseases, autoimmune dis- els, and 6 of these athletes had deficient levels.14 The causes of vitamin D deficiency can be multifactorial It is estimated that 1 billion people, including the and can often relate to reduced skin synthesis and/or elderly, young adults, and children, are vitamin D deficient absorption of dietary vitamin D. There are several well- or insufficient.11 In a recent study performed at an urban known acquired and heritable disorders of vitamin D hospital in Boston, it was estimated that 42% of the adoles- metabolism that can also lead to deficiency.11 The main cent patients examined had vitamin D deficiency.11 An cause of vitamin D deficiency in the athletic population is additional study in Israel found that 48% of the young ath- the direct result of decreased ultraviolet B (UVB) radiation letes and dancers examined were vitamin D insufficient absorption into the skin; therefore there is a concomitant while another 25% were vitamin D deficient.7 A recent ret- decrease in the cutaneous synthesis of vitamin D. This rospective study found that 43% of preoperative orthopae- especially affects indoor athletes and athletes who live dic surgery patients were vitamin D insufficient, and of and train in northern latitudes; the lack of UVB absorption these 40% had deficient levels.4 The specialty-specific has a similar effect on dark-skinned athletes with data revealed that 52.3% of the sports service patients, which included patients undergoing anterior cruciate This article provides an overview of the physiology of vitamin D and its role in musculoskeletal health. In partic-ular, we will focus on the effects of vitamin D deficiency asit relates to the athlete in terms of bone and muscle func- tion as well as the athlete's physical performance.
Address correspondence to Scott A. Rodeo, MD, 535 East 70th Street, New York, NY 10021 (e-mail: rodeos@hss.edu).
*Hospital for Special Surgery, New York, New York.
ySummit Medical Group, Morristown, New Jersey.
The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.
The main function of vitamin D is to maintain calcium andphosphate homeostasis within the body by targeting The American Journal of Sports Medicine, Vol. 41, No. 2 organs such as the intestine, kidney, parathyroid glands, DOI: 10.1177/0363546513475787Ó 2013 The Author(s) bone, and skeletal muscle. Sources of dietary vitamin D include foods such as fatty fish, eggs, and dairy products.
increased glycogen granules.1,6 These changes appear to The dietary intake and intestinal absorption of vitamin D be reversible; several studies have shown an increase in is a minor part of the total vitamin D requirement.
type II fiber composition after supplementation with vita- The major source of vitamin D is provided through the interaction of the skin with UVB light. In the skin, 7-dehydrocholesterol is converted into previtamin D3 byUVB radiation (wavelength 290-315 nm). The previtamin D3 is slowly isomerized into vitamin D3 (cholecalciferol)and then bound by vitamin D binding protein, and trans- The role of vitamin D in skeletal bone mineralization and ferred to the liver with its metabolites.
calcium homeostasis is well known. In its active form, Once in the liver, the cholecalciferol is hydroxylated to 25- 1,25(OH)D3 is an important factor in activating intestinal hydroxyvitamin D (25(OH)D3; calcifediol), which is the major calcium absorption and raising serum calcium concentra- circulating metabolite in the body. The 25(OH)D3 is then tions. Many studies have identified a direct relationship further metabolized in the kidney by 25-hydroxyvitamin between serum vitamin D levels and bone mineral density D-1a- hydroxylase (CYP27B1) to its biologically active form, 1,25-dihydroxyvitamin D (1,25(OH)D3; calcitriol).11 This When serum vitamin D levels fall below 30 ng/mL, para- hydroxylation is controlled by calcium, phosphate, and para- thyroid hormone levels are increased, which triggers an thyroid hormone levels.11 Vitamin D production is influenced increase in osteoclastic activity in bone.11,16 Additionally, by age, season, geographic location, and skin pigmentation.5 1,25(OH)D3 directly stimulates osteoblasts to produce These are important considerations for the athlete; the train- receptor activator nuclear factor-kB (RANKL), which in ing environment may affect vitamin D production, specifi- turn enhances osteoclastogenesis and mobilization of cal- cally indoor training, winter sports, and people who live in cium from the bone.11 This can potentially affect athletes who are at an increased risk for stress fractures based onactivity or sport levels. Work by Lappe and colleagues13has shown that calcium and vitamin D supplementation significantly decreased the incidence of stress fracturesamong female military recruits.
Much of the initial work examining the relationship betweenvitamin D and muscle function was done by Birge and Had-dad.2 They found that calcifediol regulates the intracellular accumulation of phosphate within the muscle cells, and thishelps to maintain muscle function and metabolism. On A link between vitamin D and athletic performance has a molecular level, vitamin D has its effect on muscle via sev- been known for many years. Seasonal variability of athletic eral known pathways. The active metabolite of vitamin D, performance within the northern hemisphere was reported 1,25(OH)D3, binds to the muscle nuclear hormone receptor, as early as the mid 1950s, with peak performance occur- vitamin D receptor (VDR). This pathway promotes gene tran- ring during the late summer months when sun exposure scription, leading to increased cell protein synthesis and was maximal and then declining to a low point in the win- growth.5 A VDR knockout mouse model demonstrated a phe- ter.9 These findings have been supported by further stud- notype with abnormal muscle fiber development and matura- ies that have shown consistently improved athletic tion. As a result, the rodents were found to have poor motor performance in summer, with a gradual decline and a nadir and balance function, as indicated by poor swimming abil- in winter months despite consistent training throughout ity.15 Furthermore, work by Bischoff-Ferrari and colleagues3 the year. There appears to be a direct correlation between have shown that vitamin D receptor expression within mus- the seasonal variation of athletic performance and the sea- cle tissue decreases with age, which may provide a partial sonal fluctuations in serum vitamin D levels.1,12 explanation as to why athletic performance declines with Furthermore, UVB radiation exposure has long been age. All of these findings suggest that vitamin D is directly thought to improve athletic performance. Russian researchers related to muscle strength, mass, and function. Such factors as far back as 1938 found improvements in 100-m dash times are crucial to the performance of an athlete.5,6 in subjects who had UV radiation as compared with nonirra- Vitamin D also exerts its effects through various cellular diated controls.5 Another study from Germany in 1952 signaling cascades, one of which is the mitogen-activated pro- showed UV irradiation improved cardiovascular fitness on tein kinase (MAPK) signaling pathway. Once activated, this a bicycle ergometer in schoolchildren. When the control, non- pathway initiates myogenesis, cell proliferation, and differen- irradiated children were given vitamin D supplementation, tiation in muscle tissue. Studies in vitamin D-deficient rats their performance approached that of the irradiated group.5 have shown that supplementation increases protein synthe- More recent research by Ward and colleagues19 found sis and muscle mass; there was also a decrease in the rate a direct relationship between serum 25(OH)D3 levels and of exercise-induced muscle cell apoptosis.5,6 muscle power, force, velocity, and jump height as deter- Muscle biopsy specimens from adults with low vitamin mined by jump mechanography in girls aged 12 to 14 D levels have revealed atrophic changes predominantly of years. A similar study by Foo et al8 noted an increased the type II muscle fibers. There was enlargement of the hand grip strength in 301 teenage girls with normal vita- min D levels compared with those who were deficient.
damage.18 Further study is clearly necessary to identifythe role of vitamin D in athletic performance.
The treatment of an athlete should begin with an appropri- Despite the lack of level 1 evidence, the sports medicine ate assessment of the vitamin D level. The best measure is physician should be aware of the effects of vitamin D defi- the serum concentration of the inactive 25(OH)D3 level; this ciency on athletic performance and overall musculoskeletal represents the vitamin D level from dietary intake, sunlight health, including such potential problems as stress frac- exposure, and adipose stores. Recent studies have recom- tures and muscular injuries. Based on the current evi- mended a normal range between 30 and 50 ng/mL; serum dence, we recommend assessing total serum 25(OH)D3 concentrations below this value stimulate the production levels in high-risk athletes and treating those who show of parathyroid hormone. Additionally, optimal calcium absorption requires at least 30 ng/mL of vitamin D inhealthy adults.16,17 The latest United States recommended dietary allowance An online CME course associated with this article is (RDA) for vitamin D is 600 IU per day for children (over available for 1 AMA PRA Category 1 CreditTM at http:// the age of 1 year), adolescents, and adults up to 70 years of ajsm-cme.sagepub.com. In accordance with the standards age. This represents the recommended dietary intake to of the Accreditation Council for Continuing Medical Edu- achieve serum concentration of 25(OH)D3 between 30 and cation (ACCME), it is the policy of The American Ortho- 50 ng/mL. However, dietary intake may vary between indi- paedic Society for Sports Medicine that authors, editors, viduals based on diet and intestinal absorption, and serum and planners disclose to the learners all financial rela- concentrations can be significantly affected by sunlight expo- tionships during the past 12 months with any commercial sure. As the potential for vitamin D toxicity is extremely rare, interest (A 'commercial interest' is any entity producing, supplementation can be prescribed aggressively, especially in marketing, re-selling, or distributing health care goods or services consumed by, or used on, patients). Any and Vitamin D2 or D3 can be used for oral supplementation all disclosures are provided in the online journal CME (D2 being approximately 30% as effective as D3 in achiev- area which is provided to all participants before they ing desired serum levels), and both can often be found in actually take the CME activity. In accordance with over-the-counter formulations as high as 10,000-IU tab- AOSSM policy, authors, editors, and planners' participa- lets. For the deficient patient, treatment regimens include tion in this educational activity will be predicated upon 50,000-IU capsules of vitamin D2 (prescription strength) timely submission and review of AOSSM disclosure. Non- every week for 8 weeks, followed by 50,000 IU of vitamin compliance will result in an author/editor or planner to be D2 every 2 to 4 weeks for maintenance based on a repeat stricken from participating in this CME activity.
serum concentration at 8 weeks. Alternative regimensinclude daily intake of 1000 IU of vitamin D3 or 3000 IUof vitamin D2 for 8 weeks, followed by a repeat serum 25(OH)D3 level and adjustment of dosing accordingly.11 1. Bartoszewska M, Kamboj M, Patel DR. Vitamin D, muscle function, and exercise performance. Pediatr Clin North Am. 2010;57(3):849- 2. Birge SJ, Haddad JG. 25-hydroxycholecalciferol stimulation of mus- Numerous studies have identified vitamin D deficiency in cle metabolism. J Clin Invest. 1975;56(5):1100-1107.
the adolescent and adult athlete populations.1,5,6,11,16,17 3. Bischoff-Ferrari HA, Borchers M, Gudat F, Durmuller U, Stahelin HB, This is especially a problem for athletes who have limited Dick W. Vitamin D receptor expression in human muscle tissue sun exposure because of geography and limited seasonal decreases with age. J Bone Miner Res. 2004;19(2):265-269.
4. Bogunovic L, Kim AD, Beamer BS, Nguyen J, Lane JM. Hypovitamino- UVB exposure. It can also be a problem for athletes who sis D in patients scheduled to undergo orthopaedic surgery: a single- use excessive sunscreen and patients with dark skin pig- center analysis. J Bone Joint Surg Am. 2010;92(13):2300-2304.
mentation. Current evidence suggests that the treatment 5. Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Athletic per- of athletes who are vitamin D deficient may help to formance and vitamin D. Med Sci Sports Exerc. 2009;41(5):1102-1110.
improve their athletic performance. The magnitude of 6. Ceglia L. Vitamin D and its role in skeletal muscle. Curr Opin Clin Nutr this improvement has not been determined, and the spe- Metab Care. 2009;12(6):628-633.
7. Constantini NW, Arieli R, Chodick G, Dubnov-Raz G. High prevalence cific benefits of supplementation for athletes who have of vitamin D insufficiency in athletes and dancers. Clin J Sport Med.
insufficient levels have also not been determined. There is currently no level 1, randomized controlled trial that 8. Foo LH, Zhang Q, Zhu K, et al. Low vitamin D status has an adverse examines the ideal vitamin D levels for peak athletic per- influence on bone mass, bone turnover, and muscle strength in Chi- formance. Additionally, there are no data to suggest that nese adolescent girls. J Nutr. 2009;139(5):1002-1007.
vitamin D supplementation (supraphysiologic) is a source 9. Hettinger T, Muller EA. Seasonal course of trainability of musculature [in German]. Int Z Angew Physiol. 1956;16(2):90-94.
of performance enhancement for sports activities. In fact, 10. Holick MF. Sunlight and vitamin D for bone health and prevention of a recent report from the Institute of Medicine suggests autoimmune diseases, cancers, and cardiovascular disease. Am J daily intake of higher levels of vitamin D may be linked Clin Nutr. 2004;80(suppl 6):1678S-1688S.
to other health problems such as kidney and tissue 11. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266-281.
12. Koch H, Raschka C. Circannual period of physical performance ana- 16. Powers S, Nelson WB, Larson-Meyer E. Antioxidant and vitamin D lysed by means of standard cosinor analysis: a case report. Rom J supplements for athletes: sense or nonsense? J Sports Sci.
13. Lappe J, Cullen D, Haynatzki G, Recker R, Ahlf R, Thompson K. Cal- 17. Rosen CJ. Clinical practice. Vitamin D insufficiency. N Engl J Med.
cium and vitamin D supplementation decreases incidence of stress fractures in female navy recruits. J Bone Miner Res. 2008;23(5):741-749.
18. Ross AC, Taylor CL, Yaktine AL, Del Valle HB, eds. Dietary Reference 14. Lovell G. Vitamin D status of females in an elite gymnastics program.
Intakes for Calcium and Vitamin D. Washington (DC); The National Clin J Sport Med. 2008;18(2):159-161.
15. Minasyan A, Keisala T, Zou J, et al. Vestibular dysfunction in vitamin 19. Ward KA, Das G, Berry JL, et al. Vitamin D status and muscle func- D receptor mutant mice. J Steroid Biochem Mol Biol. 2009;114(3- tion in post-menarchal adolescent girls. J Clin Endocrinol Metab.
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