The Effect of Abnormal Vitamin D Levels in Athletes


Jakub Sikora-Klak, MD; Steven J Narvy, MD; Justin Yang, MD;
Eric Makhni, MD; F Daniel Kharrazi, MD; Nima Mehran, MD

Perm J 2018;22:17-216 [Full Citation]
E-pub: 07/05/2018


Vitamin D is a lipophilic prohormone integral to musculoskeletal, autoimmune, oncologic, cardiovascular, and mental health. Of particular importance to the orthopedic surgeon is the role of vitamin D in the regulation of bone mass, muscle strength, and physical performance. Although vitamin D-related skeletal pathologies are rare in industrialized nations, emerging research in the field has shown that most American adults have inadequate levels of vitamin D. Even among athletes, there is a high prevalence of vitamin D deficiency, which may place competitors at risk of stress fractures, illness, and delayed muscle recovery. Adequately identifying vitamin D-deficient individuals in need of supplementation is important to help optimize performance and prevent future injury. The goal of this review is to describe the epidemiology of vitamin D deficiency and its effects on athletic performance and musculoskeletal health. Future double-blinded studies of vitamin D supplementation in athletes are needed. We recommend treating athletes who have insufficient or deficient vitamin D levels.


Vitamin D deficiency is common, even among athletes. The goal of this review is to describe the epidemiology of vitamin D deficiency and its effects on athletic performance and musculoskeletal health.


Vitamin D deficiency is a common finding among Americans: 36% to 57% of adults are deficient.1 Causes include low ultraviolet (UV) exposure, lack of fortified nutrition, skin pigmentation, and malabsorption disorders.1 Public health initiatives, including food fortification and education among pediatric and adolescent populations, have significantly decreased the prevalence of such developmental problems as rickets and growth retardation.1-3 However, symptoms of vitamin D deficiency in adults such as osteoporosis, osteomalacia, myalgias, and immune deficiencies are often ignored. Patients with vitamin D deficiency presenting as musculoskeletal pain are often misdiagnosed with fibromyalgia, chronic fatigue syndrome, and myositis, among others.4

Vitamin D deficiency is defined as having a level below 20 ng/mL, and vitamin D insufficiency is defined as a vitamin D level under 30 ng/mL. Worldwide, 1 billion people are estimated to fall into these categories.1 Both vitamin D insufficiency and deficiency are increasing in prevalence.3

Professional athletes are similarly affected. In professional basketball, 32% of athletes are found to be deficient and 47% are found to be insufficient with respect to vitamin D levels.5 Among players in the National Football League, 26% were found to have deficient vitamin D levels, and 42% to 80% of the athletes had levels defined as insufficient.6,7 Only 36% of Liverpool’s professional soccer academy players were found to be either deficient or insufficient.8 Among professional hockey players, Mehran et al9 found vitamin D deficiencies in 0% and insufficiency in only 13%. The authors attributed these low numbers to race, given that 96.2% of the hockey players were white. Deficiencies or insufficiencies have been found in most dancers, taekwondo fighters, jockeys, elite wheelchair athletes, handball players, track and field athletes, weightlifters, swimmers, and volleyball players.10-15

Multiple studies have shown that athletes with darker skin are at higher risk of vitamin D abnormalities developing.6,16,17 One study, for example, demonstrated that black race (odds ratio [OR] = 19.1; p < 0.0001) and dark skin tones (OR = 15.2; p < 0.0001) were the greatest predictors of abnormal vitamin D levels.16 One study demonstrated that athletes with high concentrations of melanin in their skin need up to 10 times longer UVB exposure times to generate the same vitamin D stores as fair-skinned athletes do.18


Vitamin D controls the body’s phosphate and calcium stores. The major source of vitamin D is from sunlight, but other sources include fish, mushrooms, eggs, fortified foods, and supplements. With the help of solar UVB radiation, 7-dehydrocholesterol is converted to previtamin D3. Previtamin D goes into the circulation and is hydrolyzed by the liver to create 25-hydroxyvitamin D (25[OH]D), the major form that clinicians use to measure vitamin D status. The kidneys then create the biologically active form of 1,25-dihydroxyvitamin D (1,25[OH]2D).

The biological feedback loop is a complex interplay between bone, intestines, and the parathyroid glands. Vitamin D receptors are found throughout the body and affect the skeletal muscle, bones, immune system, gastrointestinal tract, kidneys, parathyroid glands, cardiovascular system, and some cancers.19,20 More than 1000 genes expressed are often dictated by vitamin D, including those of angiogenesis, cellular proliferation, differentiation, and apoptosis.4,21,22 Vitamin D receptors, when activated, promote cell protein synthesis and have associations with muscle mass and function.22-24 Levels of less than 30 ng/mL decrease gastrointestinal calcium absorption and increase parathyroid hormone activity, resulting in the dissolution of bone matrix by osteoclasts to maintain serum calcium levels within physiologic range.25-27 Deficiencies prevent the maximum deposition of calcium in the skeleton.28


Vitamin D deficiency leads to structural pathology of muscle tissue. Muscle specimens of vitamin D-deficient individuals exhibit enlarged interfibrillar spaces and infiltration of fat, fibrosis, and glycogen.29 A South Korean study showed that higher serum vitamin D was associated with less fatty degeneration in rotator cuff muscles and had a positive correlation to muscle torque.30 Type 2 muscle fibers, also known as fast twitch fibers, have a direct association with vitamin D. Biopsies of 12 vitamin D-deficient patients, before and after vitamin D treatment, found atrophy of type 2 muscle fibers before treatment and significant improvement after treatment.31 Additionally, Heath and Elovic32 found that 93% of patients presenting to a community clinic with nonspecific musculoskeletal pain were found to have vitamin D deficiency. Furthermore, Ahmed et al33 reversed myositis-myalgia in statin-treated patients who had vitamin D deficiency using vitamin D supplementation. Athletes in the National Football League Combine with a history of lower extremity muscle strain and core muscle injury had a higher prevalence of inadequate vitamin D.34


Vitamin D can reduce inflammation by its inhibitory effect on proinflammatory cytokines such as Interleukin-6, which converts monocytes to macrophages, which in turn produce more inflammatory cytokines. Interleukin-6 can be increased very early in a single workout35 and has been hypothesized to be related to the occurrence of muscle damage in a workout.36 Vitamin D has also been shown to reduce the production of other proinflammatory cytokines such as interferon-a, Interleukin-2, and tumor necrosis factor-6.37-40


UV irradiation of athletes to improve performance has been an area of intrigue far before its relationship with vitamin D was established. Studies dating to the 1930s and 1940s have noted improvement in running speed and bike ergometer readings among study participants.41-43 More recent work has shown that UV radiation improved forearm strength, work performance on bike ergometers, and strength and speed of college women.44-47

In 1952, Ronge48 was the first to hypothesize that the production of vitamin D explained the success of UV radiation in physical performance. He supplemented nonirradiated German schoolchildren with a single dose of vitamin D and greatly improved their cardiovascular performance, equivalent to a group of radiation-treated children. The UVB range was the most effective wavelength in consistently reducing resting pulse, lowering the basal metabolic rate, and increasing work performance on a bike ergometer.49


Vitamin D supplementation has been shown in multiple studies to affect muscle performance, kinetics, and efficiency.50,51 Close et al8 demonstrated that professional soccer players increased their vertical jump and 10-m sprints (p = 0.008) when taking vitamin D supplements. Additionally, ballet dancers who supplemented with vitamin D showed they had a 7% higher vertical jump (p < 0.01) and an 18% increase in isometric strength (p < 0.01).52 A British study using novel jump mechanography found a positive relationship between serum vitamin D levels and jump height, velocity, and power (p = 0.005, 0.002, and 0.003, respectively) in postmenarchal adolescent girls.51 In a randomized, double-blind trial, judo athletes supplemented with vitamin D3 demonstrated a 13% increase in muscle strength compared with a placebo group (p = 0.01).53


Athletes with subtherapeutic vitamin D levels may be at higher risk of missing practices and games as a result of stress fractures, muscle injuries, and upper respiratory tract infections. Serum 25(OH)D levels less than 20 ng/mL have been associated with double the risk of tibial and fibular stress fractures in female naval cadets than those with serum levels greater than 40 ng/mL (OR = 0.51, 95% confidence interval = 0.34-0.76, p ≤ 0.01).54 In a large prospective study of 756 Finnish military recruits with a mean age of 19 years old, a multivariate analysis showed that serum 25(OH)D levels below 30.4 ng/mL significantly correlated with stress fractures (OR = 3.6, p = 0.002).55 

Vitamin D levels have also been shown to affect muscular injury rates. Lower levels of serum vitamin D have been associated with increased amounts of muscle weakness after injury (p < 0.05).56 Ballet dancers who received vitamin D supplementation sustained fewer injuries than did those who did not receive supplementation (p < 0.01),52 and injury incidence was lower in summer, when vitamin D was at higher levels (p < 0.05).57 After decreases in serum 25(OH)D levels, collegiate swimmers have been shown to be at increased risk of connective tissue and muscle injuries.58 

Acutely after endurance exercises, the immune system is suppressed and the body is vulnerable to infection,59,60 and vitamin D is vital in expression of antimicrobial cells.13,61,62 In 1945, UV-irradiated University of Illinois students not only did better on physical examination tests but also had half as many viral respiratory tract infections.43 Elite athletes have a higher incidence (incidence rate = 4.04, confidence interval = 95%, p < 0.05) of upper respiratory tract infections than do recreationally competitive athletes, putting them at higher risk of missing playing time.63 Additionally, athletes with optimal vitamin D levels (> 48.08 ng/mL [> 120 nmol/L]) present significantly less often for treatment of upper respiratory tract infections, and their severity scores and days experiencing illness are significantly lower than those with vitamin D deficiency (< 12.02 ng/mL [< 30 nmol/L]).13


A patient’s vitamin D status can be assessed with a blood draw assessing 25(OH)D level. The Endocrine Society64 defines vitamin D deficiency as 25(OH)D level below 20 ng/mL, insufficiency as 21ng/mL to 29 ng/mL, and sufficient as above 30 ng/mL. Recommended daily intake varies by age. To achieve blood levels of 25(OH)D consistently above 30 ng/mL, children aged 1 to 18 years are recommended to consume at least 1000 IU/d; adults in the 19- to 50-year range may need at least 1500 IU/d to 2000 IU/d to reach the same level.64 Vitamin D toxicity manifests with hypercalcemia-related symptoms such as nausea, vomiting, fatigue, and weakness65 and can occur when doses reach greater than 50,000 IU/d, with blood levels above 150 ng/mL. Sunlight alone cannot cause toxicity, as excess vitamin D is broken down by sunlight.66

Although doses of 10,000 IU/d for 5 months do not cause toxicity,67 it is suboptimal to overload the body in this fashion to raise vitamin levels. A dose of 70,000 IU/wk has been shown to be detrimental to increase 25(OH)D blood levels; after stopping the supplementation, serum 24,25(OH)2D persists at high levels, which inhibits the bioactivity of 1,25(OH)2D.68 


Future research is greatly needed, focusing on double-blinded supplementation and optimal vitamin D levels in athletes. We recommend that vitamin D levels should be checked on an annual basis in all athletes. If their level is deficient or insufficient, athletes should be supplemented with vitamin D to help decrease the risk of injuries while possibly improving performance. In patients who are vitamin D deficient or insufficient, we recommend a treatment dosage of 50,000 IU/wk for 8 weeks. Once the treatment regimen has been completed, the physician may choose to recheck vitamin D levels and then initiate another 8-week round of treatment if levels remain deficient. If the patient’s vitamin D level is adequate after 1 round of treatment, we recommend a daily maintenance dose as described by the Endocrine Society.64

Disclosure Statement

The author(s) have no conflicts of interest to disclose.


Kathleen Louden, ELS, of Louden Health Communications provided editorial assistance.

How to Cite this Article

Sikora-Klak J, Narvy SJ, Yang J, Makhni E, Kharrazi FD, Mehran N. The effect of abnormal vitamin D levels in athletes. Perm J 2018;22:17-216. DOI:

1.    Holick MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clin Proc 2006 Mar;81(3):353-73. DOI:
    2.    Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res 2011 Jan;31(1):48-54. DOI:
    3.    Ginde AA, Liu MC, Camargo CA Jr. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med 2009 Mar 23;169(6):626-32. DOI: 10.1001/archinternmed.2008.604.
    4.    Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr 2004 Dec;80(6 Suppl):1678S-88S. DOI:
    5.    Fishman MP, Lombardo SJ, Kharrazi FD. Vitamin D deficiency among professional basketball players. Orthop J Sports Med 2016 Jul 6;4(7):2325967116655742. DOI:
    6.    Maroon JC, Mathyssek CM, Bost JW, et al. Vitamin D profile in National Football League players. Am J Sports Med 2015 May;43(5):1241-5. DOI:
    7.    Shindle MK, Voos J, Gulotta L, et al. Vitamin D status in a professional American football team. Med Sci Sports Exerc 2011 May;43(Suppl 1):511. DOI:
    8.    Close GL, Russell J, Cobley JN, et al. Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: Implications for skeletal muscle function. J Sports Sci 2013;31(4):344-53. DOI:
    9.    Mehran N, Schulz BM, Neri BR, Robertson WJ, Limpisvasti O. Prevalence of vitamin D insufficiency in professional hockey players. Orthop J Sports Med 2016 Dec 23;4(12):2325967116677512. DOI:
    10.    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. DOI:
    11.    Flueck JL, Hartmann K, Strupler M, Perret C. Vitamin D deficiency in Swiss elite wheelchair athletes. Spinal Cord 2016 Nov;54(11):991-5. DOI:
    12.    Krzywanski J, Mikulski T, Krysztofiak H, Mlynczak M, Gaczynska E, Ziemba A. Seasonal vitamin D status in Polish elite athletes in relation to sun exposure and oral supplementation. PLoS One 2016 Oct 12;11(10):e0164395. DOI:
    13.    He CS, Handzlik M, Fraser WD, et al. Influence of vitamin D status on respiratory infection incidence and immune function during 4 months of winter training in endurance sport athletes. Exerc Immunol Rev 2013;19:86-101.
    14.    Dubnov-Raz G, Livne N, Raz R, Rogel D, Cohen AH, Constantini NW. Vitamin D concentrations and physical performance in competitive adolescent swimmers. Pediatr Exerc Sci 2014 Feb;26(1):64-70. DOI:
    15.    Wilson G, Fraser WD, Sharma A, et al. Markers of bone health, renal function, liver function, anthropometry and perception of mood: A comparison between Flat and National Hunt Jockeys. Int J Sports Med 2013 May;34(5):453-9. DOI:
    16.    Villacis D, Yi A, Jahn R, et al. Prevalence of abnormal vitamin D levels among Division I NCAA athletes. Sports Health 2014 Jul;6(4):340-7. DOI:
    17.    Bescós García R, Rodríguez Guisado FA. Low levels of vitamin D in professional basketball players after wintertime: Relationship with dietary intake of vitamin D and calcium. Nutr Hosp 2011 Sep-Oct;26(5):945-51. DOI:
    18.    Cannell JJ, Hollis BW, Zasloff M, Heaney RP. Diagnosis and treatment of vitamin D deficiency. Expert Opin Pharmacother 2008 Jan;9(1):107-18. DOI:
    19.    Brown AJ, Dusso A, Slatopolsky E. Vitamin D. Am J Physiol 1999 Aug;277(2 Pt 2):F157-75.
    20.    Holick MF. Vitamin D deficiency. N Engl J Med 2007 Jul 19;357(3):266-81. DOI:
    21.    Nagpal S, Na S, Rathnachalam R. Noncalcemic actions of vitamin D receptor ligands. Endocr Rev 2005 Aug;26(5):662-87. DOI:
    22.    Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Athletic performance and vitamin D. Med Sci Sports Exerc 2009 May;41(5):1102-10. DOI:
    23.    Bischoff-Ferrari HA, Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B. Fracture prevention with vitamin D supplementation: A meta-analysis of randomized controlled trials. JAMA 2005 May 11;293(18):2257-64. DOI:
    24.    Minasyan A, Keisala T, Zou J, et al. Vestibular dysfunction in vitamin D receptor mutant mice. J Steroid Biochem Mol Biol 2009 Apr;114(3-5):161-6. DOI:
    25.    Holick MF. Resurrection of vitamin D deficiency and rickets. J Clin Invest 2006 Aug;116(8):2062-72. DOI:
    26.    Bakhtiyarova S, Lesnyak O, Kyznesova N, Blankenstein MA, Lips P. Vitamin D status among patients with hip fracture and elderly control subjects in Yekaterinburg, Russia. Osteoporos Int 2006;17(3):441-6. DOI:
    27.    Powers S, Nelson WB, Larson-Meyer E. Antioxidant and Vitamin D supplements for athletes: Sense or nonsense? J Sports Sci 2011;29 Suppl 1:S47-55. DOI:
    28.    Cooper C, Javaid K, Westlake S, Harvey N, Dennison E. Developmental origins of osteoporotic fracture: The role of maternal vitamin D insufficiency. J Nutr 2005 Nov;135(11):2728S-34S. DOI:
    29.    Yoshikawa S, Nakamura T, Tanabe H, Imamura T. Osteomalacic myopathy. Endocrinol Jpn 1979 Jun;26(Suppl):65-72. DOI:
    30.    Oh JH, Kim SH, Kim JH, Shin YH, Yoon JP, Oh CH. The level of vitamin D in the serum correlates with fatty degeneration of the muscles of the rotator cuff. J Bone Joint Surg Br 2009 Dec;91(12):1587-93. DOI:
    31.    Young A, Edwards R, Jones D, Brenton D. Quadriceps muscle strength and fibre size during treatment of osteomalacia. In: Stokes IF, editor. Mechanical factors and the skeleton. Vol 12. London, England: John Libbey Publishing; 1981. p 137-45.
    32.    Heath KM, Elovic EP. Vitamin D deficiency: Implications in the rehabilitation setting. Am J Phys Med Rehabil 2006 Nov;85(11):916-23. DOI:
    33.    Ahmed W, Khan N, Glueck CJ, et al. Low serum 25 (OH) vitamin D levels (<32 ng/mL) are associated with reversible myositis-myalgia in statin-treated patients. Transl Res 2009 Jan;153(1):11-6. DOI:
    34.    Rebolledo BJ, Bernard JA, Werner BC, et al. The association of vitamin D status in lower extremity muscle strains and core muscle injuries at the National Football League combine. Arthroscopy 2018 Apr;34(4):1280-5. DOI:
    35.    Ostrowski K, Hermann C, Bangash A, Schjerling P, Nielsen JN, Pedersen BK. A trauma-like elevation of plasma cytokines in humans in response to treadmill running. J Physiol 1998 Dec 15;513(Pt 3):889-94. DOI:
    36.    Bruunsgaard H, Galbo H, Halkjaer-Kristensen J, Johansen TL, MacLean DA, Pedersen BK. Exercise-induced increase in serum interleukin-6 in humans is related to muscle damage. J Physiol 1997 Mar 15;499(Pt 3):833-41.
    37.    Lemire JM. Immunomodulatory role of 1,25-dihydroxyvitamin D3. J Cell Biochem 1992 May;49(1):26-31. DOI:
    38.    Müller K, Diamant M, Bendtzen K. Inhibition of production and function of interleukin-6 by 1,25-dihydroxyvitamin D3. Immunol Lett 1991 May;28(2):115-20. DOI:
    39.    Rigby WF, Denome S, Fanger MW. Regulation of lymphokine production and human T lymphocyte activation by 1,25-dihydroxyvitamin D3. Specific inhibition at the level of messenger RNA. J Clin Invest 1987 Jun 1;79(6):1659-64. DOI:
    40.    Calton EK, Keane KN, Newsholme P, Soares MJ. The impact of vitamin D levels on inflammatory status: A systematic review of immune cell studies. PLoS One 2015 Nov 3;10(11):e0141770. DOI:
    41.    Gorkin Z, Gorkin MJ, Teslenko NE. [The effect of ultraviolet irradiation upon training for 100m sprint]. [Article in Russian]. Fiziol Zh USSR 1938;25:695-701.
    42.    Lehmann G, Mueller EA. [Ultraviolet irradiation and altitude fitness]. [Article in German]. Luftfahrtmedizin 1944;9:37-43.
    43.    Allen RM, Cureton TK. Effects of ultraviolet radiation on physical fitness. Arch Phys Med Rehabil 1945 Oct;26:641-4.
    44.    Hettinger T, Seidl E. [Ultraviolet irradiation and trainability of musculature]. [Article in German]. Int Z Angew Physiol 1956;16(3):177-83.
    45.    Cheatum BA. Effects of a single biodose of ultraviolet radiation upon the speed of college women. Res Q 1968 Oct;39(3):482-5.
    46.    Rosentsweig J. The effect of a single suberythemic biodose of ultraviolet radiation upon the strength of college women. J Assoc Phys Ment Rehabil 1967 Jul-Aug;21(4):131-3.
    47.    Rosentsweig J. The effect of a single suberythemic biodose of ultraviolet radiation upon the endurance of college women. J Sports Med Phys Fitness 1969 Jun;9(2):104-6.
    48.    Ronge HE. [Increase of physical effectiveness by systematic ultraviolet irradiation]. [Article in German]. Strahlentherapie 1952;88(3-4):563-6.
    49.    Hettinger T, Muller EA. [Seasonal course of trainability of musculature]. [Article in German]. Int Z Angew Physiol 1956;16(2):90-4.
    50.    Rodman JS, Baker T. Changes in the kinetics of muscle contraction in vitamin D-depleted rats. Kidney Int 1978 Mar;13(3):189-93. DOI:
    51.    Ward KA, Das G, Berry JL, et al. Vitamin D status and muscle function in post-menarchal adolescent girls. J Clin Endocrinol Metab 2009 Feb;94(2):559-63. DOI:
    52.    Wyon MA, Koutedakis Y, Wolman R, Nevill AM, Allen N. The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: A controlled study. J Sci Med Sport 2014 Jan;17(1):8-12. DOI:
    53.    Wyon MA, Wolman R, Nevill AM, et al. Acute effects of vitamin D3 supplementation on muscle strength in judoka athletes: A randomized placebo-controlled, double-blind trial. Clin J Sport Med 2016 Jul;26(4):279-84. DOI:
    54.    Burgi AA, Gorham ED, Garland CF, et al. High serum 25-hydroxyvitamin D is associated with a low incidence of stress fractures. J Bone Miner Res 2011 Oct;26(10):2371-7. DOI:
    55.    Ruohola JP, Laaksi I, Ylikomi T, et al. Association between serum 25(OH)D concentrations and bone stress fractures in Finnish young men. J Bone Miner Res 2006 Sep;21(9):1483-8. DOI:
    56.    Barker T, Henriksen VT, Martins TB, et al. Higher serum 25-hydroxyvitamin D concentrations associate with a faster recovery of skeletal muscle strength after muscular injury. Nutrients 2013 Apr 17;5(4):1253-75. DOI:
    57.    Wolman R, Wyon MA, Koutedakis Y, Nevill AM, Eastell R, Allen N. Vitamin D status in professional ballet dancers: Winter vs summer. J Sci Med Sport 2013 Sep;16(5):388-91. DOI:
    58.    Lewis RM, Redzic M, Thomas DT. The effects of season-long vitamin D supplementation on collegiate swimmers and divers. Int J Sport Nutr Exerc Metab 2013 Oct;23(5):431-40. DOI:
    59.    Kakanis MW, Peake J, Brenu EW, et al. The open window of susceptibility to infection after acute exercise in healthy young male elite athletes. Exerc Immunol Rev 2010;16:119-37. DOI:
    60.    Shephard RJ, Shek PN. Effects of exercise and training on natural killer cell counts and cytolytic activity: A meta-analysis. Sports Med 1999 Sep;28(3):177-95. DOI:
    61.    Yim S, Dhawan P, Ragunath C, Christakos S, Diamond G. Induction of cathelicidin in normal and CF bronchial epithelial cells by 1,25-dihydroxyvitamin D3. J Cyst Fibros 2007 Nov 30;6(6):403-10. DOI:
    62.    Wang TT, Nestel FP, Bourdeau V, et al. Cutting edge: 1,25-dihydroxyvitamin D3 is a direct inducer of antimicrobial peptide gene expression. J Immunol 2004 Sep 1;173(5):2909-12. DOI:
    63.    Spence L, Brown WJ, Pyne DB, et al. Incidence, etiology, and symptomatology of upper respiratory illness in elite athletes. Med Sci Sports Exerc 2007 Apr;39(4):577-86. DOI:
    64.    Holick MF, Binkley NC, Bischoff-Ferrari HA, et al; Endocrine Society. Evaluation, treatment, and prevention of vitamin D deficiency: An Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2011 Jul;96(7):1911-30. DOI:
    65.    Kulie T, Groff A, Redmer J, Hounshell J, Schrager S. Vitamin D: An evidence-based review. J Am Board Fam Med 2009 Nov-Dec;22(6):698-706. DOI:
    66.    Holick MF, Garabedian M. Vitamin D: Photobiology, metabolism, mechanism of action, and clinical applications. In: Favus MJ, editor. Primer on the metabolic bone diseases and disorders of mineral metabolism. 6th ed. Washington, DC: American Society for Bone and Mineral Research; 2006. p 129-37.
    67.    Vieth R. Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults. J Steroid Biochem Mol Biol 2004 May;89-90(1-5):575-9. DOI:
    68.    Owens DJ, Tang JC, Bradley WJ, et al. Efficacy of high-dose vitamin D supplements for elite athletes. Med Sci Sports Exerc 2017 Feb;49(2):349-56. DOI:


Click here to join the eTOC list or text ETOC to 22828. You will receive an email notice with the Table of Contents of The Permanente Journal.


2 million page views of TPJ articles in PubMed from a broad international readership.


Indexed in MEDLINE, PubMed Central, EMBASE, EBSCO Academic Search Complete, and CrossRef.




ISSN 1552-5775 Copyright © 2021

All Rights Reserved