Jump to content
We need you! See something you could improve? Make an edit and help improve WikSM for everyone.

Vitamin D

From WikiSM

Alternative Names

  • Cholecalciferol (Vitamin D3)
  • Ergocalciferol (Vitamin D2)
  • Calciferol
  • 25-hydroxyvitamin D
  • 25(OH)D

Background

  • This page provides a summary of Vitamin D and all its various formulations

History

  • 1920s: Elmer McCollum identified Vitamin D as the fat-soluble factor preventing rickets [1]
  • 1930s: Introduction of Vitamin D fortification in milk led to a major decline in rickets prevalence [2]
  • Late 20th century: Research demonstrated Vitamin D’s role in muscle strength, performance, and fall prevention, expanding its use as a supplement beyond bone health [3]
  • 21st century: High prevalence of Vitamin D deficiency identified in athletes, with supplementation linked to improved performance and reduced stress fracture risk [4]

Introduction

Vitamin D Supplement

Schematic overview of vitamin D metabolism in humans. ↑ indicates an increase, ↓ indicates a decrease. Abbreviations: ultraviolet light short wavelength (UVB); calcidiol (25(OH)D); calcitriol (1,25(OH)2D); retinoid X receptor (RXR); vitamin D receptor (VDR); vitamin D response element (VDRE); parathyroid hormone (PTH); calcium (Ca).[5]
Vitamin D food sources

General

  • Vitamin D deficiency is common in athletes, particularly those training indoors, at high latitudes, or with darker skin pigmentation [6]
  • Adequate levels support muscle strength and performance, while deficiency may impair power and increase fatigue [7]
  • Low Vitamin D is associated with increased stress fracture risk, making supplementation important in high-risk athletes [8]
  • Vitamin D may enhance immune function and recovery, particularly during periods of intense training [9]
  • Supplementation is commonly used to maintain levels ≥30–40 ng/mL, with typical dosing of 1000–4000 IU daily depending on deficiency status [10]

Formulations

  • Vitamin D3 (Cholecalciferol)
    • Most commonly used supplement form
    • Derived from animal sources (lanolin)
    • More effective at raising serum 25(OH)D levels
  • Vitamin D2 (Ergocalciferol)
    • Plant-derived (yeast/fungi)
    • Less potent and shorter duration than D3
    • Often used in prescription formulations
  • Calcitriol (1,25-dihydroxyvitamin D)
    • Active form of Vitamin D
    • Used in patients with renal failure or impaired activation
    • Higher risk of hypercalcemia
  • Calcifediol (25-hydroxyvitamin D3)
    • Intermediate form (liver metabolite)
    • Faster increase in serum levels
    • Used in select deficiency cases

Sources of Vitamin D

  • Sunlight
    • UVB radiation converts 7-dehydrocholesterol → Vitamin D3
    • Most efficient natural source
  • Dietary Sources
    • Fatty fish (salmon, mackerel, sardines)
    • Fortified milk and cereals
    • Egg yolks
  • Supplements
    • Vitamin D3 (preferred due to higher potency)
    • Vitamin D2 (plant-based alternative)

Mechanism

  • Converted to active form (calcitriol) via liver and kidney hydroxylation[6]
  • Binds to Vitamin D receptors (VDR) in target tissues to regulate gene expression [11]
  • Increases intestinal absorption of calcium and phosphate [12]
  • Promotes bone mineralization and remodeling[12]
  • Modulates immune and muscle cell function via genomic and non-genomic pathways[6]

Controversies in Vitamin D

  • Optimal serum levels remain debated, with differing definitions of sufficiency (≥20 vs ≥30 ng/mL) [13]
  • Routine supplementation in non-deficient individuals shows limited benefit, with unclear impact on clinical outcomes [14]
  • Non-skeletal benefits are inconsistent, with conflicting evidence regarding cardiovascular, cancer, and immune effects [15]
  • Performance benefits in athletes are unclear, particularly in those who are already Vitamin D sufficient [16]
  • High-dose supplementation carries potential risks, with concerns about falls, fractures, and toxicity in certain dosing strategies [17]

Athletic Performance Benefits

Vitamin D Benefits

Vitamin D for Athletes


Muscle Strength and Power

  • Improves muscle fiber function (particularly type II fibers) and force production
  • Deficiency is associated with decreased strength and increased fatigue[18]

Neuromuscular Function and Coordination

  • Enhances neuromuscular signaling and motor control
  • May reduce risk of falls and non-contact injuries[19]

Bone Health and Stress Fracture Prevention

  • Increases calcium absorption and bone mineral density
  • Lower levels are associated with higher rates of stress fractures in athletes[20]

Recovery and Inflammation

  • Modulates inflammatory cytokines following exercise
  • May improve muscle recovery and reduce delayed onset muscle soreness (DOMS)[21]

Immune Function

  • Supports innate and adaptive immune responses
  • May reduce incidence of upper respiratory infections during heavy training[22]

Aerobic Performance (VO₂ Max)

  • May improve oxygen utilization and aerobic capacity in deficient athletes
  • Evidence is mixed and population-dependent[23]

Hormonal Effects (Testosterone)

  • Some studies show increased testosterone levels with supplementation
  • Potential impact on strength, recovery, and performance[24]

Other Health Benefits

Causes of vitamin D deficiency and diseases and disorders associated with vitamin D deficiency[25]

Bone Health and Fracture Prevention

  • Enhances calcium and phosphate absorption, supporting bone mineralization
  • Reduces risk of osteomalacia and contributes to fracture prevention, especially in older adults[6]

Immune System Modulation

  • Regulates innate and adaptive immune responses
  • Associated with reduced risk of certain infections, including respiratory illnesses[26]

Cardiovascular Health

  • May influence blood pressure regulation and endothelial function
  • Observational studies link low Vitamin D levels with increased cardiovascular risk, though causation remains unclear[27]

Cancer Risk and Cell Regulation

  • Involved in cell differentiation, apoptosis, and inhibition of tumor growth
  • Evidence for cancer prevention is mixed and remains an area of ongoing research[28]

Mood and Mental Health

  • May play a role in neurotransmitter regulation and brain function
  • Low levels have been associated with depression, though supplementation benefits are inconsistent[29]

Metabolic Health

  • May influence insulin sensitivity and glucose metabolism
  • Associations exist with type 2 diabetes risk, though interventional data are variable[30]

Dosing

Vitamin D Doing Guide

  • Maintenance dosing typically 800–2000 IU daily, adjusted based on baseline levels and patient risk factors[6]
  • Deficiency treatment often uses high-dose regimens (e.g., 50,000 IU weekly for 6–8 weeks) followed by maintenance therapy [6]
  • Higher doses may be required in obesity, malabsorption, or chronic illness due to altered metabolism [31]
  • Target serum 25(OH)D levels generally ≥20–30 ng/mL, with some recommending ≥30–40 ng/mL in high-risk populations[13]
  • Athletes may require individualized dosing based on training environment, sun exposure, and deficiency status [32]

Safety Profile

  • Generally well tolerated at recommended doses, with a wide therapeutic index[6]
  • Safe upper intake level typically cited as 4000 IU daily for most adults [33]
  • Long-term high-dose supplementation increases risk of toxicity, particularly without monitoring [34]
  • Requires caution in patients with renal disease or hypercalcemia[11]
  • Monitoring recommended in high-risk or high-dose patients[6]

Adverse Effects

  • Hypercalcemia is the primary toxicity, leading to nausea, vomiting, and confusion [35]
  • Hypercalciuria may occur, increasing risk of nephrolithiasis[6]
  • Chronic excessive dosing can lead to soft tissue and vascular calcification[11]
  • Symptoms of toxicity are typically seen with prolonged intake >10,000 IU/day [36]
  • Rare at standard supplementation doses[6]

Pharmacokinetics

  • Absorbed in the small intestine as a fat-soluble vitamin, enhanced by dietary fat[12]
  • Stored in adipose tissue and liver, contributing to long half-life[6]
  • Converted in liver to 25(OH)D and in kidney to active 1,25(OH)₂D (calcitriol)[12]
  • Circulates bound to vitamin D–binding protein (DBP)[11]
  • Half-life of 25(OH)D is approximately 2–3 weeks, allowing for intermittent dosing[6]

Interactions

  • Glucocorticoids reduce Vitamin D metabolism and calcium absorption, increasing deficiency risk [37]
  • Anticonvulsants (e.g., phenytoin) increase Vitamin D breakdown via hepatic enzyme induction [38]
  • Orlistat and cholestyramine reduce absorption due to fat malabsorption[6]
  • Thiazide diuretics may increase risk of hypercalcemia when combined with Vitamin D[11]
  • Calcium supplements may enhance therapeutic effects but increase hypercalcemia risk if excessive[13]

WADA Considerations

  • Vitamin D is not on the World Anti-Doping Agency prohibited list
  • Widely used and permitted in competitive athletes for performance, recovery, and bone health
  • No known ergogenic advantage beyond correcting deficiency, and not considered a performance-enhancing drug
  • Safe for use in sport when taken within recommended dosing ranges
  • Athletes should ensure supplement quality to avoid contamination with prohibited substances [39]

See Also

References

  1. ↑ McCollum, Elmer V., et al. “Studies on Experimental Rickets.” Journal of Biological Chemistry, vol. 53, 1922, pp. 293–312.
  2. ↑ Rajakumar, Kumaravel. “Vitamin D, Cod-Liver Oil, Sunlight, and Rickets: A Historical Perspective.” Pediatrics, vol. 112, no. 2, 2003, pp. e132–e135.
  3. ↑ Bischoff-Ferrari, H. A., et al. “Effect of Vitamin D on Falls: A Meta-Analysis.” JAMA, vol. 291, no. 16, 2004, pp. 1999–2006.
  4. ↑ Close, G. L., et al. “The Role of Vitamin D in Athletic Performance and Recovery.” International Journal of Sport Nutrition and Exercise Metabolism, vol. 23, no. 6, 2013, pp. 609–620.
  5. ↑ Spyksma, Eva E., et al. "An overview of different vitamin D compounds in the setting of adiposity." Nutrients 16.2 (2024): 231.
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 Holick, Michael F. “Vitamin D Deficiency.” New England Journal of Medicine, 2007.
  7. ↑ Owens, Daniel J., et al. “Vitamin D and the Athlete.” Sports Medicine, 2015.
  8. ↑ Lappe, Joan M., et al. “Vitamin D and Calcium Supplementation Reduces Stress Fractures.” Journal of Bone and Mineral Research, 2008.
  9. ↑ He, Chunyan S., et al. “Vitamin D and Respiratory Infection in Athletes.” Exercise Immunology Review, 2010.
  10. ↑ Close, G. L., et al. “Vitamin D in Athletic Performance.” International Journal of Sport Nutrition and Exercise Metabolism, 2013.
  11. ↑ 11.0 11.1 11.2 11.3 11.4 DeLuca, Hector F. “Overview of General Physiologic Features and Functions of Vitamin D.” American Journal of Clinical Nutrition, 2004.
  12. ↑ 12.0 12.1 12.2 12.3 Christakos, Sylvia, et al. “Vitamin D: Metabolism, Mechanism of Action, and Clinical Applications.” Physiological Reviews, 2016.
  13. ↑ 13.0 13.1 13.2 Rosen, Clifford J., et al. “The Nonskeletal Effects of Vitamin D: An Endocrine Society Scientific Statement.” Endocrine Reviews, 2012.
  14. ↑ Manson, JoAnn E., et al. “Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease.” New England Journal of Medicine, 2019.
  15. ↑ Autier, Philippe, et al. “Vitamin D Status and Ill Health: A Systematic Review.” Lancet Diabetes & Endocrinology, 2014.
  16. ↑ Owens, Daniel J., et al. “Vitamin D and the Athlete.” Sports Medicine, 2015.
  17. ↑ Sanders, Kerrie M., et al. “Annual High-Dose Oral Vitamin D and Falls and Fractures in Older Women.” JAMA, 2010.
  18. ↑ Owens, Daniel J., et al. “Vitamin D and the Athlete: Current Perspectives and New Challenges.” Sports Medicine, 2015.
  19. ↑ Bischoff-Ferrari, H. A., et al. “Effect of Vitamin D on Falls: A Meta-Analysis.” JAMA, 2004.
  20. ↑ Lappe, Joan M., et al. “Vitamin D and Calcium Supplementation Reduces Stress Fractures in Female Navy Recruits.” Journal of Bone and Mineral Research, 2008.
  21. ↑ Close, G. L., et al. “The Role of Vitamin D in Athletic Performance and Recovery.” International Journal of Sport Nutrition and Exercise Metabolism, 2013.
  22. ↑ He, Chunyan S., et al. “Influence of Vitamin D Status on Respiratory Infection Incidence in Athletes.” Exercise Immunology Review, 2010.
  23. ↑ Koundourakis, Nikolaos E., et al. “Vitamin D and Exercise Performance in Professional Soccer Players.” PLoS One, 2014.
  24. ↑ Pilz, Stefan, et al. “Effect of Vitamin D Supplementation on Testosterone Levels in Men.” Hormone and Metabolic Research, 2011.
  25. ↑ Charoenngam, Nipith, and Michael F. Holick. "Immunologic effects of vitamin D on human health and disease." Nutrients 12.7 (2020): 2097.
  26. ↑ Aranow, Cynthia. “Vitamin D and the Immune System.” Journal of Investigative Medicine, 2011.
  27. ↑ Wang, Thomas J., et al. “Vitamin D Deficiency and Risk of Cardiovascular Disease.” Circulation, 2008.
  28. ↑ Feldman, David, et al. “The Role of Vitamin D in Reducing Cancer Risk and Progression.” Nature Reviews Cancer, 2014.
  29. ↑ Anglin, Rebecca E. S., et al. “Vitamin D Deficiency and Depression in Adults.” British Journal of Psychiatry, 2013.
  30. ↑ Pittas, Anastassios G., et al. “Vitamin D and Risk of Type 2 Diabetes.” Journal of Clinical Endocrinology & Metabolism, 2007.
  31. ↑ Wimalawansa, Sunil J. “Vitamin D in the New Millennium.” Endocrine Reviews, 2012.
  32. ↑ Owens, Daniel J., et al. “Vitamin D and the Athlete.” Sports Medicine, 2015.
  33. ↑ Institute of Medicine. “Dietary Reference Intakes for Calcium and Vitamin D.” 2011.
  34. ↑ Vieth, Reinhold. “Vitamin D Toxicity, Policy, and Science.” Journal of Bone and Mineral Research, 2007.
  35. ↑ Vieth, Reinhold. “Vitamin D Toxicity.” Journal of Bone and Mineral Research, 2007.
  36. ↑ Vieth, Reinhold. “Vitamin D Toxicity.” Journal of Bone and Mineral Research, 2007.
  37. ↑ Compston, Juliet. “Glucocorticoid-Induced Osteoporosis.” Lancet, 2018.
  38. ↑ Pack, Alison M. “The Association Between Antiepileptic Drugs and Bone Disease.” Epilepsy Currents, 2003.
  39. ↑ Owens, Daniel J., et al. “Vitamin D and the Athlete.” Sports Medicine, 2015.
Created by:
John Kiel on 1 April 2026 22:04:56
Authors:
Last edited:
2 April 2026 01:45:24
Categories:
Retrieved from "https://wikism.org/w/index.php?title=Vitamin_D&oldid=42222"