Vitamin D3
Vitamin D3
Snapshot
Vitamin D3 (cholecalciferol) is a fat‑soluble prohormone vital for calcium and phosphorus balance, bone mineralization, immune regulation, and muscle performance.
What is Vitamin D3 (Cholecalciferol)?
Vitamin D3, or cholecalciferol, is synthesized in the skin from 7‑dehydrocholesterol under ultraviolet B exposure. It is hydroxylated in the liver to 25‑hydroxyvitamin D and then in the kidneys to active 1,25‑dihydroxyvitamin D (calcitriol), which binds the vitamin D receptor to regulate gene transcription.
Where It Comes From
Endogenous production occurs in sun‑exposed skin. Dietary sources include fatty fish (salmon, mackerel), fish liver oils, egg yolks, and fortified foods. Supplements provide cholecalciferol in oil‑based softgels, tablets, or liquids.
Key Nutrients & Compounds
Provides cholecalciferol, which is converted to 25(OH)D in the liver and to calcitriol (1,25(OH)₂D) in the kidneys, modulating intestinal calcium‑binding proteins and parathyroid hormone secretion.
Health Benefits
Vitamin D3 enhances intestinal absorption of calcium and phosphorus for bone strength; reduces fracture risk and supports skeletal health; modulates innate and adaptive immune responses; promotes muscle function; and may protect against autoimmune and chronic diseases.
Recommended Dosage
The RDA for adults is 600 IU (15 µg)/day up to age 70 and 800 IU (20 µg)/day over age 70. To achieve serum 25(OH)D ≥30 ng/mL, 1,000–2,000 IU daily is common. Higher doses (5,000–10,000 IU/day) may be used short‑term under medical supervision to correct deficiency.
How to Use It
Take Vitamin D3 supplements with a fat‑containing meal to enhance absorption. For weekly dosing, divide the total dose evenly (e.g., 10,000 IU twice weekly). Monitor serum 25(OH)D and calcium levels periodically to adjust dosing and prevent toxicity.
Who Should Use It?
Individuals with limited sun exposure, older adults, those with darker skin, obesity, malabsorption disorders, or diets low in vitamin D may require supplementation. Athletes and those at risk for osteoporosis often benefit from maintaining optimal levels.
Possible Interactions or Cautions
Excessive Vitamin D3 can lead to hypercalcemia, hypercalciuria, and soft tissue calcification. Caution when combined with thiazide diuretics or high‑dose calcium supplements. Discontinue or reduce dose if serum calcium or 25(OH)D levels become elevated.
Final Thoughts
Vitamin D3 is essential for musculoskeletal integrity and immune health. Personalized supplementation based on baseline serum 25(OH)D, risk factors, and response ensures optimal benefits and safety.
Scientific Studies
Holick MF. Vitamin D3 production following UVB exposure exceeds that of oral supplementation in humans. J Clin Endocrinol Metab. 2010;95(5):2253–2260. https://doi.org/10.1210/jc.2010-0681
Bischoff‑Ferrari HA, Giovannucci E, Willett WC, et al. Estimation of optimal serum concentrations of 25‑hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006;84(1):18–28. https://doi.org/10.1093/ajcn/84.1.18
Manson JE, Cook NR, Lee IM, et al. Vitamin D supplementation and prevention of cancer and cardiovascular disease. N Engl J Med. 2019;380(1):33–44. https://doi.org/10.1056/NEJMoa1809944