What form of vitamin D is typically used for supplementation?

Forms of Vitamin D Used for Supplementation

Cholecalciferol (vitamin D3) is the preferred form of vitamin D for supplementation due to its superior efficacy in raising and maintaining serum 25(OH)D levels compared to ergocalciferol (vitamin D2). 1

Sources and Forms of Vitamin D

Vitamin D supplementation is available in two main forms:

1. Cholecalciferol (Vitamin D3):

   • Derived from animal sources
   • Naturally produced in human skin when exposed to UVB radiation 2
   • Found in dietary sources such as fatty fish, eggs, and liver 2
   • More stable and has a longer shelf life 3

2. Ergocalciferol (Vitamin D2):

   • Plant-derived form 2
   • Commonly used in supplements 2
   • Less stable and more susceptible to breakdown during storage and cooking 4

Comparative Efficacy

Research clearly demonstrates that vitamin D3 is superior to vitamin D2:

• Vitamin D3 is more effective at raising serum 25(OH)D levels (mean difference: 15.69 nmol/L higher than D2) 1
• D3 has stronger binding to vitamin D binding protein (DBP) in plasma 3
• D3 has a more physiologic metabolism pattern 3
• D3 demonstrates greater bioefficacy in all primate species, including humans 3

Metabolism and Activation

Both forms undergo similar activation processes:

1. Initial conversion to 25-hydroxyvitamin D (25(OH)D) primarily in the liver 2
2. Further hydroxylation to the active form 1,25(OH)2D3 primarily in the kidneys 2

However, the metabolism differs in efficiency:

• D3 maintains 25(OH)D levels for a longer time when longer dosing intervals are employed 2
• When taken orally, approximately 35% of ingested vitamin D is carried in lipoproteins rather than vitamin D binding protein (DBP) 2

Recommended Supplementation

Current guidelines recommend:

• 600 IU daily for individuals 1-70 years of age 5
• 800 IU daily for individuals over 70 years 5
• For correction of deficiency, higher doses may be needed initially followed by maintenance doses 5
• A daily vitamin D3 supplementation of 2000 IU (50 μg) may be considered a simple, effective, and safe dosage to prevent and treat vitamin D deficiency in adults 6

Clinical Considerations

When prescribing vitamin D supplements:

• Form selection: Choose cholecalciferol (D3) over ergocalciferol (D2) whenever possible 3, 1
• Dosing: For patients with malabsorptive conditions (e.g., after bariatric surgery), intramuscular administration may be more effective than oral supplementation 2
• Monitoring: Measure serum 25(OH)D levels at least 3 months after starting supplementation 5
• Target levels: Aim for serum 25(OH)D levels above 30 ng/mL (75 nmol/L) for optimal health 5

Potential Pitfalls

• Assuming D2 and D3 are equivalent (they are not - D3 is more potent) 3
• Using vitamin D2 for long-term supplementation when D3 is available 4
• Failing to account for malabsorption when choosing between oral and parenteral routes 2
• Not considering that vitamin D is fat-soluble and requires proper absorption through the intestinal tract 2

In conclusion, while both forms of vitamin D can be used for supplementation, cholecalciferol (D3) is the preferred form due to its superior efficacy, stability, and physiological compatibility with human metabolism.