Doctors have valid reasons for prescribing vitamin D2 supplements instead of vitamin D3. While both D2 and D3 increase vitamin D levels, there are some key differences between the two forms that influence which doctors choose to prescribe.
What is the difference between vitamins D2 and D3?
Vitamins D2 and D3 have the same basic function – to increase vitamin D levels in the body. However, their chemical structures differ slightly:
- Vitamin D2, also known as ergocalciferol, is derived from plants and yeast.
- Vitamin D3, also known as cholecalciferol, is derived from animal sources and produced by the human body when skin is exposed to sunlight.
This difference in origin leads to some variation in how the two forms of vitamin D behave in the body:
- Vitamin D2 has a shorter shelf life and degrades faster than D3.
- Vitamin D3 has greater potency and raises vitamin D levels more effectively than D2.
- Vitamin D3 remains active in the body for a longer period of time compared to D2.
Why do some doctors prefer to prescribe vitamin D2?
Despite its lower potency, vitamin D2 is still effective at increasing vitamin D levels. Here are some reasons why a doctor may choose to prescribe D2 instead of D3:
Dietary restrictions
For patients following a vegetarian or vegan diet, vitamin D2 from plant sources may be preferred over D3 from animal sources for ethical reasons.
Cost differences
In some cases, vitamin D2 supplements are more economical for patients compared to D3. Doctors may prescribe D2 to help lower costs for patients with limited budgets.
Regulations and insurance coverage
In some countries, vitamin D2 is more readily available and covered by insurance plans. Doctors may prescribe D2 to comply with local regulations and policies.
Reliable dosing
The dosing of vitamin D2 in supplements tends to be more consistent compared to vitamin D3. For doctors monitoring patient doses carefully, D2 offers more reliable dosing.
Patient preferences
Some patients may specifically request or prefer to take vitamin D2 supplements. Doctors may prescribe D2 to accommodate patient preferences.
Why do most doctors prefer prescribing vitamin D3?
While vitamin D2 has some benefits, most doctors prefer prescribing vitamin D3 due to the following key advantages:
Higher potency
Vitamin D3 has been shown in studies to raise vitamin D levels in the blood significantly more than vitamin D2 at the same dosage. For efficiently boosting low vitamin D levels, most doctors prefer the higher potency of D3.
| Study | Findings |
|---|---|
| Aranow et al. 2009 | 50,000 IU of D2 weekly was less effective than 50,000 IU of D3 weekly at raising vitamin D levels over a 12-week treatment period. |
| Holick et al. 2008 | A single 50,000 IU dose of D2 raised vitamin D levels to a lesser extent than an equal dose of D3. |
Longer lasting
Due to its longer half-life, vitamin D3 remains active in the body for a longer period of time. A single dose of D3 can sustain vitamin D levels for weeks or months. In comparison, D2 may need to be taken more frequently to maintain vitamin D sufficiency.
Better absorption
Studies indicate vitamin D3 is better absorbed in the body than vitamin D2. One 3-month study found that vitamin D3 supplementation resulted in 2-fold higher serum levels compared to equal doses of D2.
Addresses deficiencies more efficiently
For patients with diagnosed vitamin D deficiencies, vitamin D3 is superior at normalizing vitamin D levels quickly. Clinical practice guidelines generally recommend D3 for treating deficiencies.
May have additional health benefits
Some research indicates vitamin D3 may offer additional health benefits beyond D2, such as improving cardiovascular health markers. However, more research is still needed.
Conclusion
While both supplements effectively increase vitamin D levels, vitamin D3 is the preferred form for most doctors due to its substantially greater potency, duration of action, and absorption. Exceptions may include accommodating dietary restrictions, managing costs, or meeting individual patient preferences.
However, both vitamin D2 and D3 can be effective options depending on the clinical context. Doctors weigh the advantages and disadvantages of each form to make individualized prescribing decisions in the best interest of each patient.