Quick Summary

Vitamin D2, also known as ergocalciferol, is a fat-soluble form of vitamin D primarily obtained from fungal and plant sources. It plays a role in maintaining vitamin D status in the human body, which is important for general health. However, specific information about recommended intakes, main biological functions, food sources, deficiency symptoms, supplementation benefits, and safety considerations for vitamin D2 alone is limited. Vitamin D2 is one of two main forms of vitamin D, the other being vitamin D3 (cholecalciferol), and both contribute to overall vitamin D activity.

What is Vitamin D2?

Vitamin D2, chemically known as ergocalciferol, is a type of vitamin D that is classified as fat-soluble. It is produced by exposing ergosterol—a compound found in fungi and some plants—to ultraviolet (UV) light. As a vitamin D form, it contributes to maintaining vitamin D levels in the body, although both D2 and D3 are metabolized differently.

Main Functions in the Body

Direct data specific to vitamin D2’s distinct biological roles is not separately available. Vitamin D, in its broader sense (including D2 and D3), contributes to:

Vitamin D is converted in the liver and kidneys into its active hormonal form, calcitriol, which regulates calcium absorption and other physiological processes. Both vitamin D2 and D3 can serve as precursors to active vitamin D, though some evidence suggests differences in potency and metabolism.

Recommended Intake and Upper Limit

Currently, there is no separate recommended daily allowance (RDA), adequate intake (AI), or upper intake level (UL) established exclusively for vitamin D2. Intake recommendations generally refer to total vitamin D (both D2 and D3 combined), and these vary by age, sex, and life stage. For specific guidance, consumers should refer to vitamin D intake recommendations provided by relevant health authorities in their regions.

Best Food Sources

Vitamin D2 is typically found in certain mushrooms exposed to ultraviolet light and fortified foods, although quantitative data on vitamin D2 content alone is scarce. Natural dietary sources of vitamin D primarily provide vitamin D3, with vitamin D2 contributing mainly via fortified foods or supplements sourced from fungi and yeast.

Deficiency: Causes, Symptoms, and Risk Groups

Information specific to vitamin D2 deficiency is not established, as deficiency is typically discussed in terms of total vitamin D status. Inadequate vitamin D (both D2 and D3) can relate to insufficient sunlight exposure, poor dietary intake, malabsorption disorders, or certain medical conditions.

  • Risk groups: Individuals with limited sun exposure, older adults, people with darker skin, individuals with gastrointestinal disorders, and those using certain medications may be at higher risk of low vitamin D status.
  • Symptoms: Low vitamin D levels may contribute to bone pain, muscle weakness, and increased risk of fractures, but these relate to total vitamin D status rather than vitamin D2 specifically.

Supplement Forms

Vitamin D2 is available as a dietary supplement, often in capsule, tablet, or liquid forms. It is used both as a prescription medication and an over-the-counter supplement to improve vitamin D status. Vitamin D2 supplements are typically sourced from fermented yeast or fungi exposed to UV light.

Potential Benefits: What Does the Evidence Say?

Evidence specifically isolating the effects of vitamin D2 is limited. Most clinical studies and reviews focus on total vitamin D or compare vitamin D2 with vitamin D3. Some research indicates that vitamin D2 can effectively raise serum 25-hydroxyvitamin D levels, although vitamin D3 may be more efficacious in some contexts. Research also explores vitamin D’s role in bone health, immune function, and chronic disease risk but does not distinctly evaluate vitamin D2 independently.

Side Effects and Toxicity

Reported side effects of vitamin D2 supplementation are uncommon at typical doses. Excessive intake of vitamin D (including D2) can potentially lead to toxicity characterized by hypercalcemia and related complications. However, specific toxic dose thresholds for vitamin D2 alone, separate from total vitamin D, are not well-defined. Users should avoid excessive high-dose supplementation without medical supervision.

Drug and Nutrient Interactions

There are no detailed documented interactions specific to vitamin D2 alone. Vitamin D (both forms) may interact with certain medications such as corticosteroids, anticonvulsants, and weight-loss drugs, potentially affecting vitamin D metabolism or calcium levels. Consultation with a healthcare provider is advised if taking other medications.

Who Should Be Careful?

  • Pregnant or breastfeeding women should consult healthcare professionals before taking vitamin D2 supplements.
  • Individuals with kidney or liver disorders or those with granulomatous diseases should use vitamin D supplements cautiously.
  • People on medications influencing vitamin D metabolism or calcium balance warrant medical advice before supplementation.

Frequently Asked Questions

What is the difference between vitamin D2 and D3?
Both are forms of vitamin D; D2 is derived from plant and fungal sources, while D3 is synthesized in the skin and found in animal-based foods. D3 may raise and maintain vitamin D levels more effectively according to some studies, but both contribute to overall vitamin D status.
Can I get enough vitamin D2 from food?
Vitamin D2 is primarily present in ultraviolet-exposed mushrooms and fortified foods but generally in small amounts. Most natural vitamin D intake comes from vitamin D3-containing foods or sun exposure.
Is vitamin D2 as effective as vitamin D3?
There is ongoing research comparing both, with some evidence suggesting vitamin D3 may be more potent in raising blood vitamin D levels, though vitamin D2 is still used therapeutically.
Are there risks to taking vitamin D2 supplements?
At recommended doses, vitamin D2 supplementation is generally safe. Excessive intake can cause adverse effects related to elevated calcium levels. Always follow dosing instructions and consult healthcare providers.

Evidence Limitations

There is a lack of comprehensive, specific data on vitamin D2 independent of total vitamin D studies. Most evidence focuses on overall vitamin D status or compares vitamin D2 and D3 in combined or mixed contexts, limiting the ability to draw firm conclusions about vitamin D2 alone. Furthermore, key data on recommended intake levels, deficiency markers, detailed side effect profiles, and authorized health claims for vitamin D2 separately are unavailable.

References

Disclaimer

This information is intended for educational purposes and does not substitute for professional medical advice. Individuals who are pregnant, breastfeeding, have existing medical conditions, or are taking medications should consult their healthcare provider before starting vitamin D2 or any other supplement.

Last Reviewed

June 2024