Ergocalciferol: The Plant-Based Vitamin D2
Ergocalciferol is the technical term for vitamin D2, a fat-soluble vitamin crucial for human health. Unlike its counterpart, vitamin D3 (cholecalciferol), ergocalciferol is predominantly sourced from non-animal origins. It is formed when ergosterol, a compound found in plants, fungi, and yeast, is exposed to ultraviolet (UV) radiation. This makes ergocalciferol the version of choice for many fortified foods and for individuals following a vegan diet.
While both D2 and D3 are used in supplements, there are notable differences in their sources and physiological effects in the human body. Ergocalciferol is commonly found in UV-exposed mushrooms and is used to fortify foods like milk, cereals, and orange juice. Its ability to increase vitamin D levels has been a subject of extensive research, with some studies suggesting it is less potent and has a shorter shelf-life than vitamin D3.
Comparing Ergocalciferol (D2) and Cholecalciferol (D3)
Despite their similar functions in regulating calcium and phosphate, a growing body of evidence indicates that D2 and D3 are not metabolically equivalent. The key distinctions lie in their sources, potency, stability, and effect on circulating vitamin D levels.
| Feature | Ergocalciferol (Vitamin D2) | Cholecalciferol (Vitamin D3) |
|---|---|---|
| Primary Source | Plants, fungi, and yeast exposed to UV light. | Animal-sourced foods (fatty fish, fish oil, egg yolks) and produced in human skin when exposed to sunlight. |
| Effectiveness | Considered less potent and effective at raising serum vitamin D levels, especially in higher doses. | More effective at raising and maintaining serum vitamin D levels over time. |
| Duration in Body | Shorter duration of action in the body compared to D3. | Stored in the body for longer periods. |
| Metabolism | Metabolized by the liver into 25-hydroxyvitamin D2, which some studies suggest may be less efficient. | Metabolized by the liver into 25-hydroxyvitamin D3, producing a more stable and potent compound. |
| Supplementation | Available in prescription and over-the-counter strengths; often used in fortified foods. | Widely available over-the-counter; the more common recommendation for supplementation due to higher efficacy. |
| Vegan-Friendly | Yes, derived from plants and fungi. | Can be vegan-friendly if sourced from lichen, but traditionally from animal sources. |
How Ergocalciferol Functions in the Body
Regardless of its origin, vitamin D in its D2 or D3 form is biologically inactive until it undergoes two essential hydroxylation steps. The first occurs in the liver, where it is converted into 25-hydroxyvitamin D (25(OH)D). This is the main form of vitamin D measured in blood tests to determine a person's vitamin D status. The second hydroxylation takes place in the kidneys, where it is transformed into the active hormonal form, calcitriol.
Calcitriol plays a critical role in calcium and phosphate homeostasis, stimulating intestinal absorption and regulating their levels in the blood. It also supports bone mineralization, muscle function, and immune health. However, some research suggests that ergocalciferol's metabolites may bind less effectively to the vitamin D binding protein in plasma, contributing to its lower efficacy compared to cholecalciferol.
Dietary and Supplemental Sources
Individuals can obtain ergocalciferol through several food sources, particularly mushrooms and fortified products. Sunlight-exposed mushrooms, including portobello, maitake, and shiitake, are some of the most concentrated natural sources of vitamin D2. Fortified foods, which are a primary source for many, include certain brands of cereals, plant-based milks, and orange juice.
For those who do not get enough vitamin D from their diet or sun exposure, supplements are a common way to treat or prevent deficiency. When choosing a supplement, it is important to check whether it contains ergocalciferol (D2) or cholecalciferol (D3). While D2 is available both over-the-counter and by prescription, D3 is often the form recommended by healthcare providers due to its greater potency and stability.
Conclusion
To answer the question, ergocalciferol is vitamin D2, the form of vitamin D found predominantly in plant-based sources and fortified foods. It plays the same fundamental role as vitamin D3 (cholecalciferol) in supporting calcium regulation and bone health. However, studies consistently indicate that vitamin D3 is more effective at raising and maintaining active vitamin D levels in the blood. While both forms are useful in treating and preventing vitamin D deficiency, the choice between them may depend on dietary restrictions and a healthcare provider's recommendation based on individual health needs. Consulting a physician before starting any new supplement is always recommended.
Frequently Asked Questions
What are the main differences between vitamin D2 and vitamin D3?
Vitamin D2 (ergocalciferol) comes from plant and fungal sources, while vitamin D3 (cholecalciferol) is from animal sources and is synthesized in human skin from sunlight. Research shows D3 is generally more effective at raising and maintaining vitamin D blood levels than D2.
Why might someone choose a vitamin D2 supplement over D3?
People who follow a strict vegan diet will typically choose a vitamin D2 supplement or a vegan D3 supplement derived from lichen, as D3 is traditionally sourced from animals. Some fortified foods are also made with the D2 version.
Which foods contain ergocalciferol (vitamin D2)?
Ergocalciferol is found in mushrooms that have been exposed to ultraviolet (UV) light, such as portobello, maitake, and crimini mushrooms. It is also commonly added to fortified foods like certain brands of milk, cereals, and orange juice.
Is ergocalciferol as effective as cholecalciferol?
While both can treat vitamin D deficiency, vitamin D3 (cholecalciferol) is considered more potent and effective at increasing and maintaining vitamin D levels in the blood. Several studies have shown that D3 produces a more stable and prolonged elevation in serum 25-hydroxyvitamin D concentrations.
Can you take vitamin D2 and D3 together?
Generally, healthcare providers do not recommend taking both vitamin D2 and D3 simultaneously. High doses of vitamin D can be harmful, and it is best to stick to one form at the dose recommended by a doctor to avoid toxicity.
How can I tell if my vitamin D supplement is D2 or D3?
The label on your supplement bottle will specify whether it contains ergocalciferol (D2) or cholecalciferol (D3). If it is not listed, the manufacturer's website may provide more information, or you can contact them directly.
Is vitamin D2 safe to take?
Yes, ergocalciferol is safe when taken at the recommended dosages. Excessive doses of any form of vitamin D can lead to toxicity and other side effects. It is important to consult a healthcare provider to determine the correct dosage for your needs.
