The Core Difference: Cholecalciferol vs. Ergocalciferol
To understand why not all vitamin D has cholecalciferol, one must first recognize that the term "vitamin D" refers to a group of related fat-soluble secosteroids. The two primary forms of this vitamin found in foods, supplements, and our bodies are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Their chemical structures differ slightly, with the most significant variation lying in their origin.
Cholecalciferol (Vitamin D3)
Cholecalciferol is the type of vitamin D that is naturally synthesized in the skin of animals, including humans, when exposed to ultraviolet B (UVB) radiation from sunlight. For many people, this cutaneous synthesis is the primary source of vitamin D. It is also found naturally in a limited number of animal-based foods, such as the fatty flesh and liver oils of fish like salmon and trout, as well as in egg yolks and cheese. Vitamin D3 is widely used in dietary supplements and for fortifying products like cow's milk. Vegan-friendly D3 supplements are also now available, sourced from lichen.
Ergocalciferol (Vitamin D2)
Ergocalciferol, or vitamin D2, is produced by plants and fungi, such as mushrooms, when they are exposed to UV light. Historically, D2 was the most common form of vitamin D used to fortify foods like milk, breakfast cereals, and orange juice. It is also found in many plant-based supplements. For individuals on a strict vegan or vegetarian diet, D2 supplements and UV-exposed mushrooms have traditionally been the main dietary sources of vitamin D.
Comparison of Vitamin D2 and Vitamin D3
| Feature | Cholecalciferol (Vitamin D3) | Ergocalciferol (Vitamin D2) |
|---|---|---|
| Primary Source | Skin synthesis (from sun), animal products (fatty fish, egg yolks), supplements from lanolin or lichen | Plant and fungi products (mushrooms exposed to UV), fortified foods, supplements |
| Animal-Free Option | Yes, derived from lichen | Yes, is inherently plant-based |
| Efficacy | Generally considered more potent and effective at raising and maintaining serum 25(OH)D levels in the bloodstream | Less effective than D3 at raising and sustaining serum vitamin D levels, though still effective for preventing and treating deficiency |
| Manufacturing | Produced industrially by irradiating 7-dehydrocholesterol from lanolin (sheep's wool) or lichen | Produced commercially by irradiating ergosterol from yeast |
Why Potency and Source Matter
Research has shown that while both forms are effective at increasing blood vitamin D levels, vitamin D3 is more efficacious at raising and sustaining those levels over a longer period. This difference in potency is a key consideration when choosing supplements, especially for those with vitamin D deficiency. The liver metabolizes D2 and D3 slightly differently, leading to D3 resulting in higher concentrations of calcifediol, the main circulating form of vitamin D. For this reason, many healthcare professionals may favor vitamin D3 supplementation.
It is also crucial to consider the source when making dietary choices or selecting supplements.
- For omnivores: The body can create its own D3 from sunlight, and it is found in certain animal products. Supplements are available in both D2 and D3 forms.
- For vegans/vegetarians: D2 is readily available from fortified plant-based foods and supplements. Vegan D3 derived from lichen offers another effective option for those seeking a non-animal source.
- For those with limited sun exposure: Living in a region with limited winter sunlight, or staying indoors frequently, can reduce the body's natural production of D3, making supplementation or consuming fortified foods essential.
To ensure you are getting the vitamin D that aligns with your dietary preferences and health goals, always check the product's label. This is especially important for those following plant-based diets, as many fortified products traditionally contained D2, though this is changing with the availability of vegan D3.
The Final Word: Does all vitamin D have cholecalciferol?
No, all vitamin D does not have cholecalciferol. The term encompasses multiple forms, primarily ergocalciferol (D2) and cholecalciferol (D3). While both are important for health and bone structure, they have different origins and potencies, with D3 generally considered more effective at raising and maintaining blood levels. The choice between D2 and D3 depends on dietary preferences, lifestyle factors, and specific health needs. Always consult with a healthcare provider to determine the best course of action for your individual situation. For more detailed information on vitamin D, its forms, and its role in the body, the NIH Office of Dietary Supplements provides authoritative fact sheets.
Lists of Vitamin D Forms and Sources
Common Forms of Vitamin D:
- Cholecalciferol (Vitamin D3): Made in the skin from sunlight; found in fatty fish, egg yolks, and some fortified foods.
- Ergocalciferol (Vitamin D2): Produced by UV-exposed plants and fungi; found in some mushrooms and fortified products.
Natural Sources of Vitamin D3:
- Fatty fish (salmon, tuna, mackerel)
- Fish liver oils
- Egg yolks
- Beef liver
Natural Sources of Vitamin D2:
- UV-exposed mushrooms
Commonly Fortified Foods:
- Milk (cow's and plant-based)
- Ready-to-eat cereals
- Orange juice
- Yogurt
- Margarine
Important Consideration for Vegans:
- Check labels for 'vegan D3' from lichen to ensure you are consuming a non-animal source of cholecalciferol.
