What is vitamin D otherwise known as?
While "vitamin D" is the common term, this vital nutrient is also known by several other, more specific names. These different names refer to the various forms of the vitamin, from its inactive precursors to its most biologically active state. The most common alternative name is undoubtedly the "sunshine vitamin," a nickname earned because the body can produce it when the skin is exposed to sunlight.
The sunshine vitamin: A nickname from its source
One of the most defining characteristics of vitamin D is its ability to be synthesized in the skin when exposed to ultraviolet B (UVB) radiation from the sun. This unique production method is why it is colloquially known as the "sunshine vitamin." The process begins when UVB light converts a compound in the skin, 7-dehydrocholesterol, into previtamin D3, which then quickly isomerizes into cholecalciferol. Since sun exposure is the primary way most people naturally obtain this vitamin, the nickname is both accurate and widely used.
The two main forms: Cholecalciferol (D3) and Ergocalciferol (D2)
In foods and dietary supplements, vitamin D primarily exists in two forms that have different origins. Both of these are inactive and must be metabolized by the body to be useful.
Cholecalciferol (Vitamin D3)
Also known as calciol, cholecalciferol is the type of vitamin D produced by the skin in animals, including humans, upon exposure to UVB light. It is also found in some animal-based foods, such as fatty fish, beef liver, egg yolks, and cheese. Many dairy products and fortified foods in some countries are also enriched with vitamin D3.
Ergocalciferol (Vitamin D2)
Ergocalciferol is derived from plant sources, including yeast and fungi, through exposure to ultraviolet light. Foods like UV-irradiated mushrooms and yeast are natural sources of vitamin D2, and some fortified foods also use this form. Historically, this was one of the first forms to be chemically characterized.
The active form: Calcitriol
Regardless of whether it starts as D2 or D3, the vitamin must undergo a two-step activation process to become its biologically active form, calcitriol.
- First, the liver converts D2 and D3 into 25-hydroxyvitamin D, also called calcifediol. This is the major circulating form of vitamin D in the body and is what is typically measured to assess a person's vitamin D status.
- Second, the kidneys convert calcifediol into 1,25-dihydroxyvitamin D, which is calcitriol. This is the potent hormone that helps regulate calcium and phosphate levels.
A comparison of Vitamin D2 and Vitamin D3
| Feature | Vitamin D2 (Ergocalciferol) | Vitamin D3 (Cholecalciferol) |
|---|---|---|
| Source | Plants, yeast, and fungi | Sunlight exposure on skin, animal products (fatty fish, eggs) |
| Efficacy | Less effective at raising and sustaining blood levels of 25(OH)D compared to D3 | Generally more effective at increasing serum 25(OH)D levels |
| Stability | More susceptible to degradation | More stable, making it a reliable option for fortification and supplements |
| Primary Use | Often used in fortified foods and supplements, suitable for vegans | Sourced for most supplements and common in fortified dairy products |
Beyond the names: The role of Vitamin D
Understanding the various names for vitamin D is important, but it is equally vital to remember its crucial function in the body. Once activated into calcitriol, it helps maintain healthy calcium and phosphate levels by increasing intestinal absorption. This is essential for building and maintaining strong bones and preventing disorders like rickets in children and osteomalacia in adults. Beyond bone health, calcitriol also modulates cell growth, neuromuscular and immune function, and helps reduce inflammation. Maintaining sufficient vitamin D levels is important for overall health.
Lists of alternative names for vitamin D
Here are some of the most common alternative names for vitamin D and its various forms:
- Sunshine Vitamin: A popular and widely used nickname.
- Calciferol: A general term used to describe the vitamin D family of compounds.
- Cholecalciferol (D3): The form produced in the skin of animals when exposed to sunlight.
- Ergocalciferol (D2): The form produced in plants and fungi under UV light.
- Calcitriol (1,25-dihydroxyvitamin D): The biologically active hormone form created in the kidneys.
- Calcifediol (25-hydroxyvitamin D): The precursor to calcitriol, converted in the liver.
Conclusion
The question "What is vitamin D otherwise known as?" has a multifaceted answer. While most people know it as the "sunshine vitamin," its specific name depends on its source and stage of metabolism. Cholecalciferol (D3) comes from animal sources and sunlight, while ergocalciferol (D2) is plant-based. Both are converted in the body to the active hormone, calcitriol, which is critical for calcium regulation, bone health, and immune function. Knowing these different names allows for a deeper understanding of this complex and essential nutrient, including its various sources and its potent effects on overall health. Whether obtained through sun exposure, diet, or supplements, maintaining adequate vitamin D levels is crucial for preventing deficiency and supporting overall well-being.
An authoritative outbound link for further reading is provided via the National Institutes of Health {Link: National Institutes of Health https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/}.
