Vitamin D is a fat-soluble vitamin essential for calcium absorption, bone health, and immune function. It exists in two main forms: D2 (ergocalciferol) and D3 (cholecalciferol), both of which are converted to the active form, calcitriol.
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important forms are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol). Vitamin D3 is naturally produced in human skin by exposure to ultraviolet B (UVB) light from sunlight. Vitamin D2 is derived from plant sources and yeast. Both forms are converted in the liver and kidneys to the active form, calcitriol, which regulates calcium homeostasis.
Key Information
Inside Body Harmful Score
Common Dosage
400-2000 IU daily
Source Type
Natural (D3 from sunlight or animal sources), Synthetic (D2 and some D3)
Production Process
Vitamin D3 is produced commercially by irradiating 7-dehydrocholesterol (derived from lanolin) with ultraviolet light. Vitamin D2 is produced by irradiating ergosterol (derived from yeast).
Use Type
Inside BodyClassification
Dietary Category
Vitamins
Primary Category
Vitamin D
Efficacy Tier
Tier 2: Moderate/StandardVitamin D3 and D2 require conversion in the liver and kidneys to their active form, calcitriol. This two-step conversion process results in moderate bioavailability.
Conversion Steps
2 steps (Minor conversion)
Potential Benefits
Enhances bone density, strength, and integrity by supporting bone formation, calcium absorption, and reducing age-related bone loss. Improves overall skeletal health and function, ultimately reducing the risk of fractures.
Muscle preservation maintains existing muscle mass and prevents atrophy by balancing anabolic and catabolic processes through resistance exercise, adequate protein and caloric intake, and hormonal regulation. It's vital for strength, mobility, and metabolic function.
Prenatal health focuses on the well-being of pregnant women and their developing fetuses through adequate nutrition, managing health conditions, and preventing complications. This care aims to reduce birth defects, promote healthy development, and optimize maternal and infant health.
Hair loss prevention reduces hair thinning and shedding by improving scalp health, strengthening hair follicles, and addressing hormonal imbalances. This leads to increased hair density, new hair growth, and improved hair appearance.
Possible Side Effects
High vitamin D can cause high calcium, leading to nausea and weakness.
Long-term high calcium from vitamin D may increase kidney stone risk.
Scientific Evidence
Numerous studies demonstrate Vitamin D's role in calcium absorption, bone health, and immune modulation. Evidence levels vary based on the specific health outcome but are generally moderate to very strong (levels 3-5) for bone health and immune function.
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