Vitamin D

From WikiMD's Health & Wellness Encyclopedia

Vitamin D is a vitamin that plays a role in the absorption of calcium by the intestines and is essential for healthy bones and teeth.


Vitamin D plays a critical role in the body's absorption of calcium, phosphorus, and magnesium. Known as the "sunshine vitamin," it is synthesized by the body upon exposure to sunlight. Besides promoting healthy bones and teeth, vitamin D supports immune system function, cardiovascular health, and regulation of certain hormones.

Vitamin D exists in two primary forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both forms can be ingested from dietary sources or supplements, while vitamin D3 can also be synthesized in the skin in response to ultraviolet-B (UVB) radiation from the sun.


Vitamin D's most recognized role is in regulating the absorption of calcium and phosphorus in the intestines, thus ensuring proper formation and maintenance of bones and teeth. This vitamin also influences cell growth, immune function, and inflammatory response.

Bone Health

Vitamin D is critical for the prevention of rickets in children and osteomalacia in adults, both conditions characterized by soft, weak bones. It also helps to reduce the risk of osteoporosis, a condition that leads to bone fragility and increased fracture risk.

Immune System

Vitamin D modulates both innate and adaptive immune responses. Deficiency in this vitamin has been linked to increased susceptibility to infection, autoimmune diseases, and a higher incidence of certain types of cancer.

Cardiovascular Health

Emerging research suggests a role for vitamin D in maintaining cardiovascular health, with deficiency associated with an increased risk of hypertension, heart failure, and ischemic heart disease.

Sources and Requirements

Vitamin D can be obtained through diet, supplements, and exposure to sunlight. Food sources rich in vitamin D include fatty fish (like salmon and mackerel), fish liver oils, and egg yolks. Many countries also fortify certain foods, such as milk and cereal, with vitamin D.

The recommended dietary allowance (RDA) for vitamin D varies by age, pregnancy/lactation status, and other factors. As a general guideline, many health organizations recommend a daily intake of 600 to 800 international units (IU) for most adults.

Deficiency and Toxicity

A deficiency in vitamin D can result in rickets in children and osteomalacia in adults. Symptoms of deficiency include bone pain, muscle weakness, and fatigue. On the other hand, too much vitamin D can lead to hypercalcemia, a condition characterized by high levels of calcium in the blood, potentially causing nausea, vomiting, frequent urination, and heart rhythm problems.

See Also


(References about vitamin D, its functions, sources, and health effects can be included here.)


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Contributors: Prab R. Tumpati, MD, Spt