Vitamin D (Calciferol)

Vitamin D is known as the “sunshine vitamin” because modest exposure to sunlight should be sufficient for most people to produce their own vitamin D using ultraviolet light and cholesterol in the skin. In this form, vitamin D3 (1,25­dihydroxyvitamin) plays an important role in the maintenance of calcium homeostasis and healthy bones and teeth, as well as influencing hundreds of genes. Little vitamin D is stored in the liver.

Functions

  • Vitamin D maintains calcium and phosphorus homeostasis
  • Essential for normal bone growth during childhood
  • Integrated function with parathyroid hormone in stabilization of calcium level in blood

Sources

Vitamin D3 exists naturally in animal products, and the richest sources are fish liver oils. It is found in only small and highly variable amounts in butter, cream, egg yolk, and liver. Human milk and unfortified cow’s milk tend to be poor sources of vitamin D3, providing only 0.4 to 1 mcg/L.

Deficiency
Vitamin D deficiency manifests as rickets in children and as osteomalacia in adults. Vitamin D deficiency can also precipitate and exacerbate osteoporosis and fractures in adults and is associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases. Inadequate vitamin D intake is prevalent around the world, regardless of age or health status.   

It has been estimated that as little as 10 to 15 minutes of sun exposure on a clear summer day two or three times a week is sufficient to prevent osteomalacia among most older adults. Osteomalacia can be treated effectively with vitamin D3 in doses of 25 to 125mcg (1000 to 1250 IU/day); in those whose conditions are complicated by lipid malabsorption, daily doses as large as 1250 mcg (12,500 IU) have been used.


 

Signs of Vitamin D Toxicity :

  • Excessive calcification of bone
  • Kidney stones
  • Metastatic calcification of soft tissues (kidney, heart, lung, and tympanic membrane)
  • Hypercalcemia
  • Headache
  • Weakness
  • Nausea and vomiting
  • Constipation
  • Polyuria
  • Polydipsia

DRIs (Recalculated in micrograms of D3: IU 0.025 mcg; 1mcg 40 IU.)

Infants:  10 mcg (400 IU)

Children and adolescents:  15 mcg (600 IU)

Adults:  15 mcg (600 IU)

Adults > age 70:  20 mcg (800 IU)

Pregnant:  15 mcg (600 IU)

Lactating : 15 mcg (600 IU)