Vitamin D is not true vitamin can be partially synthesized in the body.

Vitamin D is lipid soluble pro hormone that is vital for bone and muscle health by promoting the metabolism of calcium and phosphate.

Vitamin D available in 2 forms a)vitamin D2 (ergocalciferol found in plants not well absorbed hence is not of nutritional valve) b) vitamin D3 (cholecalciferol synthesized in skin)

Dietary sources of vitamin D (fish liver oil, egg yolk, cheese, fortified milk, cod liver oil)

Functions of vitamin D
a) Maintain adequate level of calcium in plasma
b) Increased absorption of calcium from intestine
c) Vit D along with PTH helps in bone formation
d) Minimizes the excretion of calcium and phosphates and enhances reabsorption

Recommended daily dosage
a) Infants -10mcg/day or 400IU
b) Children - 15mcg/day or 600IU
c) Adults - 15mcg/day or 600IU
d) Pregnancy and lactation - 15mcg/day or 600IU
e) Above age of 70 yrs - 20mcg/day or 800IU/day

Normal vitamin D blood level
a) Normal range- 30-60ng/ml or 75 - 150nmol/L
b) Insufficiency 10-30ng/ml or 25-75nmol/L
c) Deficient- less than 10ng/ml or 25 nmol/L
d) High- 60-90ng/ml
e) Toxic - greater than 90ng/ml

Deficiency of vitamin D causes
a) Rickets in children and osteomalacia in adults

Role of vitamin D other than bone health
a) Role as anti cancer agent (prostate, colorectal, breast and ovarian )
b) Role in infertility
c) Risk of type 2 DM and increased prevalence in type 1 DM
d) Vitamin D in asthma
e) Role in depression
f) Heart disease

Vitamin D toxicity - level more than 150nmol/L
Symptoms and signs include - nausea, vomiting, muscle weakness, confusion, loss of appetite, dehydration, excessive urination and thrist and kidney stones. Extremely high levels can cause kidney failure, irregular heartbeat and even death.