VITAMIN D

Vitamin D is a fat-soluble vitamin, needed by the body especially for bone health. Vitamin D3 (cholecalciferol) is the most important form of vitamin D for human body. Vitamin D is very important for absorption of calcium and phosphorus from intestines, along with reduction of calcium and phosphorus excretion from kidneys. Through these actions, vitamin D enhances the mineralization of bones. 

Importance of Vitamin D

As mentioned above, vitamin D is very important for mineralization and strength of bones. Its deficiency, especially in children and aged people, can cause skeletal weakness and many other bone diseases.

Vitamin D supplementation can reduce the risk of several heart diseases including cardial infarction, stroke etc by about 15%.

Vitamin D is also important for immune system. Its deficiency can increase the risk of viral diseases (influenza, HIV etc) and tuberculosis.

Vitamin D also has moderate positive effects on patients with depression. 

Deficiency of Vitamin D

Deficiency of Vitamin D is the reason of major skeletal health problems. Its deficiency leads to rickets, osteomalacia and osteoporosis. All these diseases are mainly due to impaired bone mineralization.

Rickets is the disease of children. Its symptoms include tenderness of bones, weakness of muscles, teeth problems, growth disturbance, bones fractures, tetany (uncontrolled muscle spasms) etc.

Osteomalacia is the disease of adults and its reason and symptoms are quite similar to rickets. It is also called ‘rickets of adults’. Both rickets and osteomalacia can be treated by administration of adequate vitamin D.
  

Osteoporosis is the disease of women after menopause and aged men. It has no particular symptom but it reduces the strength of bones and they can easily be fractured or broken. The bones of wrist, rib, hip and vertebral column are most susceptible for fractures in osteoporosis. Its treatment is different and more complex than other bone diseases as apart from administration of calcium and vitamin D, other medications are also required for treatment. 

Daily Requirement

RDA for vitamin D is 15 microgram/day for people aged 1 to 70 years. People older than 70 years need 20 microgram/day of vitamin D.

Tolerable upper intake for 9 years and older is 100 microgram/day (4000 IU/day). 

Sources of Vitamin D

Vitamin D3 can be acquired from dietary sources and ultraviolet rays of sun. In natural dietary sources, it is only present in animal fats. It is abundant in fish oils and fatty fish species especially cod liver oil, catfish, salmon, sardines, tuna etc. Moderate amounts are also present in egg yolk and beef liver. Amount of Vitamin D  in milk can be increased by placing it under UV rays of sun.

Another important source of vitamin D3 is the ultraviolet B rays of sun. Whole-body exposure in sunlight can produce 10,000 IU (250 microgram) or more vitamin D3 in about half hour. The excess of vitamin D produces through UV rays on skin has no negative effects on body. UV rays of sunlight produces vitamin D from cholesterol beneath the skin. 

Excess of Vitamin D

Like Vitamin A, vitamin D also produces negative effects in body if taken in amount higher than upper tolerable intake. It is called hypervitaminosis D and its symptoms include decreased appetite, dehydration, irritability, vomiting, constipation, muscle weakness etc. This condition can be reversed by combining low calcium diet with corticosteroid drugs.