Vitamin D is strictly not a vitamin but a hormone. It is one of the fat-soluble vitamins and therefore can be stored in the body. Vitamin D can be classified in two major forms – vitamin D2 and vitamin D3. Vitamin D2 is ergocalciferol (from plant) while vitamin D3 is cholecalciferol (from animals and humans).

Sources of Vitamin D include sunlight, food and supplements. The body produces vitamin D naturally when the skin is exposed to the ultraviolet rays (UVR) from the sun, which is why it is sometimes referred to as ‘the sunshine vitamin’. Dietary sources include salmon, mackerel, herrings, tuna, egg yolk, cheese, butter, beef liver, fortified margarine, fortified milk, fortified cereals and mushroom. Vitamin D can also be obtained through supplements. People who spend most of their day indoors and therefore not exposed to much sunlight, especially children and the elderly, can be given vitamin D supplements in addition to their diets.

Functions of vitamin D:

  1. Needed for proper absorption of calcium to build and maintain strong bones and teeth because calcium, the primary component of bone, can only be absorbed in the presence of vitamin D.
  2. Helps regulate insulin secretion thereby protecting against diabetes or support diabetes management.
  3. Supports the immune system by helping with the proper immune function of the body.
  4. Supports the brain and nervous system.
  5. Helps with the production and functioning of hormones.
  6. Protects against various cancers, including prostate and colorectal cancers.
  7. Helps control infections and reduce inflammation.
  8. Helps control mood changes like depression.
  9. Helps with proper muscle function in healthy people.

 Many countries around the world have different guidelines for the Recommended Dietary Allowance for vitamin D intake. 400-800 IU (10-20 mcg) is the general recommended daily intake.


Deficiency of vitamin D may result to:

  1. Rickets: A disease of young children and adolescents resulting from the failure of the mineralization of newly-formed bones thereby causing bowing of legs, bone pain and increase of fracture in children.
  2. Osteomalacia: This is usually referred to as an adult form of rickets caused by deficiency or impaired metabolism of vitamin D.
  3. Osteopenia: This is an end-stage bone disease due in part to chronic and severe vitamin D deficiency leading to inadequate bone mineralization which finally results to softening of the bone.               



Those at risk of Osteomalacia include:

        • Women who have had repeated pregnancies with inadequate vitamin D status, causing a drain in calcium reserves for foetal bone mineralization and lactation;   
        • The elderly due to inadequate exposure to sunlight;
        • People with celiac disease;
        • Those with kidney or liver disorders as these organs are involved in activating vitamin D in the body;
        • People on certain medication such as those for seizures.
        • People who have undergone surgery that interferes with the absorption of vitamin D in the gastrointestinal tract.


      Treatment of Vitamin D deficiency include:

      1. Getting enough, but not excessive sunlight (15 minutes per day is considered sufficient).
      2. Eating adequate dairy products which have been fortified with vitamin D.
      3. Eating other vitamin D-rich foods like fish liver which is a very rich source.
      4. Taking vitamin D supplements to make up for inadequate intake from food sources. Daily intake depends on the severity of the deficiency and in consultation with a doctor.


      Toxicity of vitamin D causes weakness, nausea, loss of appetite, headache, abdominal pains, cramps and diarrhea. Much higher intake can cause hypercalcaemia  in which the calcium level in the blood is above normal. This can weaken the bones, may cause kidney stones to develop, and may interfere with the proper functioning of the heart, brain, lungs and blood vessels.

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