The Importance of Vitamin D

Vitamin D plays an important role in the maintenance of normal blood levels of calcium and phosphorus, as well as mineralization of bone.

Vitamin D can be produced in the skin or consumed with fortified foods. Then it requires conversion in the liver and kidney, where Vitamin D turns into its physiologically active form - 1, 25 dihydroxyvitamin D (calcitriol).

Vitamin D in foods
Food sources of vitamin D include:

  • Fortified foods, e.g. milk or breakfast cereals;
  • Fish: salmon, sardines, mackerel, tuna fish, cod;
  • Eggs.

Vitamin D in the skin
The body starts manufacturing vitamin D when the skin is exposed to the sun or UV light. The amount of vitamin D produced by the skin in a certain period mainly depends on the amount of melanin in the skin.

The role of melanin is to absorb ultraviolet radiation and protect the skin from the damaging rays.

Thus, if your skin is rich in melanin, you have to spend much more time exposed to ultraviolet B radiation, so that your skin would be able to produce sufficient amounts of vitamin D.

In addition it should be mentioned, that sunlight exposure is considered to be the major source of Vitamin D, as it is nearly impossible to obtain sufficient amounts of vitamin D from foods.

Vitamin D deficiency
There are several possible reasons for deficiency of vitamin D. These are:

  • inadequate dietary intake of vitamin D;
  • limited exposure to sunlight;
  • inability of kidney to convert vitamin D to its active form.

Vitamin D deficiency diseases
In infancy and childhood, lack of vitamin D may cause rickets, which leads to bone deformities.

In adults, vitamin D deficiency causes osteomalacia, which results in bone and muscular weakness.

It was also claimed that deficiency of vitamin D may cause a number of other diseases, including: heart disease, arterial hypertension, stroke, cancer, autoimmunity, diabetes, depression, nervousness, degenerative arthritis.

Vitamin D Excess
Excessive intake of vitamin D causes toxicity and can lead to hypercalcemia. Early signs and symptoms of Vitamin D excess are:

  • Loss of appetite,
  • Nausea,
  • Headache,
  • Excessive thirst,
  • Overall weakness.

Low-calcium diet is essential in treatment of vitamin D excess.

Adequate intake (AI) for vitamin D
In 1997, the National Academy of Sciences established the following Adequate Intake (AI) levels for vitamin D:

Infants: 5 micrograms/ 200 International units (IU)
Children: 5 micrograms / 200 IU
Teenagers: 5 micrograms / 200 IU
Adults 19-50 years of age: 5 micrograms / 200IU
Adults 51-70 years: 10 micrograms / 400 IU
Adults above 70 years: 15 micrograms / 600 IU
Pregnant and lactating women: 5 micrograms / 200 IU

Summarizing, vitamin D plays an important role in calcium absorption and mineralization of bones. Vitamin D deficiency and excess can be harmful to your body. Therefore, it is vitally important to consume AI of Vitamin D.


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