Vitamin D: Deficiency, Dosage and Sources

What is Vitamin D?

The scientific name of vitamin D is Cholecalciferol. It is a fat soluble vitamin. Vitamin D is required for bone growth and calcium metabolism. Vitamin D plays an important role in the absorption of dietary calcium from the intestine and its deposition in bone. Gross deformities of bone may therefore result if enough vitamin D is not available to the body.

How it works in our body

Vitamin D (cholecalciferol) does not act directly to discharge its functions in the body. Recent studies have shown that it is first converted into 25 hydroxy cholecalciferol in the liver and subsequently to 1,25-dihydroxy cholecalciferol (1,25 DHCC) in kidney. 1,25-DHCC is the active form of the vitamin which functions in the body. Apart from the lack of vitamin D, a deficiency in the conversion of the vitamin D to its active form can also cause rickets/osteomalacia. Vitamin D acts like a hormone in the body.

Causes of vitamin D deficiency

Deficiency of vitamin D occur when you are not taking recommended level of vitamin D as per time.
Certain people given below are at higher risk of vitamin D deficiency:

  1. who spent very less time in sunlight or keep themselves covered when outside.
  2. People who are bound to stay at closed spaces due to their work or something.
  3. People with very dark skin may have vitamin D deficient.
  4. People who eat less dairy products or are lactose intolerant.
  5. Who have certain medical conditions like bowel disease may be vitamin D deficient.
  6. Overweight people.
  7. Older adults.

Disease due to vitamin D deficiency

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Rickets is a disease of children in growing years caused by the deficiency of vitamin D and calcium. This disease leads to the softening and distortion of bones, weaker bones with abnormal shape and fracture.

Vitamin D or cholecalciferol is formed in the skin by the ultraviolet rays present in sunlight which converts a cholesterol derivative (β-dehydrocholesterol) present in the skin to vitamin D(cholecalciferol). Therefore, rickets do not generally occur in children normally exposed to sunlight, but may develop among those who live in dark and dingy households. This deficiency occur in temperate climates where exposure to sunlight is limited, unless vitamin D is obtained through food.

Probably, minor degree of rickets is more common in infants and young children. Malnourished children with protein deficiency may also develop rickets probably due to poor conversion of vitamin D to the active form of vitamin D. The most in expensive way to get vitamin D is exposure to sunlight which is freely available in plenty, particularly in tropical countries.


It is the abnormal softening of bones caused by deficiencies of vitamin D or calcium or phosphorus. Osteomalacia manifests itself initially as pain in bones, usually starts during pregnancy when the demand for calcium is
raised to meet the increased need of the growing foetus in the womb. After the child birth, the disease may regress but it may recur in a more severe form in the subsequent pregnancies. Ultimately, the bones of the victim may become so bent that the woman is unable to stand upright and distortion of the pelvis may cause child birth very difficult. A good supply of vitamin D during pregnancy benefits the mother and helps satisfactory development of the infant.


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AgeRcommended amount of vitamin D per day
0 to 1 year400 IU
1 to 70 years600 IU
over 70 years800 IU

IU- interantional units

This requirement may be obtained in great measure in tropical countries through exposure to adequate sunlight. In those cases where vitamin D requirement is not met through adequate exposure to sunlight or due to metabolic or genetic reasons, supplementation of vitamin D may be necessary. One gm of pure vitamin D is equivalent to 40 million IU, i.e., (400 IU= 10 μ g) of the vitamin. People who take certain medications or have specific medical conditions, such as osteoporosis, may have different vitamin D or calcium needs and should speak to their health care provider.


Excessive intake of vitamin D can lead to toxic symptoms, which include irritability, nausea, vomiting and constipation. Cases of toxicity in children have been reported even with prolonged daily intake of a dose as low as 1000 IU.

Sources of vitamin D


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It is the cheapest and biggest source of vitamin d. It is available almost every part of the globe. Sunlight spurs the body to make vitamin D. But because of the skin cancer risk, it is not recommended to everyone. However, a small amount of sun exposure without sun screen can be beneficial to health. About 20 to 25 minutes of exposure a day is helpful and enough. If we are at higher latitudes, sun alone can not provide your daily needs of vitamin D. This process is less efficient with age so if you are older then you may see a doctor instead of sun.

Non vegetarian sources :

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Fish – Fish can be a good source of vitamin d. common fish includes tuna, salmon, trout, mackerel and eel. Fresh fish aren’t the only way to take vitamin D, yo can get vitamin D from a can too. Canned fish like sardine and tuna are less expensive than fresh fish and have a good dose of vitamin D. they contain about 150 IUs per 4 ounces.

Egg Yolks – eggs are very convenient to get vitamin d. we can have egg in breakfast, lunch and dinner. But keep in mind that we have to consume full egg not just egg white. One egg yolk will give you about 40 IUs but try not to take all of your vitamin D just from eggs because one egg contains about 200 milligram of cholesterol and we should not consume more than 300 milligram of cholesterol a day for a good heart.

Vegetarian sources

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Fortified milk – 8 ounces of milk contain at least 100 IUs of vitamin d and 6 ounces of yogurt contain 80 IUs.

Soy yogurt – soy yogurt fortified with vitamin D has 80 UI of vitamin D in 150 gram.

Fortified cereals – you can get a part of your daily vitamin D from low calorie cereals.

Dietery supplements :

Vitamin D3

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In dietary supplements, vitamin D is available in two forms, they are vitamin D2 (ergocalciferol) and vitamin D3(cholecalciferol). But, vitamin D3 is more beneficial than vitamin D2. Before taking a vitamin D supplememt, make sure that other supplement or medication you are taking contain vitamin D. Some calcium supplements also have vitamin D in it.

You can buy vitamin D3 (5000 IU) here

To buy a high dose of vitamin D3 (once a week), check here.

It is recommended that you consult to your health care provider before taking these supplements.

Cod liver oil

Cod liver oil is well known for its naturally occuring omega 3 fatty acid vitamin A and vitamin D3. Vitamin A is essential for normal vision and vitamin D for healthy bones.

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