Causes of vitamin D deficiency
Vitamin D deficiency is common around the world. It can be caused by several factors.
Not enough sunlight
Not enough exposure to sunlight is the most common cause of vitamin D deficiency. This occurs in people who do not spend much time outside. It is also common among older or sick people who live in a nursing home, are hospitalized or housebound.
Vitamin D deficiency is also common with people who live in far northern or far southern parts of the world. This is because there is less exposure to sunlight during longer winter seasons.
This type of Vitamin D deficiency can also occur in people who keep their bodies fully covered most of the time.
Breastfed babies who are not exposed to sunlight may also be at risk for vitamin D deficiency. Breast milk does not contain enough vitamin D for their development.
Not enough in your diet
Vitamin D deficiency can also occur because you don’t get enough from your diet.
Some countries don’t fortify their milk products with vitamin D. People who are lactose intolerant or who don’t consume dairy products or vitamin-rich foods also may not get enough.
Kidney or liver disease
Some people may not have enough vitamin D because their liver or kidneys cannot convert vitamin D to its active form. This can cause deficiency.
Malabsorption disorder
Vitamin D is a fat-soluble vitamin, which means it is stored in your fatty tissue and liver.
If you have a malabsorption disorder or you are unable to absorb fats, you may not be able to absorb enough vitamin D from food.
Medications
Some medications may interfere with your body’s ability to absorb or convert vitamin D.
These may include anticonvulsants, glucocorticoids, antifungal drugs, medicines for autoimmune disorders, and the antibiotic rifampin.
Sunscreen
Even if you get enough sunlight, there may be times when your skin forms less vitamin D. This may occur in older people, people who have darker skin, and people who wear sunscreen.
Certain other conditions or diseases may also cause vitamin D deficiency. These include:
Source: http://www.medicinenet.com/script/main/art.asp?articlekey=252453
