Vitamin D is an important nutrient found in cod liver oil, sockeye salmon, mackerel, tuna, egg yolks, Swiss cheese, beef liver and fortified foods such as cereal, orange juice, milk and yogurt. The body can also synthesize vitamin D when the skin comes in contact with ultraviolet rays from sunlight. There are several different causes of vitamin D deficiency. The condition can result in weak muscles and bones, and can cause diseases such as rickets, osteomalacia and osteoporosis.
Less Exposure to Sunlight
Those that spend most of the time indoors, whether at home or at work, are unlikely to obtain sufficient amounts of vitamin D from sunlight. People that wear long robes, head coverings and other garments that cover most of the skin often have low levels of vitamin D as well. The remedy in such cases is to enhance vitamin D intake through food or supplements.
Old Age
Seniors are at increased risk of vitamin D deficiency because the skin loses its efficiency at synthesizing vitamin D from ultraviolet rays. Older people are also more likely to stay indoors most of the time, thereby reducing exposure to ultraviolet rays. Inadequate dietary intake of vitamin D is another cause of deficiency. According to the Linus Pauling Institute at Oregon State University, institutionalized seniors that do not consume vitamin D supplements have a very high risk of deficiency.
Breastfeeding among Infants
The American Academy of Pediatrics recommends a daily intake of 400 international units of vitamin D during infancy. Breast milk only provides a fraction of this amount, making breastfed infants more vulnerable to vitamin D deficiency. The risk is higher among infants that are dark-skinned, have limited exposure to sunlight or are exclusively breastfed. To prevent deficiency, caregivers must provide the recommended vitamin D supplements to infants and older babies that consume breast milk, nonfortified milk and other weaning foods.
Dark Skin
Melanin is a pigment in the skin that reduces its ability to synthesize vitamin D from sunlight. As a result, vitamin D deficiency is more common among dark-skinned people, whose skins have higher levels of melanin. The risk of deficiency is greater among dark-skinned people that live far from the equator, where there is more exposure to sunlight.
Fat Malabsorption
Fat malabsorption is the inability to efficiently absorb dietary fat from food sources. The condition adversely affects the absorption of vitamin D in the body, because it is a fat-soluble vitamin. If there is a lack of fat in the digestive tract, the body is unable to process and absorb vitamin D, resulting in a deficiency.
Obesity
Vitamin D absorption depends on body fat, but large amounts of body fat can adversely affect its availability in the body. In obese individuals, the body fat seizes a greater amount of vitamin D, which affects its circulation in the body. Gastric bypass surgery may also cause vitamin D deficiency, because it involves the bypass of a part of the intestine in which vitamin D absorption takes place.
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