Vitamin D is essential for the body's ability to absorb calcium and to maintain calcium and phosphate levels in the blood. This allows for the normal mineralization of bone, the reduction of inflammation, and healthy neuromuscular and immune function. While vitamin D is found in certain foods the primary sources of vitamin D is exposure to sunlight and fortified milks or juices. As a fat-soluble vitamin, the body stores excess vitamin D in fat cells until it is needed.
Function of Vitamin D
Vitamin D plays a major role in biological functions. According to the National Institute of Health, one of its main roles is the regulation of calcium and phosphorus blood levels. However, it also aids in the absorption of calcium helping to maintain strong bones, preventing hypocalcemic tetany, and reducing the risk of osteoporosis. Vitamin D may also reduce the risks of hypertension, cancer, diabetes, glucose intolerance, multiple sclerosis, and several other autoimmune diseases.
Sources of Vitamin D
Vitamin D can be found in some foods including fish, eggs, and fortified milks and juices. However, the body produces the majority of its vitamin D when it is exposed to sunlight. When human skin is exposed to the ultraviolet-B, or UVB, rays in sunlight, it synthesizes vitamin D3. As little as 10 minutes of sun exposure a day is enough to meet the daily requirement for vitamin D and prevent deficiencies, according to MayoClinic.com.
Deficiencies
A vitamin D deficiency occurs when the absorption of vitamin D from the digestive tract is inadequate or the exposure to sunlight is so limited the kidneys cannot convert vitamin D to its active form. Vitamin D deficiencies can lead to rickets and osteomalacia. Rickets occurs in children and can result in weak bones and skeletal deformities. In adults, a vitamin D deficiencies can lead to osteomalacia. Osteomalacia results in bone pain, a weakening of the skeletal structure and muscular weakness. However, the early symptoms of both rickets and osteomalacia are subtle and can initially go undetected.
At Risk Populations
Those who are most at risk for vitamin D deficiencies include the elderly, the obese, exclusively breastfed infants, those suffering from fat malabsorption syndromes or inflammatory bowel disease, and those who have a limited exposure to sunlight. Certain dietary restrictions, including lactose free diets and strict vegetarians, have also been associated with vitamin D deficiencies. The extensive use of sunscreen can also be a contributing factor to a vitamin D deficiency.
Dosages
Many factors dictate how much vitamin D the body can synthesis. Seasons, geographic location, time of day, cloud cover, smog, skin melanin, and sunscreen are just some of the factors which can affect the body's production of vitamin D. Complete cloud cover, windows, and properly applied sunscreen, can completely block UVB radiation. In general, around 10 minutes of sun exposure a day or 30 minutes of sun exposure at least twice a week should allow for the sufficient production of vitamin D. For those who do not get adequate sunlight, the National Institutes of Health recommends the intake for vitamin D be between 5 and 15 mcg a day, depending on age.
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