Image Caption : Sunbathing Woman with Skeletal System, Renal Anatomy and Vasculature : Vitamin D is called the "sunshine vitamin" because the body synthesizes its own Vitamin D when skin is exposed to sunlight. Small amounts are available in a handful of natural foods, though most of the Vitamin D in American diets comes from fortified foods. The type of Vitamin D synthesized from the sun's ultraviolet rays is Vitamin D3, or cholecalciferol. Vitamin D2, or ergocalciferol, originates in plants. Once in the system, both are converted by the liver and kidneys into an active form, 1,25-dihydroxyvitamin D, which is involved in several essential functions.
Health authorities scratch their heads over sunlight recommendations since UV exposure is the leading cause of skin cancer. Once you sort out the mixed messages, the upshot is that a little UV exposure without protection - about two half-hour periods in mild sun per week - is probably adequate, with Vitamin D supplies to be topped off by fortified foods. The amount of D that you derive from sunlight should be qualified by what you know about your own susceptibility to skin cancer, paying attention to risk factors such as skin type, geographical location, and family history.
Also called: Cholecalciferol, Ergocalciferol
Vitamin D helps your body absorb calcium. Calcium is one of the main building blocks of bone. A lack of vitamin D can lead to bone diseases such as osteoporosis or rickets. Vitamin D also has a role in your nerve, muscle, and immune systems.
You can get vitamin D in three ways: through your skin, from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. However, too much sun exposure can lead to skin aging and skin cancer. So many people try to get their vitamin D from other sources.
Vitamin D-rich foods include egg yolks, saltwater fish, and liver. Some other foods, like milk and cereal, often have added vitamin D.
You can also take vitamin D supplements. Check with your health care provider to see how much you should take. People who might need extra vitamin D include
- Breastfed infants
- People with dark skin
- People with certain conditions, such as liver diseases, cystic fibrosis and Crohn's disease
- People who are obese or have had gastric bypass surgery
NIH: National Institutes of Health Office of Dietary Supplements
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