Vitamin D is the only vitamin directly derived from sun exposure in any notable amount. While you do not actually absorb vitamin D from the sun's rays, exposure to UVB radiation helps your body synthesize the nutrient. You only need about 10 minutes in the sun daily to prevent a vitamin D deficiency, so simple lifestyle changes, like walking to work, can help your body be more efficient in vitamin D production.
Vitamins D-2 and D-3
According to the Mayo Clinic, there are actually two types of vitamin D that we need for good health -- vitamins D-2 and D-3. Vitamin D-2 is produced by plants, and must be consumed through the diet. Vitamin D-3 is synthesized in your body when ultraviolet B radiation strikes your skin and converts the chemical 7-dehydrocholesterol to a previtamin form, which is transformed into vitamin D-3. The UVB rays must be from direct sunlight -- light that travels through a window or sunscreen loses the UVB rays and cannot work to produce vitamin D.
Uses
Your body uses vitamin D primarily to maintain normal blood levels of the minerals calcium and phosphorus. Vitamin D also functions to keep your bones healthy by aiding in calcium absorption. A vitamin D deficiency can contribute to diseases like rickets, the softening and weakening of bones, particularly in children. Another common disease caused by vitamin D deficiencies is osteomalacia, in which patients suffer from weak muscles and bones.
Other Sources
If you are part of a group at a high risk for vitamin D deficiency, like the elderly, breastfed infants and those with little sun exposure, you can also get vitamin D through diet. Not many foods contain Vitamin D naturally, but it is plentiful in fatty fish like salmon, tuna and mackerel. It's also added to fortified foods, like cereals and milk, and you can get it from multivitamins or specific dietary supplements.
Warnings
If you are a healthy adult, your body needs 5 mcg of vitamin D daily. If you are over 50, you need closer to 10 mcg. Your body only needs about 10 minutes of exposure to produce the vitamin D it needs, so be careful to limit your sun exposure, because UV radiation can damage your skin. An accumulation of this damage can cause skin cancer and cosmetic harm.
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