Vitamin D, also known as the sunshine vitamin, is growing in popularity as more research comes out about the vitamin and its role in health care. Few foods naturally contain vitamin D, so the best sources are from sun exposure and supplementation, according to the Office of Dietary Supplements. Although there are many types of vitamin D, it has only one natural form: vitamin D3.
Vitamin D
Vitamin D is not just a vitamin; it also breaks down into prehormones and hormones in your body. Vitamin D is most noted for its role in helping with calcium and bone density. In addition, vitamin D helps with cell growth modulation, function of your immune and nervous systems and reduction of inflammation, according to the Office of Dietary Supplements.
Vitamin D3
Vitamin D3 is the only naturally occurring form of vitamin D, also known as cholecalciferol. This form does well in your body and helps with calcium absorption. Cholecalciferol breaks down into calcidiol or 25-hydroxyvitamin D and calcitriol or 1,25-dihydroxyvitamin D. When determining vitamin D levels in your body, the best form to test for is the calcidiol form, according to the Vitamin D Council.
Vitamin D2
Vitamin D2 is a synthetic form of vitamin D also known as ergocalciferol. This form of vitamin D is common in plants. The Vitamin D Council considers this form unnatural for people because it metabolizes into products not found naturally in the body. While these metabolites are not considered harmful, cases of toxicity are more strongly associated with ergocalciferol. Any vitamin D supplement prescribed by a doctor commonly contains vitamin D2. Although ergocalciferol raises serum levels of vitamin D, the Office of Dietary Supplements states that in high doses vitamin D2 is not as effective as vitamin D3.
Dosage
If vitamin D levels in the body are normal, people between the ages of 1 and 70 only needs 600 IU a day. For people older than 70 years, the minimum requirement is 800 IU a day, according to the Office of Dietary Supplements. For infants younger than 1 year there is no established dosage, but the daily adequate intake is listed at 400 IU. In general, daily intake should not exceed 4000 IU for those over the age of 9 unless a medical condition exists. People with certain health conditions or deficiencies have tolerated doses as high as 10,000 to 50,000 IU under medical supervision. It's best to consult your physician before taking large doses of vitamin D.
Sunshine
After a few minutes in the sun, your body starts to make vitamin D under the skin. The length of time it takes to do so depends on your skin tone. The darker your skin tone, the longer the sun exposure needs to be. The Office of Dietary Supplements states that 5 to 30 minutes in the sunshine twice a week is adequate. Your body has the ability to store vitamin D, and summertime sun allows many people to stock up for the winter months.
Although sun exposure is the main way your body obtains vitamin D, it is still important to use sunscreen. The Office of Dietary Supplements notes that using sunscreen with a sun protection factor of 8 or higher seems to block vitamin D synthesis--but only if enough is applied regularly to keep all skin covered, something most people don't do when using sunscreen. This means your skin most likely makes some vitamin D even when you apply sunscreen, which is necessary to reduce risks of skin cancer.
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