Vitamin D-3, or cholecalciferol, is synthesized in your skin from sun exposure. The vitamin D you take in a supplement is an inactive form that your body converts to vitamin D-3. Dietary intake is essential if you do not spend enough time outdoors or you live in areas 40 degrees latitude north or south. The sun angle will prevent adequate exposure, according to the Vitamin D Council. The recommended daily allowance for vitamin D rose in 2010.
Recommended Amount
The recommended daily allowance of vitamin D is 600 IU for adult men and women, up from the previous 400 IU. The RDA increases to 800 IU for individuals over 71 years of age. The Institute of Medicine increased the RDA in November 2010 based on scientific evidence indicating a higher need for this essential nutrient. Because vitamin D is fat-soluble, your body will store some quantities.
Benefits
The liver and kidneys convert vitamin D-3 into its active form. Its primary benefit lies in its role in calcium absorption. Without adequate vitamin D, your body cannot absorb calcium for strong bones and teeth. Instead, it will break down bone tissue to ensure adequate amounts. Its benefits do not stop at healthy bones. A 2010 study by researchers at the University of Oxford in the United Kingdom identified more than 200 genes that vitamin D influences. Scientists conclude that these findings, published in the October 2010 issue of "Genome Research," suggest a basis for the increased susceptibility to diseases stemming from vitamin D deficiencies.
Dietary Sources
Dietary sources of vitamin D are limited. Most of the vitamin D you get is probably in the form of fortified foods such as milk and breakfast cereals. Other sources include salmon, sardines and egg yolks. Vitamin D is often included in multivitamins. Select vitamins that contain no more than 100 percent of the RDA for vitamin D, making sure that the product adheres to the 2010 guidelines for dosage.
Sun Exposure
You can also ensure adequate intake through sun exposure. A 2007 study by Boston University Medical Center estimated that unprotected sun exposure can yield 10,000 IU or more of vitamin D, well over the RDA for this nutrient. However, you should limit your exposure during the peak hours of 10 a.m. and 4 p.m. to avoid increasing your risk of skin cancer.
References
- Linus Pauling Institute; Vitamin D; Jane Higdon, Ph.D., et al.; March 2004
- Vitamin D Council: UVB Exposure: Sunlight and Indoor Tanning
- Institute of Medicine; DRIs for Calcium and Vitamin D; November 2010
- Colorado State University Extension; Fat-Soluble Vitamins; J. Anderson, et al.; August 2008
- "Genome Research"; A ChIP-Seq Defined Genome-Wide Map of Vitamin D Receptor Binding: Associations With Disease and Evolution; S. Ramagopalan, et al.; 2010
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