Vitamin D is a fat-soluble vitamin that can be obtained from supplements, food sources and sunlight. It is critical for building and maintaining healthy bones and deficiency may cause bone diseases such as osteoporosis. Vitamin D is also central to a variety of body processes including immune system function, regulation of cell growth and hormone production.
Amount
The guidelines for vitamin D intake were raised by the Institute of Medicine in 2010 following a comprehensive review of scientific and medical research. The recommended dietary intake of vitamin D is 600 IU per day for women and men under the age of 70. The amount is the same regardless of whether a woman is pregnant or breastfeeding. For adults over the age of 70, the recommendation is 800 IU per day.
Supplements
Most vitamin D supplements that are available over-the-counter contain vitamin D-3, also called cholecalciferol. Vitamin D-2 is also available but appears to be less potent. Some multivitamins contain significant amounts of vitamin D; you should check the labels for dosing information before adding any additional supplements. A number of calcium supplements contain vitamin D in combination, since both compounds are important for bone health.
Food Sources
Vitamin D occurs naturally in only a few common foods. Fatty fish, such as mackerel, salmon and sardines, are high in vitamin D. In the United States and Canada, all commercially available milk is fortified with vitamin D. Some types of orange juice, cereals and breads are also fortified with this vitamin.
Sunlight
Sunlight triggers your body to produce its own vitamin D. However, people living in the northern hemisphere may not receive enough sun exposure during the winter months to meet their vitamin D needs. People with dark skin are at a higher risk because they absorb less sunlight. Sunblock also blocks the absorption of vitamin D, but is recommended because it reduces the risk of skin cancer. Taken together, these factors mean that it may be difficult to meet your vitamin D needs from sunlight alone.
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