Vitamin D-3, also known as cholecalciferol, is a form of vitamin D available in food and supplements. While the body can produce vitamin D on its own when exposed to sunshine, people living in northern climates or who do not spend much time in the sun may be at risk of deficiency if they do not get supplemental vitamin D. Because of the varying levels of vitamin D production in different people and disagreement among scientists about how much is required to remain healthy, the exact amount of vitamin D-3 needed for optimal health remains controversial.
Vitamin D3
Vitamin D-3 is produced by your skin in response to sunlight. It is also available in animal-derived foods, such as fatty fish, beef, eggs and cheese. Vitamin D-3 is better absorbed by the body than other forms, such as vitamin D-2. In the body, vitamin D works to help maintain the balance of calcium in the blood and bones. Deficiencies can cause rickets, a disorder characterized by weak, brittle bones and skeletal deformities. Vitamin D is a fat-soluble vitamin, so it can be stored in fat cells for later release.
Recommended Intake
As of 2011, the recommended daily intake of vitamin D as defined by the Institute of Medicine's Food and Nutrition Board, or FNB, is 600 IU for everyone between the ages of one and 70. Older individuals need 800 IU of vitamin D. Breastfed babies may be particularly vulnerable to a vitamin D deficiency and should be given a 400 IU supplement of vitamin D-3 every day, according to the American Academy of Pediatrics. Infant formula contains adequate vitamin D so that formula-fed babies do not need additional supplementation. These recommendations are set based on minimal sun exposure, so if you spend a lot of time outdoors and live in a southern climate with a lot of sunlight year-round, you may not need as much as these guidelines instruct. Since everyone's production of vitamin D differs, only a doctor can determine what level of sun exposure produces enough for you. According to the NIH Office of Dietary Supplements, a March 2007 report by a group of vitamin D researchers suggested that the recommended intake should be much higher, around 1,700 IU a day, although the FNB has not changed its recommendation despite this report.
Upper Limit
The Institute of Medicine's Food and Nutrition Board set the upper limit for vitamin D intake based on studies suggesting that blood serum levels of vitamin D higher than 125 to 150 nmol/L are associated with a higher risk of cardiovascular problems, some types of cancer, overall mortality and falls and fractures in elderly people. Individuals over nine years old should not take more than 4,000 IU of vitamin D a day in order to keep blood concentrations at a safe level.
Common Dosages
Most multivitamins contain vitamin D-3 in doses of 400 IU per pill or tablet. Separate supplements of vitamin D-3 as the sole ingredient usually contain between 400 IU and 2,000 IU per dose. Prescription vitamin D-3 containing up to 100,000 IU per oral or injected dose is used to treat severe deficiencies.
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