• Cholecalciferol (Vitamin D 3 ) , Ergocalciferol (Vitamin D 2 )
Vitamin D is both a vitamin and a hormone. It's a vitamin because your body cannot absorb calcium without it; it's a hormone because your body manufactures it in response to your skin's exposure to sunlight.
There are two major forms of vitamin D, and both have the word calciferol in their names. In Latin, calciferol means "calcium carrier." Vitamin D 3 (cholecalciferol) is made by the body and is found in some foods. Vitamin D 2 (ergocalciferol) is the form most often added to milk and other foods, and the form you're most likely to use as a supplement.
Strong evidence tells us that the combination of vitamin D and calcium supplements can be quite helpful for preventing and treating osteoporosis. Other potential uses of vitamin D have little supporting evidence.
As with vitamin A
- Infants 0-12 months: 200 IU (5 mcg)
Males and females
- 1-50 years: 200 IU (5 mcg)
- 51–70 years: 400 IU (10 mcg)
- 71 years and older: 600 IU (15 mcg)
- Pregnant women: 200 IU (5 mcg)
- Nursing women: 200 IU (5 mcg)
However, growing evidence suggests that these recommendations may be too low. In a study of military personnel in submarines, use of 400 IU of vitamin D daily was inadequate to maintain bone health, while six days of sun exposure proved capable of supplying enough vitamin D for 49 sunless days.
There is very little vitamin D found naturally in the foods we eat (the best sources are coldwater fish). In many countries, vitamin D is added to milk and other foods like breakfast cereals and margarine, contributing to our daily intake.
As indicated by the study of submarine personnel noted above, by far the best source of vitamin D is sunlight. However, current recommendations which stress sun avoidance and the use of sunblock may have the unintended effect of increasing the prevalence of vitamin D deficiency. Severe vitamin D deficiency was common in England in the 1800s due to coal smoke obscuring the sun. During that time, cod liver oil, which is high in vitamin D, became popular as a supplement for children to help prevent rickets. (Rickets is a disease caused by vitamin D deficiency in which developing bones soften and curve because they aren't receiving enough calcium.)
Vitamin D deficiency is known to occur today in the elderly (who often receive less sun exposure) as well as in people who live in northern latitudes and don't drink vitamin D-enriched milk.
For therapeutic purposes, vitamin D is taken at the nutritional doses described in Requirements/Sources (and sometimes in even higher amounts). If you wish to exceed nutritional levels of vitamin D intake, physician supervision is recommended (see Safety Issues
Without question, if you are concerned about osteoporosis
Other uses of vitamin D are less well documented.
Some evidence suggests that getting adequate vitamin D may help prevent
One preliminary study suggests that supplementation with vitamin D and calcium may be helpful for women with polycystic ovary syndrome.
A meta-analysis (formal statistical review) of published studies found some evidence that use of vitamin D at recommended levels may reduce overall mortality.
Vitamin D is sometimes mentioned as a treatment for
It has been suggested that since vitamin D levels in the body drop in the wintertime, vitamin D supplements might be helpful for
Vitamin D supplements also do
appear to help enhance growth in healthy children.
What Is the Scientific Evidence for Vitamin D?
Individuals with severe
often have low levels of vitamin D.
Interestingly, vitamin D may offer another benefit for osteoporosis in seniors: most (though not all) studies have found that vitamin D supplementation improves balance in seniors (especially female seniors) and reduces risk of falling.
Supplementation with vitamin D plus calcium may aid healing
a fracture has occurred.
When taken at recommended dosages, vitamin D appears to be safe. However, when used at considerable excess, vitamin D can build up in the body and cause toxic symptoms. At an intake level of about 40,000 IU daily (about 100 times the recommended daily intake) vitamin D can cause dangerous elevations in blood calcium levels. 101
However, short of these vastly excessive dosages, it is not clear at what level vitamin D becomes toxic. The official safe upper limits for vitamin D daily intake are as follows:
- Infants 0-12 months: 1,000 IU (25 mcg)
- Males and females 1 year and older: 2,000 IU (50 mcg)
- Pregnant and nursing women: 2,000 IU (50 mcg)
Note, however, that some authorities believe these upper limits have been set a bit too low.
There is no disagreement that people with sarcoidosis or hyperparathyroidism should never take vitamin D without first consulting a physician.
Taking vitamin D and calcium supplements might interfere with some of the effects of drugs in the
The combination of calcium, vitamin D, and
Interactions You Should Know About
- You may need extra vitamin D if you are taking antiseizure drugs, such as:
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Last reviewed April 2009 by EBSCO CAM Medical Review Board
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