Principal Proposed Uses
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 D2 (ergocalciferol) and D3 (cholecalciferol) have similar actions in the body and can both be found in fortified food and supplements.
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.
- Infants birth to age 1 year: 400 IU
- 1-70 years: 600 IU
- 70 years and older: 800 IU
- Pregnant or nursing women: 600 IU
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.)
What Is the Scientific Evidence for Vitamin D?
- Infants 0-6 months: 1,000 IU
- Infants 6-12 months: 1,500 IU
- 1-3 years old: 2,500 IU
- 4-8 years old: 3,000 IU
- 9 years and older: 4,000 IU
- Pregnant or nursing women: 4,000 IU
There is no disagreement that people with sarcoidosis or hyperparathyroidism should never take vitamin D without first consulting a physician.
Interactions You Should Know About
- You may need extra vitamin D if you are taking certain drugs, such as:
- Primidone (Mysoline)
- Valproic acid (Depakene)
- Phenytoin (Dilantin)
- Cimetidine (Tagamet)
- Isoniazid (INH)
- Reviewer: EBSCO CAM Review Board
- Review Date: 09/2014 -
- Update Date: 01/23/2015 -