Vitamin D, a fat-soluble vitamin that is essential for human survival, can be found both from plants and animals, and it can be synthesized from sunlight. Though most people might consider vitamin D as just one vitamin, there are actually two totally different forms: vitamin D-2 or ergocalciferol, and vitamin D-3, also called cholecalciferol
Vitamin D
Vitamin D is essential for your survival. It's found in foods like milk and eggs, and is especially rich in fish and fish oil. Though it has a variety of important jobs to perform, vitamin D's main tasks include helping you to absorb calcium in order to maintain the health of your bones and teeth, and regulating both calcium and phosphorus. Vitamin D may even help to fight against some health issues including high blood pressure.
Vitamin D-2 or Ergocalciferol
Plants like fungus contain vitamin D-2. Foods and drinks that are fortified, such as some juices, can contain vitamin D-2 as well. You can pick up supplements of vitamin D-2. In 2004, "The Journal of Clinical Endocrinology and Metabolism" pointed out that vitamin D-2 actually contains less than one-third the potency that vitamin D-3 has, and that "physicians resorting to use of vitamin D(2) should be aware of its markedly lower potency and shorter duration of action relative to vitamin D(3)."
Vitamin D-3 Cholecalciferol
If you're looking strictly for vitamin D-3, then you'll have to turn to supplements derived strictly from animals. It comes particularly from the skin of animals, therefore most foods will not contain vitamin D-3, so you'll probably have to turn to its pill form instead. Vitamin D-3 can also be synthesized through your own skin while D-2 cannot. This happens when your bare skin is exposed to either UVA -- ultraviolet-aging -- or UVB -- ultraviolet-burning -- rays, both of which come from the sun.
Activation
When either vitamin D-2 or D-3 enters your body, it goes through a series of changes within your liver and kidneys to create what is called 1,25-dihydroxycholecalciferol. This substance is vitamin D's activated form, and it's only in that form that vitamin D will perform any biological activity.
Deficiency
Lack of vitamin D can lead to health issues, particularly problems in your bones. Children may suffer from rickets, or soft or weak bones. Adults may develop the bone disease osteoporosis. The U.S. Food and Drug Administration recommends that adults and children 4-years-old and older should obtain 400 IU daily, based on a 2,000 calorie diet.
Interesting Facts
MayoClinic.com explains that just standing in the sun for 10 minutes may keep you from suffering from vitamin D deficiency. Because it can be made by the body, vitamin D-3 is not actually a vitamin -- it's considered a steroid hormone. Vitamin D-3 can be found in sheep wool. Since vitamin D can come from the sun, it's sometimes called "the sunshine vitamin."
References
- DifferenceBetween.net: Difference Between Vitamin D and Vitamin D3
- "The Journal of Clinical Endocrinology and Metabolism"; LA Armas, BW Hollis and RP Heaney; November, 2004
- Pathophysiology of the Endocrine System: Vitamin D (Calcitriol)
- U.S. Food and Drug Administration: Appendix F: Calculate the Percent Daily Value for the Appropriate Nutrients
- University of California: Vitamin D and Milk
- MayoClinic.com: Vitamin D
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