Vitamin D is a fat-soluble vitamin found in certain foods including fish, eggs and fortified milk. Vitamin D is also produced in your body by converting sunlight into the vitamin. While vitamin D is often considered to be a single vitamin, it is actually a hormone and it exists in several forms. The two forms most essential to humans include vitamin D2, or ergocalciferol, and vitamin D3, or cholecalciferol. These two terms are used interchangeably with vitamin D.
Role of Vitamin D
Vitamin D is one of the more complex vitamins needed by the body. According to the Office of Dietary Supplements, vitamin D promotes calcium absorption and is needed for bone growth and maintenance. The recommended daily intake of vitamin D is about 600 IU for adults; however, some doctors recommend significantly more depending on your diet and amount of time spent outdoors.
Vitamin D3
The form of vitamin D known as cholecalciferol, or D3, is actually formed in the body. It is synthesized by the absorption of sunlight on the skin. Vitamin D3 is created by exposure to both UVA and UVB rays without the barrier of sunscreen. Vitamin D3 can also be obtained from some animal products based on their exposure to sunlight. Many vitamin D supplements are in the form of cholecalciferol. Vitamin D3 is the most natural form of vitamin D in humans.
Vitamin D2
The form of vitamin D known as ergocalciferol, or D2, is found in plant products and in foods fortified with vitamin D such as cereals and milk. Vitamin D2 may also be found in supplements; however, the Office of Dietary Supplements states that at high doses, vitamin D2 may be less potent than vitamin D3, but at nutritional doses vitamins D2 and D3 are equivalent. Vitamin D2 is considered less shelf stable than vitamin D3, which may contribute to the decreased potency.
Deficiency of Vitamin D
Children, especially breast fed infants, who do not receive adequate vitamin D in their diets may need supplements to prevent deficiencies such as rickets or soft bones. Your pediatrician will be able to direct you towards a good supplement if recommended. In adults, osteoporosis or osteomalacia may occur as a result of prolonged vitamin D deficiency. You should not rely on the conversion of sunlight to vitamin D3 alone as a means of obtaining adequate vitamin D. Differences in skin tone, latitude on the earth, time spent in the sun without sunscreen and other factors may prevent adequate levels of vitamin D from forming from sunlight. You should discuss vitamin D with your doctor to determine if you need to begin taking a vitamin D supplement.
References
- National Institutes of Health, Office of Dietary Supplements: Vitamin D
- University of California, Riverside; Vitamin D and Milk; Anthony W. Norman; Dec. 2000
- MayoClinic.com; Vitamin D Dosing; Dec. 2010
- "The Journal of Clinical Endocrinology & Metabolism"; Vitamin D2 Is Much Less Effective than Vitamin D3 in Humans; Laura A. G. Armas, Bruce W. Hollis and Robert P. Heaney; 2004
- Vitamin D Council: Understanding Vitamin D Cholecalciferol
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