| Question: |
| What is Cholecalciferol (Vitamin D3)? |
| Answer: |
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Vitamin D is a fat-soluble nutrient essential for bone growth and general health. It is
acquired through diet and exposure to sunlight. Light-induced synthesis occurs
in the skin when ultraviolet light reacts with a form of cholesterol, converting
it to vitamin D. This molecule is then altered by the liver and kidneys to form
the physiologically active vitamin.
Several forms have vitamin D or potential vitamin D activity. The most important
forms are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The latter is the form normally found in humans, and it is also the form typically
found in nutritional supplements.
A unique property of vitamin D is that it functions very much like a hormone.
Its target tissues include the kidneys, intestines, and bones, where it acts to
regulate calcium and phosphorus homeostasis. Its specific activity in the intestines involves
stimulating the synthesis of active transport proteins that mediate absorption
of calcium. In bone tissue, vitamin D plays a role in regulating calcium deposition (bone mineralization) and mobilization. A role for vitamin D in immune
system modulation is now under investigation.
As you can imagine, vitamin D is essential for normal bone development, particularly
in children. Without vitamin D, bones do not calcify properly, leading to the
condition known as "rickets." Vitamin D also plays an important role in tooth
development. It is necessary for proper tooth eruption, growth, and strength.
Through its role in regulating calcium and phosphorus metabolism, vitamin D plays a continuing role in maintaining
a stable nervous system, normal heart activity, and normal blood clotting.
Exposure to the sun is the most important source of vitamin D in humans. Good
dietary sources included fortified milk, certain types of fish, and fortified
breakfast cereals.
Although vitamin D can be toxic in very large doses, deficiencies (especially
subclinical) have become relatively common. In fact, in the most recent revision
of the RDAs, the recommended dietary intake for certain age groups was increased
as much as 50%.
For additional information (including a list of references), please refer to
the vitamin D technical bulletin at http://www.usana.com/dotCom/company/science/components.
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