Vitamin D, cholecalciferol, is a fat-soluble vitamin. It is found in food, but also can be made in your body after exposure to ultraviolet rays from the sun. It is one vitamin that you can directly get it from the sun light, for free! Sounds nice, eh? Vitamin D exists in several forms, each with a different activity. Some forms are relatively inactive in the body, and have limited ability to function as a vitamin. The liver and kidney help convert vitamin D to its active hormone form.
Vitamin D Facts
The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It promotes bone mineralization in concert with a number of other vitamins, minerals, and hormones. Without vitamin D, bones can become thin, brittle, soft, or misshapen. Vitamin D prevents rickets in children and osteomalacia in adults, which are skeletal diseases that result in defects that weaken bones.
Benefits of Vitamin D
Vitamin D and Calcium Metabolism
Vitamin D is crucial in calcium metabolism. Maintenance of blood calcium levels within a narrow range is vital for normal functioning of the nervous system, as well as for bone growth, and maintenance of bone density. This tight regulation is accomplished through a complex system, sometimes called the vitamin D endocrine system, because the active form of vitamin D3 has a mechanism of action similar to some hormones, for example, thyroid hormone.
Vitamin D and Calcidiol
Once vitamin D enters the circulation from either the diet or the skin, it is bound to the vitamin D-binding protein and transported to the liver. In the liver, vitamin D is hydroxylated on carbon molecule #25 to form 25-hydroxyvitamin D, also known as calcidiol. Though the synthesis of calcidiol is controlled in the liver, increased exposure to sunlight or increased intake of vitamin D3 results in increased blood levels of calcidiol, making it a useful indicator of vitamin D nutritional status.
Food With Vitamin D & Natural Vitamin D Source
Foods with vitamin D are limited compare to foods high in other vitamins. The rich food sources with vitamin D include the following categories:
Cod-liver Oil, Halibut-liver Oil, Herring, Salmon, Sardines, Tuna.
As you may see from the above, the food source for vitamin D is very limited compare to other vitamins. But the good news is with enough sun light exposure, your body can produce the rest of vitamin D that is needed. However, once again, an alarm bell is sounded for the people who are greater than age 50. Due to the fact that overall nutrient absorbtion is weaker (The ability of skin to convert vitamin D to its active form decreases as we age; the kidneys, which help convert vitamin D to its active form, sometimes do not work as well when people age), the elderly are at a higher risk of developing vitamin D deficiency. Therefore, older individuals may need vitamin D from a supplement.
Besides older individuals, the following types of people are also suggested to take some vitamin D supplements:
Children who live in sunshine deficient areas
Adults with limited sun exposure (for example, people who are institutionalized, use sunscreen or live in an area of limited sun exposure)
Anyone with inadequate caloric or nutritional dietary intake or increased nutritional requirements.
Pregnant or breastfeeding women
Those who abuse alcohol or other drugs
People with a chronic wasting illness
Those under excess stress for long periods
Anyone who has recently undergone surgery
Those with a portion of the gastrointestinal tract surgically removed
People with recent burns or injuries
Anyone with a liver impairment such as cirrhosis or obstructive jaundice