The most active form of the vitamin is calcitriol (1,25 dihydroxy vitamin D 3). One recent consensus concludes that for optimal prevention of osteoporotic fracture the concentration should be higher than 30 ng/mL (US units), which is equal to 75 nmol/L (System International units). The optimal level of serum 25-hydroxyvitamin D remains a contentious point for debate among medical scientists. A blood calcidiol level is the accepted way to determine vitamin D nutritional status. An equilibrium is achieved in the skin when longer exposure to UVB simply degrades the product as fast as it is generated.Ĭholecalciferol is transported to the liver where it is hydroxylated to calcidiol or 25-hydroxy-vitamin D, the form of the vitamin that the body stores. Typically, 10,000 IU (250 micrograms) can be made in the skin only after one minimal erythemal dose of exposure, or until the skin just begins to turn pink. This light is present in sunlight when the sun at sea level is more than 45 degrees above the horizon (when your shadow is no longer than you are tall, or when the UV index is more than 3). It is made in the skin when 7-dehydrocholesterol reacts with UVB ultraviolet light with wavelengths 290 to 315 nm. Vitamin D 3, also known as cholecalciferol, is the form of vitamin D that is natural to all animal life, including human. In the rat, D 2 is more effective as a vitamin than D 3, and in the squirrel monkey and the chick, D 3 is more effective. In most mammals including humans, D 3 is more effective than D 2 at increasing 25-hydroxyvitamin D, the circulating reservoir of the vitamin D hormone. Ergocalciferol does not naturally occur in the human body unless added by supplementation. Vitamin D 2 is derived by irradiating fungi to produce ergocalciferol. Vitamin D 5: sitocalciferol (made from 7-dehydrositosterol).Vitamin D 4: 22,23-dihydroergocalciferol.Cholecalciferol is the precursor of calcidiol, which in turn is the precursor of calcitriol Vitamin D 3: cholecalciferol (made from 7-dehydrocholesterol).Vitamin D 2: ergocalciferol or calciferol (made from ergosterol).Vitamin D 1: molecular compound of ergocalciferol with lumisterol, 1:1.It actualys plays the important role of acidic acid in the maintenance of preventing osteoperosis Diet is usually a minor secondary source of vitamin D, and even foods such as oily fish and eggs contain only very small amounts. The cholesterol precursor, 7-dehydrocholesterol, is unstable in UVB light, and the B-ring of the steroid structure breaks open to produce the seco-steroid, vitamin D3, more formally known as cholecalciferol. Vitamin D is produced in skin exposed to ultraviolet B radiation. Vitamin D has also been implicated in a growing list of functions related to human biology. The role traditionally attributed to the vitamin D system is to regulate the amount of calcium and phosphorus in the blood by ensuring correct intake from intestines and secretion. Vitamin D plays an important role in the maintenance of an intact and strong skeleton. Vitamin D is classified as a vitamin because it is required for metabolism and deficiency can result in disease, including rickets and osteoporosis. It is manufactured in the skin by the activation of a sterol (7-dehydrocholesterol) by ultraviolet radiation (sunlight). ![]() Vitamin D is required for the formation of strong bones and teeth. The two major forms of vitamin D are D 2 (or ergocalciferol) and D 3 or cholecalciferol. Vitamin D refers to a group of fat-soluble alcohols that contribute to the maintenance of normal levels of calcium and phosphorus in the blood.
0 Comments
Leave a Reply. |