Vitamin D

An essential vitamin produced in the skin during sun exposure. Food supplements may be necessary for those who are not exposed to sunlight. Vitamin D is a generic term for a family of compounds known as vitamins D1, D2 and D3. Chemically, these substances are called sterols and their metabolic products have the ability to prevent rickets in children or osteomalacia in adults. Vitamin D is fat soluble and requires food fats which absorb the vitamin from food sources (Vitamin D Food Sources) or supplements in the digestive tract

Vitamin D is absolutely essential for bone health. The most obvious conditions related to severe vitamin D deficiency include bone: the bone deformities of infantile rickets, the soft and painful bones of adult osteomalacia or the thin, easy-to-fracture bones of older adults with osteoporosis

Why You Need Vitamin D?

Vitamin D is a fat soluble vitamin that is produced in human skin when exposed to ultraviolet light. It can also be found naturally in some foods and is added as a supplement to other foods. Vitamin D is not active until it is metabolized in the body. You need to go through two processes called hydroxylation, one in the liver and one in the kidney. The active form of vitamin D is 1,25-dihydroxyvitamin D [1,25 (OH) 2D], also called calcitriol

• Relieves the symptoms of seasonal depression
• Plays a critical role in reducing or preventing many types of arthritis
• Reduces the chance of having a heart attack or stroke
• Improves insulin release and liver and muscle response to insulin, which means normal levels of vitamin D can help prevent diabetes
• Helps you develop a healthy immune system in childhood
• Plays a key role in regulating cell growth and differentiation, which can prevent cancer

The Forms of Vitamin D

Vitamin D is found in four forms. Cholecalciferol is produced by the skin when the skin is exposed to direct sunlight containing the form B of ultraviolet radiation (UVB). Cholecalciferol is also called vitamin D3. It is the form used in many supplements and is sometimes used in food fortification

Vitamin D3, cholecalciferol, is produced on the skin or taken as a supplement (Vitamin D supplements)

• Calcidiol is the form of conservation and circulation of vitamin D
• Calcitriol is the active form of vitamin D
• Vitamin D2, ergocalciferol, is produced by irradiating mushrooms

Calcidiol is produced by cholecalciferol in the liver. Calcidiol is the form of vitamin D that is stored in the liver. It is a precursor to the calcitriol hormone. Blood tests for calcidiol can determine if there is enough vitamin D present or if there is a deficiency. The chemical name of calcidiol is 25-hydroxyvitamin D

Calcitriol is composed of calcidiol, mainly in the kidneys. It is the most potent steroid hormone derived from cholecalciferol. Calcitriol is the active form of vitamin D. It regulates calcium and has anticancer properties. The chemical name of calcitriol is 1,25-dihydroxyvitamin D

Ergocalciferol, vitamin D2, is produced by irradiating ergosterol with ultraviolet light. Ergosterol is derived from the ergot mushroom. It is an artificial product and is not found in the human body unless taken as a supplement or in fortified foods

Normal daily requirement

The required amount of vitamin D is expressed as an adequate intake (AI) rather than a required daily amount (RDA). This is due to the difficulty of quantifying the amount of vitamin produced by the body with exposure to sunlight. Instead, AI estimates the amount needed to eat to maintain normal function. It is measured in international units (IU) and there are 40 IU in one microgram (mcg)

The recommended daily quantities (RDA) of vitamin D are: 8.5 mcg (birth - 6 months); 7 mcg (from 7 months to 3 years); 10 mcg (over 65 years and pregnant or lactating women). Most people outside these groups do not require vitamin D food supplements. 1 mcg of vitamin D equals 40 international units (IU)

How Do You Determine Vitamin D Status?

People need to take enough vitamin D to avoid failure symptoms, but some of these are not obvious. Researchers are trying to calibrate blood tests to be very consistent and correct in detecting low, normal and high levels of potentially toxic vitamin D

The best blood test currently to evaluate the state of vitamin D is the serum 25 (OH) D or hydroxyvitamin D concentration. This provides an indication of the D state when produced in the skin or taken with food or supplements

• Normal range: 16 to 65 pg / ml for 1.25 (OH) D; 50 to 70 mg / ml for 25 (OH)D

• Elevated in: excessive oral intake, tumor calcinosis, primary hyperparathyroidism, sarcoidosis, tuberculosis, idiopathic hypercalciuria