Vitamin D is a fat soluble vitamin that is found in food and can also be made in your body upon exposure to ultraviolet (UV) rays from the sun. When our body is exposed to the sun, UV rays from sunlight trigger synthesis of Vitamin D in the skin.
Vitamin D has long been known for its important role in mineralization of bone and in regulating the levels of calcium and phosphorus in our body. It may play a role in the prevention and/or treatment of the following health conditions: Atherosclerosis Heart Disease, Hypertension, Breast cancer, Colon cancer, Prostate cancer, Skin cancer, Mental Illness, Depression, Epilepsy, Muscle Weakness, Chronic Pain, Inflammatory bowel disease, Kidney disease, Liver disease, Multiple sclerosis, Osteoporosis, Osteoarthritis, Periodontal disease, Preeclampsia, Psoriasis, Tinnitus, Diabetes, Obesity, Ulcerative colitis.
It was originally classified in 1922 as a vitamin by a British researcher, Edward Mellanby while researching a disease called rickets.
Vitamins are defined as nutrients that are necessary for the proper functioning of the body’s tissues and organs but cannot be produced by our body. By this definition, although “Vitamin D” is essential for calcium and phosphorus metabolism in our body and is required for the normal development of healthy bones and teeth, it is produced by our body when our skin is exposed to ultraviolet rays from the sun and therefore it does not satisfy the definition of the “Vitamin”. To add to the confusion, scientists say that there are two types of Vitamin D; Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).
The standard for measurement of Vitamin D is 25(OH)D (25-hydroxy vitamin D) and it is the best indicator of Vitamin D in our body.
Vitamin D3 (cholecalciferol) is converted from its basic building block, cholesterol, when ultraviolet rays from the sun hit the cells of our skin. Vitamin D3 must be metabolized by the liver and then by the kidneys and converted into hormonal form of Vitamin D.
Vitamin D2 is plant-based and is converted from its basic building block, ergosterol, to Vitamin D2 state when sunlight hits the leaves of the plant. It does not occur in humans and is only half as potent as D3 (cholecalciferol), does not raise serum 25(OH)D as effectively, is less bioavailable, is poorly metabolized and has shorter half-life than Vitamin D3. It is not considered equivalent to Vitamin D3 and has been associated with most of the Vitamin D toxicity.
The Institute of Medicine of the National Academy has not established an RDA (Recommended Dietary Allowances) for Vitamin D, only an AI (Adequate Intake) for otherwise healthy persons to avoid metabolic bone disease.
It was believed that 400 iu (international unit) per day was adequate. But this level turned out to be low and even 1000 iu per day was not enough for people with low level of Vitamin D to reach optimum serum level now being recommended. The 1000 iu has now become the very basic level for normal persons in addition to sunlight. Often more, to the extent of 2000 iu per day indefinitely may be needed in some cases. However, in such cases, their Vitamin D level must be tested first and then retested yearly. Individuals with osteoporosis and breast, prostate and immune health issues have greater Vitamin D needs. These individuals and those with other health concerns should consult their doctor before beginning with Vitamin regimen.