All You Want to Know about Vitamin D
Vitamin D is a fat-soluble vitamin which acts like a hormone, regulating the formation of bone and the absorption of calcium and phosphorus from the intestine. It helps to control the movement of calcium between bone and blood, and vice versa. The two major forms of Vitamin D are vitamin D2 (or ergocalciferol) and vitamin D3 (or cholecalciferol). The term vitamin D also refers to metabolites and other analogues of these substances. Vitamin D3 is produced in skin exposed to sunlight, specifically ultraviolet B radiation.
There are three sources of vitamin D: natural sunlight, fortification of dietary foods, particularly dairy products and some cereals and oily fish. The most significant supply of vitamin D (for omnivores as well as vegans) comes from the action of ultra-violet B light on sterols in the skin. Most people, including infants require little or no extra from food when regularly exposed to sunlight when the sun is high in the sky.
Vitamin D does a lot of good to the body.
- Vitamin D plays an important role in the maintenance of organ systems.
- It regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestines, and by promoting re-absorption of calcium in the kidneys.
- It promotes bone formation and mineralization and is essential in the development of an intact and strong skeleton although, at very high levels it will promote the resorption of bone.
- It inhibits parathyroid hormone secretion from the parathyroid gland.
- Vitamin D affects the immune system by promoting immunosuppression, phagocytosis, and anti-tumor activity.
Vitamin D is rarely deficient in a person, but when it is, it causes a number of health problems:
- Impaired bone mineralization, and leads to bone softening diseases
- Rickets in children and osteomalacia in adults, and possibly contributes to osteoporosis
- Bone loss in post menopause women occurs mostly in the winter due to falling levels of vitamin D products in the blood.