The vitamins information pages - Vitamin D
Vitamin D is a fat-soluble vitamin that exists in various forms. The form mainly used by humans is cholecalciferol (vitamin D3). This vitamin is formed when cholesterol in the skin is exposed to ultraviolet sunlight. Vitamin D only has physiological effects when it is first modified by the body.
Vitamin D is essential for development bone growth and density and for functioning of the nervous system. The regulation is accomplished by the so-called vitamin D endocrine system, which functions in a way similar to the thyroid hormone. Vitamin D is also essential for heart functioning. It also plays a role in calcium metabolism. Deficiency causes rickets (child bone mineralization failure), poor growth, bone deformities such as osteoporosis and joint pain. It also interferes with T lymphocyte-mediated immunity. This means that antigens of xenobiotics (foreign substances or cells) in the body are no longer recognized, or that autoimmune disease may occur. Autoimmune disease cause the immune system to battle private body cells, rather than xenobiotics.
Vitamin D in food
Vitamin D is usually obtained from sunlight, but there are some food stuffs that contain the vitamin. Examples include dairy products, fish oil, liver and egg yolk. Margarines may be fortified with vitamin D.
Vitamin D as a supplement
Vitamin D medication is recommended to people on law fat diets, vegans and people that are usually not exposed to bright sunlight or have moved to regions with a colder climate. Calcitriol, a synthesized form of vitamin D, can be applied in case of psoriasis. Psoriasis is a skin disorder causing rapid proliferation (rapid cell division as observed in case of skin wounds) of cells. This also leads to the belief that vitamin D may aid cancer treatment and prevention. Some studies have indeed shown a correlation between vitamin D deficiency and certain types of cancer, such as prostate cancer.
Calcium deficits may lead to a lack of vitamin D adsorption and vice versa. Vitamin D increases bone calcium mobilization and calcium readsoption by the kidneys. Long-term treatment with anti epilepsy medication can affect hepatic metabolism of vitamin D. Cholesterol-lowering medication and antifungal drugs may decrease intestinal adsorption of vitamin D.
People taking heart medication may not take vitamin D.
Descriptions of vitamins on this website are based on information provided by BBC Health and The Linus Pauling Institute.