Vitamin D is a fat soluble family of compounds known as vitamins D1, D2 and D3. It is obtained from some foods such as fatty fish, fortified milk, liver and egg yolks, and, unlike other vitamins, it can be created in the skin through the action of sunlight.
The most important role of vitamin D is to regulate the absorption and use of calcium and phosphorus, vital for normal growth and development of bones and teeth. Vitamin D stimulates intestinal absorption and reabsorption in the kidneys as well as maintaining blood levels of calcium and phosphorus. It enables bones and teeth to harden by increasing the deposition of calcium and may also assist in the movement of calcium across body cell membranes.
Vitamin D plays a role in the secretion of insulin by the pancreas thus aiding in the regulation of blood sugar. It also affects the parathyroid gland and a hormone that it produces due to its calcium regulating role.
Potential benefits of vitamin D are that it fights osteoporosis, osteomalacia, breast, prostate and colon cancer, some deafness, diabetes and acne. High amounts may have been found to be anti-cancer.
The production of vitamin D in the body is blocked by anything which blocks ultraviolet light including skin pigment, smog, fog, sunscreen, windows and hats.
In cases of vitamin D deficiency the body increases production of a hormone that removes calcium from the bones. In children, this results in rickets where the bones are so soft that they become curved from supporting the weight of the body. The equivalent in adults is osteomalacia with bone pain and tenderness and muscle weakness.
Other signs of deficiency include hearing loss (due to a softening of the bones in the inner ear), senile osteoporosis (where the bones become lighter and less dense) and severe tooth decay.
People at risk of developing a vitamin D deficiency include people with limited sun exposure such as homebound individuals, people living in northern latitudes, anyone wearing long robes and head coverings for religious reasons, and people with occupations that prevent sun exposure.
Additional categories of people at risk are older adults (50 and over), people with greater amounts of melanin resulting in darker skin, people with fat malabsorption associated with a variety of medical conditions including pancreatic enzyme deficiency, Crohn’s disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease, and people who are obese (BMI ?30).
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