How Serious Is A Deficiency In Vitamin D?
Like Vitamin A, Vitamin D is also fat-soluble. It is also known as the “sunshine vitamin” as it can be produced in the skin by exposure to ultra violet light. Due to this fact there has been debate as to whether vitamin D should be classed as a vitamin or hormone. If sufficient sunlight is exposed to the skin vitamin D is produced there and travels to the liver to be utilised. However, if there is not adequate exposure to ultra violet rays then vitamin D requirements must be met by a dietary supply. Foods abundant in Vitamin D include oily fish, eggs and liver. These foods contain the substance cholecalciferol, which is the form of vitamin D produced in the skin of animals due to ultraviolet light exposure. In an effort to avoid deficiency, the government have insisted that margarine and milk are fortified with vitamin D3 or D2 – a derivative of vitamin D.
However it is obtained, whether through sunlight or dietary, Vitamin D’s main function is to maintain aid the absorption of calcium and phosphorus. If calcium or phosphorus levels drop too low, the parathyroid gland releases parathyroid hormone and stimulates kidney enzymes to convert vitamin D3 to the active form D. Once converted, vitamin D then regulates calcium and phosphorus levels. It does this in 2 ways. Firstly, within the bone vitamin D helps parathyroid hormone to release calcium and phosphorus into the blood stream to meet required levels. Secondly, in the intestines vitamin D increases “the expression of genes” and stimulates the proteins responsible for calcium transportation.
In the lack of sunlight, such as during a British winter, our diets are generally sufficient in vitamin D and are able to meet our body’s requirements. However, in cases where deficiency is present diseases such as Rickets and Osteomalacia can arise. These conditions are very similar just that rickets is the term given to children. They result from a lack of calcium (hence lack of vitamin D) and cause weak bones and bowlegs in the young. In the elderly osteomalacia is common with those who have kidney failure because the conversion of inactive to active vitamin D is reduced. The elderly are also at risk because age impairs the ability of the skin to make the vitamin therefore if the diet does not meet the requirements deficiency can be found.
Those greatly at risk are the ethnic minorities who, ironically, originate from warmer climates. Due to the nature of their darker skin the sunlight is less able to penetrate the dermis and if their diet is not satisfactory deficiency can occur.
Recommended doses of the vitamin are hard to calculate but generally 10 UG a day is sufficient.
If too much vitamin D is taken in then there is a risk that too much calcium is released causing unwanted calcification in the kidneys and even within soft tissue as well as too high blood calcium levels causing stomach upsets, illness, increased thirst and constipation.