The Importance of Vitamin D
Vitamin D has the very important role of producing the hormone calcitonin (metabolised by the liver and kidneys) which sends a message to the intestines to increase the absorption of calcium and phosphorus, therefore maintaining blood calcium levels. By promoting calcium absorption, vitamin D helps to form and maintain strong bones. Other important functions of vitamin D are maintaining a healthy immune system, regulating cell growth and preventing cancer. It has also been shown to protect against the development of autoimmune disease such as inflammatory bowel disease, multiple sclerosis and rheumatoid arthritis. A deficiency in vitamin D causes softening of the bones – rickets in children, osteomalacia in adults. To a lesser degree it can cause joint pains and stiffness, backache, tooth decay, muscle cramps and hair loss.
It differs from the other fat soluble vitamins as it can be made in the body, this occurs after exposure to ultra violet rays from the sun. The UV rays cause vitamin D to be synthesized in the skin. As sun exposure is perhaps the most important source of vitamin D, it is crucial for those living in countries with little sun to supplement their diet with 1000mg vitamin D per day (never to be taken without calcium) or to have a diet where they are taking in lots of vitamin D rich foods, such as salmon, mackerel, eggs, cod liver oil, vitamin D fortified milk, enriched breakfast cereals, herrings, cottage cheese and liver. Having said that several months supply of vitamin D can be stored in the body, so lack of sunshine from November to February during the British winter is not fatal. As well as a lack of sunlight being a barrier to the assimilation of vitamin D, fried foods and alcohol are also thought to be contributing factors. The daily recommended intake of vitamin D is 5mg (0-50) years), 10mg (51-70) and 15mg (70+years). It is important to note that although it is essential to have enough vitamin D in the body, too much can be toxic. This can lead to calcification of soft tissues, growth restriction, and excess calcium excretion via the kidney.