What is vitamin D and why do you need it?

Vitamin D is a fat soluble vitamin, which is mainly manufactured by the body itself, in the skin during exposure to sunlight. It also occurs naturally in some foods and can be added to some foods during the manufacturing process.1

The term ‘vitamin D’ actually refers to several different forms of the vitamin. Two forms, vitamin D2 (ergocalciferol) and vitamin D3 cholecalciferol) are important to human health. Vitamin D2 occurs in plants, while D3 is the form manufactured by the skin.2 These forms of the vitamin are both biologically inactive forms, which must be activated in the liver and kidneys.3

Vitamin D is an important nutrient for our overall health.4 It plays an essential role in normal bone development and maintenance, through the regulation of calcium and phosphorous levels.3 It does this by facilitating calcium absorption from the digestive tract and maintaining normal levels of calcium and phosphate in the bloodstream. This supports proper mineralisation of bones and healthy muscle function.

Vitamin D is also necessary for bone growth and without enough vitamin D, bones can become brittle, thin or malformed. Although the link between vitamin D and healthy bones has been established for many years, recent research shows it is connected to a number of other health conditions as well.4 Vitamin D is also necessary for the proper function of the immune system, hormones and cardiovascular health.3

Most of the vitamin D that we need is produced by the body through regular exposure to sunlight. However, low vitamin D levels in Australia are still a problem due to health concerns caused by the health risks of sun exposure. Moddern lifestyles that often involve long hours working indoors in an office environment are also thought to be a causative factor, especially in winter.5

A vitamin D deficiency may cause hormone imbalances, low bone mineral density, fractures or osteoporosis.2 Muscle function is also often affected and is evident long before any signs are visible in the bones. In the elderly, the effect of low vitamin D levels in muscles is evident by the increased risk of falls among this group. A decrease in the risk of falling occurs after vitamin D supplementation and is thought to be because of improved muscular function in response to improved vitamin D levels.6