Vitamin D is a nutrient that is vital for the development of healthy bones.

Vitamin D serves several important functions in relation to calcium metabolism. However, before it can work effectively, vitamin D needs to be activated by the liver and kidney. Vitamin D helps to increase calcium absorption in the gastrointestinal system and kidney (by enhancing the action of parathyroid hormone) and thereby make it available to body tissues and the blood. It also functions to aid the deposition of calcium in bone.

Vitamin D also helps in maintaining muscle strength. This may help to reduce falls in the elderly population⁹⁷.

Apart from its important role in maintaining bone health, vitamin D may also have an important role in other diseases such as diabetes, cancer and infection⁹⁸. These are currently areas of intense research.

The body’s main source of vitamin D arises from the manufacture of this vitamin in the skin on exposure to sunlight. Research has found many people are deficient in vitamin D due to more time being spent indoors. Only 10-15 minutes of exposure to outdoor sun per day is necessary for the production of adequate vitamin D. You cannot become vitamin D toxic through excessive sunlight exposure; but it is important to avoid excessive exposure to sunlight, particularly in summer, due to the risk of skin damage and skin cancers.

Dietary sources of vitamin D are limited and can come from plants (vitamin D2) or animal sources (vitamin D3). These sources of vitamin D from the diet arise often from foods fortified (boosted) with vitamin D such as milk, soy drinks, margarine and cereals. It is also found naturally in liver, fish (tuna, salmon, sardines, herring and mackerel) and egg yolk.⁶

Certain individuals with limited exposure to sunlight are at risk of vitamin D deficiency. The institutionalised,⁷ housebound elderly,⁸ veiled women and dark skin individuals may be at risk of vitamin D deficiency,⁹ It is also frequently observed that vitamin D levels are seasonal and fall in the winter and early spring when people are less likely to be outdoors. Also individuals with illnesses of the gastrointestinal system such as Coeliac disease¹⁰ may not absorb adequate amounts of vitamin D from the diet. In high-risk individuals such as the elderly or those found to have low levels of vitamin D, vitamin D supplements are appropriate.^11,12 In addition, if calcium intake from dietary sources is inadequate, the use of calcium supplements may be necessary.

You should discuss with your doctor whether you require supplements of calcium or vitamin D.

Further Resources

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 Vitamin D 95.53 Kb

Content updated July 27, 2011