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Hot topic - Vitamin D, sunlight and cancerUpdated 23 March 2004. First published: 26 November 2003 - written by Bupa's Health Information Team A letter was published in the 22 November 2003 British Medical Journal by Professor Cedric Garland that argues that a lack of sunlight may be responsible for increasing the risk of developing certain cancers. The idea that vitamin D may play a useful role in helping to prevent breast cancer was given a boost by UK research presented in March 2004. The researchers announced at a British Endocrine Societies meeting that they had found an enzyme in breast tissue that converts vitamin D into a cancer-fighting compound called calcitriol. Until now, it had been thought that this enzyme was only present in the kidneys. Below we explore the role vitamin D may play in preventing cancer and the best advice for making sure that our bodies are getting enough vitamin D. Doesn't sunlight cause cancer?Yes, long-term exposure to ultraviolet radiation from the sun (UVA and UVB) has been shown to increase the risk of skin cancer. This is why it is recommended that we wear sunscreen and sun-protective clothing during the summer months. For more on this, please see our Sun care article: How can sunlight also protect against cancer?The answer lies in a vitamin that may play a role in controlling the production of cells - vitamin D. Vitamin D is manfactured in the skin when it is exposed to sunlight and it is this vitamin that may have a protective effect against certain cancers by preventing the overproduction of cells. So, are sunscreens and suncreams bad for us?No, suncreams block out the harmful UVA and UVB radiation, reducing the chance of developing skin cancer. However, by blocking out the ultraviolet radiation, they also reduce the skin's ability to manufacture Vitamin D. Should we stop using sunscreens and wearing sun-protective clothing?The definitive answer is no. The protection that sunscreens and sun-protective clothing offers from skin cancer is too valuable to be lost. The only issue is whether or not we should spend a few minutes in the sun without protection to let our bodies manufacture vitamin D. Professor Garland thinks that we should aim for 10-15 minutes a day in the sun without sunscreen, when the weather allows, to allow our bodies to produce enough vitamin D. But Cancer Research UK argues that we get a sufficient dose of vitamin D from our daily routine exposure to the sun. The charity says that specific exposure to the sun does not confer health benefits. Click here for Cancer Research UK's advice. Professor Garland's letter is published in the 22 November issue of the British Medical Journal (Cedric F Garland. More on preventing skin cancer: Sun avoidance will increase incidence of cancers overall. BMJ 2003; 327: 1228.) What does Vitamin D do?Vitamin D promotes the absorption of calcium and phosphate from food and is essential in the formation of bones and teeth. A deficiency of vitamin D leads to a failure of the bones to grow and causes rickets in children and osteomalacia in adults. Recent studies on animals (and some human surveys) have also suggested that it might have an effect in reducing the following cancers:
Vitamin D is now believed to play an important role in regulating the production of cells, this control is missing in cancer. For more information on the studies showing the effects of vitamin D on prostate, colon and breast cancer, please click on the links below:
How much vitamin D do we need?Professor Garland recommends 10 micrograms (400IU) of vitamin D per day for children aged 1 year and older and for adults. While for older adults (those aged more than 71 years old) he would suggest an intake of 15 micrograms (600IU) a day. In contrast, the European Recommended Daily Amount (RDA) is 5 micrograms. How much vitamin D is too much?The UK Food Standards Agency (FSA) recommends that people should not exceed a guidance level of 25 micrograms of vitamin D supplement a day. Apart from absorbing sunlight, how else can we increase our daily intake of vitamin D?Vitamin D can be found in certain foods, namely:
For more information on food sources for vitamin D, please see the British Nutrition Foundation website. What happens if we get too much vitamin D?Too much vitamin D can lead to problems with the levels of calcium and phosphate in the body. High levels of calcium in our blood can lead to kidney stones, muscle weakness, stomach upsets and thirst. It can also lead to to problems with growth in children. More information on vitamin D can be found in the FSA vitamins guide. Links for more information
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