Vitamin D, sunlight and cancer

Main Category: Cancer / Oncology
Article Date: 29 Nov 2003 - 0:00 PDT

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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.

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:
/health_information/asp/healthy_living/general/sun_care/

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 preventin

g 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.

For on Cancer Research UK's advice, please click on the following link:
http://www.cancerresearchuk.org/aboutcancer/reducingyourrisk/sun_uv.

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:
• breast
• colon
• prostate

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:

• Johnson CS, Hershberger PA, Trump DL. Vitamin D-related therapies in prostate cancer. Cancer Metastasis Rev. 2002;21(2):147-58.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12465754&dopt=Abstract

• Konety BR, Johnson CS, Trump DL, Getzenberg RH. Semin Urol Oncol. 1999 May;17(2):77-84 Vitamin D in the prevention and treatment of prostate cancer
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10332920&dopt=Abstract

• Getzenberg RH, Light BW, Lapco PE, et al. Vitamin D inhibition of prostate adenocarcinoma growth and metastasis in the Dunning rat prostate model system. Urology. 1997 Dec;50(6):999-1006
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9426741&dopt=Abstract

• Guyton KZ, Kensler TW, Posner GH. Vitamin D and vitamin D analogs as cancer chemopreventive agents.Nutr Rev. 2003 Jul;61(7):227-38
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12918875&dopt=Abstract

• Makishima M, Lu TT, Xie W, Whitfield GK, et al. Vitamin D receptor as an intestinal bile acid sensor. Science. 2002 May 17;296(5571):1313-6
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12016314&dopt=Abstract

• Lowe L, Hansen CM, Senaratne S, Colston KW. Mechanisms implicated in the growth regulatory effects of vitamin D compounds in breast cancer cells. Recent Results Cancer Res. 2003;164:99-110.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12908448&dopt=Abstract

• O'Kelly J, Koeffler HP. Vitamin D analogs and breast cancer. Recent Results Cancer Res. 2003;164:333-48
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12899532&dopt=Abstract

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. For more recommended daily amounts, please click on the following link:
http://www.nhsdirect.nhs.uk/en.asp?TopicID=656&AreaID=4321&LinkID=3396

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.
For more on the FSA's recommendations for vitamins, please click on the following link:
http://www.food.gov.uk/multimedia/pdfs/vitmin2003.pdf

Apart from absorbing sunlight, how else can we increase our daily intake of vitamin D?

Vitamin D can be found in certain foods, namely:
• cod liver oil
• sardines
• herring
• salmon
• tuna
• milk
• cheese
• eggs
• fortified margarine
• fortified breakfast cereals
For more information on food sources for vitamin D, please see:
http://www.nhsdirect.nhs.uk/en.asp?TopicID=656&AreaID=4321&LinkID=3396 and 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:
http://www.food.gov.uk/multimedia/pdfs/vitmin2003.pdf

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