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Sunlight prevents cancer - SunSmart recommendations risk health

24.03.2005


The health of the public is being put at risk by recommendations to cover up and stay out of the sun in the UK. These recommendations, which are part of Cancer Research UK’s SunSmart programme, increase the risk of several types of cancer, and may also increase deaths from melanoma, the most serious form of skin cancer.



Increased exposure to sunlight or greater intake of vitamin D has been found to reduce the risk of five common cancers in case/control studies. These are cancer of the colon, breast, ovary, prostate and lymphoma (1-7). Additional evidence based on differences in incidence of cancer in northern versus southern states of America have found that some 16 or more different types of cancer are less common in the sunny south (8).

For example, the risk of prostate cancer, which causes some 10,000 deaths a year in England, has been found to be reduced by sunbathing and by foreign holidays. And sunburn in childhood is even associated with a reduced risk of prostate cancer, presumably because people who become sunburnt have greater exposure to the sun(9).


Some 50 per cent of people in Britain and Ireland obtain insufficient vitamin D which increases their risk of cancer and other diseases (10). Sunlight is the major source of vitamin D in the UK. Only small amounts are obtained in foods such as eggs, butter or margarine, meat, some breakfast cereals and oily fish. Vitamin D supplements do not provide enough extra vitamin if taken at the usually recommended levels.

The SunSmart recommendations are likely to cause vitamin D shortage if followed carefully. And, if the latest research is correct, following SunSmart may increase the risk of several cancers including melanoma. Two recent scientific articles suggest that increased sun exposure reduces the risk of either getting melanoma or of dying from it (11,12). Other studies have found that adults who work outdoors and children who play outdoors where they are regularly exposed to the sun are less likely to develop melanoma than those who work or play indoors (13,14).

Occasional or irregular exposure of the skin to the sun is associated with an increased risk of melanoma, possibly because it is associated with low levels of vitamin D or because irregular exposure does not lead to a protective tan and skin thickening. The slogan “there is no such thing as a healthy tan”, used to promote SunSmart, has put a generation of people at increased risk of melanoma. Sunburn, which is most likely to occur in people who have irregular exposure, is associated with an increased risk of skin cancer including melanoma (11).

The increase in melanoma in the UK may be caused in large part by increases in obesity, and lack of exercise, together with increased travel by car and increased indoor leisure activities which keep people out of the sun as well as reducing exercise (15-17). Foreign travel to sunspots where skin is exposed without any previous tanning may also be a factor.

Other diseases linked to insufficient vitamin D

Bones: Sunlight and vitamin D are vital for bone health – both for preventing fractures which cost the Health Service more than £2bn a year and for preventing rickets in infants (18,19). Children from immigrant families are particularly vulnerable to rickets because dark skin takes up to six times as long to make the same amount of vitamin D as white skin. Vitamin D supplements have been shown to prevent both falls (due to the action of the vitamin on the nervous system) and fractures in a number of double blind randomised trials (20).

Multiple sclerosis: A study of nurses in the US has shown that those who consume more vitamin D in food and supplements have less risk of vitamin D (21). A very comprehensive study of MS in northern countries including Canada, UK, Denmark and Sweden has shown that people who are born in May (after the winter) have an increased risk of MS while those born in November, who benefit from higher summer levels of vitamin D in the mother during the last months of pregnancy, have a decreased risk of MS (22). Ring Professor George Ebers for more information: 01865 228579 or 228568.

Diabetes: Risk of diabetes type 1 is also increased in people whose mothers had insufficient vitamin D during pregnancy (23,24). High blood pressure: Sunbathing on sunbeds has been shown to reduce blood pressure significantly (25).

References

1. Pritchard, R. S., Baron, J. A. & Gerhardsson de Verdier, M. Dietary calcium, vitamin D, and the risk of colorectal cancer in Stockholm, Sweden. Cancer Epidemiol Biomarkers Prev 5, 897-900 (1996).
2. White, E., Shannon, J. S. & Patterson, R. E. Relationship between vitamin and calcium supplement use and colon cancer. Cancer Epidemiol Biomarkers Prev 6, 769-74 (1997).
3. Grau, M., Baron, J., Sandler, R. & al, e. Vitamin D, calcium supplementation, and colorectal adenomas: results of a randomised trial. J Natl Cancer Inst 95, 1765-71 (2003).
4. Peters, U., McGlynn, K., Chatterjee, N. & al, e. Vitamin D, calcium, and vitamin D receptor polymorphism in colorectal adenomas. Cancer Epidemiol Biomarkers Prev 95, 1267-71 (2001).
5. Emerson, J. & Weiss, N. Colorectal cancer and solar radiation. Cancer Causes Control 3, 95-9 (1992).
6. Smedby, K., Hjalgrim, H., Melbye, M. & al, e. Ultraviolet radiation exposure and risk of malignant lymphomas. J National Cancer Institute 97, 199-209 (2005).
7. Hughes, A., Armstrong, B., Vajdik, C. & al, e. Sun exposure may protect against non-Hodgkin lymphoma: a case control study. Int J Cancer 112 (2004).
8. Grant, W. An estimate of premature cancer mortality in the United States due to inadequate doses of solar ultraviolet-B radiation. Cancer 94, 1867-75 (2002).
9. Luscombe, C., Fryer, A., French, M. & al, e. Exposure to ultraviolet radiation: association with susceptibility and age at presentation with prostate cancer. Lancet 358, 641-2 (2001).
10. Gillie, O. Sunlight Robbery: Health Benefits of sunlight are denied by current public health policy in the UK. Health Research Forum Occasional Reports 1, 1-41 (2004).
11. Kennedy, C., Bajdik, C. D., Willemze, R., de Gruijl, F. R. & Bouwes Bavinck, J. N. The influence of Painful Sunburns and Lifetime Sun Exposure on the Risk of Actinic Keratoses, Seborrheic Warts, Melanocyctic Nevi, Atypical Nevi, and Skin Cancer. Journal of Investigative Dermatology 120, 1087-1093 (2003).
12. Berwick, M. et al. Sun exposure and mortality from melanoma. Journal of the National Cancer Institute 97, 1-15 (2005).
13. Kaskel, P. et al. Outdoor activities in childhood: a protective factor for cutaneous melanoma? Results of a case-control study in 271 matched pairs. Br J Dermatol 145, 602-9 (2001).
14. Hakansson, N., Floderus, B., Gustavsson, P., Feychting, M. & Hallin, N. Occupational sunlight exposure and cancer incidence among Swedish construction workers. Epidemiology 12, 552-7 (2001).
15. Shors, A. R., Solomon, C., McTiernan, A. & White, E. Melanoma risk in relation to height, weight, and exercise (United States). Cancer Causes Control 12, 599-606 (2001).
16. Kirkpatrick, C. S., White, E. & Lee, J. A. Case-control study of malignant melanoma in Washington State. II. Diet, alcohol, and obesity. Am J Epidemiol 139, 869-80 (1994).
17. Grant, W. Melanoma has a complex etiology that includes UV exposure, skin pigmentation and type, diet and obesity. British Medical Journal 327, 1306 rapid response (2003).
18. National Service Framework for Older People. Department of Health (2001).
19. Trivedi, D., Doll, R. & Khaw, K. Effect of four monthly oral vitamin D3 (cholecalciferol) supplementation on fractures and mortality in men and women living in the community: randomised double blind controlled trial. British Medical Journal 326 (2003).
20. Bischoff-Ferrari, H. et al. Effect of vitamin D on falls: a meta-analysis. Journal of the American Medical Association 291, 1999-2006 (2004).
21. Munger, K., Zhang, S., O’Reilly, E. & al, e. Vitamin D intake and incidence of multiple sclerosis. Neurology 62, 60-5 (2004).
22. Willer, C., Dyment, D., Sadovnick, A., Rothwell, P. & Ebers, G. Timing of birth influences multiple sclerosis susceptibility: the Canadian Collaborative Study Group. British Medical Journal 330, 120-123 (2005).
23. Hypponen, E., Laara, E., Reunanen, A., Jarvelin, M. R. & Virtanen, S. M. Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study. Lancet 358, 1500-3 (2001).
24. Stene, L. C., Ulriksen, J., Magnus, P. & Joner, G. Use of cod liver oil during pregnancy associated with lower risk of Type I diabetes in the offspring. Diabetologia 43, 1093-8 (2000).
25. Krause, R., Bohring, M., Hopfenmuller, W. & al, e. Ultraviolet B and blood pressure. Lancet 352, 709-10 (1998).
26. Statement by Cancer Council Australia, Osteoporosis Australia and other health organisations. See website: www.cancer.org.au/documents/Risks_Benefits_Sun_Exposure_MAR05.pdf

Oliver John Gillie | alfa
Further information:
http://www.healthresearchforum.org.uk

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