Sunlight prevents cancer

Mar 23 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. 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.

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.

Some 50 per cent of people in Britain and Ireland obtain insufficient vitamin D which increases their risk of cancer and other diseases. 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. 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.

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.

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. 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. 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.

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. 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.
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. High blood pressure: Sunbathing on sunbeds has been shown to reduce blood pressure significantly.