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Vitamin D, Melanomas and the Sun

Each summer the media, dermatologists and cancer councils tell us to be careful and diligent when it comes to spending time in the sun. We are warned that ultra violet rays (UVR) are extremely dangerous; therefore the message to avoid the sun between the hours of 10am and 2pm and to SLIP SLOP SLAP is repeated continuously. Anti-skin cancer organisations are also sending out the message that the number of melanomas (a deadly form of skin cancer) has doubled in the last 2 decades and that these statistics will continue to rise. On the other hand UVR are crucial for the synthesis of Vitamin D in the human body. Vitamin D is an essential nutrient for the body and was recently found to be linked to the prevention of many cancers and auto immune diseases. A study conducted at Oxford University found that serious diseases including breast cancer, leukaemia and multiple sclerosis are linked to deficiency in Vitamin D. So are we actually doing ourselves more harm than good by heeding the warnings of the media, dermatologists and anti-cancer organisations?

The sun’s rays provide all living creatures with light and warmth. For human beings the sun is important for general mood and wellbeing, for stimulating blood circulation as well as synthesising Vitamin D. As an essential nutrient to the human body, Vitamin D has a number of roles including enhancing the absorption of calcium, helping to control blood levels of phosphorus and calcium, maintaining strong and healthy bones and enabling genes (or DNA) to properly express themselves. If there is an inadequate level of vitamin D present in the body, serious illness can develop.

Vitamin D can be found in some foods, however this is through fortification as the nutrient does not occur naturally in food. Sun exposure and supplementation are the two other ways to obtain Vitamin D. In Australia Vitamin D is best synthesised after exposure to midday sun, ironically between the hours we are told to avoid. The fear of getting a tan and possibly developing a melanoma has meant that many people avoid the sun as much as possible and slip slop slap religiously when they are in the sun. We were created to have sun exposure because the human body requires it for survival, therefore to avoid unnecessary fear it is worth understanding that the relationship between sun exposure and skin cancer is not as close as we think it is.

When UVR strike the skin a natural reaction occurs, tanning. Melanocytes (a skin cell) produce melanin, a chemical used to darken the skin and provide a natural protective colouring. When melanocytes can no longer keep up with the required melanin production a message is sent to the mother melanocyte cells to divide, creating sister melanocytes which produce more melanin. Once the required number of melanocytes have been produced a message is sent to the mother cells to stop dividing. On occasion the message to stop dividing can get jumbled and a sister cell will not cease to divide, causing a melanoma. While the media implies that there is a direct relationship between sun exposure and the development of melanomas, it is actually a coincidental link. Despite this fact the belief that UVR exposure causes skin cancer is causing mass public anxiety and sun avoidance, this behaviour can be more dangerous for overall health than reducing UVR exposure.

The increase in anxiety regarding skin cancer risk has led to an epidemic of skin cancer screening as well as dramatic increase in reported incidents of melanomas, despite increased public awareness regarding the dangers of excessive sun exposure. The Dermatology Department at Norfolk and Norwich University in Norwich, UK conducted a study to investigate the possibility of a diagnostic drift (classifying benign tumours as stage 1 melanomas). The study analysed the historical diagnosis, mortality and incidence of all legions reported as melanomas in East Anglia from 1991 – 2004. During the study period 3971 melanomas were diagnosed; the annual incidence of melanoma rose from 9.39 to 13.91 per 100,000 per year. Interestingly the documented rise was almost entirely due to stage 1 diagnosis. There was no change seen in the combined incidence of other stages of the disease and death from melanoma experienced only a slight rise from 2.16 to 2.54 cases in 100,000 per year. The study found that the large increase in reported incidences was likely to be due to a diagnostic drift which classified benign tumours as stage one melanomas. The study also found that the melanoma lesions often occurred in places not regularly exposed to sunlight, suggesting the link between melanomas and ultraviolet radiation was not as strong as once thought. The study called for a re-evaluation of the role of UV radiation in melanoma development and recommendations for protection from it.

There is no question that chronic, excessive exposure to UVR could increase your risk of developing melanoma; however it would be through a coincidental link rather than direct relationship. There is very little evidence to support the theory that sensible, moderate sun exposure increases you risk of melanoma, in fact, there is more research out to suggest that getting a minimum of 2 to 3 hours of sun per week (without sunscreen) is healthy for you. Getting a tan will provide skin with a protective barrier to UVR, increase one’s Vitamin D levels, and reduce one’s risk of developing melanoma as well as other deadly cancers and autoimmune diseases. If we were designed not to need the sun it wouldn’t exist so make sure you get adequate sun exposure to ensure you stay healthy and happy.

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