We are constantly being told to avoid the sun as much as possible. We are told to cover up and nearly every skin product that we buy seems to contain sunscreen. However, now there is some evidence that a small amount of sun exposure may actually be healthy.
There are two most frequent reasons that we are told to avoid exposure to the sun are skin cancer and aging. This article is going to discuss some new studies on melanoma, how the situation may not be so straightforward, and some evidence that a small sensible amount of exposure to sunlight may have health benefits.
There are a number of types of skin cancer, with melanoma being the one that scares us. Other precancerous and cancerous lesions such as actinic keratoses, squamous cell carcinoma and basal cell carcinoma are much more common. These other types of skin cancer, particularly if they are detected early, are in most cases very treatable.
Is the rate of melanoma increasing or not?
An increasing rate of melanoma is often given as evidence for not getting sun exposure. Data collected has suggested that there has been quite a significant rise in the number of cases of that have been diagnosed.
However, a new study (Br. J. Dermatol. 161:630-4, 2009) suggests that the rates may not really be rising. This study found that diagnoses of Stage 1 have risen by about 50%, but the number of people with late stage, and number of deaths from melanoma has not risen significantly.
The authors conclude that the apparent increase in early stage diagnoses is due to more benign (non-cancerous) lesions being diagnosed as Stage 1. They think that there has been “diagnostic drift” and there should be development of better diagnostic criteria for deciding what is or is not Stage 1. Additionally, this suggests a second opinion may be a good idea upon diagnosis with melanoma.
If the incidence of melanoma is not rising as the research suggests, what effect does this have on recommendations for sun exposure?
Why do we need vitamin D? How does this vitamin impact melanoma?
When skin is exposed to moderate to strong sun, it makes pre-vitamin D (D3, cholecalciferol). This process is very tightly regulated, once enough has been made, the body will break down the extra in the skin. The pre-vitamin is converted, as required, to the final form by the liver and kidneys. Generally our diet, even when eating fortified foods does not contain sufficient of this vitamin.
Vitamin D is important for a number of body processes. A deficiency results in a weaker immune system, higher blood pressure, osteoporosis and a range of other poor health conditions. As discussed below, Vitamin D seems to play a role in cancer prevention.
Additionally, new research compared the level of vitamin D, at the time of diagnosis, to the outcomes of those diagnosed with melanoma. Those with higher levels of the vitamin had thinner tumors and a better survival rate. (J. Clin. Oncol. Sept 21 epub ahead of print; Newton-Bishop et al.) This researchers did not differentiate between those who got more sun exposure and those who took supplements. However, this is certainly another piece of evidence for the benefits of not being vitamin D deficient. Hopefully the researchers are analyzing their data further, to establish if the source of vitamin D is important.
Does some sun exposure equal less overall cancer risk?
It has been known for many years that there the overall rate of many cancers cancer drops moving closer to the equator, from the more temperate latitudes. Cancers for which there is a lower incidence include breast, colon, ovarian and prostate. This suggests that those exposed to sun on a daily basis may have more protection against cancer.
Interestingly, when looking at populations in countries at different latitudes there are often similar ranges of vitamin D levels in the bodies of those with high levels of sunlight and those who live in regions with less sunlight. (This could be due to the supplementation of foods in the higher latitudes.) However, there is still the gradient of cancers. This suggests that is not just vitamin D that is key but the making of the vitamin is made by the body is important (PNAS 105:668-73, 2008).
In Australia for many years there has been a very aggressive campaign to get people to get much less sun exposure. The campaign is called Slip-Slop-Slap, which is slip on a shirt, slop on sunscreen and slap on a hat. The campaign was started in 1981 and is now part of the culture. However, the (apparent) incidence of melanoma has continued to increase (though the incidence of squamous cell and basal cell carcinomas have decreased). This increase is thought to be due to more of the population becoming vitamin D deficient since now many are getting little or no sun exposure on the skin.
Sensible sun exposure
If you get little or no sun, should you start to get more? This is for you to decide. If you decide that you want to get your vitamin D from the sun, the key is sensible sun exposure. The current guidelines suggest 10 to 15 minutes, twice per week, on part of the body, in the summer when UV levels are high, and proportionally more in the winter. The body parts can be arms, back, tummy, legs – it does not have to be the face. Sitting out for extended periods in the sun is definitely more harmful than getting no exposure at-all. Make any sun exposure that you get sensible.
The incidence of melanoma may actually not be rising. The apparent increase may be due to more benign lesions being classed as Stage 1.
Perhaps, the current advice that any and all sun exposure is bad, may soon be revised, and medicinal doses of sun prescribed.
An increasing number of pieces of evidence suggest that we may actually be healthiest if we get small amounts of sensible sun exposure.
Judith Airey, PhD, is a biomedical researcher who is interested in all aspects of health, and additionally how some of them relate to aging.