Featured photo courtesy of Kelly Sue.
So far this Sunlight Series has discussed exactly what sunlight is, how it is produced, how it interacts with Earth’s atmosphere, what reaches the surface, and an initial look at what happens when it hits your skin. The last post focused on how UV-B radiation creates vitamin D in your skin,
and how ample vitamin D levels are extremely important for optimal human health. Sunlight has other benefits too, such as nitric oxide production and the control of circadian rhythms. Clearly, for optimal health, human beings require sunlight, yet most health advice cautions against intense sunlight.
Almost everybody who is fair-skinned (or even darker skinned) has likely at some point in his or her life received a painful sunburn. It is understandable that many people believe sunlight is dangerous as extreme sunburns are indeed painful and can lead to skin cancers. Sunlight exposure can be a factor in the development of a skin cancer, but the process is misunderstood. There are three main types of skin cancer, with only one, melanoma, being a real threat to survival. Generally speaking, one can increase one’s resistance to being sunburned, and significantly lower any chance of developing a skin cancer, particularly melanoma, all the while reaping ample vitamin D levels and helping to prevent the development of all cancers. This will be discussed in a later post.
For this post, let’s take a look first at what a sunburn is, followed by the different types of skin cancer.
What is a Sunburn?
In a similar way that UV-B radiation is able to turn 7-dehydrocholesterol into vitamin D3 (as explained in the previous post), UV-B radiation is intense enough to cause changes in other molecules as well. UV-B radiation is able to break molecules apart in your skin cells, including DNA, which causes a cascade of reactions.
If enough skin cells are damaged, the body’s immune system will react with inflammation in the form of increased blood flow causing redness and swelling. Pain receptors at the site of damage will also be activated. The skin then needs to be repaired, and one way of doing that is replacing the skin, which the sunburned-individual will experience as peeling. Skin damage also leads to the formation of melanin, which causes the oft-desired tan colour. Individuals with naturally darker skin have naturally higher concentrations of melanin even without UV-B induced production. Melanin also acts as a photoprotectant (protects against sunlight), and when sufficiently concentrated, can disperse up to 99.9% of UV-B radiation. Once enough melanin is produced (either through genetics or UV-B exposure), sunburns, including damage to DNA, become very unlikely.
Conventional medicine believes that unrecognized errors in the DNA repair process are the cause of all cancers in general, and the errors resulting from UV radiation exposure are the cause of skin cancers. It is hypothesized that if DNA is not repaired properly, then mutant DNA can proliferate, which if left unchecked can result in tumours. The work of Dr. Seyfried makes an opposing case that it is damage to mitochondria, and not DNA that causes cancer. Either way, with regard to skin cancer, UV-radiation is almost always implicated as the cause. The below case argues that this is illogical.
There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma. The entire category of skin cancers comprises the most common type of cancer in the US, with more than 3.5 million cases in over 2.0 million people being diagnosed annually. 80% of these 3.5 million cases are of the basal cell carcinoma variety, close to 20% are of the squamous cell carcinoma variety, and less than 1% of all skin cancer cases are life-threatening melanoma. It is estimated that all cancers (not just skin) will be responsible for 580,350 deaths in the US in 2013, of which 12,650 (2%) are the result of melanoma.
The post on ozone depletion vs. global dimming explained that despite anthropogenic emissions decreasing the concentration of UV-blocking ozone in the stratosphere, the overall amount of sunlight (and accompanying UV radiation) hitting Earth’s surface at has decreased due to global dimming. In addition, it is estimated by the EPA that Americans (and presumably citizens of other developed countries) spend a whopping 90% of their time indoors. From these combined effects, although there has been an overall decrease in average sun and UV exposure, melanoma rates in the UK more than quadrupled from 1975-2010, with similar dramatic increases in the US as well.
How can UV radiation be the cause of melanoma if UV exposure is decreasing while melanoma rates are skyrocketing? It is the aim of this author to prove that sunlight and UV radiation is not the sole cause of skin cancer and that it has a myriad of health benefits, and that exposure should be encouraged.
First, let’s take a look at the three types of skin cancer.
Basal Cell Carcinoma:
Basal cell carcinoma (BCC), by far the most common type of skin cancer, is rarely fatal (fatal in less than 0.1% of diagnosed cases) although it can be disfiguring if its growth is left unchecked. Basal cells are the inner layer of the epidermis. Current thought has BCC generally associated with chronic ultraviolet exposure with a list of other contributing factors such as inflammatory skin conditions and complications resulting from burns, scars, and infections. Fair-skinned caucasians are the most likely to develop BCC. It is more prevalent amongst older people with a history of intense sun exposure. Although most tumors grow on sun-exposed areas of the body, BCC tumors arise on non-exposed parts of the body (the nether regions…), indicating that UV exposure is not always a factor. A photo of a BCC tumour is shown below.
Squamous Cell Carcinoma:
Squamous cell carcinoma (SCC), the second most common type of skin cancer, is also rarely fatal (fatal in less than 0.5% of diagnosed cases), but can also be disfiguring in serious cases. Squamous cells are the outer layer of the epidermis. As with BCC, UV exposure gets most of the blame for causing SCC, and fair skinned individuals are most at risk. Most of these tumours are on sun-exposed parts of the body, but again, these do pop up in non-exposed areas as well, implying that UV exposure is not the only factor in tumour development. An image of a SCC tumour is below:
Melanoma is by far the least common skin cancer, but also by far the most deadly (death in 12.4% of cases). Melanoma is a cancer of the melanocytes, which are responsible for producing melanin (tan pigment). Once again, Caucasians are the most at risk. Treatment is usually surgical removal, and if the tumour returns, then chemo- and radiation-therapy is pursued. Although UV-radiation is generally implicated as the causative factor, one study found that up to 75% of melanoma tumours occur on relatively unexposed body sites. This observation has lead many researchers to hypothesize that when a certain area of the body is usually unexposed and is infrequently exposed to high doses of UV-radiation, that the skin is not “prepared” (ie: tanned) for the radiation assault and thus is more damaged which leads to skin cancer. However, there are exceptional cases where melanoma develops on areas that are almost never exposed to sunlight, including the male scrotum and urethra. The urethra is definitely one area where the sun don’t ever shine. A photo of a melanoma tumour is below.
Based on the information presented above, the following conclusions can be made:
- UV exposure can be a factor in the development of skin cancer, especially amongst caucasians, but skin cancer also develops in areas of the body that are not exposed to sunlight.
- The vast majority of skin cancer cases are not life threatening.
- Despite the average amount of UV-exposure decreasing in developed countries, rates of skin cancer, including melanoma, are skyrocketing. UV radiation cannot explain the massive increase in skin cancer rates.
There are strategies to increase your skin’s resistance to the damage incurred by sunlight exposure through dietary and exposure habits. These will be discussed in the next post, where these practices will be outlined with the intention of educating on how to reap all the disease preventing benefits of sunlight exposure, while minimizing damage. Sounds like a win-win, and it is indeed possible.
Until next time,