With the sunny summer weather upon us, many of us will look to soak up some much needed sun following a gruelling winter season. We all know that too much sun exposure can lead to nasty sunburn’s and can increase our risk of getting skin cancer. In the US, skin cancer affects nearly 5 million people per year and the number of new skin cancer cases each year actually out numbers the cases of breast, prostate, lung and colon cancer combined. Melanoma, which is the most dangerous form of skin cancer, kills one person nearly every hour. To combat this terrible disease, we are often told to wear sunscreen or cover up to protect ourselves from the harmful UV rays of the sun. For some people though, the thought of lying under the sun getting a copper glow is too enticing to consider avoiding excessive UV exposure. In fact, it has been suggested that this behaviour may addictive. Even if you did happen to get a little too much sun (by accident or otherwise), many of us might assume that once you get out of the sun, the damage stops. Unfortunately, recent research published in Science, suggests that the sun can damage your skin long after you have retreated to the shade.
Inside your skin cells there resides the pigment melanin whose purpose in life is to protect you from sunburns, DNA damage and eventually skin cancer. Melanin is made by melanocytes and comes in three different types: eumelanin (the most common), pheomelanin (responsible for red hair), and neuromelanin (exists in the brain). People who have more pheomelanin then eumelanin, blondes and redheads, are at a greater risk for developing cancer than dark haired individuals. Melanin works by absorbing energy from UV rays to prevent that energy from damaging your DNA. If the melanin does not absorb this energy it can damage your DNA making what are known as cycobutane pyrimidine dimmers (CPDs) which are basically bulges in your DNA structure. These can cause mutations when cells begin to divide. It was originally thought that these CPDs formed shortly after exposure to UV rays and that once the UV exposure went away, so did the damage to the DNA. Not so apparently. The researchers saw that when they exposed mouse and human melanocytes to UV light and then turned the UV light off, the cells continued to accumulate DNA damage for the next 3 hours! What could possibly be causing this damage even when the UV rays were removed? The researchers saw that the energy the melanin had absorbed from the UV rays put it into an excited state. This excited molecule of melanin slowly released some of that energy over the next 3 hours, continuing the damage to the DNA.
If that doesn’t make sense, think of it this way. Your child finds your chocolate covered espresso beans and they start to run around screaming with excitement and excessive energy. Every time they scream, it hurts your ears and begins to give you a headache. The screams of the child are like the energy being released by your melanin and the pain you feel from those screams is like the DNA damage. After enough screams you get a migraine, this can be thought of as the cancer. After enough DNA damage caused by the slowly released energy, your cells DNA accumulates mutations and could develop into a melanoma.
So what are we to do? We all love the sun and exposure to sunlight is vital for the manufacturing of vitamin D in our body and it helps ward off depression. The researchers suggest that the application of a lotion that could contain a quencher would help limit the damage caused by this absorbed energy. A quencher would act as a sponge, sucking up all the excess energy from the melanin so it can’t damage your DNA. There is still more work to be done to see if we can replicate these results in human skin samples and it should be noted that the average person walking in the sun likely won’t have to worry much about this effect. The body has an arsenal of tools to help deal with DNA damage and would more than likely be able to deal with this. These results are more likely to be applicable to people who work outside under the sun for long hours or who are frequent tanners (indoor or outdoor). So remember enjoy your sun, but in moderation and with the proper protection.