Skin Cancer Risk Goes Up In the Afternoon Sun

beer drinking party afternoon sun cancer A new study has found that afternoon sun is five times riskier than than sun caught in the morning hours.

Are you one of those people who slather sunscreen all over your face come high noon, but remove the T- shirt later in the day to catch those warming, vitamin D-making rays? Well if you are one of those people (which was me until I read this study)  who take joy in basking in the “safe” late day sun drinking a beer or sailing your sailboat, be warned: according to a relatively recent study published in PNAS (links to PDF), afternoon sun ups your risk of getting skin cancer five fold.

And it’s not because of anything the sun did: according to the researchers it’s all about our internal circadian clocks and our DNA’s ability to fend off the damaging effects of UV radiation. It turns out that our DNA is less protected to mutations late in the day. Simply put: our body works less good after a long day on the job. The bad news: more DNA damage is found to occur. This damage can result in skin cancer.

Aziz SAncar researchers circadian clocks and skin cancer caused by the sun Skin cancer is the most common form of cancer in the United States and statistics in sunny countries, especially in the Middle East, see similar numbers. The main cause of skin cancer is DNA damage caused by the UV component of sunlight.

In humans and mice, the researchers led by Dr. Aziz Sancar (inset), a professor of biochemistry at the University of North Carolina School of Medicine, found that mice exposed to UV radiation (UVR) at 4:00 AM display a decreased latency and about a fivefold increased multiplicity of skin cancer (invasive squamous cell carcinoma) than mice exposed to UVR at 4:00 PM.

“We conclude that time of day of exposure to UVR is a contributing factor to its carcinogenicity in mice, and possibly in humans,” the write.

They add: “With these considerations, then, we suspect that by restricting UVR exposure to morning hours would reduce the risk of skin cancer in humans. This recommendation, however, must be considered provisional until actual DNA repair rates are measured in the skin of human volunteers.”

Our basic advice is this: wear a hat and long sleeves and pants when you can (long protective fashion is the fashion in the Middle East for a reason!), and wear sunscreen.

There are all kinds of natural sunblocks to choose from, and Karen provides a DIY organic sunscreen recipe to make your own, one without all the parabens and yucky chemicals in the commercial long-shelf life brands. If you have kids, make it with them and teach them the dangers of sun exposure at the same time.

Whether you live in a sunny country or are visiting one this winter, love the sun, but stay safe.

Image of drinking beer in the sun from Shutterstock

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