Shining a light on impulse to seek sun

[Ezliving_Jim]

Shining a light on impulse to seek sun

Judy Foreman -- Medical Matters
Originally published May 25, 2007

Are people genetically programmed to seek the sun?

Personally, I've always thought so. And now a new study suggests that there may really be a genetic impulse to seek the sun, though there's plenty of evidence that excess exposure to sunlight can cause skin cancer.

In the study, published in the March 9 issue of CELL, Dr. David E. Fisher, director of the melanoma program at the Dana-Farber Cancer Institute, reported that the same biochemical process that leads to skin tanning also raises levels of a natural opiate, the "feel good" chemical, beta-endorphin.

Evolution might have favored this because, by making sunning pleasurable, the body increases production of melanin, the pigment that makes the skin tan. People who can tan have a much lower risk of skin cancer, including melanoma, than non-tanners.

The link between sun exposure and release of beta-endorphins "is an intriguing hypothesis worthy of pursuit," said Dr. Hensin Tsao, director of the Massachusetts General Hospital melanoma and pigmented lesion center. He said he'd like to see follow-up research examine whether enough beta-endorphins are released during tanning to make people want to spend more time in the sun.

There's another interesting tidbit in all this: The body makes vitamin D in response to sunlight. As our ancestors migrated away from the equator, their skins got lighter. Gene mutations that triggered lighter skin would have allowed people to make sufficient vitamin D, even as sunlight became weaker.

But the cautious take: You should protect your skin most of the time with sunscreen and clothing, especially if you have fair skin and do not tan.

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