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The early bird gets the worm—and may avoid skin cancer. Because a new mouse study suggests that, for humans, tanning in the mornings may be less likely to permanently¹ damage DNA² and cause skin cancer.

 

A mouse's levels of the DNA-repairing protein XPA are different from ours—they peak in the morning and bottom out in the evening. Researchers exposed mice to UV radiation when their XPA was at its minimum level, around 4 a.m., and others to the same rays around 4 p.m., when XPA levels peaked.

 

Mice who tanned while low on the repair protein developed skin cancer faster and five times more frequently than their evening-tanning counterparts. The study is in the Proceedings³ of the National Academy of Sciences.

 

Unlike mice, humans are not nocturnal, so their XPA levels rise and fall at different times. In people, XPA is at prime DNA-repairing levels in the morning, which thus looks the safest time for UV exposure. So if you want to avoid skin cancer, probably go to the tanning salon⁴ early—or better yet, don't go at all.

 

Thanks for the minute. For Scientific American's 60-Second Science, I'm Sophie Bushwick.

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