Mind & Body

For a Healthier Tan, Limit Sunbathing to Every Other Day

Getting a tan is one of those pesky beauty rituals that is as popular as it is damaging. But let's face it — many of us do it anyway. Luckily, whether you're planning to hit the beach this summer or just sit in your backyard and hope it looks like you went to the beach, science can help you get your best tan with the least amount of damage.

What Is a Tan?

Let's get this straight right off the bat: A tan is technically a sign of sun damage. The dark coloring you get after a day in the sun comes from pigment-producing cells in your skin, called melanocytes, that kick into gear as a response to UV radiation exposure.

The pigment melanocytes produce is known as melanin, and it acts as a sort of sun umbrella for DNA. It absorbs UVB radiation before it can reach the DNA and cause damage. More melanin means more pigment in your skin, and greater UVB protection next time you hit the pool. But if you go through this sun-damage cycle too often, you increase your risk of skin cancer. In fact, in areas with a lot of sun, 95 to 99 percent of all skin cancers are directly attributable to sun exposure.

But we do need sunlight. Your body uses sunlight to synthesize vitamin D, a critical vitamin that's essential for strong bones and may protect against certain types of cancer, heart disease, and even depression. So how much sun is the right amount? According to a 2017 study, 10 to 20 minutes of unprotected sun exposure is enough to get the recommended amount of vitamin D during the spring and summer months (although winter is another story).

Two Lines of Defense

A tan is one method your body uses to protect itself from DNA damage, but it's not the first line of defense. The first is a sunburn. When damage is detected after sun exposure, a flurry of protective measures take place, including the production of proteins and enzymes that provoke an inflammatory response and recruit immune cells to the damaged areas. Basically, all that redness, swelling, and pain is a sign that your body is trying to heal itself and protect your DNA.

That DNA-repair process also activates a protein called microphthalmia-associated transcription factor, or MITF. This protein regulates several skin-protection mechanisms, and one of its roles is to tell melanocytes to produce more melanin. But a recent study published in Molecular Cell found that MITF only triggers melanin production every 48 hours, which means that timing your tanning sessions to coincide with MITF activity might better protect you from UV damage.

It's All About Timing

For the study, the researchers exposed different groups of mice to UVB rays every 24, 48, or 72 hours over two months. While you might think that the mice with most frequent exposure got the deepest tans, that wasn't the case. Instead, the researchers found that those that were exposed every 48 hours — that is, every other day — produced more melanin but had less DNA damage than the other groups. The team also triggered melanocyte activity in human skin cells on the same time cycles, and just like the mice, the human cells with melanocyte activity every 48 hours made the most melanin.

It appears that exposing skin cells to UV rays every day messes with MITF activity and interrupts melanin production. But why? It may have something to do with good ol' vitamin D.

"We do know that vitamin D, which the skin produces upon exposure to the sun, is stable in the blood for 48 hours post-exposure," said senior author Carmit Levy in a press release. "Perhaps there is a link."

So if you must get your tan on, limit it to every other day. You'll get a better tan and you'll be protecting your DNA. It's a win-win!

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For more simple skincare science, check out "The Skincare Bible: Your No-Nonsense Guide to Great Skin" by dermatologist Anjali Mahto. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Julia Wilde July 1, 2019

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