Does Sun Exposure Cause Melanoma?

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Let’s talk about melanoma and sun exposure!

1.) Most melanomas (~80%) are present on areas rarely or intermittently exposed to sunlight.

2.) Meta-analyses linking sun exposure to melanoma find that chronic sun exposure is not related to the risk of melanoma, but intermittent exposure and sunburning are.

Weird, right? Why would these observations exist if sun exposure caused melanoma? Maybe it’s more complicated than most make it seem…

We evolved under chronic sun exposure, so it would make sense that we have developed internal defense mechanisms against sun damage. That defense mechanism is tanning. When we chronically expose ourselves to low-doses of UVB radiation, our melanocytes produce melanin pigment that blocks UV radiation and prevents it from damaging the deep layers of your skin.

If you let yourself turn pink or red, you have damaged yourself. That’s a clear indication, and that’s problematic. But sun exposure without redness isn’t damaging and just serves to bolster inborn defenses against future insults.

Frankly, most mechanistic data looks at high doses of isolated UV radiation (like what you’d get in a tanning bed, which is problematic and potentially harmful). You can’t conflate that with natural sun exposure, which puts out an array of bioactive light wavelengths. Red and infrared light, for example, increases our skin’s resilience to UV radiation.

Again, high doses of exposure that cause reddening of the skin are harmful. We recommend avoiding that. But low doses of sun exposure aren’t harmful. If anything, it’s beneficial and increases resilience to future damage and provides multiple other advantages.

Thought experiment: would you conclude exercise is harmful if you saw an obese person have a heart attack while running a marathon? Of course not. That was way too much exposure for someone not conditioned for it. Same for sun exposure. Just because someone who spends all day inside and then burns on the beach gets melanoma doesn’t mean that sun exposure is harmful for the person who is chronically exposed to lower doses that build up resilience.

Stay tuned for our upcoming book on the benefits of sun exposure, where all this gets broken down into bite-size, evidence-based pieces.

Comment over here.

#melanoma #skincancer #sunexposure #brianatheroux #alexleaf #science #sun #sunscreen #bioactivelight

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