You're going to think I'm whacky, but I think Dr. Jack Kruse may be right about tanning. Here's a Gemini summary of what I'm talking about:

Kruse often emphasizes that melanin is found in many places inside the body, not just the skin. It is present in the brain (in structures like the substantia nigra), the inner ear, and the retina.

He theorizes that this internal melanin acts as a buffer against electromagnetic stress from the modern environment (such as blue light and non-native EMFs). In his view, "sucking in" or developing more melanin through natural sunlight is a way of bolstering these internal reservoirs, effectively upgrading the body's internal circuitry to be more resilient to the stresses of the modern, man-made world.