Aren't those links about "people with naturally darker skin"? I'm not sure how cultural changes can affect that. Rich people may eat caviar, but eating caviar won't make you rich...
It's not particularly clearly worded but to me that seems to suggest that tanning increases melanin and that melanin helps prevent cancer regardless of whether your dark skin is natural or tanned.
For a fixed amount of sun exposure, spreading out the duration is better both to establish a tan and to allow more time for skin recovery. But there isn't really a case where tanning increases safety, because you get the tan via exposure.
It's like saying pilots who practice a lot are safer; for any given flight it might be true, but cumulative risk can only rise.
https://www.scientificamerican.com/article/fact-or-fiction-a...
You clearly get more than SPF 3 with a deep tan as you can spend 8 hours in direct sun without obvious problems. Without any tan you get a burn in under an hour suggesting ~SPF 10+.
So think about it this way:
If you're genetically predisposed to having very dark skin, you will be able to tolerate more UV exposure without significantly increasing your risk of cancer. And by continuing to be exposed to high UV levels, your body will continue to produce melanin to keep you protected. It's a feedback loop.
If you're genetically predisposed to having pale skin, but then expose your skin to higher levels of UV than your low melanin levels can guard against, you will sustain significant sunburn, and if you do this repeatedly you'll significantly increase your risk of skin cancer. But if you gradually expose yourself to moderate levels of UV you can gradually increase your melanin levels more safely, but only as far as your genetics allow. (This is theoretical of course; we know very well that it's very hard for fair-skinned people to expose themselves to UV light from the sun or tanning beds without overdoing it, hence the widespread occurance of skin cancer.)
My educated guess about the notion that dark skinned people are experiencing higher levels of cancer would be that if a dark-skinned person keeps avoiding UV for long enough, their melanin levels start to decline (due to it not being an optimal use of resources), but then if/when sun exposure happens, the protection isn't as strong and the risk of cancer is higher.
I'm curious as to whether your educated guess derives from a clinical background, or reddit?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671032/
http://www.skincancer.org/prevention/skin-cancer-and-skin-of...
https://theconversation.com/amp/sun-damage-and-cancer-how-uv...
I know, I acknowledged that in my comment.
My main point was only about the extent to which people with genetically high melanin levels are at much lower risk of cancer (which your first link confirms), but how their risk might increase if their melanin levels drop.
I don't dispute that it's a complex and dangerous topic. And as someone with genetically very pale skin, I most certainly steer well clear of direct sunlight and make no efforts to develop a tan.
I'm curious as to whether your educated guess derives from a clinical background, or reddit?
That's a low blow :)
I rarely go anywhere near Reddit, certainly not for anything to do with health. I have spent 10+ years researching health topics for reasons to with serious, chronic, illnesses I've endured, and have now largely overcome thanks to what I've learned.
And even last year I heard girls talk about building up a 'base tan' before summer. Roasting like rotisserie chickens under the solarium lamps.
> people who were previously were at lower risk of cancer due to their skin pigmentation/higher melanin