Skin colour is intended to regulate the amount of UV we receive in order to synthesise vit D. We are all Africans, but a few thousand years ago some of us were stupid enough to walk up to Northern Europe and we had to go pale in order to get enough UV.
Now we wear clothes and live indoors all year round.
Low sun exposure for people with dark skin can be very unhealthy; pregnant women in Iran for example are suffering widespread vitamin D deficiency and of course that is very bad for their foetuses. Black people living in Blighty are at risk of low bone density etc.
We have all got to die of something and you may consider an unseen internal problem vs one on the surface that you can spot early. Each of us, individually need balance.... read up on Homeostasis if you've not heard of it.
The big problem for white people is 50 weeks of darkness and clothes then 2 of ridiculous intense sunlight in combination with skin that adapts to sunlight very slowly, you can't adapt in 2 weeks, you will burn!
The key is to try to keep your exposure as constant as possible year-round, keep it at generally low level if you are very white and quite high if you are dark.
White people that go to the Med in Jul/Aug are nutts in my opinion.... try going on holiday in the winter and pay the stupid School Fine.... it is lovely, sunny - even better than Blighty's 'summer', not too hot and because it is cheaper, you can go for longer, and more often.
Finally lying in the sun is bad because you are getting no exercise and certain parts get hammered badly while other areas get nothing + your circulation shuts down and your skin overheats.
Holiday in winter, wear a hat, go out morning and afternoon to avoid the mid day, and when you do get sun, move about, go cycling or something, get sunshine evenly and lightly. If the sun comes out and is direct on your skin, get in the shade or put something thin on.