>>11632464Yes, it is absolutely essential. A very large majority of skin aging is caused by UV-A rays penetrating the skin, which destroy collagen. UV-B rays however, cause sunburn. They penetrate the skin at different levels and affect the skin differently.
I've done an insane amount of research on sunscreen and skin aging, and the problem is, not all sunscreens are as effective as one another. American ones hardly do shit, European ones are very effective but not cosmetically elegant, Asian ones are more cosmetically elegant but not as effective as European.
Other contributing factors to skin aging are not taking care of it (cleansing, moisturizing, constant repetitive facial motions over a long period of time, sleeping on your face), alcohol, smoking, poor diet, stress, and of course genetics in the end.
The people over at /r/asianbeauty on reddit do an actual shocking amount of legitimate research on the efficacy of skincare products, there's many frequent posters there who are chemists, biochemists, gerontologists (as far as I know), dermatologists, etc.
There's one post you can find online searching 'chinese sunscreen test' that shows the efficacy of different sunscreens.
Me personally, I'm a bit vain, but I would never even so much as step outside in the sunlight without a wide brimmed hat and sunscreen. Some people call it overboard, but I would rather take (at most) 5 more minutes out of my day and be a little cautious than to have old skin by the time i'm 40. As far as Vitamin D, you still get a sufficient amount with sunscreen, and it doesn't hurt to take a supplement, nor is it that bothersome or expensive to do so.
TL;DR Yes, sunscreen is absolutely necessary if you want to stay looking young and have your skin retain it's elasticity, shine, and nice color.
If you don't care too much about appearances and you're at peace with the fact that you will visibly age, then no I don't think it's necessary.
