While vitamin C won’t protect the skin the same way sunscreen does, topical serums and creams with the famous antioxidant still play a role in keeping your skin healthy on a cellular level. This is because the exposure of skin to UV rays generates free radicals that have the potential to start a chain reaction that may lead to interference with normal cellular function.
When the skin is put into an extended state of oxidative stress (thanks to the free radicals), physical skin aging (think sagging, fine lines, etc.) might follow suit. Luckily, vitamin C’s antioxidant properties work to limit free radical effects, thus playing a significant role in preventing signs of skin aging triggered by UV rays.
Again, vitamin C will not replace your sunscreen in any way. That being said, a vitamin C serum is a worthy step to layer under your go-to SPF every morning.