I was wondering if sunscreen would diminish the skin's ability to produce Vitamin D.
Yes, a UVB-blocker with SPF 8 will inhibit about 95% of vitamin D production in the skin it covers (acc. to Wikipedia).
there are essentially two types of sunrays, UVA and UVB, does sunscreen blockout both of them?
Depends on the sunscreen. Almost all sunscreens block UVBs because those are the tanning & carcinogenic rays. More recent formulae also block UVAs, which contribute to skin aging throughout our lives and are also modestly carcinogenic.
I was just wondering if sunscreen is a must as natural sun exposure might provide pros that outweigh the cons.
I don't think the increased risk of skin cancer and the progressive skin degradation/aging that UVs give you can ever be outweighed by the vitamin D production (which reinforces your immune system) if you take into account that there are alternative sources of vit. D (foods, supplements) that you can tap, which don't do any such damage to the skin.
In the end, it's just a question of how important your skin's (long-term) health is to you (because it involves conscious effort - choosing the foods or taking the pills - to maintain your vit. D levels while using sunscreen on a daily basis).
- After all, Number One, we're only mortal.
- Speak for yourself, sir. I plan to live forever.