Of course when heading down the sunscreen isle, people reach for the highest SPF they can find. Why? It's because they think this means the sunscreen will last longer. However, this is completely untrue. SPF doesn't indicate the product's ability to shield from cancer-causing UVB rays and UVA rays - which are linked to causing wrinkles and aging skin.
What's your best bet? It is recommended to seek out sun protection like MD Sun Protection that is labeled "Broad Spectrum," which means it covers both UVA and UVB rays and an SPF of 30. Why the lower SPF? While an SPF of 15 screens out only about 93% of UVB light, an SPF of 30 filters out 97% - and any higher SPFs don't offer much more of a benefit.