The most effective way to delay signs of aging is to wear broad-spectrum sunscreen with good UVA protection daily—not only when you go to the beach. But beware: Products boasting high SPF numbers can be very misleading. High SPF ratings, in the 40s, 50s and even higher, indicate complete, broad-spectrum, UVB/UVA protection. The implication is that the higher the number, the greater your level of protection.
The solution: Wear broad-spectrum sunscreen containing zinc oxide, preferably non-nano, i.e., particles >100 nm.
Zinc oxide is the only sunscreen ingredient to protect across the entire UV spectrum: UVA both short (320-340 nm, a.k.a UVA-2) and long (340-400 nm, a.k.a. UVA-1), as well as UVB rays. Regular zinc oxide also blocks visible light up to wavelengths 700 nm, whereas zinc nanoparticles block only up to 380-400 nm, depending on the specific formulation. As a single ingredient, zinc oxide, especially bulk, is the broadest range sunscreen on the market.
Zinc oxide has a long history of safe use. It’s not irritating, and it is compatible with sensitive skin. In fact, zinc oxide is an anti-inflammatory, widely used in treating various forms of dermatitis/skin irritation including diaper rash.
Bulk zinc oxide (particles >100 nm) is highly stable under most conditions. Zinc oxide nanoparticles are far more reactive/catalytic than regular zinc oxide and break down quickly in the presence of UV to generate free radicals. Most manufacturers use coated zinc oxide nanoparticles to minimize free radical formation.
An elegant study by Dr. Brian Gulson et. al., definitively demonstrated that small amounts of zinc from zinc oxide particles in sunscreens are absorbed through human skin. This suggests that particles, especially nanoparticles, of other substances used in sunscreens, such as titanium dioxide, also probably penetrate past the epidermal barrier. Zinc oxide breaks down into zinc ions that the body can utilize; titanium dioxide does not break down. It’s this difference that begs the question: What happens to some of the substances we put on our skin?