How Does Sunscreen Work, and Does It Block Vitamin D? Here's What Dermatologists Say

The experts also detail the difference between how chemical and mineral SPFs protect the skin.

woman applying sunscreen to shoulder
Photo: boonchai wedmakawand / Getty Images

Beauty trends come and go, but there are some items in your skin care arsenal that should always be in rotation no matter what. One of the most important products? Sunscreen. While we already know that SPF is loaded with protective ingredients to shield skin from the sun, what's less understood is why and how these agents act as shields in the first place. So, how, exactly, do these formulas work? Another sunscreen query involves vitamin D: If these products do act as shields, do they prevent the body from absorbing enough of this nutrient? Here, we've tapped dermatologists to explore both topics. Ahead, they reveal the inner workings of sunblock and share how it influences the amount of vitamin D you truly get while in the sun.

How Does Sunscreen Work?

Sunscreens come in many forms, including gels, lotions, oils, and creams, and often feature several different blocking agents. According to Dr. Naana Boakye, MD, a dermatologist and the co-founder of Karité, there are currently 16 filters on the United States market—including zinc oxide, titanium dioxide, avobenzone, and oxybenzone—that can either block, absorb, or scatter the ultraviolet (UV) light from sunlight, which is made up of UV light, visible light, and infrared light. This means that sunscreens work by shielding against both UV ray types (UVA, which penetrates deep into the dermis, causing premature aging and fine lines, and UVB, which is typically responsible for sunburn, since it impacts the outermost layers of the skin), Dr. Howard Sobel, a dermatological surgeon and the founder of Sobel Skin Rx, adds.

What's the Difference Between Chemical and Mineral Sunscreen?

"Chemical sunscreens are composed of an organic structure," Dr. Boakye explains. "These filters absorb UVB and some UVA rays." These blockers sink into the skin, where they absorbs UV rays and convert them to heat before they are released from the body. Mineral sunscreens, on the other hand, sit on top of the skin and reflect and scatter UV light altogether. These formulas usually contain zinc oxide, which that protects against the entire UVA range and some UVB rays. Titanium dioxide is another common component. Dr. Boakye prefers mineral sunscreens that have a combination of zinc oxide, titanium dioxide, and iron oxide for optimal protection.

Does Sunscreen Block Vitamin D?

Even though sunscreen is meant to block harmful UV rays, it won't prevent you from getting vitamin D from sunlight altogether (and shouldn't deter you from wearing sunblock!). "Vitamin D is a hormone that is naturally produced in the body or obtained by supplementation like fatty fish, mushrooms, and eggs—[and it's] produced by UVB rays," Dr. Boakye says. "Many studies have shown that sunscreen usage has minimal impact on vitamin D levels; sunscreen usage is important, especially with individuals with genetic and acquired photosensitive disorders."

How Can You Get Enough Vitamin D?

Ensure you're getting plenty of vitamin D with supplementation. "Minimal sun exposure is okay," Dr. Boakye says. "The key is to practice safe sun care practices, like wearing wide-brim hats, broad spectrum sunscreen, and UPF shirts." Plus, Dr. Sobel says there are ways you can change your diet to get more vitamin D if it's a concern "I recommend that everyone, especially women over 30, take a vitamin D supplement (600 IU) daily to keep levels optimal, as vitamin D is responsible for bone health," he says. "Also, there are many vitamin-D rich foods that help keep levels high—try snacking on eggs, salmon, yogurt, milk, and fortified orange juice."

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