Sunscreen's Vitamin D Effect Isn't What You Think

One of the most common reasons people give for skipping sunscreen is vitamin D — the idea that sun protection blocks your skin from making enough of it. It's not a baseless worry: sunscreen really does interfere with the same UVB rays your skin uses to make vitamin D. For years the real-world size of that effect was genuinely unclear — but 2025 brought the first randomized controlled trial built to answer it directly, and the picture is more specific now than a flat yes-or-no.

What The Research Actually Shows

Vitamin D synthesis starts when UVB rays hit your skin. Sunscreen works by filtering UVB (and UVA), so in a lab setting, where it's applied at the full tested amount, it does measurably cut vitamin D production. That part of the myth is grounded in something real.

What used to be genuinely unclear was whether that lab effect showed up in how people actually use sunscreen day to day. The NIH's Office of Dietary Supplements has long noted that real-world use varies too much — most people apply less than the tested amount, miss spots, and don't reapply on schedule — to know for sure. The Sun-D Trial, published in the British Journal of Dermatology, closed that gap: 628 Australian adults were randomized to routine daily SPF 50+ application versus discretionary use for a year, and the routine group had a 33% higher relative risk of vitamin D deficiency. It's a real, measurable effect — but a small one, well short of the distance between the deficiency and sufficiency thresholds.

The American Academy of Dermatology's position doesn't hinge on the size of that effect either way. Its stated position is that there is no scientifically proven safe level of UV exposure from the sun that allows for maximum vitamin D synthesis without also increasing skin cancer risk. In other words, even where unprotected sun exposure would boost vitamin D, dermatologists still don't recommend it as the way to get there — the Academy directs people toward diet, fortified foods, and supplements instead. What's changed with the new trial data isn't that recommendation — it's that daily, high-SPF sunscreen use is now a specific, evidence-backed reason to check your vitamin D, not just a hypothetical one.

Where Your Vitamin D Should Actually Come From

If you're worried about your levels — and if you wear high-SPF sunscreen daily, that's now a concrete reason to check, not just a hypothetical one — the guidance points to the same few places, not unprotected sun.

• Eat vitamin D–rich foods regularly: fatty fish like salmon (about 570 IU in a 3-ounce cooked serving), fortified milk (about 120 IU per cup), or fortified plant milk and cereal.
• Ask your doctor about a 25(OH)D blood test, especially if you use high-SPF sunscreen daily and consistently. Under 12 ng/mL is associated with deficiency, and most people are considered sufficient at 20 ng/mL or above, per the National Academies' Food and Nutrition Board.
• If your levels come back low, ask your doctor about a supplement rather than more unprotected sun — there's no UV dose proven safe for that purpose.
• Know if you're in a higher-risk group: people who are largely homebound, cover most of their skin, have a naturally darker skin tone (which the Endocrine Society notes needs three to five times longer UV exposure for the same synthesis as lighter skin, and which most sunscreen-and-vitamin-D trials still underrepresent), older adults, or — per the 2025 trial data — anyone who applies high-SPF sunscreen daily and consistently.
• Keep using broad-spectrum SPF 30 or higher and reapplying as directed — the skin cancer risk from skipping sunscreen is well established and large; the vitamin D effect from using it is real but small, and a test or a modest supplement closes that gap without reopening the bigger one.