Sun-D Trial 2025: Daily High-SPF Lowered Vitamin D — Supplement, Don't Skip
A 2025 randomized trial found daily high-SPF sunscreen nudged vitamin D down — but the answer is a supplement, not skipping your sunscreen.
The open-label randomized Sun-D Trial of 628 Australian adults found daily high-SPF sunscreen produced a between-group vitamin D treatment effect of -5.2 nmol/L, with deficiency (<50 nmol/L) more common in the sunscreen group (45.7% vs 36.9%; prevalence ratio 1.33).
The trial authors concluded that regular sunscreen users may benefit from vitamin D supplementation, framing supplementation — not abandoning daily SPF — as the appropriate response to the modest reduction they measured.
Questions we get a lot
What did the 2025 Sun-D Trial actually find?
The open-label randomized Sun-D Trial of 628 Australian adults found that daily high-SPF sunscreen produced a between-group vitamin D treatment effect of -5.2 nmol/L. Deficiency, defined as below 50 nmol/L, was more common in the sunscreen group at 45.7% versus 36.9%, a prevalence ratio of 1.33. The reduction was real but modest.
Does this mean I should stop wearing sunscreen?
No. The trial authors concluded that regular sunscreen users may benefit from supplementation, not that they should skip sun protection. The risks of unprotected UV exposure remain significant, while a modest vitamin D shortfall can be addressed safely with a supplement. Supplementing lets you keep both your skin protection and your vitamin D.
Who should consider a vitamin D supplement if they use SPF daily?
People who wear high-SPF sunscreen every day — especially those with limited sun exposure or known low vitamin D — are reasonable candidates to consider supplementation, based on the Sun-D Trial's conclusion. The trial measured a modest reduction and a higher rate of deficiency in the sunscreen group. Discuss testing and dosing with your clinician.
r/SkincareAddiction: 'I saw a TikTok saying a 2025 study proves sunscreen causes vitamin D deficiency — is that actually what the research found?'