Does Sunscreen Cause Vitamin D Deficiency in Adults Over 75?
By: Abby Lu
The sunscreen industry is valued at over $15 billion in 2025, and major health organizations recommend reapplying SPF 50+ every two hours outdoors (AAD, 2024; Grand View Research, 2025). Melanoma is most frequently diagnosed between ages 65 and 74, and adults over 65 account for more than 40% of US melanoma cases and over 60% of melanoma-related deaths (Garcovich et al., 2017; National Cancer Institute, 2024).
But sunscreen blocks UV rays, and UV rays are how your body makes Vitamin D. Vitamin D deficiency is linked to falls, hip fractures, heart disease, and immune dysfunction, especially concerning for elderly where a hip fracture can be life-threatening (Holick, 2007; Magaziner et al., 1997). So the question naturally arises: does wearing sunscreen regularly cause Vitamin D deficiency in this population?
How Vitamin D Works
When UVB radiation hits your skin, it converts a cholesterol compound into Vitamin D3. The liver processes this into calcidiol, the standard clinical measure of Vitamin D status, and the kidneys convert it further into calcitriol, the active hormone form (Holick, 2007). Deficiency is defined as calcidiol falling below a specific threshold, though the Endocrine Society’s 2024 guidelines acknowledged ongoing uncertainty about exactly where that threshold should be (Demay et al., 2024).
However, skin over 70 produces roughly four times less previtamin D3 per unit of UVB than younger skin (MacLaughlin and Holick, 1985). So even before sunscreen enters the picture, adults over 75 are already severely disadvantaged. On top of that, limited mobility, lower dietary intake, certain medications, obesity, and declining kidney function all independently lower Vitamin D in this population (Forrest and Stuhldreher, 2011; Holick, 2007).
The Case That Sunscreen Isn't the Problem
A 2017 German study found that SPF 50+ sunscreen reduced Vitamin D production at the skin level by 75–92%, yet reduced circulating Vitamin D levels by only 7–13% in young adults, suggesting the body has other methods that enhance Vitamin D buffering capacity (Libon et al., 2017). They theorize that older people’s buffering capacity may diminish as they age.
The most cited clinical trial is a 1995 Australian study comparing daily SPF 17 sunscreen to no sunscreen over a full summer (Marks et al., 1995). Both groups showed nearly equivalent rises in Vitamin D, and nobody became deficient. This is frequently used to argue sunscreen is harmless, but SPF 17 may be weaker than the SPF 50+ recommended today (AAD, 2024), the study was conducted in a high-UV Australian environment that doesn’t reflect most US conditions (Webb et al., 1988), and the over-70 subset was never reported separately (Marks et al., 1995).
The most rigorous evidence comes from a 2025 randomized controlled trial published in the British Journal of Dermatology, enrolling 628 Australian adults aged 18–70 (Tran et al., 2025). Participants assigned to daily SPF 50+ ended the year with Vitamin D levels 5.2 nmol/L lower than controls, and 45.7% met the deficiency threshold compared to 36.9% of controls—a statistically significant difference—and the first controlled evidence that high-SPF daily use causally lowers Vitamin D (Tran et al., 2025).
The limitations are important though: the trial was open-label (participants knew their group, potentially changing outdoor behavior), excluded people already taking supplements, was conducted in high-UV Australia, and crucially, enrolled nobody over 70 (Tran et al., 2025). The population this question most concerns is entirely absent from the data.
A 2025 meta-analysis of 22 studies and nearly 9,500 participants found sunscreen associated with a mean Vitamin D reduction of about 5 nmol/L across all ages (Gatta and Cappelli, 2025). This is modest but potentially meaningful for adults over 75 who are already starting from lower baseline levels (Schleicher et al., 2016).
Why this is a mess?
Clinical trial on this question has either excluded adults over 70 or enrolled too few to report results for that group. The 1995 trial didn’t report its over-70 subset (Marks et al., 1995). The 2025 trial capped enrollment at 70 (Tran et al., 2025). The meta-analysis pooled all ages without stratified estimates for older adults (Gatta and Cappelli, 2025). Thus, whether SPF 50+ daily sunscreen meaningfully lowers Vitamin D in adults over 75 whose synthesis capacity is already severely compromised has little direct controlled evidence either way.
Most older studies also used SPF 15–17, not the SPF 50+ now recommended (AAD, 2024). Furthermore, guideline definitions of deficiency have shifted as studies reporting “no participant reached deficiency” measured against a threshold the Endocrine Society has since revised (Demay et al., 2024).
Final Takeaways
For adults over 75, the evidence suggests sunscreen is a minor contributor to Vitamin D deficiency compared to aging skin, indoor lifestyle, diet, and declining kidney function (MacLaughlin and Holick, 1985; Forrest and Stuhldreher, 2011; Demay et al., 2024). The 2025 trial provides evidence that SPF 50+ daily use lowers Vitamin D meaningfully but its population was capped at 70, was Australian, and was open-label, limiting how directly it applies here (Tran et al., 2025). The observed 5.2 nmol/L reduction is also within the range that basic oral supplementation can replace (Demay et al., 2024).
The Endocrine Society’s 2024 guidelines already recommend empiric Vitamin D supplementation for adults over 75 regardless of measured levels (Demay et al., 2024), making the practical answer straightforward: keep using sunscreen and supplement for this population. The research answer is less tidy: the trial specifically needed to settle this question, in this population, still needs further exploration.