Sunscreen and Vitamin D: Does SPF Cause Deficiency?
- , by SANUSq Research team
- 10 min reading time
If sunscreen blocks the UV rays your skin uses to make vitamin D, does daily use leave you short?
The question behind the worry
Your skin makes vitamin D when UVB rays from the sun reach it. Sunscreen works by blocking UV — so on paper, there's an obvious tension: if you cover your skin in SPF every day, are you switching off your own vitamin D supply? It's a fair question, and one that genuinely matters, because vitamin D is important for bone health, immunity and more, and deficiency is already common.
The honest answer has become more nuanced over time, so it's worth walking through what the evidence actually shows rather than settling for a slogan.
Does sunscreen block vitamin D?
In the laboratory, yes: applied thickly and evenly, sunscreen can substantially reduce the skin's vitamin D production. But laboratory conditions aren't real life. For years, the reassuring view — based on real-world observation — was that people apply less sunscreen than in experiments, miss patches, and get incidental sun, so everyday use didn't appear to cause deficiency.
A systematic review concluded that while experimental studies support a theoretical risk that sunscreen can reduce vitamin D synthesis, the weight of evidence from field trials and real-world observational studies suggested the risk was low (Neale et al., 2019).
Why laboratory results and real life differ
The gap between those two pictures is less a contradiction than a difference in conditions. Laboratory tests apply sunscreen at a standard thickness, evenly, across the whole test area. In everyday use people apply considerably less than that standard amount, spread it unevenly, miss the edges of the face, the ears, the neck and the backs of the hands, and reapply less often than the label advises. The practical result is that a product rated at a high SPF delivers rather less protection on real skin than on test skin — a problem for sun protection, and part of the reason some vitamin D synthesis carries on regardless.
On top of that, most people get incidental ultraviolet that has nothing to do with a deliberate trip outdoors: walking between buildings, hanging out washing, sitting in a garden with a cup of tea. That background exposure is one reason the older observational research kept failing to find the deficiency the laboratory work predicted.
What newer, higher-quality evidence adds
That reassuring picture has been complicated by better data. When researchers ran a proper randomised controlled trial — having people apply high-SPF sunscreen daily for a year — the sunscreen group ended up with lower vitamin D levels and a higher rate of deficiency than the control group. In other words, diligent daily use of high-SPF sunscreen can measurably affect vitamin D status, more than the older real-world studies suggested.
In the randomised Sun-D trial, one year of daily high-SPF sunscreen use resulted in lower average 25-hydroxyvitamin D levels and a higher prevalence of vitamin D deficiency compared with the control group (Tran et al., 2025).
It's worth keeping perspective: this is not a reason to abandon sun protection, which prevents skin cancer, as we cover in sunscreen safety and UV filters. It's a reason to be deliberate about keeping your vitamin D up by other means.
Sunscreen and vitamin D: weighing two very different risks
When two risks appear to pull in opposite directions, the useful questions are how serious each one is and how easily it can be undone. Ultraviolet exposure is an established cause of skin cancer and of the visible ageing that comes with it, the damage accumulates over a lifetime, and none of it can be reversed later. A vitamin D shortfall is a different kind of problem altogether: it can be measured with a blood test, it can be corrected through food or a supplement, and correcting it requires exposing your skin to nothing at all.
Put that way, the sensible order is obvious. Keep the protection, and settle the vitamin D question by a route that carries no cost. Nothing in the recent trial data is an argument for wearing less sunscreen; what it argues for is not assuming that sunlight alone will keep your level where it needs to be.
How to keep your vitamin D up — without skipping protection
The takeaway isn't "stop wearing sunscreen"; it's "don't rely on unprotected sun for your vitamin D". A few sensible habits cover it: eat vitamin D-rich foods such as oily fish, egg yolks and fortified products; get brief, incidental sun exposure without deliberately burning; and, where diet and lifestyle fall short — which is common, especially in winter and at higher latitudes — consider a vitamin D supplement. We look at how widespread shortfalls are in vitamin D deficiency during winter.
What determines how much vitamin D sun exposure actually gives you
Sunscreen is only one variable here, and usually not the largest. How much vitamin D your skin makes depends on how much UVB reaches it, and that varies enormously. Latitude and season set the ceiling: when the sun sits low in the sky, the atmosphere filters out almost all the UVB, which is why skin in northern Europe makes little or none for a good part of the year no matter how long you stand outside. Time of day works the same way. Skin tone matters, because melanin absorbs ultraviolet, so more time is needed for the same effect. The skin's capacity also declines with age, and how much of it is uncovered obviously changes the arithmetic. Ordinary window glass blocks UVB, so a sunny room contributes nothing, and heavy cloud or urban air pollution cuts down what gets through.
The honest conclusion from that list is not that anyone should chase sunlight harder. It is that sun exposure is an unreliable and largely unmeasurable way to guarantee a level, which is precisely why the dietary and supplemental routes are easier to control.
For readers who want a simple way to keep levels topped up, SANUSq offers a liposomal Vitamin D3 + K2.
Frequently asked questions
Does sunscreen cause vitamin D deficiency?
It can contribute. In the lab, sunscreen reduces vitamin D production, and a recent randomised trial found that a year of daily high-SPF use lowered vitamin D levels and raised deficiency rates. Earlier real-world studies suggested the effect was small, so the best summary is that diligent daily high-SPF use can matter — but it is easily offset by diet and supplements.
Should I stop wearing sunscreen to get more vitamin D?
No. Sunscreen prevents skin cancer, and that benefit is well established. The better approach is to keep protecting your skin and top up vitamin D through food, brief incidental sun, or a supplement.
How much sun do I need for vitamin D?
It varies enormously with skin tone, season, latitude and how much skin is exposed, so there's no single figure — and deliberately seeking a burn is never the answer. Where sunlight is limited, food and supplements are the reliable route.
Does a higher SPF block more vitamin D?
Higher-SPF products block more UV overall, and the recent trial that found an effect used high-SPF sunscreen. That's another reason to maintain vitamin D through other means rather than relying on sun exposure.
Does having a tan mean I have made plenty of vitamin D?
No. A tan is the skin's response to ultraviolet damage, not a record of how much vitamin D was produced, and the extra melanin it represents slows subsequent production rather than speeding it up. Burning tells you less still: it is an injury, and there is no point at which more redness means more vitamin D. The only way to know where your level actually sits is a blood test through your healthcare professional.
Do sunbeds count as a way of getting vitamin D?
They are not a sensible route to it. Sunbeds deliver an ultraviolet output weighted quite differently from sunlight, and they carry a recognised skin cancer risk, which is why health authorities advise against using them for this purpose. The trade-off described above applies here with more force, not less, and the dietary and supplemental routes remain the ones that cost your skin nothing.
Who is most at risk of low vitamin D?
People with limited sun exposure, those at higher latitudes or during winter, people with darker skin, and those who cover up or stay indoors are most at risk — independent of sunscreen. A blood test through your healthcare professional is the reliable way to check.
Keep your levels topped up
Protect your skin and maintain healthy vitamin D with our liposomal Vitamin D3 + K2.
References
- Neale RE, Khan SR, Lucas RM, et al. The effect of sunscreen on vitamin D: a review. Br J Dermatol. 2019;181(5):907–915. PMID 30945275
- Tran V, Duarte Romero BL, Andersen H, et al. Effect of daily sunscreen application on vitamin D: findings from the open-label randomized controlled Sun-D Trial. Br J Dermatol. 2025;193(6):1128–1137. PMID 40927943
Read more on the blog
- Sunscreen safety: chemical UV filters
- Vitamin D deficiency during winter
- Vitamin D: the natural antibiotic
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We wish you good health on your terms.
The team at SANUSq.
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The health information in this article is provided for educational purposes only. Consult your healthcare professional before making any medical decisions.
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