Sunscreen and vitamin D: using sun protection wisely
- , by SANUSq Research team
- 10 min reading time
Even the safest sunscreen is only part of sun protection — how you use it, and how you keep your vitamin D up, matter just as much.
In our companion article on chemical UV filters we looked at which sunscreen ingredients are worth trusting and which are worth avoiding. But choosing a good product is only half the story. How you use sun protection — and what you do about the vitamin D your skin would otherwise make in the sun — matters just as much. This piece tackles the questions that cause the most confusion: does sunscreen leave you short of vitamin D, how do you keep your levels up, and does a higher SPF actually keep you safer? It also takes an honest look at why skin-cancer rates have climbed even as sunscreen use has grown.
Does sunscreen cause vitamin D deficiency?
Vitamin D is unusual among nutrients: your skin makes most of it when UVB rays strike it, which is why sunlight rather than food is the main source for most people. It matters because vitamin D supports calcium absorption and bone strength, normal immune function and muscle function, and sustained deficiency is linked to weakened bones in adults and rickets in children. Because sunscreen is designed to block the very UVB that drives this process, it is reasonable to ask whether regular use leaves you short.
In a laboratory, sunscreen does reduce vitamin D production. Real life is more reassuring. The largest review to date — covering 75 experimental, field and observational studies — concluded that while lab studies confirm the theoretical risk, the weight of real-world evidence shows the risk is low, largely because people apply sunscreen thinly and patchily, leaving plenty of skin and time for synthesis (Neale et al., 2019). The effect is not quite zero: a 2025 meta-analysis found a small average reduction in vitamin D among sunscreen users (2025), and the newest randomised trial found that diligent daily use of SPF 50+ over a year did raise the risk of deficiency (Sun-D Trial, 2025). So the fair summary is that the effect is real but modest for most people.
The bigger drivers of low vitamin D have little to do with SPF. The people most likely to run low are those who get little UVB in the first place: anyone living at higher latitudes, where winter sun is too weak for months; people with darker skin, since more melanin means less vitamin D per unit of sun; older adults, whose skin synthesises less with age; and those who spend most daylight hours indoors or keep their skin covered. If you recognise yourself there, the answer is not to abandon sun protection — it is to top your vitamin D up another way.
So how do you keep your vitamin D up?
You have three levers, and the smartest approach usually combines them. Brief, incidental everyday sun exposure — the kind you get simply going about your day — contributes without the burn risk of deliberate sunbathing. Diet helps a little: oily fish such as salmon, mackerel and sardines, egg yolks and fortified foods are the main sources, though it is genuinely hard to reach an adequate intake from food alone. For anyone in the higher-risk groups above, a supplement is the most reliable, sunburn-free option — it lets you protect your skin properly without worrying about the trade-off at all.
This is where the form matters. Our liposomal vitamin D3+K2 pairs vitamin D3 with vitamin K2: D3 increases how much calcium your body absorbs, and K2 plays a role in directing that calcium toward your bones, which is why the two are commonly taken together. The liposomal delivery is intended to improve absorption compared with standard tablets. As always, a supplement supports good sun habits rather than replacing them, and it is worth checking your level with your doctor before taking higher doses.
Higher SPF can give a false sense of security
It helps to know what the SPF number actually means. SPF measures protection against UVB, the sunburn-causing rays, and the scale is not linear: SPF 30 filters roughly 97% of UVB and SPF 50 about 98%, so jumping from 30 to 50 adds only about one percentage point — not double the protection. SPF also tells you nothing about UVA, the deeper-penetrating rays involved in ageing and skin cancer; for those you need a product labelled broad-spectrum. And the rated SPF assumes a thick, even layer — about 2 mg of product per square centimetre of skin — that almost nobody applies. Most people use only a quarter to a half of that, so real-world protection sits well below the number on the bottle.
On top of the maths, there is a behavioural catch. Because sunscreen delays burning, it can quietly encourage people to stay out longer. A double-blind randomised trial found that young holidaymakers given SPF 30 spent significantly more time in the sun than those given SPF 10, without burning any more (Autier et al., 1999). A later review put this in perspective: sunscreen lengthens sun exposure mainly among people actively trying to tan — by 13–39% — and not among those whose exposure is incidental (Autier, 2007).
The practical takeaway: SPF is not a force field, and a bigger number is not a licence to stay out all day. Applying enough, reapplying every two hours and after swimming or sweating, and choosing broad-spectrum cover all matter more than chasing SPF 50 over SPF 30. Sunburn — which a good sunscreen genuinely does reduce — is itself a melanoma risk factor, so the aim is real protection, not a longer day in the sun.
Why skin-cancer rates rose even as sunscreen use grew
You may have seen the striking claim that melanoma rates climbed over recent decades even as sunscreen sales boomed — sometimes presented as though sunscreen were to blame. The honest explanation is more mundane. A 2023 analysis set out the leading reasons: decades of rising recreational and cumulative UV exposure; far better detection and screening, which finds many more early melanomas (including some that would never have caused harm); older sunscreens that guarded mainly against UVB sunburn rather than the deeper-penetrating UVA; and the risk-compensation effect described above (Lapides et al., 2023). In other words, the rise reflects how people have lived and how cancers are now found — not evidence that sunscreen causes melanoma. As covered in the companion article, randomised trials actually show that regular sunscreen use reduces melanoma and squamous cell carcinoma.
Using sun protection well
Pulling the practical threads together — and you'll find the ingredient detail in the companion article:
- Apply enough, and reapply. Use a generous layer, top it up every two hours, and reapply after swimming or sweating — under-application is the single biggest reason "I wore sunscreen" still ends in sunburn.
- Choose broad-spectrum, mineral where you can. Zinc oxide and titanium dioxide, with broad-spectrum UVA cover; the companion piece explains why they're the better-evidenced choice.
- Don't rely on sunscreen alone. Shade at peak hours, a wide-brimmed hat, sunglasses and UV-protective clothing carry much of the load with no chemical exposure.
- Keep your vitamin D up separately. Through diet or a supplement — not by leaving your skin unprotected.
Related reading: Sunscreen safety: what the science really says about chemical UV filters — which UV filters are worth trusting, the truth about oxybenzone and systemic absorption, the reef-safe debate, and how to choose safer protection.
Frequently asked questions
Will wearing sunscreen make me vitamin D deficient?
For most people, no. Lab studies show sunscreen can block the UVB that makes vitamin D, but in real-world use people apply too little for that to cause deficiency, and the main causes of low vitamin D are latitude, skin tone, age and indoor living. If you're at risk, top up through diet or a supplement rather than skipping sunscreen.
How much sun do I need to make enough vitamin D?
There's no single answer — it depends on your skin tone, the season, your latitude and the time of day, so health bodies increasingly steer people toward diet and supplements rather than deliberate unprotected sun. Short, incidental everyday exposure usually contributes, and a supplement reliably covers the rest if you're in a higher-risk group.
Is a higher SPF always better?
Higher SPF blocks marginally more UV and reduces sunburn, but the added benefit shrinks as the number climbs, and a high SPF can tempt you to stay out longer. Applying enough and reapplying matters more than chasing a bigger number.
If I take a vitamin D supplement, can I skip sunscreen?
No — they do different jobs. A supplement maintains your vitamin D; sunscreen, along with shade and clothing, protects against UV damage and skin cancer. Use both rather than trading one for the other.
References
- Neale RE, Khan SR, Lucas RM, Waterhouse M, Whiteman DC, Olsen CM. The effect of sunscreen on vitamin D: a review. Br J Dermatol. 2019;181(5):907–915.
- Sunscreen and 25-hydroxyvitamin D levels: friends or foes? A systematic review and meta-analysis. Endocr Pract. 2025.
- 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.
- Autier P, Doré JF, Négrier S, et al. Sunscreen use and duration of sun exposure: a double-blind, randomized trial. J Natl Cancer Inst. 1999;91(15):1304–1309.
- Autier P, Boniol M, Doré JF. Sunscreen use and increased duration of intentional sun exposure: still a burning issue. Int J Cancer. 2007;121(1):1–5.
- Lapides R, Saravi B, Mueller A, et al. Possible explanations for rising melanoma rates despite increased sunscreen use over the past several decades. Cancers (Basel). 2023;15(24):5868.
The health information contained in this article is for educational purposes only. Consult your healthcare professional before making any medical decisions.
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