Can wearing sunscreen every day lower your vitamin D?

A new study suggests that regular SPF50+ use can make a small difference. But that does not mean we should stop protecting our skin.

As a doctor, I want your skincare routine to support your health as a whole. For those of us living in Switzerland, questions about sunscreen, vitamin D and changing seasons are especially relevant. Here is my analysis of the newest australian Sun-D Trial, what it found, and what I would take from it for your everyday routine.

First, why do we need vitamin D?

Vitamin D helps your body use calcium and phosphate, which are important for healthy bones and muscles. Your skin can make vitamin D when it is exposed to UVB rays from sunlight. You can also get it from certain foods and supplements.

It is a fat-soluble vitamin that helps your body absorb calcium, supports healthy bones, helps muscles work and supports normal immune function.

How does sunlight help your skin make vitamin D?

UVB rays start the process in your skin, turning a naturally occurring compound into vitamin D3. Your liver and kidneys then help convert it into its active form. Sunlight starts the process; your body does the rest.

Sunscreen reduces the UV rays reaching your skin. So it makes sense to ask whether it also affects vitamin D. The answer depends on what happens in real life: how much sunscreen you apply, how much skin is covered by clothing, how long you spend outdoors and the season.

When doctors check vitamin D, the blood test usually measures 25(OH)D. You do not need to remember that name—it is simply the blood marker used to assess your vitamin D supply.

The study explained simply: two groups, different sunscreen habits

Imagine taking a large group of adults and asking half of them to make sunscreen part of their morning routine, while the other half continue deciding for themselves when to use it. Then you compare their vitamin D levels over time. That is essentially what the researchers did.

They recruited 639 adults aged 18–70 in eastern Australia. A computer assigned them to two groups by chance. This is called a randomized trial: it helps make the groups comparable so researchers can better assess the effect of the change in sunscreen habits.

• Group one made SPF50+ a routine. They received broad-spectrum sunscreen and were asked to apply it in the morning to skin not covered by clothing whenever the forecast UV index was 3 or higher. The UV index tells you how strong the sun's ultraviolet radiation is.
• Group two chose when to use sunscreen. They could still apply it whenever they wanted. Both groups received usual sun-protection advice.

Researchers checked vitamin D before the study, after summer and after winter, over roughly a year. They analysed results from 628 participants who provided at least one follow-up blood sample.

The study was “open-label”, meaning people knew which group they were in. However, the laboratory measuring vitamin D did not know the assignments, and the main statistical analysis was prepared without knowing the true groups. These steps help reduce bias.

The key detail: this was regular sunscreen use compared with use whenever people chose—not sunscreen compared with never using it.

What did the researchers find?

The regular SPF50+ group had a small but clear reduction in vitamin D compared with the other group. Across the two follow-up checks, the adjusted difference in change from the starting level was 5.2 nmol/L lower.

That is a difference between groups, not a prediction of how much your own vitamin D will change. For readers who enjoy the numbers, the 95% confidence interval was −7.2 to −3.2 nmol/L.

At the final winter check, more people in the regular sunscreen group were below the study's vitamin D threshold:

Put simply, that is about 46 out of 100 people versus 37 out of 100—a difference of around nine people per hundred. The exact difference was 8.8 percentage points.

The researchers' adjusted relative comparison was 1.33, with a 95% confidence interval of 1.14–1.55. This does not mean sunscreen reduced everyone's vitamin D by 33%.

The study called a level below 50 nmol/L (20 ng/mL) vitamin D deficiency. Different guidelines use different thresholds. This part of the analysis was exploratory, meaning it was an additional finding rather than the main outcome the trial was designed around.

Among participants who followed their assigned sunscreen habits, the difference was slightly larger: 6.7 nmol/L. The effect also remained in analyses limited to people who did not take vitamin D supplements.

Does this change what we thought about sunscreen?

It adds useful detail. Earlier randomized studies found little or no difference in vitamin D, but they used sunscreens with an SPF of around 16. This study looked at SPF50+, which is closer to what many people now choose for daily facial sun protection.

For me, “sunscreen never affects vitamin D” is too strong a statement. A more accurate explanation is that regular high-SPF use can modestly lower vitamin D levels, so it is sensible to pay attention to your vitamin D needs too.

What does this mean for skincare in Switzerland?

If you are building a skincare routine in Switzerland—whether your focus is sensitive skin, pigmentation or healthy skin ageing—sun protection still has an important place. This study gives us a reason to think about vitamin D alongside that routine.

However, the research was done in Australia. Switzerland has different seasonal sunlight and everyday habits, so we cannot assume the same numbers apply here. The trial also covered skin exposed beyond the face. It cannot tell us exactly what happens when someone only applies facial sunscreen.

Another point I would keep in mind: the study measured vitamin D levels. It did not establish that this difference caused more fractures or other illness. Participants had skin types I–IV, so it also does not directly answer the question for the darkest skin types.

People did not always follow the sunscreen instructions perfectly, some in the comparison group used sunscreen frequently, and dietary vitamin D was not measured. These are useful limits to remember when interpreting the findings.

My advice: protect your skin and look after your vitamin D

Keep applying enough sunscreen

I would not recommend using less sunscreen or switching to a lower SPF just to make more vitamin D. UV exposure contributes to skin cancer, premature skin ageing and uneven pigmentation.

Choose broad-spectrum SPF30 or higher; SPF50+ is a useful daily option. Apply generously to exposed skin and follow the label. Reapply about every two hours when outdoors and after swimming or sweating. Shade, clothing, a hat and sunglasses matter too. For sport or swimming, choose a suitable water-resistant sunscreen.

Give vitamin D a place in your health routine

Oily fish, eggs and foods fortified with vitamin D can contribute to your intake. Check labels, because fortification varies and food alone may not meet everyone's needs.

If you spend little time outdoors, have had low vitamin D before, or have a condition affecting absorption or bone health, ask your doctor or pharmacist whether a supplement would be helpful. Your needs may also deserve a fresh look as the seasons change.

Natural vitamin D sources beyond sunlight

Vitamin D production in your skin varies with the season, skin tone, age and how much skin is exposed. Sitting in sunlight through a window is not a useful way to make vitamin D because glass blocks most UVB.

Natural food sources include oily fish such as salmon, sardines and mackerel, with smaller amounts in egg yolks. Mushrooms exposed to UV light can provide vitamin D2. The amount varies between foods, so these sources may not meet every person’s needs.

You do not automatically need a blood test

Wearing sunscreen every day does not mean everyone needs an immediate vitamin D test. General guidance advises against routine screening in otherwise healthy adults. Your medical history, symptoms and individual risks help determine whether testing is useful.

If you need a supplement, choose the dose with appropriate advice. Avoid high doses or combining several vitamin D products without checking the total amount. More is not always better.

Find a sunscreen that feels good on your skin

When choosing a Korean sunscreen for your daily routine, I would focus on reliable protection, a comfortable texture and how it suits your skin and activities. The trial did not compare brands or mineral versus organic filters. It cannot tell us that one sunscreen preserves vitamin D better than another.

You can browse my sun protection collection at More About Skin to compare options available in Switzerland.

Quick answers to common questions

Can SPF50+ cause low vitamin D?

The Sun-D Trial found modestly lower levels with routine SPF50+ use, and more people fell below its chosen threshold. That does not mean every sunscreen user will develop deficiency. Your starting level, diet, exposure and health also matter.

Should I skip sunscreen to get vitamin D?

I would keep protecting your skin and address vitamin D through food and, when appropriate, supplements. Deliberately increasing unprotected UV exposure is not the solution I would recommend.

Does everyone who wears sunscreen need supplements?

No single answer fits everyone. The study suggests regular users may need to consider their vitamin D intake, but it did not test a supplementation plan or establish a dose for all sunscreen users.

Sources and further reading

1. Swiss Federal Food Safety and Veterinary Office (FSVO/BLV). Swiss Food Composition Database: Vitamin D — background on vitamin D, UVB synthesis and dietary intake.
2. Swiss Federal Food Safety and Veterinary Office (FSVO/BLV). Vitamin D recommendations for Switzerland.
3. 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. British Journal of Dermatology. 2025;193(6):1128–1137. doi:10.1093/bjd/ljaf310.
4. American Academy of Dermatology. Sunscreen FAQs and How to apply sunscreen.
5. Demay MB, Pittas AG, Bikle DD, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. 2024;109:1907–1947. doi:10.1210/clinem/dgae290.

This article provides general education and does not replace an individual medical assessment.

Find your daily sunscreen

Here are three sunscreens from my More About Skin collection to explore for your routine. These are shop recommendations, not products evaluated in the Sun-D Trial, and none is claimed to preserve vitamin D better than another. Check each product page for the formulation and usage details.

Explore all sun protection →