Sunscreen and Vitamin D Deficiency: What the Newest Trial Actually Found
In 2019 a research team reviewed everything published on sunscreen and vitamin D. In 2025 the same team ran their own trial and got a different number.
The short version: the question of sunscreen and vitamin D deficiency got a new answer last year, and it’s a small one rather than a scary one. In an Australian trial, people asked to apply SPF 50+ on every day with a UV index of 3 or higher gained 5.2 nmol/L less in blood vitamin D over the year than people who used sunscreen whenever they felt like it.[1] Both groups went up over the study. The trial’s own conclusion isn’t “wear less”. It’s that regular sunscreen users may need a supplement.[1]
Two answers on sunscreen and vitamin D deficiency, six years apart
The 2019 answer was a review, not an experiment. It pulled together four lab studies, three field trials and 69 observational studies published up to November 2017, and it found a split: under artificial UV lamps sunscreen cut vitamin D production a lot, but out in the world it didn’t show up.[2] The field trials that found nothing used sunscreen around SPF 16.[2]
The 2025 answer is a randomized trial, and it changed two things at once: the SPF went up and the application became routine instead of occasional.
| Neale 2019 review[2] | Sun-D trial 2025[1] | |
|---|---|---|
| What it is | Review of 76 published studies | Randomized controlled trial |
| People | not applicable | 639 enrolled, 628 analyzed, ages 18 to 70, Australia |
| Sunscreen | Field trials used about SPF 16 | SPF 50+, on every day with UV index 3 or higher |
| How long | not applicable | About a year |
| Finding | Little evidence of a drop in real-life use | Sunscreen group gained 5.2 nmol/L less over the year |
So the older answer isn’t a mistake somebody has to take back. It described the evidence that existed, and most of that evidence was about weaker sunscreen used sometimes. The new trial asked a harder question, and got a small yes.
How much is 5.2 nmol/L in numbers I can actually use?
On its own, not much. Here is the shape of it.
Both groups started at about the same place, 63.5 nmol/L in the sunscreen group and 62.1 in the control group, and both went up by the end.[1] The sunscreen group rose 1.6 nmol/L and the control group rose 6.8.[1] Nobody’s level collapsed. One group just gained less.
The number that’s easier to feel is the count of people who fell under the line. The trial treated a blood level below 50 nmol/L as deficient, and by that definition 45.7% of the sunscreen group and 36.9% of the control group were deficient, which is 139 people out of 304 against 115 out of 312.[1] That’s a gap of about nine people in a hundred.
Nine in a hundred is not nothing, and it isn’t a crisis either. It’s the size of thing you fix with breakfast or a pill.
Does this mean I should skip sunscreen on some days?
The people who ran the trial didn’t say that, and it’s worth reading their sentence rather than a summary of it. Their conclusion was that routinely applying high SPF sunscreen gives lower vitamin D than discretionary use, and that regular sunscreen users may need vitamin D supplementation.[1] The fix they point at is the supplement, not the sunscreen.
The American Academy of Dermatology has been saying a version of this for years. Their wording is that sun protection may decrease your skin’s production of vitamin D, and that healthy adults should get enough of it from food that’s naturally rich in vitamin D or fortified with it.[3] That advice doesn’t change because of this trial. It fits it.
If you’re here because you’re trying to decide how much sunscreen to use in the first place, our piece on how much to apply is the more useful one, and the main guide covers choosing one.
I wear SPF every single day, so what should I do?
Talk to a doctor about it rather than to a blog, including this one. A blood test is the only way anyone finds out where you personally sit, and vitamin D dosing is a medical question. The AAD says the same thing: if you’re worried you aren’t getting enough, discuss your options with your doctor.[3]
Two things are worth bringing to that conversation. The first is that this trial deliberately recruited people who weren’t already taking vitamin D supplements and weren’t regular sunscreen users.[1] If you already take a supplement, the trial says nothing about you. The second is that this trial asked people to apply on days when the UV index was forecast to reach 3 or higher.[1] If your own exposure is mostly through a window, the indoor piece covers what does and doesn’t reach you there.
What the trial didn’t test
Reading a single trial as the last word is how people end up wrong twice.
- It ran in Australia.[1] Latitude, how much sun a year actually delivers, skin tone and diet all differ, and this study can’t tell you what the same routine does in Seoul or Seattle.
- It ran for about a year.[1] A one-year gap of 5.2 nmol/L doesn’t tell you what ten years look like in either direction.
- It used one deficiency line, and that count was a side question. Below 50 nmol/L was the trial’s definition, the deficiency count was listed as an exploratory outcome, and the primary outcome was the change in blood level from baseline.[1] Other bodies draw the deficiency line elsewhere, so the 45.7% figure belongs to this study’s ruler.
- It was open-label, meaning people knew which group they were in.[1] That’s normal for a study like this and still a limit.
- It didn’t compare brands or formulas. Nothing here separates a Korean SPF 50+ from any other SPF 50+.
FAQ
Am I going to be deficient because I wear sunscreen every day?
Not automatically. In the trial, 45.7% of the daily-sunscreen group and 36.9% of the control group came in under 50 nmol/L, so most of the difference is a shift in odds rather than a result you can read off your own routine.
Was the old answer that sunscreen doesn’t affect vitamin D just wrong?
It was an accurate summary of weaker sunscreen used occasionally. The 2019 field trials that found no effect used about SPF 16. The 2025 trial asked people to use SPF 50+ routinely and found a small drop.
Should I stop wearing sunscreen in winter to top my levels up?
That isn’t what the researchers concluded, and it isn’t advice we can give you. Their sentence points at supplementation for regular sunscreen users, and dosing is a conversation for your doctor.
Does this apply to me if I don’t live somewhere as sunny as Australia?
Unknown from this trial. It recruited Australian adults aged 18 to 70, and it doesn’t measure what the same routine does at a different latitude.
What should I actually do with this?
Keep the sunscreen habit, and take the vitamin D question to a doctor instead of solving it by getting more sun. The AAD’s own route is food that’s rich in or fortified with vitamin D.
Sources
Randomized trial (abstract read directly):
[1] 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. Australian population-based open-label randomized controlled trial; 639 participants aged 18–70 not regularly using sunscreen or vitamin D supplements; intervention group applied SPF 50+ on days the UV index was forecast to reach 3 or higher, for about one year, control group used sunscreen discretionally; 628 analyzed. Adjusted mean change 1.6 nmol/L (intervention) vs 6.8 nmol/L (control); between-group treatment effect −5.2 nmol/L (95% CI −7.2 to −3.2). Primary outcome was change in 25(OH)D from baseline; vitamin D deficiency in the final sample, defined as 25(OH)D < 50 nmol/L, was an exploratory outcome: 45.7% (139/304) vs 36.9% (115/312), prevalence ratio 1.33 (95% CI 1.14–1.55). Baseline 63.5 (SD 21.9) vs 62.1 (SD 22.8) nmol/L. Conclusion: “Routinely applying high SPF sunscreen results in lower 25(OH)D concentrations than would be seen with discretionary sunscreen use. Regular sunscreen users may need vitamin D supplementation.” PMID 40927943: link
Systematic review (abstract read directly):
[2] Neale RE, Khan SR, Lucas RM, Waterhouse M, Whiteman DC, Olsen CM. “The effect of sunscreen on vitamin D: a review.” British Journal of Dermatology 2019;181(5):907–915. Studies published 1970 to November 2017: four experimental studies, three field trials, 69 observational studies. Experimental studies under artificial UV showed a substantial reduction; field trials using sunscreen of about SPF 16 found no reduction. Conclusion: “There is little evidence that sunscreen decreases 25(OH)D concentration when used in real-life settings, suggesting that concerns about vitamin D should not negate skin cancer prevention advice. However, there have been no trials of the high-SPF sunscreens that are now widely recommended.” PMID 30945275: link
Professional body statement (read directly):
[3] American Academy of Dermatology, sunscreen resource: “Using sun protection may decrease your skin’s production of vitamin D”; “The AAD recommends that healthy adults should obtain an adequate amount of Vitamin D from a diet that includes foods naturally rich in vitamin D and/or foods/beverages fortified with vitamin D”; “If you are concerned that you are not getting enough vitamin D, you should discuss your options for getting vitamin D with your doctor”: link
This article reports published research. It isn’t medical advice, and it can’t tell you your own vitamin D level or what to do about it. That’s a conversation for a doctor. We draw the same line on other medical questions, like what a pregnancy-safe label can and can’t tell you.
