Researchers in Australia wanted to know if using sunscreen every day actually prevents your body from making vitamin D. They followed 628 people for a year—some used strong sunscreen regularly, while others used it whenever they wanted. The results showed that people who used sunscreen daily had slightly lower vitamin D levels than those who didn’t use it as much. However, the difference was small, and most people in both groups had enough vitamin D. If you use sunscreen regularly to protect your skin from sun damage, you might want to talk to your doctor about whether you need a vitamin D supplement.

The Quick Take

  • What they studied: Does using strong sunscreen (SPF 50+) every day reduce the amount of vitamin D your body makes from sunlight?
  • Who participated: 628 Australian adults between 18 and 70 years old who didn’t usually wear sunscreen or take vitamin D supplements. About two-thirds were women, and the average age was 52.
  • Key finding: People who used sunscreen daily had vitamin D levels that were about 5 points lower than people who used sunscreen only sometimes. More importantly, 46% of daily sunscreen users had low vitamin D levels compared to 37% of occasional users.
  • What it means for you: If you wear sunscreen regularly to protect your skin from sun damage and skin cancer, you might have slightly lower vitamin D. Talk to your doctor about whether you need a vitamin D supplement, especially if you live somewhere with less sun or spend most of your time indoors.

The Research Details

This was a carefully designed experiment where researchers randomly assigned 639 Australian adults into two groups. One group was told to apply SPF 50+ sunscreen on days when the UV index was forecast to be high (3 or above), while the other group could use sunscreen whenever they wanted. The study lasted about one year, from mid-2022 to late 2023. Researchers measured vitamin D levels at the beginning of the study, at the end of summer 2023, and at the end of winter 2023. This timing was important because vitamin D levels naturally change with the seasons—they’re usually higher in summer when there’s more sun.

The researchers used a special method called ‘stratified randomization’ to make sure the two groups were as similar as possible at the start. They also made sure that the people analyzing the results didn’t know which group each person was in, which helps prevent bias. The study was conducted in Australia, which is important because Australia has very strong sun exposure and high rates of skin cancer, making it a good place to study sunscreen use.

Previous lab studies showed that sunscreen blocks vitamin D production, but those were done in controlled settings that don’t reflect real life. This study is important because it tested what actually happens when real people use sunscreen in their daily lives over a full year. The results help us understand whether the lab findings actually matter in the real world.

This study has several strengths: it was randomized (which reduces bias), it had a large number of participants (628), it lasted a full year (long enough to see real effects), and it measured vitamin D at multiple time points including different seasons. The researchers also made sure they didn’t know which group people were in when analyzing the results. However, it was ‘open-label,’ meaning participants knew whether they were using sunscreen regularly or not, which could have affected their behavior. The study was conducted in Australia, so results might be different in other countries with less sun.

What the Results Show

The main finding was that people who used sunscreen daily had vitamin D levels that dropped by only 1.6 points on average, while people who used sunscreen occasionally had levels that increased by 6.8 points. The difference between the two groups was about 5.2 points—a small but measurable difference. To put this in perspective, vitamin D levels are measured in nanomoles per liter (nmol/L), and doctors generally consider levels below 50 nmol/L to be deficient (not enough).

When the researchers looked at vitamin D deficiency specifically, they found that 46% of people in the daily sunscreen group had deficient levels, compared to 37% in the occasional sunscreen group. This means that using sunscreen daily increased the risk of vitamin D deficiency by about 33%. However, it’s important to note that even in the daily sunscreen group, more than half the people (54%) still had adequate vitamin D levels.

The effects were consistent across almost all subgroups—whether people lived in areas with more or less sun, whether they spent more time outdoors, or whether they wore more or less clothing. This suggests that the effect of sunscreen on vitamin D is fairly predictable across different situations.

The researchers also looked at how the results changed depending on where people lived and how much sun exposure they got. Interestingly, the effect of daily sunscreen use was similar regardless of these factors. This suggests that sunscreen’s impact on vitamin D is relatively consistent, whether you live in a sunny area or a cloudier one, and whether you spend a lot of time outdoors or mostly stay inside.

This study confirms what laboratory experiments had suggested—that sunscreen does reduce vitamin D production. However, the effect in real life is smaller than some people worried it might be. The study also shows that many people can use sunscreen regularly and still maintain adequate vitamin D levels, especially if they get some sun exposure on days when they’re not wearing sunscreen or on parts of their body that aren’t covered.

The study was conducted only in Australia, which has very strong sun exposure. Results might be different in countries with less sun, like Canada or northern Europe. The study lasted one year, which is good, but longer studies might show different effects. Because participants knew whether they were using sunscreen regularly or not, they might have changed their behavior in other ways (like spending more or less time outdoors) that could have affected the results. The study also excluded people who were already taking vitamin D supplements or using sunscreen regularly, so results might not apply to people who already have these habits.

The Bottom Line

If you use sunscreen regularly to protect your skin from sun damage and skin cancer, consider talking to your doctor about vitamin D levels. You might benefit from a vitamin D supplement, especially if you live in an area with less sun, spend most of your time indoors, or have darker skin (which makes it harder to produce vitamin D from sunlight). However, don’t stop using sunscreen—the benefits of protecting your skin from sun damage far outweigh the small risk of lower vitamin D. Instead, consider getting vitamin D from food sources like fatty fish, egg yolks, and fortified milk, or from a supplement if your doctor recommends it.

This research matters most for people who use sunscreen daily, especially those who live in areas with less sun or spend most of their time indoors. It’s particularly relevant for people with darker skin, older adults, and people who cover most of their body with clothing. People who already have low vitamin D levels or risk factors for deficiency should definitely talk to their doctor. However, this research should NOT discourage anyone from using sunscreen—the risk of skin cancer from sun exposure is much greater than the risk of vitamin D deficiency from using sunscreen.

Vitamin D levels can change fairly quickly—the study measured changes over a few months. If you start taking a vitamin D supplement, it typically takes a few weeks to see improvements in blood levels. However, you won’t feel immediate changes; vitamin D works slowly in your body to support bone health, immune function, and other processes. If you’re concerned about your vitamin D levels, ask your doctor to test them, and if you start supplementing, plan to recheck levels after 2-3 months.

Want to Apply This Research?

  • Track daily sunscreen application (yes/no) and note the UV index for that day. This helps you see patterns between your sunscreen use and sun exposure over time. You can also note any symptoms of vitamin D deficiency like fatigue or muscle weakness.
  • If you use sunscreen daily, set a reminder to take a vitamin D supplement at the same time each day (like with breakfast). You could also track which days you get outdoor sun exposure without sunscreen to understand your total vitamin D production. Use the app to log foods rich in vitamin D when you eat them.
  • Log your sunscreen use consistently for 3 months, then ask your doctor to check your vitamin D levels. If you start supplementing, recheck levels after 2-3 months. Use the app to track whether any symptoms improve (like energy levels or muscle aches). Set a reminder to discuss vitamin D status with your doctor at your next annual checkup.

This research shows that daily sunscreen use may slightly lower vitamin D levels, but it should NOT discourage you from using sunscreen. Protecting your skin from sun damage and skin cancer is very important. If you’re concerned about vitamin D levels, talk to your doctor about testing and supplementation options. This information is for educational purposes and should not replace medical advice from your healthcare provider. Always consult with your doctor before starting any new supplements or changing your sun protection habits, especially if you have existing health conditions or take medications.