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Does Sunscreen Reduce Vitamin D Levels?

Posted on 3 June 2024

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Chris Head from Leicester was always a sporty child who loved playing outdoors. His mother Suzi described him as a ‘happy, smiley, independent child’. Yet around the age of 6, Chris started to experience pain and fatigue when walking, to the point that he needed to be carried about during outings. Chris was diagnosed with rickets, a softening and weakening of the bones caused primarily by severe vitamin D deficiency. Vitamin D is necessary for calcium absorption in the gut and consequently for bone development, with vitamin D deficiency leading to soft and malformed bones.

The incidence of rickets, once considered a disease of the Victorian era, has increased in many developed countries over the past few decades. This is partly because of children spending more time indoors, changing ethnic makeup (dark-skinned people are more at risk) and dietary deficiencies. About 90% of the vitamin D we need is produced by our own bodies using sunlight, so how did a boy who spent plenty of time outdoors become vitamin D deficient? It seems likely that sunscreen played a role. Suzi always made sure her son was fully covered in factor 50 sunscreen every time he went outdoors to ensure he was protected against cancer-causing ultraviolet B rays. Yet those same UVB rays are required for vitamin D production, and Chris’s mum did not realise that overzealous use of sunscreen could result in a serious disease.

It’s important to keep these cases in perspective. The incidence of rickets in developed countries is still low in the grand scheme of things – about one case per 200,000 children under the age of 16 annually in the UK, and not all of these have anything to do with sunscreen. Most cases occur in children with dark skin tones who do not get enough dietary vitamin D to compensate for the lack of sunlight exposure. There are also rare genetic conditions that can cause rickets. Wearing an appropriate SPF (Sun protection factor) and quantity of sunscreen during the hours of the day when the Sun is at its strongest is not going to cause rickets.

Photo by Onela Ymeri on Unsplash

Is Sunscreen Affecting Your Vitamin D Levels?

OK, but what about the titular question? It’s possible to have below healthy vitamin D levels without having rickets or osteomalacia (an adult condition similar to rickets), so you would be forgiven for wondering: does the normal, responsible use of sunscreen have any impact on vitamin D levels in children or adults? After all, sunscreen does block the UVB rays that are primarily used to synthesise vitamin D, and the incidence of vitamin D insufficiency and deficiency among adults is high in many developed and developing countries alike. Could sunscreen be playing a role in this?

Good news: the answer is no, at least as far as the available evidence shows. Experiments in the lab show that when people wear sunscreen, their vitamin D production when exposed to artificial UV light does indeed decrease as you might expect. This would seem to support the theory that sunscreen might contribute to vitamin D deficiency. However, when people are randomised to wear either real sunscreen or fake sunscreen under real world conditions, available studies repeatedly find no significant difference in vitamin D levels. How come? Sunscreen doesn’t block 100% of UV light, people don’t cover their entire bodies with it, and the effectiveness of sunscreen tails off after a few hours (which is why you need to reapply it). Most people also don’t wear sunscreen every single time they go outside, so the Sun exposure they get here and there is more than enough to sustain normal vitamin D production. In fact, studies looking at self-reported sunscreen use often find that using more sunscreen is associated with higher vitamin D levels, because the people using the most sunscreen are the ones going outside the most. So if you care about vitamin D levels, the last thing you want to do is stop wearing sunscreen and then be stuck indoors because you don’t want to risk getting sunburnt.

The only caveat is that these studies typically used lower SPF sunscreens. Since those studies were done, higher SPF sunscreens have become available. However, these are supposed to be used when lower SPF creams don’t provide sufficient protection and not before. If you are using sunscreen with an appropriate SPF for your level of exposure and skin tone, it is unlikely to have a significant impact on vitamin D levels unless you are slathering it on all day every day.

Other Reasons Not To Wear Sunscreen?

Lastly, we should mention one other potential motivation for not wearing sunscreen, which is the presence of certain chemical compounds that can penetrate the skin, enter the bloodstream and potentially influence hormone balance. Stories about these chemicals are published every summer, with oxybenzone being the most common cause for concern. The available research suggests that compounds like oxybenzone can indeed influence the levels of some hormones in humans, but there is so far no indication that they are capable of causing health problems, though there may be some environmental risks. For those who remain concerned about these chemicals, mineral sunscreens are available. In the place of chemicals that absorb UV light, mineral sunscreens contain metal oxides that form a physical barrier on the surface of the skin to reflect UV light. The absence of chemicals like oxybenzone makes them potentially safer, thought they generally are not as effective when it comes to Sun protection.

The Take-Home Message:

Overuse of high SPF sunscreen may contribute to vitamin D deficiency in some rare cases, but there’s no evidence that normal use of sunscreen can affect vitamin D levels, let alone cause deficiency. If you struggle to get sufficient sunlight, the risk of vitamin D deficiency can be mitigated by consuming a diet rich in vitamin D and by taking vitamin D supplements. On the other hand, there is little you can do to mitigate the risk of skin cancer when you burn under the Sun.

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    Title image by Daoudi Aissa, Upslash

    Increase in rickets linked to overuse of sunscreen

    Rickets and osteomalacia

    Nutritional rickets under 16 years: UK surveillance results

    The effect of sunscreen on vitamin D: a review

    The Banned Sunscreen Ingredients and Their Impact on Human Health: A Systematic Review

    Environmental impacts due to the use of sunscreen products: a mini-review

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