Does Sunscreen Block Vitamin D?

In the ongoing discourse surrounding sun exposure, sunscreen, and vitamin D, there's often a lingering concern: does sunscreen use lead to vitamin D deficiency?

The short answer is no, and the science behind it is worth exploring.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that plays a crucial role in various bodily functions, including bone health, skin health, immune function, and hormone regulation. It helps regulate calcium and phosphate levels in the body, essential for maintaining strong bones and teeth. Its deficiency has been linked to autoimmune conditions and other health issues.

Vitamin D can be synthesized in the skin when it's exposed to UVB radiation from sunlight. Specifically, UVB rays convert a precursor molecule in the skin into vitamin D3. This process occurs most effectively when the skin is exposed to sunlight during certain times of the day, especially noon.

Additionally, vitamin D can be obtained through dietary sources such as fatty fish (like salmon and mackerel), egg yolks, fortified foods (such as milk and cereal), and supplements. However, dietary intake alone may not always be sufficient to meet the body's needs, especially in regions with limited sunlight exposure or for individuals with specific dietary restrictions. Therefore, a balance of sunlight exposure, dietary sources, and supplementation is often recommended to maintain optimal vitamin D levels.

Sunscreen Vs Vitamin D Synthesis

The misconception that sunscreen use impedes the body's ability to synthesize vitamin D primarily stems from a misunderstanding of how sunscreen works and its impact on UV radiation penetration.

Sunscreen is designed to block harmful UV rays, including UVB rays, which are necessary for the skin's synthesis of vitamin D. However, sunscreen isn't a complete block; it reduces UVB exposure but doesn't eliminate it entirely. Certain experts in the US advocate for short, non-burning exposures (5–30 minutes of sun exposure, 2-3 times a week) that will provide you with adequate vitamin D. Longer sun exposure increases your risk of melanoma and other skin cancers, particularly if you end up sunburnt.

UVB doesn’t pass through glass, so sunlight through a closed window won’t help your vitamin D levels but will increase UVA damage.

A significant portion of the global population remains deficient in vitamin D. Once deficiency sets in, relying solely on "sun exposure" isn't a viable solution. At that point, sunscreen doesn't help the situation, but the solution isn't to stop applying it altogether. Supplementation becomes necessary.

While sun exposure is vital for vitamin D synthesis, it's crucial to balance it with adequate sun protection. Cumulative UV exposure, even without sunburns, can lead to premature aging and increase the risk of skin cancer. Therefore, relying solely on sunlight for vitamin D isn't advisable, especially considering the dangers of excessive UV exposure.

Conclusion

There is a theme in medicine: we never evolved to live past our early twenties. Cumulative UV exposure (not sunburns) makes skin look older, splotchier, thinner, more wrinkly, and also predisposes us to more indolent types of skin cancer (like basal cell carcinoma).

Cumulative sunburns predispose us to more aggressive forms of skin cancer (like melanoma).

There's no such thing as a safe tan (except for the one you're born with or the one you spray on).

Sunscreen use, when applied correctly, doesn't significantly hinder vitamin D synthesis. And for anyone planning on living past 25, your vitamin D should come from your diet, not UV radiation.

Studies:

https://pubmed.ncbi.nlm.nih.gov/30945275/

https://pubmed.ncbi.nlm.nih.gov/31069787/

Shop Now