Nutrition
Vitamin D and the Sun: What's True, What's Hype
How much sun do you really need for vitamin D? A balanced look at what the evidence supports — and what it doesn't.
Vitamin D is one of the most cited reasons people skip sunscreen. The reality is more nuanced: sun exposure does drive vitamin D synthesis, but it does not require sunburn-level doses, and supplementation is a safe alternative.
How sun makes vitamin D
UVB converts 7-dehydrocholesterol in the skin to previtamin D3, which the liver and kidneys later activate. Most people produce adequate vitamin D from short, casual sun exposure — roughly 5–15 minutes on arms and legs a few times a week, depending on latitude and skin type.
Sunscreen does not cause deficiency
Multiple studies (including a 2019 meta-analysis in the British Journal of Dermatology) show that real-world sunscreen use does not meaningfully reduce serum 25(OH)D levels. People apply far less than the lab-tested amount, and incidental UV is enough.
When to consider supplementation
If you live above 35° latitude in winter, work indoors, or have darker skin, ask your doctor about a daily 800–2000 IU vitamin D3 supplement. It avoids the cancer risk trade-off entirely.
Key takeaways
- Casual incidental sun is enough for most people.
- Sunscreen does not meaningfully cause vitamin D deficiency.
- Supplementation is safe and effective if needed.