"‘Sunscreen prevents vitamin D – so it’s better not to use it at all.’ This myth persists stubbornly. The data presents a different picture: Correctly applied broad-spectrum protection products can prevent sunburn and skin cancer while still allowing measurable vitamin D production. In a holiday study, vitamin D levels increased despite consistent sun protection – especially with high UVA protection, which allows more UVB for vitamin D synthesis ^[1]. It’s time to rethink the balance: maximize protection, avoid deficiency.

Sunlight contains UV radiationinvisible, high-energy light components to the eye, particularly UVBspectral range that tans the skin, causes sunburn, and produces vitamin D and UVApenetrates deeper into the skin, drives skin aging, and can contribute to cancer. In the skin, 7-dehydrocholesterol is converted into Vitamin D3cholecalciferol, precursor of active vitamin D through UVB and is then transformed by the liver into 25(OH)Dcalcifediol, main marker of vitamin D status. SPFSun Protection Factor, protection against UVB-induced sunburn primarily measures erythemal protection; a high UVA-PFprotection factor against UVA complements the broad-spectrum protection. Important: The spectra for sunburn and vitamin D production overlap, but they are not identical. Depending on application, sunscreen may not completely block UVB – in reality, the dose decreases, but vitamin D synthesis can still occur ^[1]. Indoor tanning devices emit artificial UV radiation; they are classified as carcinogenic and are not a safe way to achieve vitamin D ^[2].

A good vitamin D status supports bone metabolism, the immune system, and possibly the prevention of chronic diseases; deficiencies are widespread and associated with increased morbidity ^[3]. At the same time, excessive UV exposure is a central risk factor for skin cancer. Tanning beds increase the risk of melanoma, basal cell carcinoma, and squamous cell carcinoma, with a clear dose-response relationship and particularly high risk with early initiation ^[2]. Combined high sun exposure and tanning bed usage further increase the risk of basal cell carcinomas, demonstrating that “double doses of UV” not only add up but interact unfavorably ^[4]. For high performers, this means: energy, performance, and longevity benefit from stable vitamin D levels – but never at the cost of avoidable UV damage.

A field study in Tenerife examined the impact of consistent sun protection on vitamin D. Despite SPF 15 and correct application, 25(OH)D levels significantly increased; formulations with high UVA protection resulted in even greater increases, as they allow relatively more UVB while effectively preventing sunburn ^[1]. This practical relevance is crucial: In everyday life, people often apply sunscreen thinly and unevenly – in the study, it was applied correctly, and yet D-synthesis occurred. Another central building block is diet. Since only a few foods naturally contain high levels of vitamin D, fortified products and 25(OH)D3-based fortifications are gaining relevance; 25(OH)D3 can increase serum levels faster and more efficiently than D3, depending on the context by several times ^[5]. Finally, large cohorts show that tanning bed usage poses an oncological risk; in the Nurses’ Health Study II, the combination of high sun exposure and early tanning bed use was associated with an increased risk of basal cell carcinoma – a practical hint that “tanning strategies” are no substitute for smart prevention ^[4]. Together, these studies provide a clear course of action: consistently avoid sunburn, use short targeted sun windows to produce D, and strengthen the second pillar with diet and, if necessary, fortification – while strictly avoiding artificial UV sources.

- In everyday life, use broad-spectrum sunscreen with at least SPF 30 and high UVA-PF, especially between 10:00 AM and 4:00 PM. When applied correctly, it protects against sunburn and skin cancer without significantly hindering vitamin D synthesis ^[1].
- Plan daily short "light windows": 10–15 minutes between 10:00 AM and 3:00 PM with face/arms uncovered and without sunscreen to stimulate the body's vitamin D production. After that, protect again. The duration remains consciously short to minimize the risk of sunburn ^[6].
- Strengthen the second pillar: Consume vitamin D-rich foods (fatty fish, egg yolks) regularly and use fortified products. In the dark season, 25(OH)D3 in fortified foods or as a supplement can raise levels faster than D3 ^[5].
- For longer outdoor activities, seek shade: Umbrellas, awnings, or trees significantly reduce UV exposure; larger and lower structures generally offer better protection, while legs tend to remain most exposed – plan to wear clothing ^{[7] [8] [9]}.
- Avoid tanning beds consistently. They increase the risk of melanoma, BCC, and cSCC; “pre-tanning” does not protect and is not a safe way to achieve vitamin D ^{[2] [4]}.

The next evolution of sun protection is smart: context-dependent dosing, broad-spectrum protection, allowing targeted short sun exposure, and utilizing diet. Future research on personalized UV doses (skin type, sensors, season) and 25(OH)D3 fortification could further refine the balance – for greater vitality, performance, and healthy longevity."