A COMMON CONCERN
As awareness of skin cancer has increased, sunscreen has become a routine part of daily life. Alongside this shift, a persistent question has emerged. Does sunscreen block Vitamin D production? The concern is understandable. Vitamin D is produced in the skin through exposure to ultraviolet B (UVB) radiation, the same portion of sunlight that sunscreens are designed to reduce.
Yet the relationship between sunscreen use and Vitamin D status is often simplified, leading to confusion. According to decades of photobiology research summarised in Feldman’s Vitamin D, the answer is more nuanced than commonly assumed.
HOW VITAMIN D IS MADE IN THE SKIN
Vitamin D₃ synthesis begins when UVB radiation, approximately 290 to 315 nm, penetrates the skin and converts 7-dehydrocholesterol into previtamin D₃. This process is rapid and self limiting. Once a certain threshold is reached, excess UVB does not increase Vitamin D production, as previtamin D₃ and Vitamin D₃ are further photodegraded into inactive compounds.
Feldman and colleagues emphasise that Vitamin D synthesis occurs early during exposure and plateaus quickly, a property that has important implications for sunscreen use [1].
WHAT SUNSCREEN DOES IN THEORY
In laboratory conditions, sunscreens with a high sun protection factor (SPF) can significantly reduce the transmission of UVB radiation to the skin. In theory, this could limit the cutaneous production of Vitamin D₃.
However, Feldman notes that these theoretical calculations assume:
> uniform, thick application
> complete coverage
> no degradation, sweating, or movement
These conditions rarely reflect real-world use.
WHAT SUNSCREEN DOES IN REAL LIFE
In practice, sunscreen is typically applied less generously than tested in laboratories, is unevenly distributed, and is often reapplied inconsistently. As a result, some UVB penetration usually still occurs.
Feldman’s review of observational and interventional studies shows that routine sunscreen use does not consistently result in lower Vitamin D status in free living populations [2]. Individuals who regularly use sunscreen are often exposed to sunlight for longer periods overall, offsetting reductions in UVB transmission.
This distinction between theoretical blockage and practical exposure is central to understanding why sunscreen use and Vitamin D deficiency are not reliably linked.
BEHAVIOUR MATTERS MORE THAN FORMULATION
The most significant determinant of Vitamin D status is not sunscreen itself, but overall sun exposure behaviour. Feldman highlights that time spent outdoors, clothing coverage, latitude, season, and lifestyle patterns exert a greater influence on Vitamin D synthesis than sunscreen use alone.
In other words, sunscreen does not operate in isolation. It modifies exposure, but does not eliminate it under normal conditions of use.
SKIN PROTECTION AND PHYSIOLOGY ARE NOT IN CONFLICT
Importantly, Feldman does not frame sunscreen use and Vitamin D synthesis as competing priorities. Preventing excessive ultraviolet exposure remains essential for skin health. At the same time, Vitamin D requirements can be met through a combination of incidental sunlight exposure, dietary intake, and supplementation.
This integrated approach reflects modern physiology rather than historical extremes. Vitamin D status is maintained over time, not determined by single exposures or single behaviours.
WHERE SUPPLEMENTATION FITS IN
Because sunscreen use may reduce UVB exposure in some individuals, particularly those who avoid sunlight, wear protective clothing, or live at higher latitudes, dietary Vitamin D intake and supplementation play an important role.
Feldman emphasises that supplementation provides a UV independent source of Vitamin D, allowing individuals to maintain adequate status without compromising skin protection strategies [1].
This is especially relevant in winter months, when UVB radiation may be insufficient for cutaneous Vitamin D synthesis regardless of sunscreen use.
WHY THIS MATTERS
Public concern about sunscreen and Vitamin D reflects a broader challenge. It involves reconciling evolutionary biology with modern health practices. Sunscreen changes how sunlight interacts with the skin, but it does not negate the body’s ability to maintain Vitamin D status when other sources are considered.
Understanding this distinction helps reduce unnecessary anxiety and supports informed, balanced health decisions.
CONCLUSION
Sunscreen reduces ultraviolet exposure by design, but its impact on Vitamin D production in everyday life is often overstated. According to the scientific evidence summarised in Feldman’s Vitamin D, routine sunscreen use does not reliably cause Vitamin D deficiency.
Maintaining Vitamin D status in a modern environment is best achieved through a combination of sensible sunlight exposure, diet, and supplementation, while continuing to protect skin health through appropriate sun protection practices.
DISCLAIMER
This article is for educational and informational purposes only. It does not constitute medical advice. Health claims are made in accordance with EU Regulation (EC) No 1924/2006. Individuals concerned about vitamin D intake or sun exposure should consult a qualified healthcare professional.
REFERENCES
[1] Holick MF. Photobiology of Vitamin D. In: Feldman D, Pike JW, Bouillon R, et al., eds. Vitamin D. 4th ed. Academic Press; 2018.
[2] Matsuoka LY, Ide L, Wortsman J, MacLaughlin JA, Holick MF. Sunscreens suppress cutaneous vitamin D₃ synthesis. J Clin Endocrinol Metab. 1987;64(6):1165–1168.
(Discussed and contextualised in Feldman D et al., Vitamin D*, 4th ed.)*
