Over the past decades, numerous studies have significantly increased the understanding of vitamin D's role in the body's functioning. Because of its wide range of biological effects, vitamin D has come to be regarded as a hormone that influences essential physiological processes.

Vitamin D is synthesized in the skin under sunlight and comes from foods such as fish, milk, bread, and mushrooms. Our modern lifestyle, characterized by long periods of indoor living, contributes to an epidemic of vitamin D deficiency. Paradoxically, this epidemic is accompanied by an increase in the incidence of skin cancer [1].

In vitro studies in animals and cell cultures show that vitamin D affects cancer cells' differentiation, proliferation, and apoptosis, making it a candidate for anticancer therapeutic agents [1]. However, epidemiologic evidence supporting the positive role of vitamin D in skin cancer prevention is scarce. Whether vitamin D prevents human cancer development or limits its progression remains unresolved.

Kanasuo E. et al. studied the relationship between oral vitamin D intake, photoaging, actinic keratosis, and malignant skin neoplasms [2]. The study included 498 patients aged 21–79 years (253 men, 245 women), at high risk of developing any type of skin cancer. Participants were divided into three groups based on their self-reported use of oral vitamin D supplements: non-use, occasional use, or regular use. Serum 25-hydroxyvitamin-D levels were analyzed in 260 individuals. Participants who regularly took oral vitamin D were significantly less likely to have melanoma than patients who did not (18.1% vs. 32.3% and 62.1% vs. 74.7%, respectively). No relationship was found between vitamin D intake and the photoaging severity or the incidence of actinic keratosis. Serum 25-hydroxyvitamin-D levels had no statistically significant effect on the incidence of different types of skin cancer. Thus, there was a clear relationship between regular vitamin D intake and a decrease in the incidence of melanoma.

According to a study by Gracia-Darder I. et al., vitamin D has an impact not only on the incidence of melanoma but also on the course of the disease. A lower survival rate among participants with low vitamin D levels characterized a sample of 264 patients with invasive melanoma. The authors emphasize the significant influence of vitamin D serum levels on the disease outcome [3].

At the Second International Conference on Vitamin D Use Controversies, the consensus conclusion was that serum vitamin D levels < 50 nmol/L may have adverse health effects [1].

Although the mechanisms responsible for the beneficial effects of vitamin D on reducing melanoma incidence and disease course have not yet been precisely defined, practical recommendations regarding melanoma prevention should not be ignored.

• If you have an increased risk of skin cancer, you should ensure your skin is adequately protected from the sun.
• Neither natural nor artificial sun exposure should be encouraged as a primary source of vitamin D. Given that vitamin D in pharmaceuticals and supplements is functionally identical to that formed after UV exposure and is also more reliable and quantifiable, it should be preferred.
• In patients with melanoma or at risk of developing skin cancer, serum vitamin D levels should be checked to detect or prevent deficiency in time [1].

 References

1. Martin-Gorgojo A., Gilaberte Y., Nagore E. Vitamin D and Skin Cancer: An Epidemiologic, Patient-Centered Update and Review. Nutrients. 2021; 13(12): 4292.
2. Kanasuo E., Siiskonen H., Haimakainen S., et al. Regular use of vitamin D supplement is associated with fewer melanoma cases compared to non-use: a cross-sectional study in 498 adult subjects at risk of skin cancers. Melanoma Res. 2023; 33(2): 126–135.
3. Gracia-Darder I., Carrera C., Alamon-Reig F., et al. Vitamin D deficiency in melanoma patients is associated with worse overall survival: a retrospective cohort study. Melanoma Res. 2022; 32(5): 384–387.