A link between vitamin D and skin cancer?
Skin cancer is the most frequent tumour in Caucasians. A team of researchers from Université Paris-Saclay and international laboratories has conducted a meta-analysis of prospective studies about the association between vitamin D and the risk of skin cancer.
Some types of skin cancer, such as basal cell carcinoma, are easily treated, whereas other more severe forms, such as melanoma, make skin cancer a major public health concern. Many scientific publications have tried to understand the role of vitamin D (calciferol) in the development of skin cancer. However, no consensus has been reached. Some publications even contradict each other.
Yahya Mahamat-Saleh, from the Centre for Research in Epidemiology and Population Health (CESP – UPSaclay, UVSQ, Inserm), has been working with colleagues from Norway and Germany to shed light on the subject. They conducted a thorough review of the literature and a meta-analysis of prospective studies into the link between the consumption of vitamin D in the diet and supplements, blood levels and the risk of skin cancer. They identified over 27,500 articles and finally chose 13 prospective studies.
High blood levels and increased risk: the importance of sun
The researchers investigated the hydroxylated form of the molecule, 25-OH vitamin D, or 25(OH)D, which is considered to provide a reliable assessment of vitamin D reserves. They found that high levels of 25(OH)D circulating in the blood are associated with a higher risk of melanoma and skin carcinomas. Their study showed that each increase of 30 nmol/L in 25(OH)D increased the risk by 42%, 30% and 41% respectively for melanoma, skin carcinoma, and basal cell carcinoma.
Given that exposure to the sun is the main source of vitamin D serum, increased risk due to high levels of vitamin D is probably linked to significant exposure to UV rays. Such exposure leads to both higher levels of vitamin D and a higher risk of skin cancer. The results suggest that it is impossible to distinguish between the effect of vitamin D from exposure to the sun and the risk of developing these cancers. The research also showed that dietary supplements and total vitamin D intake are not associated with a risk of melanoma and skin carcinomas.
Overall, this work is another reminder of the importance of protecting yourself from the sun’s UV rays. Yahya Mahamat-Saleh concluded: "Sufficient vitamin D must be consumed as part of a healthy diet or vitamin D supplements to avoid increased risk of skin cancer."
Mahamat-Saleh, Y., Aune, D., & Schlesinger, S. (2020). 25-Hydroxyvitamin D status, vitamin D intake, and skin cancer risk: a systematic review and dose–response meta-analysis of prospective studies. Scientific Reports, 10(1), 1-15.