Although keratinocyte cancers (KCs), namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), have low mortality rate, they have relevant impact on quality of life and healthcare costs 6, 7. Melanoma is the most lethal form of skin cancer 5, with highest incidence rates observed in Australia and New Zealand, followed by Northern America and Europe, and the lowest rates in Asian and African populations 1. Skin cancers are the most common type of malignancies in Caucasian populations 1 and their incidence has risen worldwide over the past decades 2, 3, 4. We found no associations between vitamin D intake skin cancers, except positive associations with BCC risk. This meta-analysis suggests positive associations between circulating 25(OH)D level and risk of melanoma and KC, however, this finding is most likely confounded by sun exposure. However, while we found that vitamin D intake (from diet, supplemental and total) was not associated with risks of melanoma and SCC, vitamin D intake was associated with slightly increased BCC risk, albeit with no heterogeneity across skin cancer type. The SRR (95% CI) per 30 nmol/L increase in 25(OH) D level was 1.41 (1.19–1.67), and 1.57 (0.64–3.86), for basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs), respectively. Overall, thirteen prospective studies were included. Random effects dose–response meta-analyses were used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs). Relevant studies were identified by searching the PubMed database up to 30th August 2019. A systematic review and dose–response meta-analyses of prospective studies was conducted to clarify these associations. However, while experimental evidence suggests that vitamin D may have a protective effect on skin cancer risk, epidemiologic studies investigating the influence of 25-hydroxyvitamin D (25(OH)D) level and/or vitamin D intake on skin cancer risk are conflicting. Sun exposure is a major environmental risk factor for skin cancers and is also an important source of vitamin D.
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