25-Hydroxyvitamin D status, vitamin D intake, and skin cancer risk: a systematic review and dose-response meta-analysis of prospective studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of prospective observational cohort studies
PubMed 32753685 · doi:10.1038/s41598-020-70078-y
What was done
The authors searched PubMed through August 30, 2019, to identify prospective studies investigating associations between circulating 25-hydroxyvitamin D [25(OH)D] levels or vitamin D intake (dietary, supplemental, and total) and skin cancer risk. Random-effects dose-response meta-analyses were conducted to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs). Thirteen prospective studies were included.
What was found
Each 30 nmol/L increase in circulating 25(OH)D was associated with a higher risk of melanoma (SRR 1.42, 95% CI: 1.17–1.72) and keratinocyte cancer (SRR 1.30, 95% CI: 1.13–1.49). When evaluated by specific cancer type, the SRR per 30 nmol/L increase was 1.41 (95% CI: 1.19–1.67) for basal cell carcinoma (BCC) and 1.57 (95% CI: 0.64–3.86) for squamous cell carcinoma (SCC). Vitamin D intake was not associated with melanoma or SCC risk, but was associated with a slight increase in BCC risk (the abstract does not report numerical values for intake associations).
Why it matters
This review indicates that elevated circulating 25(OH)D is correlated with higher skin cancer incidence, primarily reflecting underlying ultraviolet radiation exposure rather than an intrinsic carcinogenic effect of vitamin D. It underscores the difficulty of separating serum vitamin D levels from behavioral sun exposure in observational epidemiology.
Limits
The literature search was restricted to a single database (PubMed). The findings are susceptible to substantial residual confounding by solar ultraviolet exposure and outdoor activity. The abstract omits quantitative effect estimates and dosage metrics for dietary and supplemental vitamin D intake.
Cited by
- contradicts Skin cancer patients have relatively low levels of vitamin D rather than elevated levels.