25-Hydroxyvitamin D status, vitamin D intake, and skin cancer risk: a systematic review and dose–response meta-analysis of prospective studies

Scientific Reports
Q1
Aug 2020
Citations:51
Influential Citations:5
Systematic Reviews / Meta-Analyses
85
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Enhanced Details

Methods
Prospective cohort studies; 13 cohorts included; melanoma: 1,644 cases among 241,893 participants; KC: 7,485 cases among 249,108 participants; studies conducted in North America (7 studies), Europe (5), and Australia (1); age and sex details not reported; no dosing information.
Results
Circulating 25(OH)D levels are positively associated with melanoma and keratinocyte cancer (KC) risk. RR per 30 nmol/L increase: melanoma 1.42 (1.17-1.72); KC 1.30 (1.13-1.49). Highest vs lowest levels: melanoma 1.60 (1.18-2.17); KC 1.82 (1.49-2.21). Within KC, BCC per 30 nmol/L increase 1.41 (1.19-1.67); SCC per 30 nmol/L increase 1.57 (0.64-3.86). Vitamin D intake from diet, supplements, and total is not associated with melanoma or SCC; however dietary vitamin D shows a small positive association with BCC risk (per 100 IU/day: 1.04 [1.02-1.06]); supplemental and total vitamin D show no clear associations with BCC or SCC. Nonlinear dose-response suggests KC risk may peak around 60 nmol/L 25(OH)D; nonlinearity for SCC not evident. The positive associations with circulating 25(OH)D are likely confounded by sun exposure. Vitamin D intake from foods or supplements does not meaningfully reduce skin cancer risk. Practical implications: avoid unprotected sun exposure to achieve adequate vitamin D, and obtain vitamin D primarily through diet or supplements; findings do not support increasing vitamin D status via sun exposure for skin cancer prevention.
Limitations
Observational design; reliance on a single baseline 25(OH)D measurement; potential reverse causation and residual confounding (notably sun exposure); risk of bias among included studies (several serious); heterogeneity across studies; limited data for nonlinear dose-response analyses and subgroup analyses; limited generalizability to non-study populations.

Abstract

Sun exposure is a major environmental risk factor for skin cancers and is also an important source of vitamin D. However, while experimental evidence suggests that vitamin D may have a protective effect on skin cancer risk, epidemiologic studies inve...