Background: Vitamin D status in relation to pancreatic cancer risks is still inconsistent. This study was performed to evaluate the association between vitamin D status and risk of pancreatic cancer using a meta-analysis approach.
Methods: A systemic review of all relevant literature in English was performed by searching Pubmed, Web of Science and Embase to identify eligible studies from the earliest available date to April 1, 2012. The search terms "vitamin D", "25-hydroxyvitamin D", "pancreatic cancer" or "pancreatic neoplasms" were used to retrieve relevant papers. Inclusion criteria were: (1) the exposure of interest was intake of vitamin D or blood levels of vitamin D; (2) the outcome of interest was pancreatic cancer; (3) data on high and low intake or blood vitamin D in cases and controls were available; (4) odds ratio (OR) estimates with 95% confidence interval (CI) were provided; (5) primary epidemiological data were provided reporting pancreatic cancer incidence. The combined OR values and their 95% CIs were calculated via a meta-analysis. The potential presence of publication bias was estimated using Egger's regression asymmetry test.
Results: Nine studies with a total of 1 206 011 participants met the inclusion criteria. The test for heterogeneity showed there were significant differences among the included studies (I(2)=70.9%, P=0.001), so a randomized-effects model was used in the meta-analysis. The pooled OR of pancreatic cancer for the highest versus the lowest categories of vitamin D level was 1.14 (95% CI 0.896-1.451), and the Z-score for the overall effect was 1.06 (P=0.288), showing that there was no significant association between vitamin D levels and the risk of pancreatic cancer. Egger's test indicated there was a low possibility of publication bias in this study (P=0.348).
Conclusion: Dietary vitamin D or circulating concentrations of 25-hydroxyvitamin D are not associated with the risk of pancreatic cancer based on evidence from currently published studies.