Vitamin D, calcium, and retinol intake, and pancreatic cancer in a population-based case–control study in the San Francisco Bay area

OBJECTIVE: The aim of this study was to evaluate a complex association among intake of dietary vitamin D, calcium, and retinol, and pancreatic cancer risk. METHODS: Pancreatic cancer cases (n = 532) diagnosed in 1995–1999 were identified using rapid case ascertainment methods and were frequency matched to population-based controls (n = 1,701) in the San Francisco Bay Area. Detailed dietary data were collected during in-person interviews using a validated semi-quantitative food-frequency questionnaire. Adjusted unconditional logistic regression was used to estimate odds ratios (ORs) and confidence intervals. RESULTS: In men, increased pancreatic cancer risk was associated with currently recommended dietary vitamin D intake levels (highest (≥450 IU/day) vs. lowest (<150 IU/day) intake, OR = 2.6, trend-p = 0.009) and total vitamin D intake from diet and supplements (for <800 IU/day). ORs for dietary vitamin D intake remained increased after adjustment for intake of retinol and calcium, although confidence intervals included unity. Stratified analyses showed that ORs were higher among men with lower intake of retinol and lower physical activity but there was no evidence of statistical interaction. No associations with vitamin D intake were observed among women, although ORs typically were elevated. ORs increased with increased dietary calcium intake among men (trend-p = 0.008) and not women. CONCLUSIONS: Our results among men showing an increased risk of pancreatic cancer associated with dietary intake of vitamin D and of calcium require confirmation in further studies. Continued investigation is needed to clarify the complex role of vitamin D and calcium in pancreatic cancer risk and to determine their optimal intake level and preventive effects for pancreatic cancer.