Association between dietary intake and urinary concentrations of caffeine and caffeine metabolites and elevated serum prostate-specific antigen (PSA) among men at risk for prostate cancer

Purpose Prostatic chronic inflammation has been found to be associated with prostate cancer risk. Caffeine intake has shown to exhibit anti-inflammatory properties. The relationship between caffeine and prostatic inflammation remains not known. We examined whether dietary intake and urinary concentration of caffeine and its metabolites are associated with serum prostate-specific antigen (PSA) levels, a surrogate marker of prostatic inflammation, among prostate cancer-free men. Methods Cancer-free men, aged >= 40 years, with dietary caffeine intake and serum PSA results were identified from the 2001-2010 National Health and Nutrition Examination Survey. Elevated serum PSA was based on age- and race-specific definitions. Weighted logistic regression analysis with survey sample weights was used to examine the association between dietary intake and urinary concentration of caffeine and its metabolites and elevated serum PSA. Results There were 5,456 men included. Approximately 6.4% of them had an elevated serum PSA. Men with an elevated serum PSA (geometric mean: 63.4 mg) had statistically significantly lower dietary caffeine intake compared to men with a normal serum PSA (geometric mean: 80.9 mg) (p value < 0.01). After adjusting for confounders, dietary caffeine intake and urinary caffeine and its metabolites concentrations were not statistically significantly associated with elevated serum PSA. Conclusion Men with elevated serum PSA had lower dietary caffeine intake compared to men with a normal serum PSA. However, dietary caffeine intake and urinary caffeine concentration were not associated with elevated serum PSA, after adjusting for confounders. Prospective studies that investigate relationships among caffeine intake and prostatic inflammation are warranted.