Tea consumption and risk of ovarian cancer

Abstract

Although the growth inhibitory effects of tea, particularly green tea, and tea polyphenols have been demonstrated in animal models of ovarian cancer, the results of epidemiological studies have been inconclusive. We investigated this issue using data from an Australian population-based, case-control study (1,368 cases; 1,416 controls). We also systemically reviewed all the available evidence regarding the potential association between green tea and risk of ovarian cancer, given the abundance of bioavailable polyphenols and higher antioxidant capacity of green tea than black tea, to provide the best summary estimate of the association. In our case-control study, while we found uniformly inverse odds ratios (OR) for tea drinkers compared to non-tea drinkers [4 + cups/day any tea OR 0.71 (95% CI 0.52-0.97); green tea OR 0.82 (95% CI 0.38-1.79); herbal tea OR 0.77 (95% CI 0.28-2.14): black tea OR 0.88 (95% CI 0.66-1.18)], we saw no dose-response trends. Our meta-analysis provided some evidence that women who drink green tea have a lower risk of ovarian cancer, although the summary estimate did not reach statistical significance (0.58, 95% CI 0.33-1.01 for >or=1 cup/green tea day). This result is consistent with two recent meta-analyses that evaluated the association of tea (all types combined) and ovarian cancer risk. Overall, our findings provide some support for the hypothesis that tea consumption reduces the risk of ovarian cancer.