Tea drinking, in general, does not appear to decrease the risk for ovarian cancer, according to combined data from nine studies.
But in one of these studies, conducted in China where the majority of tea drinkers drink green tea, Dr Bin Wang and colleagues noted a downward trend for ovarian cancer risk in conjunction with an increased duration of tea drinking.
This implies, the investigators note, that there might be important differences between the study conducted in China and studies in Western populations where tea drinkers mostly consume black tea.
Wang, of Nanjing Medical University, in Jiangsu Province, China, and colleagues looked at the association between tea drinking and ovarian cancer risk by pooling evidence from eight studies conducted in Western countries and one study from China.
Tea consumption in these studies varied from as little as one cup a month to 4 or more cups daily, the researchers report in the American Journal of Obstetrics and Gynaecology.
Overall, they did not find that tea consumption was associated with a decreased risk for ovarian cancer. One study associated tea drinking with increased risk, one associated a significantly decreased ovarian cancer risk with tea drinking, and the other 7 studies suggested non-significant or null findings.
Moreover, Wang told Reuters Health, "Our findings did not support that black tea consumption was related to the decreased risk of ovarian cancer."
The investigators suggest that black and green teas may show different associations with ovarian cancer risk. This may partially be caused by the different production methods used for black and green teas, which result in the teas having very different chemical compositions.
However, because of the numerous factors involved in the development of ovarian cancer, such as environment, genetics, hormones, and lifestyle, Wang and colleagues suggest that further epidemiological studies should consider how these factors, as well as black or green tea consumption, might impact ovarian cancer rates.
SOURCE: American Journal of Obstetrics and Gynecology, December 2007