Cancer rates among drinkers of black tea.

Studies in experimental animals have shown that compounds in tea can inhibit the process of carcinogenesis, with the beneficial effects accruing to both green and black teas. Herein epidemiologic studies around the world are reviewed to assess the rates and risks of cancer among black tea drinkers. Ecologic data suggest at most a modest benefit on total cancer, as there is considerable international variation in black tea consumption but generally small differences in overall cancer rates. Cohort studies of tea drinkers and case control studies of specific cancers show mixed results. Consistent dose-related patterns have yet to emerge, although detailed data from these studies on cancer risks according to amount and duration of black tea intake are often limited. Several investigations point to the possibility of somewhat lowered risks of digestive tract cancers among tea drinkers, but the evidence is inconclusive. Further research, especially involving populations with wide ranges of tea consumption, is needed to clarify black tea's impact on cancer risk.