Geologic and botanic evidence suggested that the tea plant was originated from China (30) . Tea leaves are primarily manufactured as green, black, or Oolong tea in China. It has been observed that both green tea and black tea are effective antioxidants (34 , 35) . Previous evidence also revealed that the tumor-inhibitory effect of tea may depend on its intake level. However, the protective effect of black tea or Oolong tea consumption needs to be additionally investigated because of the fewer participants that drank black or Oolong tea in our study.