Diet and nasopharyngeal carcinoma: a case-control study in Guangzhou, China

We conducted interviews on 306 histologically confirmed incident cases of nasopharyngeal carcinoma (NPC) occurring in residents of Guangzhou City, China, who were under the age of 50 years, and an equal number of age-, sex-, and neighborhood-matched controls. We also interviewed 110 mothers of patients under age 45 years and 139 mothers of controls who were matched to patients under age 45 years, to obtain information on childhood exposures of study subjects. Exposure to salted fish, whether in adulthood or in childhood, was significantly associated with an increased risk of NPC. The association was strongest for exposure during weaning, and exposures at all other periods were no longer related to NPC risk after adjustment for exposure during weaning. Besides salted fish, childhood exposure to 5 other preserved foods (fermented fish sauce, salted shrimp paste, moldy bean curd, and 2 kinds of preserved plum) was significantly related to NPC, and the effects were independent of salted fish exposure. Finally, cases ingested significantly less fresh vegetables and fruits than controls, especially during early childhood, and the differences were not explained by their differing consumption pattern of salted fish and other preserved foods.