Preserved foods and nasopharyngeal carcinoma: a case-control study in Guangxi, China.

One hundred twenty-eight mothers of nasopharyngeal carcinoma (NPC) cases under age 45 in Yulin Prefecture, China and 174 mothers of population controls were interviewed as part of an epidemiological study to examine childhood exposures in relation to the development of NPC. Exposure before age 2 years to a number of fermented foods was a risk factor for NPC. During weaning, intake of salted fish [relative risk (RR) = 2.6, one-sided P (P) = 0.01], salted duck eggs (RR = 5.0, P = 0.03), salted mustard green (RR = 5.4, P = 0.03), and chung choi (RR = 2.0), P = 0.003), a kind of salted root, was significantly related to an increased risk of NPC. Between ages 1 and 2 years, intake frequency of dried fish [P for linear trend test (linear trend P) = 0.002], fermented black bean paste (linear trend P = 0.0009), and fermented soy bean paste (linear trend P = 0.007) was also positively associated with NPC. A multivariate analysis of these different foods showed all except fermented black bean paste to be independently related to NPC.