Diet and nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is a disease with a remarkable racial and geographical distribution. It is very rare (incidence of less than 1 per 100,000 person-years) in most parts of the world and only a handful of populations are known to deviate from this low-risk profile, which include people of southern China, Eskimos and other natives of the Arctic region, natives of southeast Asia, and the mainly Arab populations of north Africa and Kuwait. There is now convincing evidence implicating dietary factors as the primary cause of NPC among Chinese. A series of case-control studies conducted in various Chinese populations with distinct risks of NPC, ranging from the very high-risk Cantonese to the relatively low-risk Northern Chinese, have suggested that ingestion of salted fish and other kinds of preserved foods by the Chinese constitutes the most important cause of NPC development among these people. Preliminary data on Malays in southeast Asia, Eskimos in Alaska, and Arabs of north Africa also suggest that ingestion of preserved foods by these population groups may be responsible for their raised incidence of NPC. Regardless of race and geography, the commonest form of nasopharyngeal cancers are those that arise from the epithelial cells lining the nasopharynx. These carcinomas (commonly referred to as NPCs) constitute 75-95% of nasopharyngeal cancers in low-risk populations and virtually all nasopharyngeal cancers in high-risk populations (Ho, 1971; Sugano et al, 1978; Levine and Connelly, 1985).