Adulthood consumption of preserved and nonpreserved vegetables and the risk of nasopharyngeal carcinoma: A systematic review

Abstract

The incidence rates of nasopharyngeal carcinoma (NPC) are dramatically higher in certain regions of Asia compared to the rest of the world. Few risk factors for NPC are known; however, in contrast to the hypothesized health benefits of nonpreserved vegetables, it is thought that preserved vegetable intake may play a role in contributing to the higher incidence of NPC in high-risk regions. Therefore, the purpose of this study was to systematically review the epidemiologic evidence on the associations between adulthood intake of preserved and nonpreserved vegetables and NPC risk. A search of the epidemiological literature from 1966 to 2004 was performed using several bibliographic databases, including PubMed and the Chinese Biomedical Literature Database System. There were no language restrictions. Meta-analysis was conducted to obtain pooled odds ratios (ORs) for the highest-versuslowest categories of preserved and nonpreserved vegetable intake. A total of 16 case-control studies were identified in the search. Results showed that highest-versus-lowest preserved vegetable intake was associated with a 2-fold increase in the risk of NPC (Random Effects Odds Ratio (RE OR) 2.04; 95% Confidence Limits (CL) 1.43, 2.92). Conversely, high nonpreserved vegetable intake was associated with 36% decrease in the risk of NPC (RE OR 0.64; 95% CL 0.48, 0.85). Findings for both preserved and nonpreserved vegetables were consistent across vegetable type and by country of study. Further research in high-risk areas to gain insight into the risk associated with preserved vegetables and protection associated with nonpreserved vegetables may advance understanding of NPC and yield clues for prevention. ' 2006 Wiley-Liss, Inc.

The Enigmatic Epidemiology of Nasopharyngeal Carcinoma

“…In studies of Chinese populations, the relative risk of NPC associated with weekly consumption, compared with no or rare consumption, generally ranged from 1.4 to 3.2, whereas that for daily consumption ranged from 1.8 to 7.5 (136)(137)(138)(139)(140)(141). NPC risk is also elevated in association with other preserved food items, including meats, eggs, fruits, and vegetables, in southern Chinese, Southeast Asians, North Africans/Middle Easterners, and Arctic natives (38,39,(138)(139)(140)(141)(142)(143)(144)(145)(146)(147), as well as in low-incidence northern Chinese (148) and the U.S. population (excluding type I NPC; ref. 149).…”

Chemical Carcinogenesis and Nasopharyngeal Carcinoma

“…This indicates that consumption frequency of salt-preserved fish is associated with the risk of NPC. However, elevated NPC risk is also associated with other preserved food items, including meats, eggs, fruits, and vegetables [4][5][6][7][8][9][10][11][12][13][14][15].…”

“…Furthermore, salted fish is a traditional weaning food and is fed early and frequently to infants, especially in the Cantonese population [4,14] and in families of lower socioeconomic status [3,18]. Childhood exposure, especially at weaning, appears to be more strongly related to NPC risk than exposure during adulthood [3,4,14,15,17,[19][20][21]. This dietary association may partly explain the international distribution of NPC incidence.…”

“…In addition, some bacteria can also induce conversion of nitrate to nitrite, which forms important carcinogenic N-nitroso compounds [26]. Experiments in rats have demonstrated the carcinogenicity of nitrosamines and Nnitroso compounds such as diethylnitrosamine (DEN), dimethlbenzanthracene anthracene (DMBA), and Dinitrosopiperazine (DNP) [6,15,30].…”

Downregulation of expression of transporters associated with antigen processing 1 and 2 and human leukocyte antigen I and its effect on immunity in nasopharyngeal carcinoma patients

“…The EBV-associated, undifferentiated form of NPC exhibits the most consistent association with EBV worldwide and is particularly common in China and Southeast Asia, reaching a peak incidence of ~20-30 cases per 100,000 individuals (3). In addition to genetic predisposition, EBV infection and environmental factors, such as dietary and geographic components, were considered to be important in the aetiology of NPC (4)(5)(6). Previous studies that used quantitative polymerase chain reaction to measure circulating tumor-derived EBV DNA in the blood of NPC patients demonstrated that the level of pre-treatment EBV DNA was significantly associated with overall survival and that post-treatment EBV DNA levels predicted progression-free and overall survival (7,8).…”