Jia et al. BMC Cancer 2010, 10:446 http://www.biomedcentral.com/1471-2407/10/446 cured meat were all risk factors for NPC, with elevated ORs of 2.45 (95% CI: 2.03-2.94), 3.17(95% CI: 2.68-3.77) and 2.09 (95% CI: 1.22-3.60) respectively, for the most frequently consumption stratum during childhood. Con- sumption of fresh fruit was inversely associated with NPC risk, with ORs of 0.38 (95% CI: 0.28-0.50) and 0.12 (95% CI: 0.09-0.16) for monthly and “weekly or more” stratum during childhood respectively. While all these associations were observed both in adulthood and child- hood, the effects of consumption of salted fish and fresh fruit were stronger in childhood than in adulthood. However, preserved/cured meat has a stronger effect in adulthood than in childhood. When samples were strati- fied by sex, region or age group, the analyses did not yield significant evidence of heterogeneity in the odds ratios (data not shown). Interestingly, a reduced risk of NPC was newly observed for the consumptions of Canton-style herbal tea and herbal slow-cooked soup (Table 3). For herbal slow-cooked soup, both intake frequency and duration were associated with reduced risk with a dose-depen- dent relationship. ORs were 0.49 (95% CI: 0.27-0.87) and 0.58 (95% CI: 0.47-0.72) for “monthly” and “weekly or more” group compared with reference of “less than monthly” group, P trend < 0.0001. ORs were 0.67 (95% CI: 0.50-0.90), 0.53(95% CI: 0.42-0.67) and 0.22 (95% CI: 0.18-0.28) respectively for consumption duration of year Table 3 Relationship between dietary habits with Chinese herbs and NPC Intake frequency * and duration Case/Ctrl OR (95%CI)# P trend Herbal tea habit Less than monthly (ref) Monthly Weekly or more Herbal tea (years) Less than monthly (ref) 1-9 10-19 ≥20 Slow-cooked soup habit Less than monthly (ref) Monthly Weekly or more Slow-cooked soup (years) Less than monthly (ref) 1-9 10-19 ≥20 439/347 425/717 369/347 439/347 237/237 88/320 146/457 1.0 0.46(0.38-0.56) < 0.0001 0.84(0.68-1.03) 1.0 0.81(0.64-1.03) < 0.0001 0.22(0.16-0.29) 0.25(0.19-0.31) 313/214 1.0 39/42 0.49(0.27-0.87) < 0.001 996/1184 0.58(0.47-0.72) 313/214 146/142 310/380 250/659 1.0 0.67(0.50-0.90) < 0.0001 0.53(0.42-0.67) 0.22(0.18-0.28) * Intake frequency was categorised as follows: less than monthly, < once per month; monthly, once per month to once per week; weekly or more, ≥ once per week; daily, ≥ once per day. # OR, odds ratio calculated among matched case and control groups, adjusting for sex, age, education, dialect and household type. Table 4 Multivariate analyses of dietary factors* Dietary Factors OR# 95%CI Salted fish in childhood Less than monthly(ref) Monthly Weekly or more Salted vegetables in childhood Less than monthly(ref) Monthly Weekly or more Salted vegetables in adulthood Less than monthly(ref) Monthly Weekly or more Fresh fruits in childhood Less than monthly(ref) Monthly Weekly or more Preserved and cured meat in adulthood Less than monthly(ref) Monthly Weekly or more Herbal tea habit Less than monthly(ref) Monthly Weekly or more Slow-cooked soup habit Less than monthly(ref) Monthly Weekly or more 1.00 2.42 1.57 1.00 1.28 1.81 1.00 2.23 1.79 1.00 0.31 0.13 1.00 8.32 12.39 1.00 0.35 0.57 1.00 0.44 0.49 1.65-3.54 1.16-2.13 0.87-1.89 1.37-2.40 1.46-3.40 1.19-2.68 0.20-0.47 0.09-0.18 Page 4 of 7 P-value < 0.001 0.003 0.215 < 0.001 < 0.001 0.005 < 0.001 < 0.001 5.46-12.69 7.60-20.19 < 0.001 < 0.001 0.27-0.47 0.41-0.78 0.21-0.93 0.37-0.65 < 0.001 0.001 0.031 < 0.001 *Logistic regression model was built by a stepwise forward method with inclusion criteria p ≤ 0.01. Both of the dietary consumptions in childhood and adulthood were used in the multivariate analysis. #OR, odds ratio calculated among matched case and control groups, adjusting for sex, age, education, dialect and household type. 1-9, 10-19, ≥20 compared with reference of “less than monthly” group, P trend < 0.0001. In a multivariate logistic regression analysis (Table 4), salted fish, salted vegetables during childhood and salted vegetables, preserved/cured meat during adulthood increased the risk of NPC, while fresh fruit consumption during childhood decreased the risk. Moreover, herbal tea and slow-cooked soup remained significantly asso- ciated with decreased risk of NPC in the multivariate logistic regression model (Table 4). Discussion Results from the present study indicate that consump- tion of salted fish, salted vegetables and preserved/cured meat is a risk factor for NPC, while consumption of fresh fruit is inversely associated with NPC risk. Con- sumption of salted fish has been validated as a