Table 2. Summary risk estimates of the association between vegetables and fruit and NPC risk.

Sub-groups	Vegetables							Fruit
Studies, n	RR(95%CI)a	Pb	Q value	I2 (%)	Pc	Pd	Studies, n	RR(95%CI)a	Pb	Q value	I2 (%)	Pc	Pd
All	11	0.60(0.47–0.76)	0.00	20.0	50.0	0.03	0.81	10	0.67(0.58–0.70)	0.00	9.0	0.0	0.78	0.60
Case-control	11	0.60(0.47–0.76)	0.00	20.0	50.0	0.03	0.81	9	0.61(0.54–0.69)	0.00	8.0	0.0	0.84	0.68
Sources of control
Population-based	7	0.80(0.65–0.99)	0.04	6.0	0.0	0.84	0.43	4	0.58(0.47–0.71)	0.00	3.1	3.3	0.38	0.75
Hospital-based	4	0.47(0.380.58)	0.00	4.9	38.9	0.18	0.51	5	0.63(0.54–0.74)	0.00	4.0	0.0	0.96	0.47
Ethnicity
Asia	7	0.58(0.39–0.85)	0.00	17.6	65.9	0.01	0.67	7	0.62(0.55–0.70)	0.00	6.1	0.0	0.59	0.69
Caucasian	3	0.65(0.45–0.94)	0.03	2.9	13.0	0.32	0.24	3	0.66(0.49–0.91)	0.01	2.0	0.0	0.68	0.42
Publication language
Chinese	1	0.44(0.27–0.72)	--	--	--	--	--	2	0.63(0.56–0.70)	0.00	1.1	0.0	1.00	0.52
English	10	0.64(0.55–0.75)	0.00	17.9	49.9	0.04	0.73	8	0.66(0.57–0.77)	0.00	7.0	0.0	0.80	0.79
Number of cases
<200	5	0.58(0.44–0.77)	0.00	4.3	8.0	0.36	0.46	4	0.63(0.49–0.82)	0.00	3.0	0.0	0.78	0.51
≥200	6	0.59(0.41–0.86)	0.01	15.4	67.6	0.01	0.52	6	0.63(0.55–0.71)	0.00	4.9	0.0	0.48	0.69
Adjustments
Smoking, yes	6	0.57(0.39–0.84)	0.00	18.8	73.4	0.00	0.63	4	0.69(0.56–0.86)	0.00	3.0	0.0	0.78	0.40
no	5	0.63(0.47–0.83)	0.00	4.0	0.0	0.88	0.49	6	0.60(0.53–0.69)	0.00	5.0	0.0	0.63	0.58
Alcohol, yes	3	0.65(0.45–0.94)	0.03	2.9	13.0	0.32	0.16	2	0.74(0.55–1.02)	0.06	1.1	0.0	0.68	0.73
no	8	0.58(0.43–0.79)	0.00	17.6	60.3	0.01	0.65	8	0.61(0.54–0.69)	0.00	7.1	0.0	0.78	0.49

aThe random effect model was adopted the pooling method if I2>50%; otherwise, the fixed effect model (I²<50%) was used as the pooling method.

bthe P value for RR; ^cthe p value for heterogeneity; ^dthe p value for publication bias.