Table 2.

Subgroup analysis of whole grains intake and risk of colorectal cancer

Subgroups	No. of studies	No. of Participants (Cases)	RR (95% CI)	P	Heterogeneity Test
					Chi-Square	I2	phet
All studies	18	1,489,581(19424)	0.89(0.84,0.93)	< 0.001	38.82	38%	0.029
Study design
Cohort	11	1,481,538(15519)	0.91(0.88,0.94)	< 0.001	22.95	30.3%	0.115
Case-control	7	8043(3905)	0.95(0.91,1.00)	0.030	13.33	47.5%	0.064
Sex
Men	7	236,055(4826)	0.80(0.69,0.92)	0.001	14.07	50.3%	0.050
Women	8	454,822(7126)	0.94(0.89,0.99)	< 0.001	6.25	0%	0.619
Geographic locations
Europe	5	311,476(3599)	0.84(0.75,0.93)	0.001	4.40	0%	0.732
America	10	1,176,927(15769)	0.92(0.88,0.95)	< 0.001	19.83	34.5%	0.099
Publication year
Before 2010	9	854,956(8822)	0.82(0.76,0.89)	< 0.001	8.07	0%	0.622
After 2010	9	634,625(10602)	0.94(0.91,0.97)	< 0.001	21.73	40.2%	0.060
Sample size
≥ 500	14	1,488,346(18809)	0.91(0.88,0.94)	< 0.001	27.76	27.9%	0.115
< 500	4	1235(615)	0.76(0.51,1.12)	0.170	8.20	63.4%	0.042
Adjustment for energy
Yes	9	881,482(10198)	0.85(0.79,0.92)	< 0.001	10.48	4.6%	0.399
No	9	608,299(9226)	0.94(0.91,0.97)	< 0.001	21.84	40.5%	0.058