Table 4.

 Subgroup analyses of cereal fibre and whole grain intake and risk of colorectal cancer, dose-response analysis

Subgroups	Cereal fibre							Whole grains
	No of studies	Relative risk (95% CI)	I2 (%)		P for heterogeneity*	P for heterogeneity†		No of studies	Relative risk (95% CI)	I2 (%)	P for heterogeneity*	P for heterogeneity†
All studies	8	0.90 (0.83 to 0.97)	0		0.78	—		6	0.83 (0.78 to 0.89)	18.2	0.30	—
Duration of follow-up:
<10 years	5	0.90 (0.82 to 0.98)	0		0.42	0.84		1	0.73 (0.63 to 0.84)	—	—	0.12
≥10 years	3	0.87 (0.71 to 1.08)	0		0.99			5	0.86 (0.80 to 0.92)	0	0.72
Sex:
Men	2	0.92 (0.80 to 1.06)	0		0.60	0.69		3	0.79 (0.72 to 0.87)	0	0.44	0.14
Women	5	0.96 (0.83 to 1.11)	0		0.98			5	0.88 (0.81 to 0.95)	0	0.58
Subsite:
Colon	3	1.03 (0.80 to 1.32)	0		0.45	0.45		4	0.86 (0.79 to 0.94)	0	0.58	0.53
Rectum	1	1.39 (0.78 to 2.48)	—		—			3	0.80 (0.56 to 1.14)	90.5	<0.001
Geographical location:
Europe	2	0.94 (0.73 to 1.21)	0		0.48	0.70		2	0.87 (0.78 to 0.96)	58.8	0.12	0.13
USA	6	0.89 (0.82 to 0.97)	0		0.65			4	0.79 (0.72 to 0.86)	0	0.57
Asia	0	—	—		—			0	—	—	—
No of cases:
<500	3	1.01 (0.77 to 1.32)	0		0.99	0.48		0				0.12
500-1499	2	0.87 (0.71 to 1.08)	0		0.92			5	0.86 (0.80 to 0.92)	0	0.72
≥1500	3	0.88 (0.77 to 1.00)	35.1		0.21			1	0.73 (0.63 to 0.84)	—	—
Range of intake:
<7 to <90 g/day‡	3	0.91 (0.68 to 1.21)	0		0.85	0.90		1	0.73 (0.63 to 0.84)			0.18
≥7 to ≥90 g/day‡	5	0.89 (0.82 to 0.97)	0		0.45			3	0.87 (0.80 to 0.94)	0	0.39
Adjustment for confounders
Alcohol:
Yes	6	0.93 (0.84 to 1.02)	0	0.98		0.27		3	0.86 (0.79 to 0.93)	0	0.92	0.51
No	2	0.86 (0.68 to 1.08)	41.9	0.19				3	0.81 (0.70 to 0.93)	60.6	0.08
Smoking:
Yes	7	0.89 (0.82 to 0.97)	0	0.76		0.47		3	0.79 (0.71 to 0.87)	1.6	0.36	0.21
No	1	1.02 (0.73 to 1.43)	—	—				3	0.87 (0.80 to 0.94)	0	0.39
Body mass index, weight, waist to hip ratio:
Yes	7	0.89 (0.82 to 0.97)	0	0.76		0.27		4	0.87 (0.81 to 0.94)	0	0.82	0.09
No	1	1.02 (0.73 to 1.43)	—	—				2	0.75 (0.67 to 0.84)	0	0.52
Physical activity:
Yes	6	0.89 (0.81 to 0.96)	0	0.68		0.38		4	0.82 (0.76 to 0.89)	20.1	0.29	0.60
No	2	1.02 (0.77 to 1.34)	0	0.97				2	0.86 (0.73 to 1.01)	47.5	0.17
Red, processed meat:
Yes	8	0.90 (0.83 to 0.97)	0	0.78		NC		3	0.84 (0.74 to 0.95)	64.0	0.06	0.81
No	0	—	—	—				3	0.82 (0.74 to 0.91)	0	0.81
Dairy products, calcium:
Yes	6	0.90 (0.83 to 0.98)	0	0.56		0.82		2	0.82 (0.65 to 1.03)	79.7	0.03	0.79
No	2	0.85 (0.59 to 1.23)	0	0.87				4	0.84 (0.78 to 0.91)	0	0.81
Folate:
Yes	5	0.88 (0.81 to 0.96)	0	0.54		0.38		1	0.73 (0.63 to 0.84)			0.12
No	3	1.01 (0.77 to 1.32)	0	0.99				5	0.86 (0.80 to 0.92)	0	0.72
Energy intake:
Yes	6	0.90 (0.82 to 0.98)	0	0.56		0.83		4	0.83 (0.74 to 0.92)	41.1	0.17	0.91
No	2	0.87 (0.71 to 1.08)	0	0.92				2	0.85 (0.77 to 0.93)	0	0.35

NC=not calculable.

*Within each subgroup.

†Between subgroups with meta-regression analysis.

‡Cereal fibre: ≥7 versus <7 g/day, whole grains: ≥90 versus <90 g/day.