. 2021 Feb 16;4(2):e2037341. doi: 10.1001/jamanetworkopen.2020.37341

Table 3. Quality of Evidence of Associations Between the Role of Diet and Reduction in Colorectal Cancer Incidence.

Classification	Exposure	Source	Comparison	Summary metric	Credibility assessment									AMSTAR-2
					Random effect size (95% CI)	P value	I², %	Largest study 95% CI	Prediction interval 95% CI	Egger P value	Excess significance test		Quality of evidence class
					Random effect size (95% CI)	P value	I², %	Largest study 95% CI	Prediction interval 95% CI	Egger P value	O/E	P value	Quality of evidence class
Macronutrient	Total dietary fiber	Reynolds et al,⁴⁹ 2019	High vs low	RR	0.84 (0.78-0.89)	<1 × 10⁻⁶	18.1	0.65-0.85	0.72-0.97	.53	6/12.1	NP	I	High
Micronutrient	Dietary calcium	Meng et al,⁵⁰ 2019	High vs low	HR	0.77 (0.73-0.82)	<1 × 10⁻⁶	0.0	0.75-0.94	0.72-0.83	.60	5/3.9	>.99	I	Moderate
Food	Yogurt	Zhang et al,²⁴ 2019	High vs low	OR	0.81 (0.76-0.86)	<1 × 10⁻⁶	0.0	0.75-0.87	0.72-0.90	.84	2/1.8	>.99	I	Moderate
Food	Dairy products	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	0.83 (0.76-0.89)	<1 × 10⁻⁶	60.3	0.83-0.95	0.65-1.04	.17	8/4.0	.99	II	High
Food	Whole grains	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	0.88 (0.83-0.94)	.00006	34.9	0.88-0.99	0.77-1.01	.07	4/1.0	.26	III	High
Dietary behavior	Adherence to healthy diet^a	Feng et al,¹⁶ 2017	High vs low	OR	0.84 (0.76-0.92)	.0003	56.2	0.69-0.90	0.60-1.17	.60	5/7.5	NP	III	Moderate
Beverage	Nonfermented milk	Ralston et al,³⁰ 2014	High vs low	RR	0.85 (0.78-0.93)	.0005	0.0	0.78-1.18	0.77-0.94	.96	3/0.9	.96	III	Moderate
Dietary behavior	Pesco-vegetarian diet	Godos et al,³⁸ 2016	Yes vs no	RR	0.67 (0.53-0.83)	.0004	0.0	0.48-0.94	0.15-2.89	.44	2/1.7	.94	III	Low
Dietary behavior	Semivegetarian diet	Godos et al,³⁸ 2016	Yes vs no	RR	0.86 (0.79-0.94)	.0007	0.0	0.76-0.95	0.72-1.04	.96	1/1.2	NP	III	Low
Micronutrient	Supplemental calcium	Heine-Bröring et al,⁴⁷ 2015	Yes vs no	RR	0.88 (0.82-0.94)	.00009	51.7	0.88-1.05	0.70-1.09	.07	3/3.4	NP	III	Low
Micronutrient	Supplemental calcium	Heine-Bröring et al,⁴⁷ 2015	High vs low	RR	0.80 (0.72-0.89)	.00002	30.9	0.72-1.02	0.63-1.01	.88	4/2.7	.95	III	Low
Dietary behavior	Adherence to Mediterranean diet	Schwingshackl et al,¹⁵ 2017	High vs low	RR	0.86 (0.80-0.92)	8.4 × 10⁻⁶	29.7	0.80-0.99	0.74-1.00	.84	3/5.0	NP	III	Critically low
Food	Vegetables	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	0.96 (0.92-1.00)	.04	25.0	0.96-1.04	0.87-1.05	.26	1/0.9	>.99	IV	High
Food	Fruits	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	0.93 (0.87-0.99)	.01	51.8	0.96-1.06	0.78-1.10	.16	3/0.9	.99	IV	High
Micronutrient	Zinc	Li et al,⁵³ 2014	High vs low	RR	0.82 (0.69-0.96)	.02	67.0	0.68-0.78	0.48-1.38	.43	2/3.8	NP	IV	Moderate
Food	Legumes	Zhu et al,²¹ 2015	High vs low	RR	0.90 (0.83-0.98)	.01	46.1	0.83-1.09	0.66-1.23	.13	5/1.0	.16	IV	Low
Macronutrient	Cereal fiber	Aune et al,⁴⁰ 2011	High vs low	RR	0.90 (0.83-0.96)	.003	0.0	0.76-0.98	0.82-0.98	.36	1/2.9	NP	IV	Low
Micronutrient	Multivitamin	Heine-Bröring et al,⁴⁷ 2015	Yes vs no	RR	0.91 (0.86-0.97)	.002	13.7	0.88-1.11	0.81-1.02	.55	2/0.8	.91	IV	Low
Micronutrient	Vitamin A	Heine-Bröring et al,⁴⁷ 2015	Yes vs no	RR	0.76 (0.62-0.94)	.01	0.0	0.50-1.10	0.48-1.21	.78	1/1.7	NP	IV	Low
Micronutrient	Vitamin B₆	Liu et al,⁴⁸ 2015	High vs low	RR	0.88 (0.79-0.99)	.03	47.2	0.66-0.99	0.62-1.26	.70	5/7.1	NP	IV	Low
Micronutrient	Folic acid	Liu et al,⁴⁸ 2015	High vs low	RR	0.88 (0.81-0.95)	.002	42.9	0.58-0.84	0.68-1.15	.08	7/13.7	NP	IV	Low
Micronutrient	Vitamin D	Liu et al,⁴⁸ 2015	High vs low	RR	0.85 (0.75-0.97)	.01	44.1	0.83-1.33	0.57-1.26	.46	2/1.5	>.99	IV	Low
Micronutrient	Vitamin E	Heine-Bröring et al,⁴⁷ 2015	Yes vs no	RR	0.87 (0.75-1.00)	.048	0.0	0.64-1.36	0.73-1.03	.75	1/NA	NA	IV	Low
Micronutrient	Magnesium	Chen et al,⁵² 2012	High vs low	RR	0.87 (0.77-0.99)	.03	0.5	0.62-1.03	0.75-1.02	.68	0/3.5	NP	IV	Critically low

Abbreviations: AMSTAR-2, A Measurement Tool to Assess Systematic Reviews; HR, hazard ratio; NA, not applicable because of nonsignificant effect estimate; NP, not pertinent because estimated number is larger than observed and there is no evidence of excess significance based on assumption made for plausible effect size; O/E, observed/expected number of studies with significant results; OR, odds ratio; RR, risk ratio.

^{^a}

Healthy diet was defined by the authors as high intakes of vegetables, fruits, whole grains, olive oil, fish, soy, poultry, and low-fat dairy.