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

Table 2. Quality of Evidence of Associations Between the Role of Diet and Increase 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
Food	Red meat	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	1.13 (1.08-1.19)	<1 × 10⁻⁶	20.5	1.15-1.19	1.02-1.26	.18	3/6.0	NP	I	High
Alcoholic beverage	Alcohol	Fedirko et al,³¹ 2011	≥4 drinks/d vs non-/occasional drinkers	RR	1.58 (1.38-1.80)	<1 × 10⁻⁶	0.0	1.27-2.16	1.33-1.87	.80	5/5.8	NP	I	Moderate
Alcoholic beverage	Alcohol	Fedirko et al,³¹ 2011	>1-3 drinks/d vs non-/occasional drinkers	RR	1.24 (1.14-1.34)	<1 × 10⁻⁶	49.3	1.01-1.13	0.95-1.61	<.001	9/2.8	.77	II	Moderate
Food	Processed meat	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	1.14 (1.07-1.23)	.0001	25.9	1.09-1.32	0.97-1.35	.98	4/6.9	NP	III	High
Dietary behavior	Adherence to Western diet	Feng et al,¹⁶ 2017	High vs low	OR	1.28 (1.13-1.45)	.0001	72.2	1.09-1.44	0.79-2.07	.17	8/6.5	>.99	III	Moderate
Food	Eggs	Schwingshackl et al,⁵⁶ 2018	High vs low	RR	1.36 (1.10-1.68)	.004	0.0	1.10-1.78	0.35-5.31	.28	1/1.2	NP	IV	High
Dietary behavior	Adherence to alcohol drinking	Feng et al,¹⁶ 2017	High vs low	OR	1.53 (1.04-2.25)	.03	93.5	1.54-2.10	0.37-6.34	.56	3/8.3	NP	IV	Moderate
Alcoholic beverage	Beer	Zhang et al,³² 2015	Drinkers vs non-/occasional drinkers	RR	1.08 (1.02-1.15)	.01	0.0	1.04-1.28	1.01-1.16	.52	1/1.5	NP	IV	Moderate
Dietary behavior	Adherence to unhealthy diet^a	Grosso et al,²⁷ 2017	High vs low	RR	1.13 (1.03-1.23)	.007	30.5	1.02-1.36	0.89-1.43	.76	2/3.7	NP	IV	Low
Food	Pork	Carr et al,⁵⁷ 2016	High vs low	RR	1.17 (1.04-1.31)	.01	0.0	0.93-1.38	0.90-1.51	.86	0/0.7	NP	IV	Low
Micronutrient	Heme iron	Qiao et al,⁵¹ 2013	High vs low	RR	1.12 (1.01-1.24)	.03	22.6	0.99-1.29	0.90-1.39	.81	1/NA	NA	IV	Critically low

Abbreviations: AMSTAR-2, A Measurement Tool to Assess Systematic Reviews; 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}

Unhealthy diet was defined by authors as characterized by, but not limited to, red and processed meat, sugary drinks and salty snacks, starchy foods, and refined carbohydrates.