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 | |||||||
O/E | P value | |||||||||||||
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 dieta | 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.
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.