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| Author (year) | Study design | Sample characteristics | Measurements of dietary fiber | Exposure and relative risk (95% CI) | Adjustment for confounders | Findings | Study limitations |
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| Shin et al. [15] | Prospective cohort (5.74 –year follow-up). | 73, 314 Chinese women, age 40–70, 283 cases. | Validated 77-item FFQ. | Dietary fiber, 1.10 (0.6–1.8). | Age, menopausal status, education, smoking, alcohol, exercise, family history of colorectal cancer, energy, vitamin supplements. | Dietary fiber intakes did not prevent colorectal cancer. | Limited follow-up, self-reported measure, no comprehensive assessment of dietary fiber intake. |
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| Butler et al. [16] | Prospective cohort (9.6 –year follow-up). | 61, 321 Chinese men and women, age 45–74, 961 cases. | Validated 165-item FFQ. | Dietary fiber, 0.98 (0.81–1.19). | Age, gender, dialect group, interview year, diabetes mellitus, smoking, body mass index, alcohol, education, physical activity, family history of colorectal cancer, energy. | Dietary fiber intakes did not prevent colorectal cancer. | Self-reported measure, no standardization for assessment of dietary fiber intake. |
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| Otani et al. [17] | Prospective cohort (5.8 –year follow-up). | 78, 326 Japanese men and women, age 40–59 (cohort 1) and 40–69 (cohort 2), 522 cases. | Validated 138-item FFQ, AOAC method. | Dietary fiber-men, 0.85 (0.53–1.4)-women, 0.58 (0.31–1.1). | Age, alcohol, smoking, body mass index, physical exercise, folate, calcium, vitamin D, red meat, study area, energy. | Dietary fiber intakes did not prevent colorectal cancer. | Limited follow-up, self-reported measure, no data combined men and women. |
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| Wakai et al. [18] | Prospective cohort (7.6 –year follow-up). | 43, 115 Japanese men and women, age 40–79, 443 cases. | Validated 40-item FFQ, AOAC method. | -Total dietary fiber, 0.73 (0.51–1.03)-soluble dietary fiber, 0.69 (0.36–1.32)-insoluble dietary fiber, 1.02 (0.54–1.94). | Age, gender, area, education, family history of colorectal cancer, alcohol, smoking, body mass index, walking, exercise, sedentary work, beef/pork, energy, folate, calcium, vitamin D. | An inverse association between total dietary fiber intake and colorectal cancer risk, no difference in the decreased risk for colorectal cancer between soluble and insoluble dietary fiber intakes. | Self-reported measure, limited food items included in the FFQ, no careful measure for confounders. |
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| Wakai et al. [9] | Case-control study (3–year follow-up). | 507cases and 2,535 controls, Japanese, age 20–79. | Validated 47-item FFQ. | -Total dietary fiber, 0.72 (0.49–1.05)-soluble dietary fiber, 0.75 (0.52–1.10)-insoluble dietary fiber, 0.65 (0.45–0.96). | Gender, age, and year of the first visit. Season of the first visit to the hospital, the reason for the visit, family history of colorectal cancer, body mass index, exercise, alcohol drinking, smoking, multivitamin use, and energy intake. | High intakes of dietary fiber associated with low colon cancer risk, specifically insoluble dietary fiber. | Self-reported measure, limited food items included in the FFQ, a discrepancy in the source population between cases and controls. |
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| Zhong et al. [19] | Case-control study (2–year follow-up). | 613 cases and 613 controls, Chinese, age 30–75. | Validated 81-item FFQ. | -Total dietary fiber, 0.38 (0.27–0.55)-vegetable fiber, 0.45 (0.32–0.64)-fruit fiber, 0.41 (0.28–0.58),-cereal fiber, 0.48 (0.35–0.67)-soy fiber, 1.25 (0.88–1.76). | Marital status, education, regular smoking, passive smoking, leisure-time physical activity, first degree relative with cancer, total energy intake, and total animal food intake. | High intakes of total fiber, cereal fiber, vegetable fiber, and fruit fiber associated with the low risk of colorectal cancer. | Self-reported measure, different sources of controls. |
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| Chiu et al. [20] | Case-control study (5-year follow-up). | 931 cases and 1552 controls, Chinese, age 30–74. | Validated 86-item FFQ. | Fruits and vegetables-men 0.7 (0.5–1.0),-women 0.6 (0.4–0.9). | Age, total energy intake, education, body mass index, monthly family per capita income, and occupational physical activity. | High fruit and vegetable fiber intake reduces the risk of colorectal cancer. | Self-reported measure, no data combined men and women, little effect of the further adjustment in the final model, random misclassification of diet in the questionnaire. |
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| Song et al. [21]. | Case-control study (1-year follow-up). | 265 cases and 252 controls, Chinese, age 30–70. | Validated 121-item FFQ. | -Total fiber intake 0.44 (0.27–0.73),-vegetable fiber intake 0.51 (0.31–0.85). | Age, gender, smoking habits, drinking habits, physical activity, body mass index (BMI), and total energy. | Vegetable fiber and total fiber associated with a low risk of colorectal cancer. | Limited follow-up, lack of validated questionnaire, little control for more confounders. |
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| Chun et al. [22] | Case-control study (1-year follow-up). | 150 cases and 116 controls, Korean, age 20–80. | Validated 102-item FFQ. | Dietary fiber 0.22 (0.08–0.56). | Gender, age, economic status, educational level, smoking, alcohol drinking frequency, and leisure-time physical activity. | High dietary fiber intakes associated with a low risk of colorectal cancer. | Limited follow-up, self-reported measure, potential recall bias, possible misclassification of dietary fiber. |
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