Table 2.
Characteristics of included studies for the risk of development of ulcerative colitis.
| Study | Total sample size | Sample size (UC) | Age (mean ± SD, years) | Sex (M/F) | Country | Cohort | Exposure | Dietary assessment tool | Outcome measurement | Lowest vs. highest intake assessment | Follow-up period (mean, years) | Person-years |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cohort studies | ||||||||||||
| Dong et al. (26) | 413,593 | 418 | 52.5 ± 8.6 | 128,214/285379 | Eight countriesa | EPIC-IBD | Meat/red meat/processed meat | ① | B | M: 0-19 g/d vs.>61 g/d; F: 0-10 g/d vs.>38 g/d |
16.8 | 6,961,118.6 |
| Lopes et al. (27) | 208,070 | 456 | 45.31 ± 10.70 | 41,871/166199 | America | NHS, NHSII, HPFS | Red meat | ② | A | NR | NR | 5,117,021 |
| Narula et al. (28) | 116,037 | 377 | 50.2 ± 9.7 | 47,305/68732 | 21 countriesb | PURE | Processed meat | ① | A | <1 serving/week vs. ≥7 servings/week | Median: 9.7 | NR |
| DeClercq et al. (29) | 12,568 | 120 | UC: 54.6 ± 8.1 C: 53.7 ± 8.8 |
UC: 42/77 C:3694/8768 |
Canada | PATH | Meat and poultry | ③ | A | Rarely/never vs. servings per month | NR | NR |
| Khalili et al. (30) | 165,331 | 321 | 42.4 | 0/165331 | USA | NHS, NHSII | Red meat/processed meat | ② | A | NR | NR | 3,038,049 |
| Song et al. (31) | 456,590 | 312 | Total: 51.8 UC: 61.3 |
258,887/197703 | China | CKB | Meat | ② | A | Never, rarely or monthly vs. ≥4 days per week | 12.1 | Never, rarely or monthly: 924,568 1–3 days per week: 1,896,199 ≥ 4 days per week: 2,535,737 |
| Case–control studies | ||||||||||||
| Bernstein et al. (32) | 1,014 | 217 | Range: 18–50 | UC: 99/118 C: 115/318 |
Canada | NA | Eating pork as a child | ④ | A | Never or less than once a month vs. 3–6 times a week or every day | NA | NA |
| Farsiz et al. (33) | 234 | 86 | UC: 40.8 ± 12.7 C: 36.4 ± 11.6 |
UC: 32/54 C: 49/73 |
Iran | NA | Red meat/processed meat | ③ | A | NR | NA | NA |
| Kurata (34) | 244 | 101 | Range: 10–39 | UC: 56/45 C: 79/64 |
Japan | NA | Meat/ham and sausage | ⑤ | B | None or hardly any vs. three to five times per week | NA | NA |
| Liu (35) | 216 | 72 | Median: UC: 43/T:45 |
UC: 32/40 C: 64/80 |
China | NA | Red meat/grilled meat | ② | A | 0–3 serving/week vs. ≥5 serving/week | NA | NA |
| Sakamoto et al. (36) | 445 | 108 | Range: 15–34 | UC: 56/52 C: 135/76 |
Japan | NA | Meats and poultry | ① | A | 0 g/d vs. 94.6 g/d | NA | NA |
| Rashvand et al. (37) | 186 | 62 | UC: 37.4 C: 36.23 |
UC: 27/35 C: 54/70 |
Iran | NA | Red meat/processed meat | ① | A | NR | NA | NA |
| Maconi et al. (38) | 243 | 41 | Total: 37.5 ± 15.2 C: 40.4 ± 14.6 |
Total: 49/34 C: 97/63 |
Italy | NA | Red meat | ① | B | NR | NA | NA |
UC, ulcerative colitis; SD, standard deviation; M, male; F, female; C, control group; NR, not reported; NA, not applicable; vs., versus; g, gram; d, day; NHS, the Nurses’ Health Study; HPFS, Health Professionals Follow-Up Study; EPIC, the European Prospective Investigation into Cancer and Nutrition; PURE, the Prospective Urban Rural Epidemiology; PATH, the Atlantic Partnership for Tomorrow’s Health; CKB, the China Kadoorie Biobank. ①, country-specific validated food frequency questionnaires; ②, semi-quantitative food frequency questionnaires; ③, food frequency questionnaires; ④, questionnaire about childhood dietary patterns; ⑤, self-administered questionnaire; A, self-reported questionnaire; B, individual interviews or self-reported questionnaire.
Denmark, France, Germany, Italy, The Netherlands, Spain, Sweden, and the UK.
Argentina, Bangladesh, Brazil, Canada, Chile, China, Colombia, India, Iran, Malaysia, Palestine, Pakistan, Philippines, Poland, South Africa, Saudi Arabia, Sweden, Tanzania, Turkey, United Arab Emirates, and Zimbabwe.