Table 3.
Characteristics of included studies for the risk of flare of ulcerative colitis.
| Study | Total sample size | Sample size (flare/UC) | Age (mean ± SD, years) | Sex (M/F) | Country | Cohort | Exposure | Dietary assessment tool | Outcome measurement | Flare assessment tool | Definition of flare | Lowest vs. highest intake assessment | Follow-up period (mean, years) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cohort studies | |||||||||||||
| Cohen et al. (39) | 6,768 | 185/597 | 44.9 | 214/383 | USA | CCFA | Red meat/processed meat | ② | A | 5-point Likert scale | Patients with active disease activity were those who reported having mild, moderate, or severe symptoms. | NR | NA |
| Barnes et al. (40) | 412 | 45/412 | Flare: 44.61 ± 12.64 Remission: 48.66 ± 14.71 |
Flare: 28/17 Not Remission: 207/158 |
USA | A consortium of academic and community gastroenterology practices | Processed meat | ① | A | SCCAI | A SCCAI ≥5 or a change in disease activity requiring a change in medication. | Never or less than once per month vs. 6 or more times per day | 1 |
| Jowett et al. (41) | 183 | 96/183 | Median:51 | 93/90 | UK | NR | Meat and meat products/red and processed meat | ③ | A | SCCAI | A score of 5 or more accurately confirms a clinician defined relapse | NR | 1 |
| Case–control studies | |||||||||||||
| Mi et al. (42) | 100 | 27/40 | Flare: 53.2 ± 12.2 Remission: 48.4 ± 15.8 |
Flare: 20/11 Remission: 11/8 |
China | NR | Beef | ① | A | Modified Truelove and Witts severity index | UC relapse refers to the recurrence of UC symptoms following natural or drug treatment into the remission period. | Not at all or occasionally vs. ≥3times per week | NA |
| Peters et al. (43) | 1790 | 94/207 | Flare: 43.2 ± 15.1 Remission: 42.1 ± 13.7 |
Flare: 92/149 Remission:100/151 |
Dutch | 1000IBD, LLD | Meat | ② | A | SCCAI | Relapse was defined as either a faecal calprotectin level≥200 mg/g or a SCCAI>2. | NR | NA |
UC, ulcerative colitis; SD, standard deviation; M, male; F, female; NR, not reported; NA, not applicable; vs., versus; g, gram; d, day; CCFA, the Crohn’s and Colitis Foundation of America; SCCAI, Short Clinical Colitis Activity Index; 1000IBD, the Groningen 1000IBD cohort; LLD, the Lifelines DEEP Cohort; 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.