Table 4.

Summary of dietary clinical trials in IBD. Current data suggest that lower meat consumption may avoid relapse, and low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) can provide relief from functional-like gastrointestinal symptoms.

Study	IBD Type	Design	N	Results
Mediterranean Diet (MD)
Papada [30]	CD	Observational	86	Higher adherence with 6-month MD was associated with higher remission rates (p = 0.005).
Lo [31]	CD/UC	Prospective cohort study	828	Higher adherence with MD was associated with decreased mortality following IBD diagnosis (HR 0.69; 95% CI 0.49–0.98).
Marlow [32]	CD	Uncontrolled study	8	6-week MD showed trend for normalization of microbiota, no effect on CRP (decrease less than 1 mg/L, p = 0.39).
Khalili [33]	CD/UC	Prospective cohort study	83,147	Higher adherence with MD was associated with a lower risk of developing CD (p = 0.03), but not UC (p = 0.61).
Albenberg [34]	CD	Prospective, controlled cohort study	214	Lower red and processed meat consumption were associated with lower relapse rates (42% vs. 62%) but no difference in time to relapse.
Vegetarian/Vegan Diet
Chiba [45]	CD	Prospective controlled study	22	Lower relapse rate in patients on semi-vegetarian diet (1/16, 6%) vs. omnivorous diet (4/6, 67%) (p = 0.0003).
Jowett [44]	UC	Prospective cohort study	191	Higher consumption of meats (OR 3.2; 95% CI 1.3–7.8), particularly red and processed meat (OR 5.19; 95% CI 2.1–12.9), protein (OR 3.00; 95% CI 1.25–7.19), and alcohol (OR 2.71; 95% CI 1.1–6.67) increased the likelihood of relapse.
Amarapurkar [7]	CD/UC	Prospective case-control study	1054	Vegetarian diet was a protective factor for UC (OR 0.29; 95% CI 0.27–0.39) and a risk factor for CD (OR 1.179; 95% CI 0.88–1.57).
Gluten-Free Diet (GFD)
Herfarth [46]	CD/UC	Cross-sectional questionnaire study	1647	66% of participants report an improvement in clinical symptoms when on GFD, although the prevalence of celiac disease was only 0.6%.
Schreiner [47]	CD/UC	Prospective cohort study	1254	GFD was not associated with IBD activity, hospitalization, or surgery rates.
Calorie Restriction/Fasting
Tavakkoli [52]	CD/UC	Prospective cohort study	60	Ramadan fasting significantly improved symptoms (CAI reduction of 1.1) in UC (p = 0.005) but not in CD.
Specific Carbohydrate Diet (SCD)
Cohen [60]	CD	Prospective, uncontrolled study	10	Significant improvement in disease activity in pediatric CD (PCDAI reduction of 13.3, p = 0.011).
Obih [61]	CD/UC	Retrospective chart review	26	Significant improvement in disease activity (PCDAI reduction 11.4 at 6 months, p = 0.03), in CRP (−0.9 mg/dL, p = 0.03) and calprotectin (−181 mcg/g, p = 0.03) in pediatric CD compared to control. No significant improvements in pediatric UC.
Kakodkar [62]	CD/UC	Case series	50	Patients in disease remission report the SCD to be effective in controlling acute flare symptoms (mean = 91.3%, range = 30% to 100%) and at maintaining remission (mean = 92.1%, range = 53% to 100%).
Suskind [63]	CD/UC	Survey study	417	42% of patients report achieving remission at 6 and 12 months while on the diet. 47% of patients report improvement in abnormal lab values.
Low FODMAP Diet (LFD)
Gearry [64]	CD/UC	Retrospective study	72	Improved symptoms after 3 months of LFD.
Prince [65]	CD/UC	Prospective study	88	Significant improvement in functional-like gastrointestinal symptoms compared to baseline (78% vs. 16% at baseline reporting satisfactory relief, p < 0.001).
Pedersen [66]	CD/UC	Controlled open-label study	89	LFD improved IBS symptoms (55 points lower IBS-SSS, p = 0.02) and health-related quality of life (SIBDQ 10 points higher, p < 0.01) compared to normal diet in IBD in remission.
Cox [67]	CD/UC	Single-blind study	52	LFD improved gut symptoms compared to control (52% reporting adequate relief on LFD vs. 16% on control, p = 0.007).
Cox [68]	CD/UC	Double-blinded, controlled, re-challenge study	32	Fructose challenge brought less relief of functional-like gastrointestinal symptoms compared with glucose (62.1% reported relief in the fructan group vs. 89.7 in glucose, p = 0.033).