Table 2.

Summary of vegetarian/vegan and gluten-free diet studies in rheumatoid arthritis and psoriasis with potential applicability to IBD.

Vegetarian/Vegan: Positive Outcomes in RA Studies Suggest Possible Benefits in IBD, Where Data on This Diet Have Been Quite Limited.
Study	Disease	Design	N	Results
Kjeldsen-Kragh [39,40]	RA	Randomized trial	53	Improvement in ESR (−4 mm/h)/CRP (−6 mg/L) (p < 0.002 and p < 0.005) seen in intervention group. However, significant dropout in study (~60% completed).
McDougall [41]	RA	Single-arm intervention	24	Improvement in RA pain scores (p < 0.004), swollen joints (p < 0.02) after switch to vegan low fat diet.
Hafstrom [42]	RA	Randomized trial	66	Higher prevalence of fulfilling ACR improvement criteria in those in the vegan diet free of gluten group (40% vs. 4%). 60% intervention group completed the 9-month follow-up.
Afifi [43]	Ps	Survey	1206	Self-reported improvement in skin symptoms in 70% of those on a vegan diet.
Gluten-free +: Benefit of this diet seen in only a subset of psoriasis patients with gliadin antibodies, which makes it difficult to extrapolate to patients with IBD.
Study	Disease	Design	N	Results
Michaelsson [48]	Ps	Single-arm intervention	39	Gluten-free diet led to an improvement in PASI (5.5 before vs. 3.6 after) in those with gliadin antibodies (p = 0.001).

⁺ Kjedsen-Kragh and Hafstrom studies (included in the vegetarian/vegan section above) included gluten-free components of the vegan intervention diet. ESR: erythrocyte sedimentation rate. CRP: C reactive protein. ACR: American College of Rheumatology. PASI: Psoriasis area and severity index.