Background: Many IBD patients report restricting their diet due to perceived positive effects on their symptoms despite a current lack of evidence-based nutritional recommendations in this specific population. To date little is known about dietary habits of IBD patients, especially on the prevalence of vegetarian diet (VD) and gluten-free diet (GFD), while to the best of our knowledge no studies have yet investigated the impact of VD on course of disease in IBD patients.
Methods: We included 1254 patients from the Swiss Inflammatory Bowel Disease Cohort Study (SIBDCS) with prospective acquisition of clinical data, psychosocial, disease-related and lifestyle factors between 2006 and 2015. Dietary habits (not part of routine enrollment and follow-up questionnaires) were subsequently inquired through a self-report questionnaire.
Results: Overall 4.1% of the IBD patients reported to follow a VD (reported underlying reasons: respect for animals, 42.3%; expected benefit for general health, 17.3%; or IBD in specific, 17,3%) and 4.7% a GFD (majority of patients referred to a perceived beneficial effect on course of their IBD as underlying reason for gluten withdrawal). We did not find any differences in essential baseline disease characteristics, such as age at diagnosis of IBD, disease duration, type of IBD and disease localization in omnivores vs. patients with a VD or GFD. However, in IBD patients following a VD there were significantly more women (p=0.002) and patients with a lower body weight (median 63 vs. 71 kg in VD vs. normal diet patients; p<0.001). No differences regarding disease activity, overall complications, fistula, hospitalization or surgery rates were observed between patients following VD or GFD vs. their counterparts with regular diet. Nevertheless, we found evidence for higher psychological impairment and lower quality of life measures with a significantly higher Post Traumatic Stress Diagnostic Scale and lower mental component levels of the Short Form 36 Health Survey (SF-36) in patients on VD or GFD as well as significantly higher indexes for anxiety and depression in the Hospital Anxiety and Depression Scale (HADS) in GFD patients.
Conclusions: In contrast to a significant fraction of patients perceiving (or potentially relying on, respectively) beneficial effects, no impact of VD or GFD on course of disease or complication rates was identified as compared to a regular diet. There was however a significant association to higher anxiety and depression as well as lower overall health score levels in VD or GFD patients. The latter may indicate, that psychosocial factors and expectations might be of higher importance in the decision to initiate and maintain a specific diet than an as a matter of fact occurring effect on course of IBD