Introduction
Dietary therapies have revolutionised treatment for irritable bowel syndrome (IBS). However, response rates to the diet with the highest evidence of efficacy (the low FODMAP diet) remain at 50-75%, suggesting other potential drivers of symptom onset. A low food chemical elimination-rechallenge diet targeting bioactive food chemicals (including salicylates, amines, glutamate and other additives), is commonly applied in Australia in patients exhibiting both gastrointestinal and extra-intestinal symptoms. However, data supporting the low chemical diet is scant, and safety concerns exist due to its restrictive nature potentially causing nutritional deficiencies and disordered eating.
Aims & Methods
This cross-sectional survey in patients with IBS and healthy controls aimed to evaluate the frequency of co-existing extra-intestinal symptoms, as well as explore patient perceptions and use of the low chemical diet. Participants with IBS (IBS-Severity Scoring System1 (IBS-SSS) >75), and healthy controls (not meeting Rome IV and ≤75 on IBS-SSS) were recruited via online advertisement. Validated questionnaires were used to assess gastrointestinal symptoms (IBS-SSS1), extraintestinal symptoms (extended PHQ-122), and food additive intake (IBD-Food additive questionnaire3). Additional questionnaires assessed use of dietary therapies with specific focus on food chemicals. Data was analysed using independent samples t-test and chi-square test.
Results
204 IBS and 22 healthy controls completed the study. Total IBS-SSS for the IBS participants was 277±79, compared to 36±28 in the healthy control group (p<0.01). IBS participants were more likely to report extra-intestinal symptoms including headaches (p<0.01), migraines (p=0.03), fatigue (p<0.01), difficulty sleeping (p=0.03), rhinitis (p=0.02), urticaria (p=0.04) and mood disturbance (p<0.01). Twenty-one (10%) of IBS participants were following a low chemical diet compared to none in the control group. Of these 21 participants, dietary advice was provided by a dietitian (n=13), general practitioner (n=6), gastroenterologist (n=6), naturopath (n=3), family/friend (n=4) and/or the diet was self-initiated (n=7). IBS participants were more likely to report at least one food chemical as a trigger for gastrointestinal (38% vs 13%, p=0.03) and/or extra-intestinal (30% vs 9%, p=0.04) symptoms (Table 1). There was no significant difference in consumption (g/day or g/kg/day) of ultra-processed, additive containing foods.
Table 1. Suspected dietary triggers (food chemical specific) for gastrointestinal and extra-intestinal symptoms
| Salicylates | MSG | Artificial colours | Sulphites | Amines |
| Suspected a trigger for gastrointestinal symptoms |
| IBS | 38 (19%) | 35 (17%)
| 28 (14%) | 25 (12%) | 26 (13%) |
| Healthy | 2 (9%) | 1 (5%) | 1 (5%) | 0 (0%) | 0 (0%) |
| Suspected a trigger for extra-intestinal symptoms |
| IBS | 19 (9%) | 30 (15%) | 23 (11%) | 24 (12%) | 29 (14%) |
| Healthy | 1 (5%) | 0 (0%) | 1 (5%) | 0 (0%) | 1 (5%) |
Conclusion
Patients with IBS are more likely to report experiencing extra-intestinal symptoms compared to healthy controls. Despite limited evidence, a low food chemical diet is utilised by patients with IBS to manage both gastrointestinal and extra-intestinal symptoms. Further data is needed to understand the efficacy and safety of the low chemical diet in IBS.
References
- Francis., et al (1997). Aliment Pharmacol Ther., 95(4), 999-1007
- Spiller., et al. (2010). Aliment Pharmacol Ther., 32(6), 811-820
- Trakman., et al. (2020). Nutrients, 12(3). 812.
Disclosure
No conflicts to declare