Abstract
Background: Irritable bowel syndrome and functional constipation are common functional gastrointestinal disorders that have both a negative impact on individuals’ quality of life and a large economic cost. Inevitably, as the prevalence of irritable bowel syndrome and functional constipation increases, so does the cumulative burden of disease, and thus, the need for affordable and effective dietary management.
Objective: This thesis aimed to assess differences in dietary intake, gastrointestinal symptom burden, symptom-free days and days without a bowel motion between healthy controls, constipation-predominant irritable bowel syndrome and functional constipation groups and between study phases. It also aimed to assess relationships between symptom burden, nutrient intake and anxiety levels.
Design: The COMFORT-PSYKI study was a single-blinded, positive-controlled, randomised, cross-over study. Participants included both healthy controls and cases who were required to meet Rome IV criteria for constipation-predominant irritable bowel syndrome or functional constipation. Participants underwent a 16-week cross- over trial including a lead-in period, two interventions (ZespriTM SunGold® kiwifruit and BonVit® orange psyllium preparation) and a washout period between March and December 2019. Three-day Food and Symptom Times diaries were completed including diet records and live gastrointestinal symptom scores during each intervention and the washout period.
Results: Forty-seven participants’ data was included in the final data analysis. Diet record analysis found no statistically significant differences in fibre intake between control (27.1 ± 12.0g/day), IBS-C (24.0 ± 9.9g/day) or FC (22.7 ± 7.4g/day) groups or between kiwifruit (26.1 ± 8.6g/day), psyllium (26.1 ± 10.3g/day) or washout (24.4 ± 13.3g/day) phases. However, participants were found to consume significantly more vitamin C whilst consuming kiwifruit (387 ± 68mg/day) compared to the psyllium (74 ± 64mg/day, P < 0.001) or the washout phase (60 ± 31mg/day, P < 0.001). Overall, participants had a greater burden of pain whilst on the kiwifruit intervention compared to the psyllium intervention (P=0.031), but not when compared to the washout period (P=0.062). However, this result was heavily influenced by outlying data. Participants also experienced significantly greater distension on the kiwifruit intervention compared to washout (P= 0.022), but not on psyllium compared to washout (P= 0.223). Spearman’s correlations found no relationship between dietary fibre and gastrointestinal symptoms. However, weak to moderate positive relationships were found between vitamin C intake and gastrointestinal symptoms as well as between anxiety scores and gastrointestinal symptoms. Participants with constipation-predominant irritable bowel syndrome consistently appeared to have fewer symptom-free days whilst on the psyllium intervention and more symptom-free days on the kiwifruit intervention. However, these differences were not statistically significant.
Conclusion: This study found that the burden of abdominal pain and distension was significantly greater whilst participants were on the SunGold® Kiwifruit intervention compared to other phases. However, during this same intervention, higher intakes of vitamin C were associated with a lower burden of all gastrointestinal symptoms. A weak positive correlation was found between anxiety and gastrointestinal symptoms, showing that as anxiety levels rose, so too did symptom burden.