Abstract
Background: Dietary fibre provides a range of health benefits, yet many New Zealand (NZ) adults are not consuming the recommended daily intake. Recent literature on demographic factors affecting dietary fibre intake of NZ adults is lacking and is of interest. As both supplemental and whole food fibre forms are often used in clinical trials, it is worth investigating how both forms may affect nutrient intake to aid in the interpretation of these clinical findings. Finally, dietary fibre has been seen to affect the microbiota, however, as research in this area is new and ongoing, further research on this is of benefit.
Objective: To assess the demographic factors which influence fibre intake, and to evaluate how a fibre intervention from both gold kiwifruit and psyllium affect dietary intake. Additionally, to identify changes to the gut microbiota following fibre interventions.
Methods: The Christchurch IBS Cohort to Investigate Mechanisms for Gut Relief and Improved Transit – Psyllium and Kiwifruit (COMFORT-PSYKI) study was a randomised, single-blind, controlled cross-over study to investigate the relationship between dietary fibre and gastrointestinal symptoms in people with functional gastrointestinal disorders and compare microbiome changes with a control group. Two groups of participants were recruited; participants with IBS-C or functional constipation and healthy adults from the general public as a control group. The present thesis focuses on the nutritional intake of solely control participants without gastrointestinal symptoms. The study consisted of two interventions which were psyllium and gold kiwifruit given daily for 4 weeks with a 4 week washout phase between interventions. Food diaries were completed by participants at the end of each intervention phase and at the end of the washout phase between interventions. Food diaries from the control participants were entered into FoodWorks 10 (Xyris Software, Australia) and analysed by participant and study phase to assess mean nutrient intakes during study phases and to compare between demographic groups. Metagenome analysis was conducted by the High Value Nutrition team.
Results: 26 participants were included in the analysis. Participants were mainly female (76.9%), New Zealand European (NZE) (80.8%), university educated (61.5%), at or above a comfortable living standard (84.6%), BMI between 18.0 – 24.9 (65.4%), and aged between 18 – 29 (50.0%). The psyllium intervention caused no changes to any aspects of dietary intake, while gold kiwifruit caused significantly higher intakes of fructose, glucose, vitamin C, vitamin E, and potassium. Age, ethnicity, living standard, and BMI appeared to be associated with fibre intake. Participants aged 18 – 29, non-NZE ethnicity, higher living standard, and with a healthy BMI had higher fibre intakes during all phases of the study. The psyllium intervention resulted in changes to 18 microbial genes that code for enzymes related to fibre digestion. Gold kiwifruit was not associated with changes to any microbial genes.
Conclusion: Certain demographic factors may influence fibre intake. A fibre intervention does not affect energy or macronutrient intake; however, gold kiwifruit does cause increases to vitamin, mineral and sugar intake. In relation to the microbiota, psyllium had a more noticeable effect than gold kiwifruit.