Chapter 3 Secondary data analysis
3.5 Discussion
Secondary data analysis provided preliminary evidence to support our hypothesis that distinctive habitual dietary intakes influence baseline gut microbiota composition and diversity, and gut microbiota response to high-dose Actazin™. We established that baseline differences in gut microbiota composition existed in nine of the 13 dietary groups analysed. Vegetable, Fruit and Carbohydrate:Protein ratio had the greatest number of taxonomic differences between comparatively different intake groups (low
versus high or low versus moderate versus high consumers) within each dietary group.
We also demonstrated that comparatively different intakes in nine of the 13 dietary groups analysed led to significant differences in gut microbiota response to high-dose
Actazin™. The dietary groups that appeared to have the largest impact on gut microbiota
responsiveness were Dietary fibre, Wholegrain, Vegetable, Plant protein and Carbohydrate:Protein ratio.
A number of studies have demonstrated that dietary interventions can elicit significant changes in gut microbiota composition and function24,26,27. It does, however,
appear that inter-individual variability in gut microbiota response to dietary interventions exists. Baseline gut microbiota composition7,10,28 and diversity11 have been suggested to
influence gut microbiota response to a dietary intervention. As diet has a major impact on the structure and function of the gut microbiota, it is plausible that habitual dietary intakes may also influence gut microbiota responsiveness. To date, no studies have been conducted with the primary aim of determining what influence habitual dietary intake has on gut microbiota response. Therefore, the results of this study are the first to suggest that habitual dietary intake may influence gut microbiota response to a dietary intervention.
106 There are some limitations to this study that require discussion including the retrospective analysis of data obtained from a previous randomised, double-blind, placebo-controlled, cross-over study with relatively small participant numbers. For the purposes of this study the retrospective analysis of the previously collected data helped determine whether there was any validity to our hypothesis before progressing to more time- and resource-intensive studies. Another limitation of this study is that the dietary intake information collected, using two 3-day diet records, may not have provided dietary intake information that was representative of habitual dietary intakes. The two diet records were completed 22 weeks apart so it is possible that the dietary intake information collected may represent habitual dietary intakes. However, in future studies it will be important to collect habitual dietary intake information using multiple diet records over a number of months or through food frequency questionnaires which require participants to indicate the number of serves of various foods consumed over the past year.
The majority of dietary groups that led to distinctive gut microbiota responses to the high-dose Actazin™ were rich in dietary fibre, i.e. Dietary fibre, Wholegrain, Vegetable, Plant Protein and Energy from carbohydrates (%). We, therefore, believe that focusing on the influence differing habitual dietary fibre intakes have on gut microbiota response to a dietary intervention should be our primary research objective in the future. To test our hypothesis that habitual dietary fibre intake will influence gut microbiota response to a dietary intervention, an in vitro three-stage continuous colonic model
107
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CHAPTER FOUR
IN VITRO THREE-STAGE COLONIC MODEL
SYSTEM
VARIABILITY IN GUT MICROBIOTA RESPONSE TO AN
INULIN-TYPE FRUCTAN PREBIOTIC WITHIN AN IN VITRO
THREE-STAGE CONTINUOUS COLONIC MODEL SYSTEM
This chapter is published as:
Healey G, Murphy R, Butts C, Brough L, Rosendale D, Blatchford P, Stoklosinski H & Coad J. Variability in gut microbiota response to an inulin-type fructan prebiotic within an in vitro three-stage continuous colonic model system. Bioactive Carbohydrates and Dietary Fibre. 2017;11:26-37.
The in vitro chapter presented in this thesis has been altered to include a document
summarising the development of the two differing fermentable carbohydrate media (Appendix 4-1).
The published in vitro study is available as Appendix 4-2. A scanned copy of the
statement of contribution to doctoral thesis containing publications is available as Appendix 4-3.
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