β2‐1 Fructan Supplementation in Healthy Adults Elicits Host‐Specific Bacterial Responses But Does Not Support a Defined Health Benefit
Authors: Brooks Stephen , Clarke Sandra , Inglis G. Douglas , Yanke L. Jay , Green Judy , Petronella Nicholas , Ramdath D. Dan , Bercik Premysl , Green‐Johnson Julia , Kalmokoff Martin 
Published: November 2023

Little data exists on physiological outcomes associated with bacterial changes that occur after fructan feeding in healthy adults. To this end, we studied potential relationships between changes in gut bacteria composition and host physiological parameters after feeding 3 × 5 g/d of β2‐1 fructan (BF) or maltodextrin to a group of 13 male and 17 female healthy adults in a placebo‐controlled, double‐blinded, randomised crossover‐study consisting of two 28‐d exposures separated by a 14‐d washout. Fasting blood and 1‐d faecal collections were obtained on d0 and d28 of each phase. Well‐being and general health, as well as gastrointestinal symptoms, were determined by questionnaire. Serum lipopolysaccharides (LPS), faecal SCFA, faecal bifidobacteria and indigestion were higher during the BF‐supplemented phase. Numbers of circulating lymphocytes and macrophages were unchanged but BF supplementation decreased serum IL‐10 and increased serum IL‐4. In addition, circulating percentages of CD282+/TLR2+ myeloid dendritic cells increased as did ex vivo responses to a TLR2 agonist. Culture‐based analysis of feces showed that 87 bacterial species encompassing 30 genera and four phyla were able to use BF as the sole carbon source. Fecal 16S rRNA analysis (26 subjects) showed BF reduced community richness. Two response patterns were observed: in 17/26 subjects, the relative abundance of Bacteroides was reduced and phylotypes within the Bifidobacterium, Faecalibacterium and the family Lachnospiraceae increased during the BF phase. In the remaining subjects, phylotypes aligning within the genera Bacteroides, Prevotella and to a lesser extent Bifidobacterium increased in abundance while abundance of phylotypes within the Faecalibacterium and the family Lachnospiraceae decreased during the BF phase. Few relationships between the faecal community composition and measured parameters were noted: (a) increases in Bacteroidetes relative abundance correlated with increased faecal propionate; (b) subjects in whom Bacteroidetes increased during the BF phase excreted more caproic acid (during both phases); and (c) subjects in whom Bacteroidetes decreased during the BF phase had higher LPS and LPS binding protein (during both phases). The most likely explanation for the observed patterns of faecal community change associated with the BF phase is a distal gut fermentation driven by differences in peptidyl nitrogen. We found no links between bacterial community changes and physiological changes nor was there evidence of physiological changes that would indicate a health benefit in these healthy subjects.

Support or Funding Information

This trial was undertaken with financial support from Agriculture and Agri‐Food Canada (RPBI# 1501, MK, GDI, LJY), Health Canada (SB), General Mills (MK), Alberta Innovates Bio Solutions (GDI), the Advanced Food and Materials Network (MK), and the National Science and Engineering Research Council (JMJG).