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Prebiotics are a class of functional foods which target beneficial microbial species of the gut to benefit host health. They consist of dietary fibres which, after ingestion, are degraded and fermented by microorganisms in the colon. Arabinoxylan (AX) is an important member of the prebiotic family. This non-digestible fibre is commonly found in cereal grains such as wheat and rice. Human in vivo studies have demonstrated that consumption of various species of AXs has profound effects on gut microorganisms. AX exists in different structures across cereal types. Structural differences of AXs impact their cleavage, degradation, and fermentation by gut microbiota. However, this structural diversity also makes it difficult to compare and contrast studies of different AXs. Nevertheless, common bacterial targets of prebiotics across all AX structures include Bifidobacterium spp. and Lactobacillus spp., which are both beneficial to human health. Existing research on AXs has primarily focused on wheat derived AX. As the structure of rice AXs varies significantly from that of wheat AXs, more research is needed on the effects of rice AXs on gut microbiota. This narrative review synthesises the current understandings of how prebiotic AX affects gut microbiota and its implications for human health.

Introduction Rice bran arabinoxylan compound (RBAC) is a nutraceutical for enhancing a depleted immune system during and after cancer treatment. This pilot feasibility trial aims to evaluate the effects of RBAC on cancer patients' quality of life during active treatment, compared to placebo, using a validated questionnaire. Other outcome measures include changes in inflammatory and nutritional status, cytokine profile, and gut microbiota. Methods/Design The study will recruit 50 participants from a regional cancer center in Australia. Patients aged 18–70, diagnosed with solid organ cancers stage II and above, and currently undergoing active systemic therapies, are eligible. Random allocation of participants into two groups is stratified based on metastatic status and treatment type. The dosage is either 3 g/day of RBAC or placebo in identical packaging. The participants, study coordinator, and treating oncologists are blinded to the interventions. Data collections are at baseline and at four follow-up sessions, which are six weeks apart (24 weeks). Statistical analysis will involve a protected p-value with multiple dependent values and analyzed by ANOVA with repeated measures on the occasion of testing and with both a full Bonferroni or Sidak corrections applied to protect against Type I errors. Any observed significance warrants further analysis with pairwise comparisons. Analysis of covariance will also be performed to assess any influence of the demographic data, cancer diagnosis, as well as changes in physical activity, dietary habits, and complementary medicine usage. Comparisons of gut microbiota will be based on the analysis of the fecal microbiome using 16S ribosomal ribonucleic acid amplicon sequencing. The proposed research timeline is from October 2018 to May 2022. Trial registration ANZCTR. Reg No: ACTRN12619000562178p.