Up to 50% of patients with end-stage renal disease undergoing hemodialysis (HD) have some degree of bone-mineral disorder (BMD), which includes high concentrations of blood phosphate, low production of active vitamin D, and high concentrations of parathyroid hormone, all of which are associated with an increased risk of fractures, hospitalizations, and lower quality of life. Furthermore, high concentrations of blood phosphate, or hyperphosphatemia, are associated with an increased risk of all-cause and cardiovascular mortality. Although multiple therapies are used to prevent this disorder, the prevalence remains high; therefore, co-adjuvant therapies are needed. Studies implementing the use of dietary fibers in other clinical populations with BMD have shown improvements, possibly mediated by the bacteria within the gut. However, this therapy has not been explored in HD patients. Therefore, the aim of this study is to assess the gut bacteria-mediated effects of the supplementation of inulin, a fermentable dietary fiber, on mineral metabolism.

In this randomized controlled cross-over design study, 20 HD patients will be randomized to the intervention group (10g inulin/day for females and 15 g/day for males) or placebo group (10g maltodextrin/day for females and 15g/day for males). Patients will consume inulin or maltodextrin for one month, rest for one week (washout period), and continue with the other group (either inulin or maltodextrin) for another month. Outcomes will be assessed at the beginning and end of each phase, 4 times in total. Our primary outcomes include changes in composition and functionality of the gut bacteria assessed by 16S ribosomal RNA gene amplification from a stool sample. Additionally, changes in blood calcium, phosphate, magnesium, and parathyroid hormone will be assessed. Our secondary outcomes include bone and body composition, cardiovascular function, and dietary patterns assessment. Results from this study will enhance our knowledge on the effects of fiber supplementation on the gut microbiota and mineral metabolism in HD patients.