Exploring the Role of Gut Microbiome in Mediating Endothelial Function Improvements With Blueberry Consumption: Insights From Fecal Microbiota Transplant in Germ-Free Mice

Objectives: To synthesize evidence from randomized controlled trials (RCT) on the role of dietary fiber types on bonerelated health outcomes in children ages 1 to 18 years.Methods: Databases, including MEDLINE, Ovid Global Health, EMBASE, and Cochrane Central of Controlled Trials, were searched from 1946 to August 2023 for randomized controlled trials reporting associations between dietary fiber intake and bone-related outcomes in children.Outcomes included bone mineral density (BMD), markers of calcium absorption, retention, bone formation and urinary calcium.Grey literature was also searched for studies published between 2018-2023.Two researchers independently screened the literature, extracted relevant data, and performed a Cochrane Risk of Bias assessment.Studies were synthesized and random-effects metaanalysis was performed when at least three similar studies reported data for the same outcome.Results: Ten studies in eleven publications met inclusion criteria.Fibers studied included inulin-type fructans reported in seven studies, soluble-corn fiber in two, and cellulose, hemicellulose, and pectin in one.With respect to outcomes, calcium absorption was reported in seven studies and urinary calcium concentration in six.Meta-analyses of five RCTs examining fractional calcium absorption and four RCTs reporting on urinary calcium did not show an effect of inulin-type fructan supplementation on these outcomes.BMD, calcium retention, bonemetabolism biomarkers, minerals and hormones, and other factors influencing bone remodeling were also reported in studies with either mixed or no effects of fiber intake.Conclusions: There is currently no consistent evidence suggesting that isolated or synthetic dietary fiber significantly impacts bone health outcomes in children.However, evidence is limited, and inconsistencies are attributed to variations in study duration, doses, and types of fiber administered.More research is needed to clarify fiber's role in improving functional health indicators associated with greater BMD and other bone-related outcomes.