Whole Wheat and Bran Cereal Affects Microbiome Stability

Abstract

ObjectivesHealth outcomes in previous fiber intervention studies have been variable, potentially due to differences in gut microbiome composition. This study aimed to determine if the effect of fiber intervention on the microbiome differs by initial microbiome or the quantity of fiber provided. MethodsThis study was designed as a randomized, un-blinded, cross-over trial of fiber cereal dosage. The cross-over design tested the effect of two 2-week long interventions with a High (28g) and Low (14g) level of daily supplemental fiber from whole wheat and bran cereal. Analysis was also completed on the overall study as a single arm, non-randomized, intervention of fiber cereal. The study enrolled 31 healthy adults. The microbiome was assessed at baseline and after intervention for changes in diversity, composition, and stability. ResultsAcross all individuals, fiber intervention increased microbiome alpha-diversity (paired t-test, P = 0.047), but the microbiome was otherwise resistant to the effects of the intervention. Increasing fiber dose (High v. Low) was not associated with consistent changes in beta-diversity (linear mixed models). Approximately 20% of subjects were identified as responders based on beta diversity effect size. At baseline, responders had higher Prevotella copri and lower Bacteroides abundance than non-responders (Wilcoxon rank sum, qval < 0.05). In responders, fiber intake caused increased abundance of Bacteroides and Alistipes and reduced Prevotella (paired Wilcoxon, q < 0.2). In all subjects, fiber intervention decreased microbiome stability (paired Wilcoxon signed rank test, P = 0.006). In responders, there was a significant effect of the fiber level on stability, with higher fiber further lowering stability (linear mixed model, P = 0.05). ConclusionsOur data suggest a responder/non-responder microbiome signature for this whole wheat and bran fiber cereal. We find that many effects were not additive by dosage level. Overall, microbiome diversity was increased and stability was decreased during the fiber cereal intervention and in responders this was dose dependent; the clinical implications of the impact of changes in stability remain unknown, and it is possible that the microbiome would stabilize in a longer intervention study. ClinicalTrials.gov identifier: NCT03623308. Funding SourcesGeneral Mills, Inc.