Effects of a Low-Carbohydrate, High-Protein Diet on Gut Microbiome Composition in Insulin-Resistant Individuals With Chronic Spinal Cord Injury: Preliminary Results From a Randomized Controlled Trial

To evaluate the effect of a low-carbohydrate, high-protein (LC/HP) diet that includes healthy dietary components (eg, lean meat, whole grains, fruits and vegetables, fiber, etc) on the gut microbiome composition in individuals with chronic spinal cord injury (SCI).A single-center randomized parallel controlled trial.Research University.Adult participants with chronic SCI (N=19, 3 years or more after the injury, C2-L2, American Spinal Injury Association Impairment Scale A-D). Participants were insulin resistant and had not received antibiotics within 4 weeks before enrolling in the study.Participants were randomized to the LC/HP diet group (40% energy from carbohydrates, 30% energy from protein, and 30% energy from fat and met dietary guideline recommendations) or the control group for 8 weeks. Participants assigned to the LC/HP group were provided with all meals delivered weekly to their homes. Participants assigned to the control group were asked to continue their usual diet.Stool samples were collected at baseline and the end of week 8. The gut microbiome 16S ribosomal RNA V4 region was sequenced, and gut microbiome diversity and taxonomical abundance were computed using the QIIME2 suite.Participants in the LC/HP group had significant changes in alpha-diversity (reduced operational taxonomic unit and Faith's phylogenetic diversity) and beta-diversity (unweighted UniFrac), while no significant differences were observed among participants in the control group after the intervention. Moreover, several taxa changed differently over time between groups, including increased Bacteroides thetaiotaomicron, Coprococcus 3, Fusicatenibacter, Tannerellaceae, and decreased Tyzzerella, Phascolarctobacterium, Romboutsia, Clostridium sensu stricto 1, Hungatella, Ruminococcus gauvreauii, family XI, and Bacillales among participants in the diet group, while these taxa did not change in the control group.An LC/HP diet with healthy dietary components improved gut microbiome composition in individuals with SCI, including increased bacteria implicated in fiber metabolism and reduced bacteria communities linked to cardiometabolic disorders.