Fig. 1

Dietary nitrate benefits cognition and restores the oral microbiota changes caused by alcohol. A Schematic diagram showing the study design for alcohol and nitrate supplementation. B The changes in body weight during six weeks among the three groups: group A had the lowest weight gain, while group HC had the highest body weight gain, with significant differences compared with group A. The body weight gain in group A + N was not statistically significant different from the other two groups except on day 42 (n = 13–14). C and D Behavioral tests showed that novelty preference in the novel-object recognition (NOR) test and spontaneous alternation in the Y-maze test were significantly decreased in group A mice compared with controls, and nitrate intake could improve cognitive function of mice with alcohol in behavioral tests (n = 13–14). E In group A, the Chao index of the oral microbiome was significantly higher compared with that in group HC, but nitrate consumption could lessen the difference (n = 13–14). F The weighted UniFrac distance varied among the three groups, demonstrating significant differences in the oral microbiota of the three groups with different kinds of food intakes (n = 13–14). G The operational taxonomic unit (OTU) Core-Pan showed that samples in group A had much more extra OTUs than the other two groups (n = 13–14). H and I Each vertical bar represents the relative abundance of the oral sample in different groups. The composition of the microbiota was substantially different among the three groups (n = 13–14). H at the phylum level, I at the genus level. J–P Genus-level differences in the relative abundance of Streptococcus, Corynebacterium, Escherichia, Lactobacillus, Pasteurella, Megasphaera and Megamonas (n = 13–14). Q Among level-3 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, differences in the lipopolysaccharide biosynthesis modules (n = 13–14). The data are expressed as the mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001