Increased Nitrate Intake From Beetroot Juice Over 4 Weeks Changes the Composition of the Oral, But Not the Intestinal Microbiome

Inorganic dietary nitrate, metabolized through an endogenous pathway involving nitrate reducing bacteria, improves cardiovascular health, but its effects on the oral and intestinal microbiomes of older adults with treated hypertension are unknown. Our study investigated the effects of nitrate from beetroot juice on the oral and intestinal microbiomes of this population. A randomized, double-blind, placebo-controlled crossover trial was conducted with 15 participants (age range: 56–71 years), who consumed nitrate-rich or nitrate-depleted (placebo) beetroot juice for 4 weeks. The oral microbiome analysis revealed an increase in Neisseria and a decrease in Veillonella relative abundance (for both, PERMANOVA p < 0.001), with no significant changes in the intestinal microbiome composition. Our findings suggest that an increased dietary nitrate intake from a vegetable source may selectively modulate the oral microbiome and promote an increased abundance of nitrate-reducing species, which was previously associated with improved cardiovascular health outcomes.