Dietary nitrate (NO3-) supplementation has been shown to reduce blood pressure (BP), improve exercise performance, and alter the oral microbiome. Following a "control" diet (CON), we manipulated dietary NO3- intake to examine the effect of a short-term (7-day) low NO3- diet (LOW) followed by a 3-day high NO3- diet (HIGH), compared to a 7-day standard (STD) NO3- diet followed by HIGH, on saliva, plasma, and muscle [NO3-] and nitrite [NO2-], BP, and cycling exercise performance in healthy young adults. We also examined the effect of LOW on the oral microbiome. Saliva [NO3-] and [NO2-], and plasma [NO3-] were significantly lower than CON following LOW (all P<0.05) but there was no change in plasma [NO2-] or muscle [NO3-] and [NO2-] (all P>0.05). Following HIGH, saliva and plasma [NO3-] and [NO2-], and muscle [NO3-], were significantly elevated above CON, LOW and STD (all P<0.05), but there was no difference between CON-LOW-HIGH and CON-STD-HIGH (P<0.05). BP and exercise performance were not altered following LOW (P>0.05). HIGH significantly reduced systolic and diastolic BP compared to CON when preceded by STD (both P<0.05) but not when preceded by LOW (P>0.05). Peak (+4%) and mean (+3%) power output during sprint cycling was significantly improved following HIGH (both P<0.05), with no differences between CON-LOW-HIGH and CON-STD-HIGH (both P>0.05). LOW altered the oral microbiome composition, including decreases in relative abundances of phylum Proteobacteria and genus Neisseria. The findings indicate that a short-term low NO3- diet lowers plasma but not skeletal muscle [NO3-]. The maintenance of plasma [NO2-] and muscle [NO3-] and [NO2-] following LOW may be indicative of their importance to biological functions, including BP regulation and exercise performance.