Following a single blind, cross-over and non-randomized design we investigated the effect of 7-day use of chlorhexidine (CHX) mouthwash on the salivary microbiome as well as several saliva and plasma biomarkers in 36 healthy individuals. They rinsed their mouth (for 1 min) twice a day for seven days with a placebo mouthwash and then repeated this protocol with CHX mouthwash for a further seven days. Saliva and blood samples were taken at the end of each treatment to analyse the abundance and diversity of oral bacteria, and pH, lactate, glucose, nitrate and nitrite concentrations. CHX significantly increased the abundance of Firmicutes and Proteobacteria, and reduced the content of Bacteroidetes, TM7, SR1 and Fusobacteria. This shift was associated with a significant decrease in saliva pH and buffering capacity, accompanied by an increase in saliva lactate and glucose levels. Lower saliva and plasma nitrite concentrations were found after using CHX, followed by a trend of increased systolic blood pressure. Overall, this study demonstrates that mouthwash containing CHX is associated with a major shift in the salivary microbiome, leading to more acidic conditions and lower nitrite availability in healthy individuals.

Humans can reduce inorganic nitrate (NO(3)(-)) to nitrite (NO(2)(-)), nitric oxide (NO), and other bioactive nitrogen oxides. The purpose of this study was to test the hypothesis that a single dose of inorganic nitrate before exercise might enhance the tolerance of endurance athletes to high intensity exercise. Eleven cyclists (age = 34.3 ± 4.8 yr, VO(2peak) = 65.1 ± 6.2 mL·kg(-1)·min(-1)) participated in this randomized, double-blind, crossover study. Subjects received dietary supplementation with nitrate (NaNO(3) 10 mg·kg(-1) of body mass) or a placebo (NaCl) 3 h before exercise. They then performed a cycle ergometer test that consisted of four 6-min submaximal workloads, corresponding to 2.0, 2.5, 3.0, and 3.5 W·kg(-1) of body mass, interspersed with 3 min of passive recovery. After a 5-min recovery period, subjects performed one incremental exercise test until exhaustion. Plasma nitrate and nitrite were significantly higher (P < 0.05) 3 h after supplementation (nitrate = 250 ± 80 μM, nitrite = 2313 ± 157 nM) than after the placebo (nitrate = 29 ± 8 μM, nitrite = 1998 ± 206 nM) at resting conditions. Nitrate supplementation significantly reduced VO(2peak)(nitrate = 4.64 ± 0.35 L·min(-1), placebo = 4.82 ± 0.33 L·min(-1), P = 0.010) and the ratio between VO(2) and power at maximal intensity (nitrate = 11.2 ± 1.1 mL·min(-1)·W(-1), placebo = 11.8 ± 1.1 mL·min(-1)·W(-1), P = 0.031). This reduction of VO(2) occurred without changes in the time to exhaustion (nitrate = 416 ± 32 s, placebo = 409 ± 27 s) or in the maximal power (nitrate = 416 ± 29 W, placebo = 410 ± 28 W). A single oral dose of inorganic nitrate acutely reduces VO(2peak)without compromising the maximal exercise performance.

Supplementation with inorganic nitrate has been suggested to be an ergogenic aid for athletes as nitric oxide donor. The purpose of this study was to determine whether ingestion of inorganic sodium nitrate benefits well-trained athletes performing a 40-min exercise test in laboratory conditions. In addition, we investigated the effect of this supplement on plasma levels of endothelin-1 (ET-1) and in nitrated proteins. Thirteen trained athletes participated in this randomized, double-blind, crossover study. They performed a 40-min cycle ergometer distance-trial test after two 3-d periods of dietary supplementation with sodium nitrate (10 mg·kg of body mass) or placebo. Concentration of plasma nitrate (256 ± 35 μM) and nitrite (334 ± 86 nM) increased significantly (P < 0.05) after nitrate supplementation compared with placebo (nitrate: 44 ± 11 μM; nitrite: 187 ± 43 nM). In terms of exercise performance, there were no differences in either the mean distance (nitrate: 26.4 ± 1.1 km; placebo: 26.3 ± 1.2 km; P = 0.61) or mean power output (nitrate: 258 ± 28 W; placebo: 257 ± 28 W; P = 0.89) between treatments. Plasma ET-1 increased significantly (P < 0.05) just after exercise in nitrate (4.0 ± 0.8 pg·mL) and placebo (2.4 ± 0.4 pg·mL) conditions. This increase was significantly greater (P < 0.05) in the nitrate group. Levels of nitrated proteins did not differ between treatments (nitrate: preexercise, 91% ± 23%; postexercise, 81% ± 23%; placebo: preexercise, 95% ± 20%; postexercise, 99% ± 19%). Sodium nitrate supplementation did not improve a 40-min distance-trial performance in endurance athletes. In addition, concentration of plasma ET-1 increased significantly after exercise after supplementation with sodium nitrate.