Oral disease is prevalent in elite athletes due to carbohydrate ingestion and frequent bouts of dehydration. These factors combine to lower salivary-pH and acidity related diseases such as caries result. Conversely, chronic ingestion of nitrate (NO3-)-rich beetroot juice has been shown to increase salivary-pH. The purpose was to determine the effect of a single dose of NO3- on salivary-pH following carbohydrate ingestion before and after exercise. Eleven male endurance runners completed a double-blind randomised placebo-controlled study comprising four experimental trials in temperature of 23 ± 1ºC, 40 ± 5% relative humidity. Participants ingested the following fluids one hour before each trial: (a) 140 ml of water (negative-control), (b) 140 ml of water (positive-control), (c) 140 ml of NO3–rich beetroot juice (~12.4 mmol NO3-) (NO3-) or (d) 140 ml NO3–depleted beetroot juice (placebo). During the negative-control trial, participants ingested 795 ml of water in three equal aliquots: before, during, and after 90 min of submaximal running. In the other trials they received 795 ml of carbohydrate supplements in the same fashion. One venous blood was collected before and after exercise. At the same time points, saliva was sampled before and repeatedly for 20 min following carbohydrate or water ingestion, area under the curve (AUC) was calculated for these samples. Values are means ± S.D., compared by ANOVA. Exercise resulted in a sweat rate of 1.2 ± 0.2 L/h which, following correction for fluid intake and urine loss, resulted in a 3 ± 1% reduction in body mass. Urine osmolality increased (pre-exercise 366 ± 190 mOsm/kg, post-exercise 595 ± 164 mOsm/kg, P0.05). Stimulated salivary flow-rate reduced from pre to post-exercise in both the positive-control (from 1.35 ± 0.60 ml/min to 0.88 ± 0.43  ml/min, P=0.02) and the placebo trial (from 1.50 ± 0.63 ml/min to 0.95 ± 0.45 ml/min, P<0.001) but did not change in the negative-control (P=0.177) or the NO3–trial (P=0.086). As expected, nitrite (NO2-) and NO3- were highest in the NO3–trial (all P<0.001). Salivary-pH followed a similar pattern (NO3–trial – Pre-exercise 7.4 ± 0.4 Post-exercise 7.4 ± 0.4, negative-control – Pre-exercise 7.1 ± 0.3 Post-exercise 7 ± 0.2, positive-control – Pre-exercise 7.1 ± 0.3 Post-exercise 6.9 ± 0.2, placebo – Pre-exercise 7 ± 0.3 Post-exercise 7 ± 0.2, all P<0.05). Compared to negative-control, salivary-pH AUC was significantly reduced following carbohydrate in positive-control and placebo (Pre-exercise – positive-control 33 ± 2.9, placebo 33.2 ± 2.7, negative-control 36.3 ± 1.8. Post-exercise – positive-control 32.1 ± 3, placebo 32.7 ± 2.4, negative-control 36.2 ± 1.9, all P<0.05). Conversely, AUC was similar in negative-control and NO3- despite ingestion of carbohydrate in the NO3–trial (Pre-exercise 34.8 ± 2.5, Post-exercise 34.5 ± 2.6, both P≥0.221). Ingesting NO3–rich beetroot juice attenuates the decrease in salivary-pH after carbohydrate supplements and protects against reduced salivary flow-rate following exercise. These results suggest that NO3- may protect athletes’ teeth from acid erosion caused by frequent carbohydrate ingestion and exercise induced dehydration.