Muscle Nitrate Concentration And Exercise Performance Are Not Altered By A Short-term (7-day) Low Nitrate Diet

Dietary nitrate (NO3-) ingestion promotes nitric oxide (NO) bioavailability and, consequently, may improve exercise performance. Whilst the potential beneficial effects of a NO3--rich diet have been widely examined, NO3- intake varies considerably (approximately 7-fold) between individuals and there may be periods during which NO3- intake is particularly low. The effects of a short-term low NO3- diet on NO bioavailability and exercise performance has not been investigated. PURPOSE: To determine the effects of a short-term (7-day) low NO3- diet on NO bioavailability and exercise performance. METHODS: Eleven participants (10 males, 1 Female; age: 22 ± 2 y; body mass: 74.8 ± 8.4 kg) were assigned in a randomized, crossover design to consume a 3-day standard (Baseline) NO3- diet (containing 180 mg NO3- per day) followed by either a 7-day low (LOW; <50 mg NO3- per day) or 7-day standard (STD) NO3- diet. At baseline, and following LOW and STD, participants completed a 10-s all-out sprint and a ramp incremental cycle test and biological samples (saliva, plasma and skeletal muscle) were collected for determination of [NO3-] and nitrite ([NO2-]) using ozone-based chemiluminescence. RESULTS: Saliva, plasma and skeletal muscle [NO3-] and [NO2-] were not different between diets at baseline (P > 0.05). Following LOW, saliva [NO3-] (363 ± 158 nmol/g) and [NO2-] (63 ± 40 nmol/g) were significantly lower than following STD ([NO3-] 1407 ± 829 nmol/g; [NO2-] 206 ± 119 nmol/g). Plasma NO3- was also significantly lower following LOW (15 ± 5 nmol/g) compared to STD (42 ± 17 nmol/g), but there was no difference in plasma NO2- (LOW, 0.2 ± 0.2 nmol/g; STD, 0.2 ± 0.1 nmol/g). Skeletal muscle [NO3-] (LOW, 41 ± 15 nmol/g; STD, 37 ± 10 nmol/g) and [NO2-] (LOW, 1.0 ± 0.4 nmol/g; STD 0.8 ± 0.4 nmol/g) were not different between diets. There was no difference in 10-s sprint or ramp incremental exercise test performance between LOW and STD. CONCLUSIONS: A short-term (7-day) low NO3- diet significantly reduced systemic NO bioavailability but did not alter skeletal muscle [NO3-] or exercise performance. The maintenance of muscle [NO3-] during dietary NO3- restriction suggests an important role for the muscle NO3- store in the preservation of biological functions including exercise performance.