TABLE 3

Clinical studies assessing the effect of nitrate supplementation upon exercise economy and/or endurance performance

ReferenceCohortInterventionDesignOutcome
Wilkerson et al., 2012Eight well trained male cyclistsNitrate-replete (∼6 mmol nitrate) or -deplete beetroot juice as placeboRandomized, single blind, crossover studyNitrate supplementation did not improve 50-mile time trial performance in well trained cyclists.
Measurements performed on two laboratory-based 50-mile time trial 2.5 h after consuming juice intervention
MacLeod et al., 201511 trained male cyclistsNitrate-replete or -deplete beetroot juice as placeboRandomized, double blind studyNitrate supplementation did not lower the O2 cost of steady-state exercise or improve exercise performance in normoxia or hypoxia in a small sample of well trained male cyclists.
Measurements 2 h after consuming 70 ml of intervention and prior to a 15-min self-selected cycling warm-up, then a fixed 15 min of steady-state exercise at 50% maximum power output, and a 10-km time trial in either normoxic or hypoxic (altitude) conditions
Peacock et al., 201210 male junior cross-country skiersNitrate-replete or -deplete beetroot juice as placeboTwo trials both randomized, double blind
Measurements 2.5 h prior to two 5-min submaximal tests on a treadmill at 10 km/h (≈55% of VO2max) and 14 km/h (≈75% of VO2max), followed by a 5-km running time trial
Nitrate supplementation did not reduce O2 cost of submaximal exercise or enhance endurance exercise performance in highly trained cross-country skiers.
Boorsma et al., 2014Eight male 1500 m elite distance runners210 ml of nitrate-replete (19.5 mmol) or -deplete beetroot juice as placeboRandomized, double blind, crossover studyAcute and chronic nitrate supplementation did not reduce running VO2 or improve time trial performance.
Volunteers supplemented for 8 days with >1 wk between interventions. On days 1 (acute) and 8 (chronic), subjects completed a submaximal treadmill run and 1500-m time trial.
Bescos et al., 201213 well trained athletesSodium nitrate (10 mg/kg) or sodium chloride (10 mg/kg) placeboRandomized, double blind, crossover study.Sodium nitrate supplementation did not improve trial performance in endurance athletes.
Measurements after a 40-min cycle ergometer distance-trial test after two 3-day periods of dietary intervention
Christensen et al., 201310 highly trained cyclists0.5 l nitrate-replete beetroot juice or 0.5 l black currant juice as a placeboRandomized, double blind, crossover studyNitrate supplementation did not affect VO2 kinetics and performance in elite cyclists.
Measurements of VO2 kinetics (3 × 6 min at 298 ± 28 W), endurance (120-min preload followed by a 400-kcal time trial), and repeated sprint capacity (6 × 20-s sprints, recovery 100 s) during two 6-day dietary intervention intervals
Porcelli et al., 201521 subjects (mean age, 22.7 ± 1.8 yr) with different aerobic fitness levelSupplementation with either 0.5 l/day of nitrate (5.5 mmol)-containing water or nitrate-free water as placeboCrossover, double blind, placebo-controlled study 6-day treatment. Participants performed an incremental running test until exhaustion and four repetitions of 6-min submaximal (approximately 80% of gas-exchange threshold) constant load exercise on a motorized treadmill. Moreover, subjects performed a 3-km running time trial on the field.Individual aerobic fitness level influenced ergogenic benefits induced by nitrate.
Muggeridge et al., 2013Eight male kayakers70 ml of nitrate-replete (5 mmol) concentrated beetroot juice or tomato juice as placeboParticipants completed four performance trials of 15 min of paddling at 60% of maximum work rate, five 10-s all-out sprints, and a 1-km time trial. The second and third trials were preceded by supplementation 3 h prior to measurementsNitrate supplementation had no effect on repeated supramaximal sprint or 1-km time trial kayaking performance.
Peeling et al., 2015Male (n = 6) athletes (Study A) and international-level female (n = 5) athletes (Study B)
Study A: a 70-ml beetroot juice shot containing ∼4.8 mmol of nitrate or placebo
Study B: two 70-ml beetroot juice shots containing ∼9.6 mmol of nitrate or placebo
Nitrate-replete or -deplete beetroot juice as placeboStudy A: participants completed three laboratory-based sessions on a kayak ergometer of 7 × 4-min step test, two 4-min maximal effort performance trials. At 2.5 h prior to the warm-up of each test, the athletes received intervention.
Study B: participants completed two field-based 500-m time trials, separated by 4 days. At 2 h prior to each test, athletes received intervention.
In national-level male and international-level female kayak athletes, nitrate supplementation improved exercise economy in tasks predominantly reliant on the aerobic energy system and time trial performance, respectively.
Hoon et al., 201410 highly trained male rowersNitrate-replete or -deplete beetroot juice as placeboPlacebo-controlled, double blind, crossover studyCompared with placebo, a high (8.4 mmol nitrate) but not moderate (4.2 mmol nitrate) dose improved rowing performance.
Nitrate-replete juice administered as a single shot containing 4.2 mmol or a double shot containing 8.4 mmol nitrateIntervention was consumed 2 h prior to undertaking a 2000-m rowing-ergometer test.
Bond et al., 201214 well trained junior male rowersBeetroot juice made from raw vegetables delivering 5.5. mmol/day of nitrate for 6 days
A commercially available black currant juice with negligible nitrate content was used as placebo
Randomized, double blind, crossover study
After supplementation, rowers completed six maximal 500-m ergometer. A 7-day washout period followed repeat of the trial. Blood pressure, oxygen saturation, maximum heart rate, urine, and lactates were measured.
Nitrate supplementation improved maximal rowing-ergometer repetitions.