Table 2.
Summary of studies that have evaluated the performance or metabolic responses after supplementation protocol with beet juice.
| Reference | Participants | Experimental Conditions | Supplementation Protocol | Variables | Results |
|---|---|---|---|---|---|
| [12] | M (n: 5) and W (n: 6), trained athletes | EC1: beet juice, EC2: placebo | EC1: beet juice (8 mmol nitrate) (90 min before) | Test 5 km: Performance, HR, RPE | Performance: Last mile 1.1: faster EC1 vs. EC2 (5%), RPE: 1 mile: lower in EC1 vs. EC2 |
| [27] | M, competitive cyclists (n: 9) | EC1: beet juice, EC2: placebo | EC1: 500 mL beet juice (6.2 mmol nitrate) (120 min before) | Tests 4 km and 16 km: respiratory parameters, performance | Performance in test 4 km: Time: lower in EC1 vs. EC2 (6.27 ± 0.35 vs. 6.45 ± 0.42 min), Power: Higher in EC1 vs. EC2 (292 ± 44 vs. 279 ± 51 W), W/VO2: Higher in EC1 vs. EC2 (93 ± 17 vs. 83 ± 9 W/L/min), Performance test of 16 km: Time: lower in EC1 vs. EC2 (26.9 ± 1.8 vs. 27.7 ± 2.1 min), Power: Higher in EC1 vs. EC2 (247 ± 44 vs. 233 ± 43 W), W/VO2: Higher in EC1 vs. EC2 (69 ± 3 vs. 64 ± 6 W/L/min) |
| [29] | M, national level athletes kayak (n: 5) | EC1: beet juice, EC2: placebo | Study A: EC1: 140 mL beet juice (4.8 mmol nitrate) (150 min before), Study B: EC1: 140 mL beet juice (9.6 mmol nitrate) (150 min before) | Study A: kayaking incremental test: Test 10 min (10 min + 5 min LT1 LT2) + 4 min test: respiratory parameters, lactate, performance (test 4 min), HR, RPE. Study B: Test 500 m | Study A: 4 min test: VO2: decreases in EC1 vs. EC2 (46.87 ± 2.56 vs. 47.83 ± 2.77 mL/kg/min), Economy: improved EC1 vs. EC2 (189.67 ± 8.17 vs. 193.90 ± 8.17 mL/kg/km). Study B: Test 500 m: Time: improved EC1 vs. EC2 (114.6 + 1.5 s vs. 116.7 + 2.2 s), Rowing often partially 100–400 m: increases in EC1 vs. EC2 (108 + 2 vs. 105 + 2 strokes), Partial speed 100–400 m: increases in EC1 vs. EC2 (4.40 + 0.03 vs. 4.30 + 0.05 m/s) |
| [30] | M, trained cyclists-triathletes (n: 13) | EC1: beet juice, EC2: placebo | EC1: beet juice 140 mL (8 mmol nitrate) (6 days) | Test 30 min at 45% MAP + 30 min at 65% MAP + test 10 km: respiratory parameters, lactate, glucose, performance (test to exhaustion at 80% VO2max), HR, RPE | Respiratory parameters VO2 at 45% MAP: lower in EC1 vs. EC2 (1.93 ± 0.05 vs. 2.0 ± 0.07 L/min), VO2 at 65% MAP: lower in EC1 vs. EC2 (2.94 ± 0.10 vs. 3.1 ± 0.09 L/min), Performance (test 10 km): improvement in EC1 vs. EC2 (953 ± 21 vs. 965 ± 21 s) |
| [31] | M, trained athletes (n: 13) | EC1: beet juice, EC2: placebo | EC1: 280 mL of beet juice (6.5 mmol nitrate) for 7 days. EC2: Control | Test 20 min (10 min to 10 min 50% + 70% VO2max): respiratory parameters | Respiratory parameters: 70% VO2max: oxygen consumption decrease in EC1 (3%) |
| [32] | M, trained cyclists (n: 8) | EC1: beet juice, EC2: placebo | EC1: 500 mL beet juice (6.2 mmol nitrate) (150 min before) | Test 50 miles: respiratory parameters, lactate, performance | Performance: last 10 miles: lower time in EC1 vs. EC2, W/VO2: higher in EC1 vs. EC2 (67.4 ± 5.5 vs. 65.3 ± 4.8 W/L/min) |
| [33] | M, trained athletes (n: 16) | EC1: beet juice, EC2: placebo | EC1: 450 mL beet juice (5 mmol nitrate) (115 min before) | Test 40 min [20 min at 50% VO2max + 20 min at 70% VO2max] + time to exhaustion at 90% VO2max: respiratory parameters, performance (test to exhaustion at 90% VO2max), lactate, HR, RPE | Respiratory parameters: RER: greater in EC1 vs. EC2 at 50% VO2max (0.89 ± 0.03 vs. 0.86 ± 0.06) and test to exhaustion (1.04 ± 0.06 vs. 1.01 ± 0.06), Performance (test to exhaustion at 90% VO2max): time increases in EC1 vs. EC2 (185 ± 122 s vs. 160 ± 109 s), Max lactate: Higher in EC1 vs. EC2 (8.80 ± 2.10 vs. 7.90 ± 2.30 mmol/L) |
| [34] | M, kayakers (n: 8) | EC1: beet juice, EC2: placebo | CE1: beet juice 70 mL (5 mmol nitrate) (180 min before) | Test 15 min at 60% MAP + 5 × 10 s. R: 50 s + 5 min recovery + Test 1 km kayak: respiratory parameters, performance (5 × 10 s) performance (1 km time trial), HR | Test 15 min at 60% MAP: respiratory parameters: VO2 lower in EC1 vs. EC2 (35.6 ± 2.5 vs. 36.8 ± 2.4 mL/kg/min), Test 1 km: respiratory parameters: VO2 lower in EC1 vs. EC2 (results not specified) |
| [35] | M, trained athletes (n: 9) | EC1: beet juice, EC2: placebo | EC1: 500 mL beet juice (8.2 mmol nitrate) | Tests to exhaustion at 60%, 70%, 80% and 100% VO2max: respiratory parameters, lactate, performance, HR | Performance: 60% VO2max: EC1 more time to exhaustion vs. EC2 (696 ± 120 vs. 593 ± 68 s), 70% VO2max: EC1 more time to exhaustion vs. EC2 (452 ± 106 vs. 390 ± 86 s), 80% VO2max: EC1 more time to exhaustion vs. EC2 (294 ± 50 vs. 263 ± 50 s) |
| [36] | M (n: 5) and W (n: 3), trained athletes (n: 8) | EC1: beet juice, EC2: placebo | EC1: beet juice 500 mL (5.2 mmol nitrate) (15 days) | Test 5 min at 90% VT 1 + incremental test: respiratory parameters, lactate, performance, HR, glucose | Respiratory parameters: Test 5 min at 90% VT1 (day 15): VO2 lower in EC1 vs. EC2 (1.37 ± 0.23 vs. 1.43 ± 0.23 L/min), Incremental test: Wpeak: Higher EC1 vs. EC2 (331 ± 68 vs. 323 ± 68 W), WVT1: Higher EC1 vs. EC2 (105 ± 28 vs. 84 ± 18 W) |
| [37] | M (n: 4) and W (n: 5), Healthy, physically active participants | EC1: beet juice, EC2: placebo | EC1: beet juice 140 mL (8 mmol nitrate) (6 days) | Test 4 min at 90% VT1 + test to exhaustion at 70% between VT1 and VO2max: respiratory parameters, lactate, performance (test to exhaustion at 70% between VT1 and VO2max), HR | Performance (test to exhaustion at 70% between VT1 and VO2max) higher EC1 vs. EC2 (635 ± 258 vs. 521 ± 158 s) |
| [38] | M, trained swimmers (n: 14) | EC1: beet juice, EC2: placebo | EC1: beet juice 500 mL (5.5 mmol nitrate) (6 days), EC2: placebo (6 days) | Incremental test in swimming | VT1: improvement in EC1 vs. EC2 (6.7 ± 1.2 vs. 6.3 ± 1.0 kg), energy expenditure: decreases in EC1 vs. EC2 (1.7 ± 0.3 vs. 1.9 ± 0.5 kcal/kg/h) |
| [39] | M, trained cyclists-triathletes (n: 9) | EC1: hypoxia (2500 m) + beet juice, EC2: hypoxia (2500 m) + placebo | EC1: beet juice 70 mL (5 mmol nitrate) (150–180 min before) | Test 15 min at 60% VO2max + test of 16.1 km in hypoxia (2500 m): respiratory parameters, lactate, performance (16.1 km time trial) | Test 15 min at 60% VO2max: respiratory parameters: VO2 lower in EC1 vs. EC2 (improvement unspecified), performance (16.1 km time trial): Time: improved EC1 vs. EC2 (1664 ± 14 vs. 1716 ± 17 s), Power: improved EC1 vs. EC2 (224 ± 6 vs. 216 ± 6 W) |
| [40] * | M, trained cyclists (n: 11) | EC1: normoxia + beet juice, EC2: normoxia + placebo, EC3: hypoxia (2500 m) + beet juice, EC4: hypoxia (2500 m) + placebo | EC1: beet juice 70 mL (6.5 mmol nitrate) (120 min before), EC3: beet juice 70 mL (6.5 mmol nitrate) (120 min before) | Test 15 min 50% + test MAP 10 km: respiratory parameters, performance (10 km), HR | No differences in analyzed variables |
| [41] | M, trained runners (n: 10) | EC1: beet juice (n: 5), EC2: placebo (n: 5) | EC1: beet juice 70 mL (7 mmol nitrate) (150 min before) | Incremental test in hypoxia (4000 m). Test of 10 km in hypoxia (2500 m) | No differences between variables |
| [42] | M, trained athletes (n: 10) | EC1: acute beet juice, EC2: acute placebo, EC1: chronic beet juice, EC2: chronic placebo | EC1: 210 mL beet juice (6.5 mmol nitrate) (150 min before), EC2: placebo (150 min before), EC1: 210 mL beet juice (6.5 mmol nitrate) (8 days), EC2: placebo (8 days) | 19 min test (7 min 50% VO2max + 7 min at 65% VO2max + 5 min at 80% VO2max) + test of 1500 m: respiratory parameters (test 19 min), performance (test 1500 m) | No significant differences between experimental conditions |
| [43] * | M, trained athletes (n: 12) | EC1: normoxia + beet juice, EC2: normoxia placebo, EC3: hypoxia (2500 m) + beet juice, EC4: hypoxia (2500 m) | EC1: beet juice 140 mL (8.4 mmol nitrate) (3 days), EC3: beet juice 140 mL (8.4 mmol nitrate) (3 days) | Test 5 min to 80% VT1 + 5 min to 75% between VT1 and VO2max + time to exhaustion at 75% between VT1 and VO2max: respiratory parameters, performance, HR | Respiratory parameters (5 min at 80% VT1): VO2: lower in EC3 vs. EC4, performance (time to exhaustion at 75% between VT1 and VO2max): higher in EC3 vs. EC4 (214 ± 14 vs. 197 ± 28 s) |
| [44] * | M, trained athletes (n: 15) | EC1: normoxia + chronic beet juice, EC2: normoxia + placebo, EC3: hypoxia (5000 m) + chronic beet juice, EC4: hypoxia (5000 m) + placebo | EC1: beet juice 500 mL (0.7 mmol nitrate/kg) (6 days), EC3: 70 mL beet juice (0.7 mmol nitrate/kg) (6 days) | Test 20 min at 45% VO2max + incremental test: respiratory parameters, lactate, performance, HR, RPE | Test 20 min at 45% VO2max: VO2: lower in EC3 vs. EC4 at rest (8%) and exercise (4%), Incremental test: time to exhaustion: higher EC2 vs. EC4 (527 ± 22 vs. 568 ± 23 s), Max. lactate: lower in EC1 vs. EC2 (9.1 ± 0.5 vs. 10.6 ± 0.3 mmol/L) |
| [45] | M, trained athletes (n: 14) | EC1: beet juice + caffeine, EC2: caffeine + placebo, EC3: beet juice + placebo, EC4: placebo | EC1: 140 mL beet juice (8 mmol nitrate) (90 min before) + 5 mg·kg−1 of caffeine (60 min before), EC2: 5 mg·kg−1 of caffeine (40 min before), EC3: 2 × 70 mL beet juice (8 mmol nitrate) (90 min before) | Test 30 min 60% + test to exhaustion at 80% VO2max: respiratory parameters, performance (test to exhaustion at 80% VO2max), HR, RPE, cortisol | RPE: lower at 15 min in test to exhaustion at 80% VO2max in EC1 (17 ± 1) vs. EC2 (18 ± 1) and EC4 (19 ± 2) |
| [46] | W, trained cyclists and triathletes (n: 14) | EC1: beet juice + caffeine, EC2: caffeine + placebo, EC3: beet juice + placebo, EC4: placebo | EC1: beet juice 70 mL (7.3 mmol nitrate) (150 min before) + 5 mg·kg−1 of caffeine (60 min before), EC2: 5 mg·kg−1 of caffeine (60 min before), EC3: beet juice 70 mL (7.3 mmol nitrate) (150 min before) | Test of 20 km: respiratory parameters, lactate, performance, HR, RPE | Respiratory parameters: RER: EC2 vs. EC3 (+0.034) and EC4 (+0.033), lactate: EC2 vs. EC3 (+2.28 mmol/L) and EC4 (+2.04 mmol/L) and EC1 vs. EC3 (+2.74 mmol/L) and EC4 (+2.50 mmol/L), Performance: power: EC2 vs. EC3 improvement (+10.3 W) and EC4 (+10.4 W), time: improved EC2 vs. EC3 (+42.4 s) and EC3 (+45.1 s), HR: EC1 vs. EC2 vs. (+8.0 bpm), EC3 (+ 5.2 bpm) and EC4 (+ 6.5 bpm) |
| [47] | M (n: 12) and W (n: 12), trained cyclists-triathletes (n: 24) | EC1: beet juice + caffeine, EC2: caffeine + placebo, EC3: beet juice + placebo, EC4: placebo | EC1: 140 mL beet juice (8.4 mmol nitrate) (8–12 h before) + 3 mg·kg−1 of caffeine (60 min before), EC2: 3 mg·kg−1 of caffeine (40 min before), EC3: 140 mL beet juice (8.4 mmol nitrate) (8–12 h before) | Test of 43.83 km M and 29.35 km W: performance, HR, RPE | Performance: power: improvement in EC1 (258 ± 59 W) and EC2 (260 ± 58 W) vs. EC4 (250 ± 57 W), M time: improvement EC1 (1:02:38 ± 0:03:31 h:min:s) and EC2 (1:02:43 ± 0:03:04 h:min:s) vs. EC4 (1:03: 30 ± 0:03:16 h:min:s), W time: improving EC1 (0: 51: 1 ± 0:02:22 h:min:s) and EC2 (0:50:50 ± 0:02:56 h:min:s) vs. EC4 (0:51: 40 ± 0:02:31 h:min:s) in W |
| [48] | M, trained athletes (n: 22) | EC1: Beet juice (n: 11), EC2: placebo (n: 11) | 6 weeks: EC1: 500 mL beet juice (5.8 mmol nitrate, approximately) + training in hypoxia (4000 m), EC2: placebo + hypoxia training (4000 m) | Progressive incremental test 30 min test: respiratory parameters, lactate, muscle glycogen, performance, HR | Incremental test: VO2max: improvement in EC1 60.1 ± 2.6 vs. 65.6 ± 2.1 L/min) and EC2 (60.8 ± 1.8 vs. 63.8 ± 1.6 L/min), HRmax: EC1 vs. EC2 lower in (186 ± 3 vs. 197 ± 2 lpm), Max Lactate: EC1 vs. EC2 lower in (10.4 ± 0.7 vs. 11.8 ± 0.4 mmol/L), W at 4 mmol/L lactate: improvement in EC1 (215 ± 10 vs. 252 ± 9 W) and EC2 (204 ± 12 vs. 231 ± 10 W), 30 min test: performance: Pmean increases in EC1 (215 ± 10 vs. 252 ± 9 W) and EC2 (204 ± 12 vs. 231 ± 10 W) |
| [49] | M, trained athletes (n: 8) | EC1: beet juice, EC2: beet juice + Mouthwash with carbohydrates, EC3: placebo | EC1: 140 mL of beet juice (8 mmol nitrate) (150 min before), EC2: beet juice 140 mL (8 mmol nitrate) + mouthwash carbohydrates (150 min before) | Test 60 min at 65% VO2max: respiratory parameters, lactate, glucose, insulin, muscle glycogen, ATP, creatine | Lactate: increased EC1, EC2 and EC3. No differences between groups. Muscle glycogen: decline in EC1, EC2 and EC3. No differences between groups Creatine decline in EC1, EC2 and EC3. No differences between groups |
ATP: adenosine triphosphate; EC: experimental condition; HR: heart rate; M: men; h: hours; kg: kilograms; km: kilometers; bpm: beats per minute; m: meter; min: minutes; mL: milliliter; MAP: maximal aerobic power; RER: respiratory exchange rate; RPE: subjective perception of effort; s: sec; VT1: first ventilatory threshold; VO2: oxygen consumption; VO2max: maximal oxygen consumption; W: Watt. All results presented reflect statistically significant differences (p < 0.05). * Studies where only the effect of beet juice vs. placebo in both hypoxic situations as compared normoxic condition.