Table 1.

Description of the included studies

Authors/design	Study sample	Nitrate (NO3-) dose	Placebo	Duration	Wash-out	Results (following NO3- vs placebo)
Behnia et al, 2018/RCT28	N=25 GOLD stage 1–4 Age (y): 68±9 Sex (M/F): 13/12	70 mL BRJ + 180 mL black currant juice	70 mL water + 180 mL black currant juice	8 days	No	No effect on VO2 at peak (p>0.05) Significant change in SBP: 11 mm Hg (p<0.05) at peak exercise in the NO3- group only compared with pre-NO3- Significant increase in FeNO (ppb) in NO3- group (p<0.05) No effect on DBP (p>0.05) No effect on heart rate (HR) (p>0.05)
Beijers et al, 2018/RXT26	N=18 GOLD stage 1–2 Age (y): 67±8 Sex (M/F): 13/5 FEV1%=69.2	Sodium NO3- (8 mmol)	NaCl ingestion	Acute and 7 days	7 days	No effect on endurance cycle time (p=0.08) No effect on VO2 on day 1 and day 7 during submaximal cycling at 70% Wmax (p=0.56) Significant increase in plasma NO3- level on day 1 and day 7 (p=<0.001) Significant increase on NO2- level on day 1 (p<0.001) and day 7 (p=0.003) No effect on SBP on day 1 and day 7 at 150 min (p=0.66) No effect on DBP on day 1 and day 7 at 150 min (p=0.35) No effect on physical activity, counts/min (p=0.53) No effect on HR on day 1 and day 7 at 150 min (p=0.76)
Berry et al, 2015/RXT16	N=15 GOLD stage 1–2 Age (y): 70±9 Sex (M/F): 12/3 FEV1%=61.8	140 mL BRJ (7.58 mmol)	163 mL prune juice (0.01 mmol NO3-)	Acute	7 days	28.8 s longer in endurance cycle time (p=0.031) No effect on VO2 at end exercise (p=0.43) Significant increase in plasma NO3- level (p<0.001) Significant increase in plasma NO2- level (p=0.001) Significant change in resting SBP: 8.2 mm Hg, p=0.019 Significant change in iso-time DBP: 6.4 mm Hg (p=0.001) Significant change end exercise in DBP: 5.6 mm Hg (p=0.08) No effect on HR, p=0.70 No effect on O2 saturation, p=1.0
Curtis et al, 2015/RXT29	N=21 GOLD stage 2–4 Age (y): 68±7 Sex (M/F): 16/5 FEV1%=50.1	140 mL BRJ (12.9 mmol)	140 mL ND-BRJ	Acute	7 days	No effect on median endurance time (p=0.50) Significantly lower iso-time VO2 (p=0.04) Significant increase in plasma NO3- level (p<0.0001) No effect on SBP Significant change in DBP: 7 mm Hg (p=0.01) No effect on MAP (p=0.07) No effect on HR (p=0.06) No effect on O2 saturation (p=0.26)
Friis et al, 2015/RXT30	N=15 GOLD stage 2–4 Age (y): 63±13 Sex (M/F): 9/6 FEV1%=44.7	140 mL BRJ	140 mL ND-BRJ	7 days	7 days	No effect on exercise capacity (p=0.46) No effect on VO2 (p=0.31) Significant increase in plasma NO2- level (p<0.01) No effect on SBP (p=0.80) Significant reduction on DBP (p<0.05) No effect on HR (p=0.86) No effect on physical activity (p>0.05)
Henrohn et al, 2018/RXT27	N=15 Pulmonary hypertension, WHO group 1 Age (y): 60±15 Sex (M/F): 7/8	140 mL BRJ (16 mmol)	140 mL ND-BRJ (0.118 mmol NO3-)	7 days	4–9 days	No effect on exercise capacity (p=0.445) No effect on VO2 (p=1.00) Significant higher in FeNO levels (p<0.001) Significant increase in plasma NO3- level (p<0.001) Significant increase in plasma NO2- level (p<0.001) No effect on SBP (p=0.482) No effect on DBP (p=1.000) No effect on HR p=0.191
Kerley et al, 2015/RXT17	N=11 GOLD stage 2–4 Age (y): 69±7 Sex (M/F): 5/6 FEV1%=43.4	140 mL BRJ + 200 mL black currant cordial	140 mL water + 200 mL black currant cordial	Acute	7 days	ISWT distance increased 25 m (p=0.005) Significant increase in plasma NO3- level (p=0.000005) Significant increase in plasma NO2- level (p<0.01) Significant change in SBP: 12 mm Hg (p=0.03) Significant change in DBP: 2 mm Hg (p=0.045) Significant change in MAP: 5 mm Hg (p=0.018) No effect on HR (p=0.19) No effect on O2 saturation (p=0.71)
Kerley et al, 2019/RXT18	N=8 GOLD stage 1–3 Age (y): 63±7 Sex (M/F): 5/3 FEV1%=55	140 mL BRJ (12.9 mmol)	140 mL ND-BRJ (0.5 mmol NO3-)	14 days	NA	ISWT distance increased 56 m (p=0.0004) Significant increase in plasma NO3- level (p=0.015) Significant increase in plasma NO2- level (p=0.02) No effect on FeNO level (p=0.095) No effect on SBP (p=0.14) No effect on DBP (p=0.35)
Leong et al, 2015/RXT31	N=19 GOLD stage 2 Age (y): 67±8 Sex (M/F): 5/14 FEV1%=62	140 mL BRJ (9.6 mmol)	140 mL ND-BRJ (0.0056–0.020 mmol NO3-)	3 days	4 days	Endurance distance increased 79 m (p=0.494) Increase time to fatigue by 6% (p=0.693) Significant change SBP in safety phase: 10 mm Hg at 1-hour standing (p=0.001) and 7.5 mm Hg at 4-hour standing (p=0.029) No effect on DBP in safety phase: 0.1 mm Hg at 1-hour standing (p=0.966) and 2.7 mm Hg at 4-hour standing (p=0.352)
Pavitt et al, 2020/RCT During PR19	N=122 GOLD stage 2–4 Age (y): 68±10 Sex (M/F): 69/53 FEV1%=49	140 mL BRJ (12.9 mmol)	140 mL ND-BRJ	56 days	No	Significant increase in ISWT distance by 60 m (p=0.027) Significant change in SBP: 5 mm Hg (p<0.0005) Significant change in DBP: 5 mm Hg (p<0.0005) Significant change in MAP: 5.0 mm Hg (p<0.0005) Significant change in the FMD in BRJ group +6.6% (p=0.046) Significant increase in physical activity by 348 step/day (p=0.02)
Shepherd et al, 2015/RXT32	N=13 GOLD stage 1–2 Age (y): 65±8 Sex (M/F): NR FEV1%=57	140 mL BRJ (13.5 mmol)	140 mL ND-BRJ (0.004 mmol NO3-)	2.5 days	7 days	No effect on 6MWD (p=0.17) No effect on baseline VO2(p=0.56) and end exercise VO2 (p=0.88) Significant increase in plasma NO3- level (p=0.002) No effect on SBP (p=0.91) No effect on DBP (p=0.25)

BRJ, beetroot juice; DBP, diastolic blood pressure; FeNO, fractional exhaled nitric oxide; FMD, flow-mediated dilatation; GOLD, Global Obstructive Lung Disease; ISWT, incremental shuttle walk test; MAP, mean arterial pressure; 6MWD, 6-minute walk distance; N, number of participants who completed the trial; NA, not available; NaCl, Sodium chloride; ND-BRJ, nitrate-depleted beetroot juice; NO₂^-, nitrite; NR, not reported; RCT, randomised controlled trial; RXT, randomised crossover trial; SBP, systolic blood pressure; VO₂, oxygen consumption.;