Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials

d’Unienville, Noah M. A.; Blake, Henry T.; Coates, Alison M.; Hill, Alison M.; Nelson, Maximillian J.; Buckley, Jonathan D.

doi:10.1186/s12970-021-00472-y

Journal of the International Society of Sports Nutrition

Table 5 Polyphenol meta-analysis and sub-group analyses

From: Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials

	All polyphenol trials					Trials with polyphenols quantified
	k	n	SMD (95% CIs)	p	I² (%)	k	n	SMD (95% CIs)	p	I² (%)
Overall	71	1227	0.17 [0.10, 0.25]	<0.001	66	45	829	0.20 [0.09, 0.30]	<0.001	72
Design			Q_b: 0.04	0.548				Q_b: 3.53	0.060
Crossover	52	730	0.16 [0.08, 0.23]	<0.001	65	34	481	0.14 [0.04, 0.24]	0.006	66
Parallel	19	497	0.24 [-0.02, 0.49]	0.069	56	12	348	0.47 [0.14, 0.81]	0.006	59
Blinding			Q_b: 0.34	0.845				Q_b: 0.13	0.714
Single blind	6	122	0.30 [-0.3, 0.91]	0.329	91	6	122	0.30 [-0.30, 0.91]	0.329	91
Double blind	58	987	0.17 [0.10, 0.24]	<0.001	51	38	674	0.19 [0.08, 0.29]	<0.001	67
Unclear	7	118	0.10 [-0.27, 0.46]	0.621	76	1	33	-0.18 [-0.8, 0.44]	0.572	-
Supplementation duration			Q_b: 0.12	0.733				Q_b: 1.46	0.228
Acute	15	243	0.21 [0.003, 0.41]	0.046	85	5	101	0.56 [-0.07, 1.19]	0.081	95
Multiple days	56	984	0.17 [0.09, 0.25]	<0.001	57	40	728	0.17 [0.07, 0.27]	0.001	61
Polyphenol quantification			Q_b: 1.13	0.287
No	26	398	0.14 [0.04, 0.25]	0.009	52
Yes	45	829	0.2 [0.09, 0.30]	<0.001	72
Sex¹			Q_b: 7.49	0.024				Q_b: 0.31	0.210
Male	45	729	0.23 [0.15, 0.32]	<0.001	42	31	556	0.20 [0.08, 0.32]	<0.001	46
Female	4	71	0.01 [-0.19, 0.20]	0.948	0	3	55	0.01 [-0.19, 0.21]	0.942	0
Mixed	19	388	0.05 [-0.09, 0.19]	0.460	78	8	179	0.26 [-0.05, 0.57]	0.098	94
Performance level			Q_b: 12.90	0.005				Q_b: 1.17	0.558
PL1	3	89	0.76 [0.37, 1.15]	<0.001	0	2	80	0.59 [-0.08, 1.25]	0.083	0
PL1 Females	-					-
PL1 Males:	3	89	0.76 [0.37, 1.15]	<0.001	0	2	80	0.59 [-0.08, 1.25]	0.083	0
GXT	2	80	0.59 [-0.08, 1.25]	0.083	0	2	80	0.59 [-0.08, 1.25]	0.083	0
TT	1	9	0.86 [0.38, 1.34]	<0.001	-	-
PL2	19	279	0.12 [0, 0.25]	0.059	36	14	207	0.21 [0.09, 0.34]	<0.001	0
PL2 Females	-					-
PL2 Males:	17	239	0.21 [0.11, 0.32]	<0.001	0	14	207	0.21 [0.09, 0.34]	<0.001	0
GXT	6	94	0.23 [-0.02, 0.47]	0.068	16	6	94	0.23 [-0.02, 0.47]	0.068	16
IGXT	1	26	2.54 [0.13, 4.96]	0.039	-	1	26	2.54 [0.13, 4.96]	0.039	-
ITTE	1	13	0.26 [-0.18, 0.7]	0.252	-	1	13	0.26 [-0.18, 0.7]	0.252	-
TT	6	64	0.18 [0.01, 0.35]	0.042	0	5	54	0.21 [0.02, 0.39]	0.028	0
TTE	3	42	0.21 [0.03, 0.4]	0.021	0	1	20	0.12 [-0.21, 0.45]	0.492	-
PL3	18	275	0.22 [0.08, 0.36]	0.002	31	13	219	0.22 [0.06, 0.34]	0.002	36
PL3 Females	2	44	0.05 [-0.17, 0.28]	0.646	0	2	44	0.05 [-0.17, 0.28]	0.646	0
PL3 Males:	16	231	0.28 [0.14, 0.42]	<0.001	36	11	175	0.28 [0.08, 0.49]	0.006	39
IGXT	1	13	0.54 [0.1, 0.97]	0.016	-	1	13	0.54 [0.1, 0.97]	0.016	-
TT	11	177	0.24 [0.08, 0.41]	0.004	59	9	152	0.24 [0.03, 0.46]	0.029	42
TTE	4	57	0.35 [-0.01, 0.71]	0.056	20	1	10	1.1 [-1.02, 3.22]	0.314	-
PL4	2	19	0.49 [0.21, 0.77]	<0.001	0	1	9	0.41 [0.08, 0.75]	0.015	-
PL4 Females	-					-
PL4 Males:	2	19	0.49 [0.21, 0.77]	<0.001	0	1	9	0.41 [0.08, 0.75]	0.015	-
TT	2	19	0.49 [0.21, 0.77]	<0.001	0	1	9	0.41 [0.08, 0.75]	0.015	-
PL5	-					-
Exercise mode			Q_b: 6.32	0.097				Q_b: 10.15	0.006
Cycling	39	589	0.15 [0.06, 0.24]	0.001	54	27	431	0.14 [0.04, 0.23]	0.004	40
Incline Walk/Run	4	83	0.54 [0.21, 0.87]	0.001	0	2	60	0.63 [0.02, 1.24]	0.043	0
Rowing	2	37	-0.32 [-1.34, 0.71]	0.556	63	1	19	-0.84 [-1.74, 0.05]	0.064	-
Running	24	489	0.22 [0.10, 0.33]	<0.001	62	13	290	0.44 [0.17, 0.71]	0.001	82
Swimming	1	11	-0.18 [-0.63, 0.27]	0.434	-	1	11	-0.18 [-0.18, 0.27]	0.112	-
Climbing	1	18	-0.62 [-1.0, -0.25]	0.001	-	1	18	-0.62 [-1.0, -0.25]	0.001	-
Test type			Q_b: 10.29	0.016				Q_b: 11.46	0.009
GXT	17	352	0.14 [-0.001, 0.28]	0.052	23	11	249	0.22 [0.04, 0.39]	0.016	37
IGXT	4	73	1.09 [0.50, 1.68]	<0.001	66	4	73	1.09 [0.50, 1.68]	<0.001	66
ITTE	1	13	0.26 [-0.18, 0.70]	0.252	-	1	13	0.26 [-0.18, 0.70]	0.252	-
TT	35	549	0.12 [0.03, 0.21]	0.011	59	24	370	0.10 [0.01, 0.20]	0.037	41
TTE	14	240	0.16 [0.01, 0.31]	0.037	63	5	124	0.17 [-0.39, 0.72]	0.563	88
Test duration			Q_b: 2.40	0.663				Q_b: 5.57	0.135
<5 mins:	4	49	0.26 [-0.08, 0.59]	0.133	91	1	12	-0.08 [-0.21, 0.06]	0.257	-
TT	2	21	0.36 [-0.55, 1.27]	0.446	93	1	12	-0.08 [-0.21, 0.06]	0.257	-
TTE	2	28	0.20 [0.07, 0.33]	0.002	0	-
5-10 mins:	9	124	0.08 [-0.14, 0.30]	0.472	73	4	56	-0.11 [-0.43, 0.22]	0.532	76
TT	3	36	-0.01 [-0.16, 0.14]	0.873	0	2	18	-0.02 [-0.17, 0.13]	0.807	0
TTE	6	88	0.11 [-0.23, 0.45]	0.532	80	2	38	-0.25 [-0.97, 0.48]	0.516	88
10-30 mins:	19	339	0.19 [0.12, 0.26]	<0.001	0	12	234	0.22 [0.1, 0.33]	<0.001	14
TT	16	264	0.21 [0.1, 0.32]	<0.001	27	10	176	0.21 [0.06, 0.36]	0.006	35
TTE	3	75	0.18 [0.02, 0.34]	0.031	0	2	58	0.21 [0.03, 0.4]	0.024	0
30-60 mins:	9	122	0.12 [0.03, 0.21]	0.008	0	6	77	0.11 [0.01, 0.2]	0.036	0
TT	7	101	0.12 [0.03, 0.21]	0.008	0	6	77	0.11 [0.01, 0.2]	0.036	0
TTE	2	21	0.04 [-0.32, 0.41]	0.828	19	-
>60 mins:	5	104	0.14 [-0.38, 0.66]	0.608	83	3	64	0.52 [-0.2, 1.4]	0.206	71
TT	4	76	-0.08 [-0.46, 0.29]	0.673	65	2	36	0.33 [-0.61, 1.27]	0.506	75
TTE	1	28	0.97 [0.21, 1.73]	0.013	-	1	28	0.97 [0.21, 1.73]	0.013	-
Overall (TT & TTE)	46	738	0.14 [0.06, 0.21]	<0.001	59	26	443	0.11 [0.01, 0.21]	0.038	61

¹ Sex not specified in three trials. Abbreviations – GXT, graded exercise test; IGXT, intermittent graded exercise test; ITTE, intermittent time to exhaustion; k, number of trials; LCI, lower confidence interval; n, pooled sample size; PL, performance level; Qb, between-group Q-statistic; SMD, standardised mean difference (Hedge’s g); TT, time-trial; TTE, time to exhaustion; UCI, upper confidence interval

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