Table 1.
Summary table of included studies.
| References | Participants | Intervention (I) vs. Control (C)* | Design | Cognitive tasks | Results** |
|---|---|---|---|---|---|
| Bondonno et al. (2014) | 30 (6 Males, Age Range: 33–61) | I: 80 g apple skin and 120 g apple flesh (184 mg of total quercetin glycosides and 180 mg of (–)-epicatechin) C: 120 g apple flesh (<5 mg of total quercetin glycosides and (–)-epicatechin) |
Blinding unknown, controlled, crossover | Simple RT Choice RT Digit Vigilance |
Simple RT – Speed: n.s. Choice RT – Accuracy: n.s.; Speed: n.s. Digit Vigilance – Accuracy: n.s.; Speed: n.s.; False Alarms: n.s. |
| Cropley et al. (2012) | 39 (20 Males, Age Range: 53–79) | I: 6 g decaf coffee (521 mg total CGA and 11 mg caffeine) C: 6 g of placebo coffee (0 mg total CGA and 0 mg caffeine) |
Double-blind, controlled, crossover | RVIP | Accuracy: n.s.; Speed: n.s. |
| Dietz et al. (2017) | 23 (4 Males, Age Range: 20–35) | I: 4 g matcha powder in tea or bar (67 mg L-theanine, 280 mg EGCG, and 136 mg caffeine) C: 2.5 g spinach powder |
Single-blind, controlled, crossover | Simple RT Choice RT Digit Vigilance |
Simple RT – Speed: faster responses in the matcha tea (vs. control) condition Choice RT – Accuracy: n.s.; Speed: faster responses in the matcha (vs. control) condition Digit Vigilance – Accuracy: n.s.; Speed: n.s.; False Alarms: n.s. |
| Field et al. (2011) | 30 (8 Males, Age Range: 18–25) | I: 35 g of the dark chocolate (773 mg of CF, 38 mg caffeine, and 222 mg theobromine) C:35 g white chocolate (trace amounts of CF, caffeine, and theobromine) |
Single-blind, controlled, crossover | Choice RT | Choice RT – Accuracy: n.s.; Speed: faster responses in the intervention (vs. control) condition during the predictable (but not unpredictable) phase of the task |
| Haskell-Ramsay et al. (2017) | 20 (7 Males, Age Range: 18–35) | I: 200 ml Welch's™ purple grape juice and 30ml Schweppes™ blackcurrant flavour cordial (Phenolic content: 1504.5 mcg/ml; 346 mg polyphenols;31.8 mg anthocyanins) C: 200 ml Welch's™ white grape juice, 10 ml blackcurrant flavour cordial, and 20 ml cold water (Phenolic content: 135.1 mcg/ml) |
Single-blind, controlled, crossover | Simple RT Choice RT Digit Vigilance |
Simple RT – Speed: not reported Choice RT – Accuracy and Speed: not reported Digit Vigilance – Accuracy, Speed, and False Alarms: not reported Composite attention measure – Accuracy: n.s.; Speed: faster responses in the intervention (vs. control) condition |
| Haskell-Ramsay et al. (2018a) | 60 (27 Males, Age Range: 18–65) | I: 500 mg brown seaweed extract tablet (>20% chlorogenic acid equivalent) C: placebo tablet |
Double-blind, controlled, parallel | Simple RT Choice RT Digit Vigilance |
Simple RT – Speed: n.s. Choice RT – Accuracy: reduced accuracy at the 120- and 160-min assessments in the control group when compared to the first assessment post-lunch, which was not apparent in the intervention group; Speed: n.s. Digit Vigilance – Accuracy: increased accuracy in the intervention (vs. control) condition during repetition 1 of the assessments; Speed: n.s.; False Alarms: n.s. |
| Haskell-Ramsay et al. (2018b) | 59 (30 Males, Age Range: 22–74) | I: 220 ml regular coffee (100 mg caffeine) C: 220 ml water (2.5 g coffee flavouring) |
Double-blind, controlled, crossover | Simple RT Digit Vigilance RVIP |
Simple RT – Speed: n.s. Digit Vigilance – Accuracy: n.s; Speed: faster responses in intervention (vs. placebo) condition; False Alarms: n.s. RVIP – Accuracy: n.s; Speed: faster responses in intervention (vs. placebo) condition; False Alarms: n.s. |
| Keane et al. (2016) | 27 (Unknown, Age Range: 45–60) | I: 60 ml Montmorency tart cherry concentrate (68.0 mg cyanidin-3-glucoside/l, 160.75 mean gallic acid equivalent/l and 0.59 mean Trolox equivalent/l) C: fruit flavoured cordial mixed with water, whey protein isolate, and maltodextrin (8·26 mean gallic acid equivalent/l) |
Double-blind, controlled, crossover | Digit Vigilance RVIP |
Digit Vigilance – Accuracy: n.s; Speed: n.s. RVIP – Accuracy: n.s; Speed: n.s. |
| Kennedy et al. (2010) | 22 (Unknown, Age Range: 18–25) | I: 500 mg trans-resveratrol C: inert placebo capsule |
Double-blind, controlled, crossover | RVIP | RVIP – Accuracy: n.s.; Speed: n.s.; False Alarms: n.s. |
| Kennedy et al. (2017) | 59 (19 Males, Age Range: 40–65) | I: 1,600 mg of green oat extract [flavonoid content, calculated as isovitexin, of ≥0.3% (w/w)] C: placebo capsule (maltodextrin) |
Double-blind, controlled, crossover | Simple RT Choice RT Digit Vigilance |
Simple RT – Speed: n.s. Choice RT – Accuracy: n.s.; Speed: n.s. Digit Vigilance – Accuracy: n.s.; Speed: n.s.; False Alarms: n.s. |
| Kennedy et al. (2020) | 132 (40 Males, Age Range: 35–65) | I: 1,290 mg Cognitaven® - 900 mg green oat extract (phenolic content unknown) C: placebo capsule (maltodextrin) |
Double-blind, controlled, parallel | RVIP | RVIP – Accuracy: n.s; Speed: n.s. |
| Massee et al. (2015) | 40 (20 Males, Age Range: 18–40) | I: 3,058 mg T. cacao seed extract (250 mg catechin polyphenols and 5.56 mg caffeine) C: placebo tablet (inert cellulose powder) |
Double-blind, controlled, parallel | Simple RT Choice RT RVIP |
Simple RT – Speed: n.s. Choice RT – Accuracy: n.s.; Speed: n.s. RVIP – Accuracy: n.s.; Speed: n.s. |
| Philip et al. (2019) | 30 (14 Males, Age Range: 18–25) | I: 600 mg grape (Vitis vinifera L.) and wild blueberry (Vaccinium angustifolium) (Memophenol™, Activ'Inside, Beychac et Caillau, France) extract (260 mg flavonoids) C: placebo capsule (maltodextrin) |
Double-blind, controlled, crossover | RVIP | RVIP – Accuracy: a trend towards increased accuracy in intervention (vs. control) condition; Speed: n.s.; False Alarms: n.s. |
| Scholey et al. (2010) | 30 (13 Males, Age Range: 18–35) | I: 994 mg CF C: 46 mg CF |
Double-blind, controlled, crossover | RVIP | RVIP – Accuracy: n.s.; Speed: faster responses in the intervention (vs. control) condition at 30 and 40-min; False Alarms: n.s. |
| Watson et al. (2015) | 36 (13 Males, Age Range: 18–35) | I: DelCyan™ Blackcurrant extract or 142 ml “Blackadder” blackcurrant fruit juice (525 ± 5 mg of polyphenols per 60 kg of bodyweight; 571 mg anthocyanins; 590 mg polyphenols and 552 mg anthocyanins; 599 mg polyphenols, respectively) C:control drink (0 mg polyphenols) |
Double-blind, controlled, crossover | Digit Vigilance RVIP |
Digit Vigilance – Accuracy: n.s; Speed: faster responses in treatment (vs. control) condition at repetition 1, 4, and 7 for “Blackadder” (but not DelCyan™) RVIP – Accuracy: n.s; Speed: attenuation in the reduction of accuracy in DelCyan™, but not “Blackadder,” (vs. control) condition, irrespective of repetition; False Alarms: n.s. |
| Watson et al. (2019) | 9 (3 Males, Age Range: Unknown) | I: Blackcurrant juice (515.7 mg polyphenols; 118.7 mg anthocyanins) C: control drink, sugar, vitamin C, and flavour matched |
Double-blind, controlled, crossover | Simple RT Choice RT Digit Vigilance |
Simple RT – Speed: n.s. Choice RT – Accuracy: n.s.; Speed: slower responses in intervention (vs. control) condition Digit Vigilance – Accuracy: n.s.; Speed: n.s.; False Alarms: n.s. |
| Wightman et al. (2014) | 23 (4 Males, Age Range: 19–34) | I: 250 mg trans-resveratrol capsule C: inert placebo capsule |
Double-blind, controlled, crossover | RVIP | RVIP – Accuracy: n.s |
| Wightman et al. (2018) | 140 (46 Males, Age Range:50–70) | I: 950 mg Sideritis scardica extract (58 mg polyphenols) C: placebo capsule (maltodextrin) |
Double-blind, controlled, parallel | Choice RT RVIP |
Choice RT – Accuracy: n.s.; Speed: n.s. RVIP – Accuracy: n.s; Speed: n.s.; False Alarms: reduced false alarms in intervention (vs. control) condition at repetition 4 |
*
Only highest dose polyphenol interventions were reported;
**
Only intervention vs. control differences were reported. Composite attention measure results were reported only when individual test results were not reported by the authors; RT, reaction time; n.s., not significant; CGA, chlorogenic acids; RVIP, rapid visual information processing; EGCG, epigallocatechin gallate; CF, cocoa flavanols; w/w, weight for weigh.