Following publication, data supporting the results reported in this paper will be openly available from the University of Reading Research Data Archive at http://researchdata.reading.ac.uk/.
Data were successfully collected for 19 participants. Due to an administrative error, data for the post-intervention time point following the 200 mg dose were missing for one further participant; however, all other data for this participant have been included in the analysis.
Visit order effects
Significant visit order effects were observed for mental fatigue [F(3,16.10) = 3.74, p = 0.033], serial 3s score [F(3,17.95) = 3.32, p = 0.043], serial 3s errors [F(3,17.53) = 3.45, p = 0.039], ANT accuracy [F(3,392.96) = 11.35, p < 0.001], and ANT RT [F(3,368.22) = 14.01, p < 0.001]. In general, cognitive performance was observed to improve over time, with higher scores, fewer errors and faster reaction times evident at later visits compared with earlier visits. In contrast, ratings of mental fatigue worsened over time.
Blood pressure and heart rate
No dose effects were observed for systolic blood pressure [F(3,41.39) = 1.54, p = 0.219]. However, significant dose effects were observed for diastolic blood pressure [F(3,34.79) = 3.85, p = 0.018] and heart rate [F(3,35.03) = 4.48, p = 0.009]. Pairwise comparisons revealed that both diastolic blood pressure and heart rate were significantly lower following the 400 mg dose when compared to the control (p = 0.012 and p = 0.020, respectively). Results are presented in Table 2.
Table 2 Mean (SE) blood pressure and heart rate following varying doses of haskap berry extract
AVLT
There were significant dose effects at recall points R4 [F(3,30.61) = 5.49, p = 0.004], R5 [F(3,34.99) = 7.34, p = 0.001], RB [F(3,32.29) = 6.82, p = 0.001], R6 [F(3,27.80) = 3.24, p = 0.037], and R7 [F(3,34.71) = 5.49, p = 0.003]. Pairwise comparisons revealed that no significant differences in recall performance were observed following the 100 mg dose, compared to the control. Performance following the 200 mg dose was significantly higher than the control at R4 (p = 0.004), R5 (p = 0.002), and R7 (p = 0.002). At R5, 200 mg dose performance was also significantly higher than the 100 mg and 400 mg doses, (p = 0.002 and p = 0.022, respectively). Performance following the 400 mg dose was significantly higher than control at R6 (p = 0.028). At RB, 400 mg dose performance was also significantly lower than the 100 mg and 200 mg doses, (p = 0.034 and p < 0.001), respectively. Results are presented in Fig. 2.
There were significant effects of dose for learning (R5–R1) [F(3,34.20) = 3.78, p = 0.019] and proactive interference (PI) (R1–RB) [F(3,16.58) = 6.01, p = 0.006], but not for retroactive interference (RI) (R5–R6) [F(3,31.96) = 0.78, p = 0.512]. Pairwise comparisons revealed no significant differences in proactive interference for any of the doses compared to control, although PI was observed to be lower following the 200 mg doses compared to the 400 mg dose (p = 0.033). Despite the significance of the learning main effect, there were no significant pairwise differences in learning between any of the doses.
For delayed recognition there was a significant effect of dose on the number of words correctly recognised [F(3,33.27) = 5.95, p = 0.002]. Pairwise comparisons revealed a significantly greater number of words recalled following the 400 mg dose compared to the control (p = 0.013). Results for AVLT calculated and recognition variables are presented in Table 3.
Table 3 Mean (SE) cognition scores following varying doses of haskap berry extract
Serial subtractions
For serial 3s, significant dose effects were evident for number of correct responses [F(3,32.5) = 5.89, p = 0.002] and number of errors [F(3,31.41) = 5.21, p = 0.005]. Pairwise comparisons revealed no significant differences in number of correct responses compared to the control; however, performance following the 200 mg dose was significantly higher than both the 100 mg and 400 mg doses (p = 0.019 and p = 0.040, respectively). The number of errors was significantly lower following the 200 mg dose compared to the control (p = 0.002). For serial 7s, significant dose effects were evident for number of errors [F(3,6.11) = 27.73, p = 0.001], but not for number of correct responses [F(3,31.01) = 0.10, p = 0.957]. Pairwise comparisons revealed significantly fewer errors (p = 0.014) following the 100 mg dose, compared to the control. However, following the 400 mg dose, significantly more errors were made compared to the control (p = 0.011). Results are presented in Table 3.
ANT
For ANT accuracy, there was no significant effect of dose [F(3,871.61) = 0.99, p = 0.399] and no significant dose interaction with congruency [F(3,854.65) = 0.46, p = 0.711], cue type [F(9,854.50) = 0.476, p = 0.892], or load [F(3,855.22) = 1.15, p = 0.329]. Similarly for ANT reaction time, there was no significant effect of dose [F(3,777.25) = 1.97, p = 0.117] and no significant dose interaction with congruency [F(3,761.25) = 0.34, p = 0.794], cue type [F(9,759.52) = 0.73, p = 0.684], or load [F(3,759.47) = 1.55, p = 0.200]. Results are presented in Table 3.
PANAS and mental fatigue
There were no significant effects of dose on mental fatigue [F(3,34.46) = 0.66, p = 0.585], positive affect [F(3,32.95) = 0.53, p = 0.664] or negative affect [F(3,37.92) = 1.69, p = 0.185]. However, analysis of individual PANAS items relating to attention revealed a significant effect of dose on ratings of alertness [F(3,36.53) = 10.57, p < 0.001], but not attentiveness [F(3,36.97) = 0.90, p = 0.448]. Pairwise comparisons revealed significantly lower ratings of alertness following the 400 mg dose compared with the control (p = 0.028) and 100 mg dose (p < 0.001). Alertness following the 200 mg dose was also rated lower than the 100 mg dose (p = 0.0010). Results for all mood variables are presented in Table 4.
Table 4 Mean (SE) subjective mood ratings following varying doses of haskap berry extract
Palatability
There were significant effects of dose on subjective ratings of sweetness [F(3,38.85) = 8.86, p < 0.001], sourness [F(3,31.48) = 10.18, p < 0.001], bitterness [F(3,28.73) = 13.16, p < 0.001], and overall pleasantness [F(3,41.58) = 6.53, p = 0.001]. Pairwise comparisons revealed that compared to control, the 200 mg and 400 mg doses were rated significantly more sour (p = 0.002 and p < 0.001, respectively), and the 400 mg dose was also rated more sour than the 100 mg dose (p = 0.035). The 400 mg was rated significantly more bitter than the control (p = 0.001), the 100 mg dose (p < 0.001), and the 200 mg dose (p = 0.048). In terms of overall taste, only the 400 mg dose was rated significantly less pleasant than the control (p = 0.002) and was also rated less pleasant than the 100 mg dose (p = 0.035). For sweetness, there were no significant differences compared to control; however, the 200 mg and 400 mg doses were rated significantly less sweet than the 100 mg dose (p = 0.001 and p = 0.008, respectively).