The effects of acute wild blueberry supplementation on the cognition of 7–10-year-old schoolchildren, Hacker News

The health benefits of berry fruits are well established, with positive outcomes from consumption associated with cardiovascular health [1], diabetes [2] and cancer preventi on [3]. These benefits are thought to be mediated by the naturally high concentrations of anthocyanins, a sub-class of flavonoids from plant-based polyphenols, found in such fruits [4,5]. In addition, berry fruit consumption has been associated with cognitive benefits. Rodent models have demonstrated significant improvements in working and short-term memory [6,7], and reversal of age-related cognitive decline in aged animals [8,9]. Positive cognitive effects have also been observed throughout the human lifespan [10,11]. The neuroprotective findings from rodent models are mirrored in older adults with a reduction of cognitive impairments and delayed onset of ageing disorders, such as Alzheimer’s disease [12,13,14,15,16]. Additionally, acute and chronic berry flavonoid interventions enhance cognition in healthy older and young adults [17,18,19,20] which builds upon the wider flavonoid literature for these populations [21,22,23,24,25]. Recently, berry flavonoid interventions have shown significant improvements in mood for both adolescents and school-aged children [26].

It is of interest to explore whether such cognitive benefits extend to child populations. For example, Calderón-Garcidueñas et al. [27] first showed that children (mean age 10 years ) supplemented daily with 680 mg cocoa-flavanols over 9 – 24 days exhibited significant improvements in short-term memory assessed by letter and object span tests. In a further acute study, Whyte and Williams [28] observed significant improvements in 8 – 10 – year-olds’ word recall performance for both short and long delays at 2h post-consumption of a 200 g fresh blueberry drink ( (mg anthocyanins). In a similar study, the cognitive performance of 7 – 10 – year-olds was examined at baseline, 1. 15 h, 3h and 6h post-consumption of two wild blueberry (WBB) interventions: a 30 g WBB drink (253 mg anthocyanins) and a g WBB drink 127 mg anthocyanins), compared to a sugar-matched placebo drink [29]. In line with previous research, significant WBB-related improvements were observed for word recognition at every time point and delayed word recall at 1. 15 h only. Additionally, significant improvements in accuracy on a cognitively-demanding executive function task were observed at 3h post-consumption of the 30 – g WBB drink. These findings highlight the potential for WBB interventions to enhance word recall and recognition performance, as well as improving executive function up to 6h post-consumption in 7 – 10 – year-olds. At this age, children experience a spurt in frontal lobe growth thought to coincide with enhanced executive functions and the progression of cognitive abilities [30,31], a phase of cognitive development where WBB supplementation may be particularly beneficial. Indeed, Whyte, Schafer and Williams [32] observed significantly faster reaction times on executive function trials requiring greater cognitive demand (incongruent, high load) at 3h post-WBB consumption compared to placebo in 7 – 10 – year-olds, thus demonstrating WBB benefits children’s executive function when performing complex and demanding cognitive tasks.

In the present study, we aim to replicate the findings from Whyte, Schafer and Williams [29,32] on memory and executive function following an acute high-flavonoid WBB intervention in 7 – 10 – year-olds. Additionally, given the boosts in cognitive performance seen after flavonoid intervention, Whyte and colleagues further suggested that such positive findings from acute WBB consumption on cognition has the potential to benefit a real-world educational scenario. We aimed to extend these cognitive findings in a learning environment by further examining whether acute WBB interventions can benefit reading ability in this population. Reading is a complex process requiring multiple aspects of cognition (e.g. memory, attention, executive functions) which are required for skills such as word learning (decoding), recognition, vocabulary knowledge and reading comprehension. Indeed, previous cognitive findings [28,29] demonstrate improvements to word recall and recognition suggesting the potential for berry flavonoids to benefit children’s visual recall ability of words stored in their internal lexicon; an ability known as sight word reading [33], and to executive functions thought to play a vital role in word learning and reading comprehension [34]. To date, the role of berry flavonoids on reading ability has not yet been examined; however, research does demonstrate a number of links between better executive function and academic performance in general. For example, greater working memory and inhibition are found to be predictive of greater maths and reading ability in 9 – 12 – year -old school children [35,36], as well as a positive association between greater processing speed and greater performance for maths, reading ability and language skills in 6 – 19 – year-olds [37,38]. Therefore, as previous berry flavonoid interventions in children have been shown to positively benefit executive function, in addition to the above literature demonstrating improvements to reading and other academic skills in line with improvements in executive functions, we hypothesise that improvements in children’s reading ability following acute WBB intervention will be observed.

There were no significant differences at baseline between groups for RCPM (T(47)=- 0. 16, (p)=0. 88), CPT commissions (t (46)=- 0. 19, (p)=0. 85), CPT omissions ( (T) (46=- 0. 13, (P)=0. 90) or age ( (T) (52)=- 0.0 34,p=0. 97; see Table(1)). There were also no significant differences between groups at baseline for MANT accuracy (T(52)=- 0. 156, (P)=0. 88), MANT RT ( (t) (52)=0. 87,p=0. 39) or for any AVLT list recalls.

The current study administered a one-off dose of flavonoid-rich wild blueberry to typically developing 7 – 10 – year-old schoolchildren following a randomized, placebo-controlled, parallel-groups design.

Beneficial effects of blueberry flavonoids were observed on an executive function task, the MANT, whereby WBB-treated participants exhibited quicker RT. No WBB effects were seen for accuracy. As expected across both treatment groups, a reduction in accuracy and RT was observed for the more cognitively demanding trials (incongruent, high load) of the MANT, when compared to less cognitively demanding trials (congruent, medium load, respectively). This reflect high internal validity and confirms that the task successfully manipulated cognitive demand, as participants performed worse on the more difficult trials.

Significantly quicker RTs were observed on 120 ms trials for WBB participants compared to place bo participants. Indeed, Simon and Berbaum [42] and Welford [43] previously noted that slower reaction times are to be expected in response to a slower stimulus duration on cognitive tasks due to a longer time required for information integration. However, findings suggest quicker RTs on trials of fast stimulus duration for WBB participants only, suggesting increased mental alertness on the faster 120 ms trials, without change to 500 ms trials (as supported by Fig.1). It is also important to note that a similar effect was not observed in accuracy performance, suggesting the quickening of reaction times was without cost to accuracy. Interestingly, Whyte et al. [32] found that it was within the slower 500 ms trials of the MANT that WBB participants overcame the effects of the most cognitively demanding trials (incongruent, high load). Such an effect was not observed in the current study.

Beneficial WBB effects were also observed on the AVLT. As expected across both treatment groups, a reduction in verbal memory 2 h post-consumption was observed compared to baseline for a variety of facets of memory (word span, final acquisition, total acquisition, words learnt, short delay, long delay, delayed recall , recognition, total recall A1 – A7 and total recall A1 – A7 B). This is indicative of an increase in fatigue and, therefore, forgetting, which is expected in a school environment, and has previously been observed by Whyte et al. [29]. In relation to this, the critical finding here was that consumption of WBB significantly attenuated forgetting for total acquisition (total recall A1 – A5) and short delay recall (recall A6), as indicated by maintenance of post-consumption word recall following WBB, in comparison with the significant decline seen following placebo for these measures. As both drinks were matched for sugar content, this cannot be explained by a glucose effect. This beneficial effect for memory is consistent with Whyte et al. [29] who reported increased verbal memory performance in children at 1. 15 h, 3h and 6h post-consumption following WBB consumption, using an identical 30 g WBB treatment and placebo as the current study, whilst children consuming placebo showed a decline in performance [29]. This further highlights the effect of WBB treatment in reducing fatigue, specifically in the domain of memory.

In addition to cognitive fatigue, between-session interference on the learning and recalling of information could also help to account for the general decline in memory performance. Words heard at the baseline session may have interfered with encoding and retrieval of new words at post-intervention. Interestingly, the present data provided no evidence of retroactive interference within session; new learning did not appear to alter retrieval of previously learned words in either treatment group. This effect was also observed by Whyte et al. [29] and implies a potentially different mechanism between stages of encoding and retrieval in children. Such interference parameters in a child population are yet to be determined and need further exploration. The general decline in memory performance could also be attributed to lunch consumption prior to testing. Research in adults indicates a post-lunch dip whereby lunch consumption negatively impacts upon cognitive performance postprandially [44] , although the limited research conducted thus far in children demonstrates no effects of post-lunch dip on cognition, executive functions in particular [45,46]. The absence of a pre-lunch test point means that a possible post-lunch dip effect remains speculative; this requires further investigation in children. It is also important to acknowledge that the cognitive benefits seen for WBB (relative to placebo) could be influenced by lunch, given that lunch was not standardized and did not occur at a standardized point prior to baseline testing (notwithstanding restriction of flavonoid intake). For practical reasons relating to the school environment the timing of the lunch was not fixed, and the content of lunch was not assessed, however, there is no reason to believe that there were significant differences in macronutrient intake between the WBB and placebo groups.

Despite the observed improvements to cognition following acute WBB intervention, no benefits were apparent for either sight word reading or phonemic decoding efficiency; however, it should be noted that children from this sample were good readers, as all performed well within or above the average range for their age group; therefore, these results cannot be generalizable to children with differing performance. Reading draws upon multiple aspects of cognition such as working memory, selective attention, and executive functions which must work together to achieve efficient reading. Therefore, it is plausible that a one-off dose of WBB may not be sufficient to elicit changes in reading, in comparison with the cognitive benefits seen here where aspects of cognition were assessed independently. Future research should consider the impact of sustained WBB supplementation on reading ability, such as a daily dose given chronically, to examine whether prolonged berry flavonoid supplementation is more beneficial to the complexity of cognitive domains that underpin reading ability. In addition, the task used to measure reading, the TOWRE-2, may not be sensitive enough to detect changes in reading ability attributable to WBB supplementation, or indeed possibly dietary interventions in general as to our knowledge it is the first time this task has been used in such a study. There is limited evidence for the effect of dietary interventions, namely polyunsaturated fatty acids, on word learning and memory using similar tasks; however, positive effects were only apparent in children with learning / behavioral difficulties or underperforming individuals [47,48], reducing translation to typical readers. The TOWRE-2 measures the fluency and accuracy of orthography, or print-based words, within a short period of time (45 s). Essentially, this timed element measures participants ’automaticity of prior letter-sound correspondences and, in particular, may detract participants from making a correct response on the phonemic decoding subtest. To account for this potential lack of sensitivity, future research should focus on a select and more specific aspect of learning to read, such as word learning which focuses precisely on learning the mappings between orthography (a written word) and phonology (pronunciation). This is how children learn to read naturally so would not only examine the effect of WBB on a developmental aspect of reading requiring word memory and retrieval (similar to that measured by the AVLT although utilizing a different modality), but will also allow generalization of findings to the real world.

There is evidence to suggest that cognitive improvements are linked to increased cerebral blood flow [10]; however, definitive mechanisms are currently unknown, especially in a child population. Further work is needed to investigate the bioavailability of flavonoids within children’s bodies via non-invasive metabolic examinations, alongside cognitive assessment, to converge findings with a robust mechanism of action.

The current study demonstrated beneficial cognitive effects of acute WBB consumption on memory and attention in healthy 7 – 10 – year-old children, although these benefits did not extend to reading ability. Such findings add to the growing body of evidence that flavonoids are beneficial for healthy brain function, and in this instance demonstrate the potential benefits of a 30 g freeze-dried WBB treatment, equivalent to a 240 g punnet or 1½ cups of fresh blueberries when relating findings to real-world applications, during critical developmental periods. Several animal and human studies have observed an increase in cognitive ability following acute blueberry interventions with adults [10,11]; however, only four previous studies have explored the effects of berry fruits in children [26,28,29,32]. Replications of such findings, alongside biological mechanisms of action, are desirable to further elicit the exact functioning of flavonoids within a child population, as well as considering the effects of chronic WBB consumption and more sensitive reading tasks when examining the effect of WBB on reading ability .