Abstract:
Background: Brain health is essential for overall well-being, but is a growing concern in society today.
A variety of dietary factors have been shown to support brain health, with polyphenols in particular
showing significant potential cognitive function. Compared to other polyphenol-rich fruits,
blackcurrants remain largely unexplored for their potential benefits for cognitive health.
Methods: Forty healthy females participated in this double-blinded, randomised, placebo-controlled
cross-over trial. Participants were recruited with a balance of ‘optimal’ and ‘sub-optimal’ diets
according to a dietary screening tool. The active intervention was the Ārepa performance beverage
(300mL), a polyphenol-rich blackcurrant drink (311mg anthocyanins) also containing l-theanine
(200mg) and pine-bark extract (150mg), which was compared to a taste- and colour-matched placebo
beverage. The trial was three months in duration, including four weeks on each intervention arm and
a four-week wash-out period between. Cognition was assessed using the Purple-Multi-Tasking
Framework (MTF), comprising of four concurrent tasks including mental arithmetic, letter recall, visual
tracking, and Stroop tests. Stress reactivity was assessed using the State-Trait Anxiety Inventory: State
Subscale and Visual Analogue Mood Scales before and after completing the 20-minute MTF, which
acts as a cognitive stressor. Differences in changes in cognitive performance and stress reactivity from
baseline to follow-up between intervention groups were assessed by a series of paired t-tests.
Results: There was a trend towards improvements in the MTF total (+1689) and letter search scores
(+955) following four weeks of daily Ārepa supplementation (p= 0.052 and 0.057, respectively),
indicating improvements in working memory and executive function. When investigating the effect of
baseline diet quality on intervention responses, we found that these benefits to MTF total and letter
search scores were driven by participants in the ‘sub-optimal’ diet group (p= 0.028 and 0.022,
respectively), while no benefit was observed in the ‘optimal’ diet group (p= 0.774 and 0.921,
respectively). No difference in change for stress reactivity measures (alertness, calmness,
contentment, fatigue, and stress) was seen between active and placebo beverages.
Conclusion: These findings add to a body of evidence demonstrating the benefit of polyphenols in
supporting specific domains of cognition, including executive function and working memory. Our
findings do not support the role of polyphenols in improving stress reactivity measures in response to
a cognitive stressor. These findings warrant future research to examine mechanistic actions, informing
recommendations for the promotion of cognitive health, and the potential attenuation of cognitive
decline.