Abstract:
Abstract – Part A: Randomised control trial Background: Optimising cognition in sport is not only important for motor control, coordination, decision making, timing and teamwork, but further, is important in reducing the stress involved with sport. It is also recognised the role of nutrition in enhancing athletic performance, with many athletes using supplements as a way to increase intake of perceived advantageous nutrients. Blackcurrants are being recognised as beneficial in enhancing the cognitive health of aging population, however, less is known about their role in healthy populations, or in specific sporting settings. Aim: Investigate the effect of a blackcurrant-based supplement (BCBS) marketed as a nootropic brain drink, on the mental performance of team sport athletes. Methods: The present study was a placebo-controlled, double-blinded, randomised-control trial with crossover design. 23 rugby league players completed seven days of once daily supplementation of either a blackcurrant-based supplement (BCBS) or placebo beverage. Following a 10-day washout each participant repeated the procedure with the opposing beverage. Participants preformed a cognitive test (Stroop) in a fatigued state following a 90- minute evening training at baseline and after each intervention period. A modified MTQ48 mental assessment (MMTQ) was used to gather subjective mental toughness and stress throughout each phase. Participants completed a one-day diet history and subjective perception of effectiveness was assessed in an end of trial questionnaire. Results: Statistically significant difference in Stroop performance for each the total score (P=<0.01), accuracy (P=<0.01) and time/response (P=0.04) following BCBS intervention compared to placebo. The BCBS did not improve the total MMTQ result, however, resulted in greater scores on question about participant’s reliability (P=0.02) and distractedness (p=0.03), while the placebo resulted in a greater score on the question addressing control of nervousness (p=0.03). Dietary data indicated participants had low intake of grain foods and vegetables. Thematic analysis of the post-trial questionnaire indicated participants found the BCBS sour, most reported no side effects, and opinion on which drink has greater efficacy was not unanimous. Conclusion: BCBS significantly increased cognitive function scores, measured by Stroop test, of rugby league players after one week of supplementation when compared to placebo. BCBS may be beneficial in a sporting setting, justifying the need for a longer-term, larger scale and more sensitive investigation. Abstract – Part B: Systematic review and meta-analysis Background: Previous reviews have highlighted the promising potential of phytochemical rich foods, particularly those containing anthocyanins such as berries, plums and red cabbage. With previous reviews including a wide number of phytochemicals, food sources and population groups, it emphasizes the need for a review with a selective focus on a specific phytochemical-rich food source and population, to reduce inconsistencies in participants and intervention phytochemical content. Thereby increasing homogeneity and allowing for quantitative assessment. Objective: To systematically evaluate the current literature investigating the effect of blackcurrant on cognitive function in a healthy population. Methods: In May 2019 a search was conducted on MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials, Food Science and Technology abstracts, PsycINFO and Scopus databases to identify literature on trials that explored blackcurrant and cognition in non-aged non-impaired populations using a pre-defined search strategy. Data on accuracy and reaction time were extracted and pooled using Review Manager software (version 5.03) using standardised mean difference between the placebo and intervention groups. Results: Four studies met criteria for inclusion in the meta-analysis. All studies administered intervention orally as a beverage. Intervention protocol ranged from a mixed berry beverage containing blackcurrant, daily for five weeks, to a one-off dose an hour before testing. The mean standardized cognitive score effect of blackcurrant on accuracy was calculated to be 0.15 (95% CI -0.12, 0.42, P=0.28). The mean standardized cognitive score effect of blackcurrant on reaction time was calculated to be 0.02 (95% CI -0.25, 0.30, P=0.86). Conclusion: Based on current research, there is insufficient evidence that blackcurrant is effective in altering cognition accuracy and response time in a healthy population. The results highlight the need for a greater number of highly powered control trials, which employ sensitive cognitive testing, to confirm the use of a blackcurrant as a means to improve cognitive function.