Introduction
Supplementation with anthocyanin-rich foods has been shown to exert beneficial effects on cognitive performance. Furthermore, effects on potential underlying mechanisms such as an improved vascular function have been described. Recently, we observed beneficial effects of Aronia Melanocarpa - an anthocyanin-rich berry - extract (AME) supplementation (16 mg anthocyanins/day) on psychomotor speed in healthy middle-aged adults. However, effects of a higher AME dose in a short-term setting, as well as in a younger population remain unknown. Therefore, the aim of this study was to investigate short-term effect of AME supplementation on cognitive performance in healthy young adults.

Materials and methods
A randomized, double-blind, placebo-controlled, cross-over study was performed in 35 apparently healthy 18–35-year-old adults. Participants consumed AME or a placebo for one week, separated by a wash-out period of two weeks. The AME extract corresponded to an anthocyanin intake of 180 mg/day. Cognitive performance was measured using the Cambridge Neuropsychological Test Automated Battery (CANTAB). Blood pressure levels, arterial stiffness, and retinal microvascular calibers were assessed through pulse wave velocity and fundus photography, respectively.

Results
A significantly faster response within the five-choice reaction time test was observed after one week of AME supplementation, compared to placebo (p<0.05). In addition, the retinal arterial diameter as well as the arteriolar-to-venular ratio were significantly increased in the AME group, compared to placebo (p<0.05). However, throughout the study, blood pressure and arterial stiffness measures remained unchanged.

Conclusion
In conclusion, one week of AME supplementation improved cognitive performance reflected by a shorter movement time on the five-choice reaction time test. The improvement in the retinal microvasculature could be an indication that optimized vascular characteristics underlie the observed effect on cognitive performance. Therefore, we suggest that additional parameters related to vascular function should be further investigated to explore potential underlying mechanisms into more detail.