Health Effects of Berry Anthocyanins: History
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Supplementation with anthocyanins, which are a type of flavonoids mainly found in various berries, is hypothesized to be a promising approach to lower the risk of developing cognitive decline. The aim of this systematic review was to provide a comprehensive overview of dietary intervention trials describing effects of berry anthocyanins on cognitive performance in humans, while also addressing potential underlying mechanisms. 

  • anthocyanins
  • cognitive performance
  • vascular function
  • cardiometabolic risk markers

1. Introduction

Cognitive performance encompasses multiple mental abilities that can be categorized into various domains, such as attention and psychomotor speed, memory, and executive function [1]. From childhood, cognitive performance quickly improves until young adulthood, after which it gradually starts declining [2]. Therefore, it is becoming increasingly relevant to focus on improving and/or maintaining cognitive performance to delay and prevent cognitive decline, and ultimately the onset of dementia [4]. This could be achieved by targeting potential mechanisms that drive cognitive performance [5,6].

An impaired vascular function is a common pathophysiological characteristic of multiple age-related conditions [7,8]. Vascular function can be assessed by determining endothelial function with methods such as brachial artery flow-mediated vasodilation (FMD) or the reactive hyperemia index (RHI) [9]. Previous research has already shown that vascular health declines with age leading to an increased risk of cognitive impairment, which may partly be explained by co-existing cardiometabolic risk factors, such as high blood pressure (BP) or a disturbed lipid profile such as altered low-density lipoprotein cholesterol (LDL-C) or high-density lipoprotein cholesterol (HDL-C) concentrations [11]. Therefore, dietary interventions that target vascular function and/or cardiometabolic risk markers may improve cognitive performance [14,15,16].

Therefore, increasing dietary intake of anthocyanins through supplementation could be a useful strategy to lower the risk of developing cognitive decline. A recent systematic review by Kent and colleagues [23] reported different intervention studies with beneficial effects of food-derived anthocyanins on cognitive performance. However, a systematic review designed to evaluate the effects of dietary anthocyanin interventions on cognitive performance and underlying mechanisms (i.e., vascular function and cardiometabolic risk markers) in an integrated manner has not been published yet. Therefore, the aim of this systematic literature review was to provide an overview of dietary intervention trials describing effects of berry anthocyanins on cognitive performance, vascular function, and cardiometabolic risk markers in humans.

2. The Effect of Berry Anthocyanins on Cognitive Performance

Of the eighteen studies that determined the effects of berry anthocyanins on cognitive performance outcomes, fifteen used a blueberry intervention, while the other three studies used either a chokeberry extract, a blackcurrant juice, or a blackcurrant extract. Results on cognitive performance were clustered based on the domains evaluated in the studies, i.e., (i) attention and psychomotor speed domain, (ii) executive function domain, (iii) memory domain, or (iv) other tests. Study results are shown in Table 2.
Table 2. The effect of berry anthocyanins on cognitive performance outcomes, compared to control.
Author (Year) Intervention Anthocyanin Dose Attention and Psychomotor Speed Executive Function Memory Other
      TMT-A MFT GPT FCRTT Miscellaneous TMT-B Stroop (M)ANT Go-No-Go Miscellaneous RAVLT - HVLT - CVLT VPAL and SPAL WRT n-back Miscellaneous  
Ahles (2020) [31] Chokeberry extract 16 mg       = (NCT)   =                  
27 mg     =   = (NCT)   =                  
Barfoot (2019) [33] Freeze-dried wild blueberry juice 253 mg                   ↑ (R)         = (TOWRE-2)
Boespflug (2018) [35] Freeze-dried blueberry powder 269 mg                           ↑?    
Bowtell (2017) [36] Blueberry extract 387 mg             =             = (ISLT) = (Groton Maze)
Cook (2020) [41] New Zealand blackcurrant extract 210 mg       = = (RVIP, SRT)         = (SWM)   = (S)        
Krikorian (2010) [53] Blueberry juice 428-598 mg 1                     ↑ (C) ↑ (V)        
Krikorian (2020) [54] Freeze-dried blueberry fruit powder 258 mg ↑?         =       ↑ (COWAT) = (H) ↑ (S)        
McNamara (2018) [58] Freeze-dried blueberry powder 269 mg =         =       = (COWAT) ↑ (H)          
Miller (2018) [59] Freeze-dried blueberry powder 230 mg # =         =   =   ↑ (TST) ↑ (C)       = (DST) = (VMWMT)
Traupe (2018) [70] Blueberry juice nr         ↑ (AMT)                 ↑ (Prose Memory)  
Watson (2019) [71] Blackcurrant juice 115.09 mg       = (DVT, SRTT)                      
Whyte (2015) [72] Blueberry juice 143 mg             =   =   =? (R)     = = (OLT)  
Whyte (2016) [73] Freeze-dried wild blueberry powder 127 mg   =             ↓? ↑? (PMT) ↑? (R)          
254 mg               = ↑? (PMT) ↑ (R)          
Whyte (2017) [74] Wild blueberry powder 253 mg                              
Whyte (2018) [75] Wild blueberry powder and extract 1.35 mg             = =     = (R)   =   = (CBT, SST, SMST)  
2.7 mg             = =     = (R)   =   = (CBT, SST, SMST)  
7 mg             = =     = (R)     ↑? (CBT); = (SST, SMST)  
Whyte (2020) [76] Wild blueberry powder 475 mg               =   ↑ (R)          
Whyte (2020) [30] Wild blueberry powder 253 mg                     = (R)       ↑ (VSGT); = (BPT, PRT)  
Wild blueberry powder 253 mg               ↑?   = Stop-Go, TST)        

↑ or ↓ or = indicates statistically significant improved or deteriorated values or no significant change in the intervention group compared to control. ? indicates a trend. # indicates that the value was calculated; 1 indicates that the dosage was dependent on body weight. Abbreviations: AMT: attention matrices test; BPT: brown peterson task; CBT: Corsi blocks test; COWAT: controlled oral word association; CVLT: california verbal learning test; DST: digit span task; DVT: Digit vigilance test; FCRTT: five-choice reaction time task; GPT: grooved pegboard test; HVLT: hopkins verbal learning test; ISLT: international shopping list task; MANT: modified attention network task; MFT: modified flanker test; nr: not reported; OLT: object location task; PMT: picture matching task; NCT: number cross out test; PRT: picture recognition task; RAVLT: rey auditory verbal learning test; RVIP: rapid visual information processing; SMST: sternberg memory scanning task; SPAL: spatial paired associates learning; SRTT: simple reaction time task; SST: serial subtractions task; SWM: spatial working memory task; TMT: trail making test; TOWRE-2: test of word reading efficiency; TST: task switching test; VMWMT: Virtual Morris Water Maze test; VPAL: verbal paired associates learning; VSGT: visuospatial grid task; WRT: word recognition task.

This entry is adapted from the peer-reviewed paper 10.3390/ijms22126482

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