Polyphenol-rich tart cherries (Prunus Cerasus, cv Montmorency) improve sustained attention, feelings of alertness and mental fatigue and influence the plasma metabolome in middle-aged adults: a randomised, placebo-controlled trial

There is accumulating evidence for the protective effects of polyphenols on risk factors associated with cognitive decline and mood disorders. Tart Montmorency cherries (MC) are a particularly rich source of anthocyanins and other polyphenols that have been shown to elicit antioxidant, anti-inflammatory and vasomodulatory actions. This study aimed to determine the influence of chronic MC supplementation on cognitive function, mood, sleep, health and cerebral blood flow. In a 3-month double-blinded, placebo-controlled parallel study, middle-aged adults (mean ± SD: 48 ± 6 years) were randomly assigned to either 30 ml twice daily of MC (n = 25) or the same amount of an isocaloric placebo (n = 25). Cognitive function and mood were assessed before and after supplementation using a computerised cognitive task battery and visual analogue scales. Cerebral blood flow was also monitored by near-infrared spectroscopy during the task battery, questionnaires were administered to determine subjective sleep and health status and plasma metabolomics was analysed before and after supplementation. After 3 months, the MC resulted in higher accuracy in digit vigilance (mean difference: 3.3, 95CI: 0.2, 6.4) with lower number of false alarms (mean difference: -1.2, 95CI: -2.0, -0.4) compared to the placebo. There was also a treatment effect for higher alertness (mean difference: 5.9, 95CI: 1.3, 10.5) and lower mental fatigue ratings (mean difference -9.5, 95CI: -16.5, -2.5) with MC. Plasma metabolomics revealed an increase in a number of amino acids in response to MC intake, but not placebo. These data suggest an anti-fatiguing effect of MC supplementation as well as the ability to improve sustained attention during times of high cognitive demand, this might be related to changes in amino acid metabolism