Abstract
We tested the hypothesis that ingestion of cocoa flavanols would improve cognition during acute hypoxia equivalent to 5500 m altitude (partial pressure of end-tidal oxygen = 45 mmHg). Using placebo-controlled double-blind trials, twelve participants ingested 15 mg.kg-1 of cocoa flavanols 90 minutes before completing cognitive tasks during normoxia and either poikilocapnic or isocapnic hypoxia (partial pressure of end-tidal carbon dioxide uncontrolled or maintained at the baseline value, respectively). Cerebral oxygenation was measured using functional near-infrared spectroscopy. Overall cognition was impaired by poikilocapnic hypoxia (main effect of hypoxia p = 0.008). Cocoa flavanols improved a measure of overall cognitive performance by 4 % compared to placebo (effect of flavanols p = 0.033) during hypoxia, indicating a change in performance from "low average" to "average". The hypoxia-induced decrease in cerebral oxygenation was two-fold greater with placebo than with cocoa flavanols (effect of flavanols p = 0.005). Subjective fatigue was increased by 900 % with placebo compared to flavanols during poikilocapnic hypoxia (effect of flavanols p = 0.004). Overall cognition was impaired by isocapnic hypoxia (effect of hypoxia p = 0.001) but was not improved by cocoa flavanols (mean improvement = 1 %; effect of flavanols p = 0.72). Reaction time was impaired by 8 % with flavanols during normoxia and further impaired by 11 % during isocapnic hypoxia (effect of flavanols p = 0.01). Our findings are the first to show that flavanol-mediated improvements in cognition and mood during normoxia persist during severe oxygen deprivation, conferring a neuroprotective effect.
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