Older adults show a preference for positive information, which disappears under high task demands. We examined whether glucose can help older adults preserve their positivity effect (PE) under high cognitive load. One hundred twenty-two adults (40 young and 42 older in Experiment 1; 40 older in Experiment 2) consumed a glucose (25 g) or a taste-matched placebo drink and completed an immediate recall task of emotional word-lists presented under high- and low-load conditions. Older adults showed PEs for low-load lists. Whereas PEs disappeared for older-placebo participants for high-load lists, older-glucose participants retained their positive preference. Providing the brain with extra energy resources can help older adults achieve PEs even under demanding conditions.