Habitual Consumption of a High-Fat-Sugar Diet: Disruptions on Hippocampal Memory and Executive Functioning

Abstract

There is growing evidence for the role of higher reported saturated fat and refined sugar diet (HFS) in impairing hippocampal-dependent memory. In consonance with animal research, human research showed that overconsumption of a HFS diet may impede the performance on supposedly hippocampal-dependent memory tasks and lead to reduced hippocampal volume. This study examines whether habitual consumption of a HFS diet disrupts performance on well-established hippocampal-dependent tasks and whether the disruption effect is partially mediated by diet’s effects on executive functions after adjusting for confounding factors. A total of 349 healthy young adults completed the hippocampal-dependent Pattern Separation and the Associative Memory task, measuring the ability to differentiate among similar memory representations and to form associations between previously unrelated items of information, respectively. Participants also completed a verbal memory task, assessing their word recall and word recognition ability, along with the Everyday Memory Questionnaire (EMQ-R) assessing subjective memory complaints. Furthermore, participants completed two executive functioning tasks: Trail Making and Stroop Task which assesses attention/ cognitive flexibility and the ability to inhibit cognitive interference, respectively. After adjusting for several potential confounding variables, we found that HFS diet predicted worse pattern separation scores and recognition memory accuracy. HFS intake was also significantly associated with poorer TMT task performance. Importantly, TMT task performance partially mediated the relationship between HFS diet and memory performance on the pattern separation task. Taken together, our findings suggest that HFS diet impairs not only hippocampus-dependent memory processing but also affects executive functioning, which can also indirectly impair memory. The findings are consistent with animal studies and call for further investigations on the psychological and neural mechanisms underlying the dietary effects on cognitive processes.