Dietary lipids are differentially associated with hippocampal-dependent relational memory in prepubescent children

Abstract

Background: Studies in rodents and older humans have shown that the hippocampus-a brain structure critical to relational/associative memory-has remarkable plasticity as a result of lifestyle factors (eg, exercise). However, the effect of dietary intake on hippocampal-dependent memory during childhood has remained unexamined.

Objective: We investigated the cross-sectional relation of dietary components characteristic of the Western diet, including saturated fatty acids (SFAs), omega-3 (n-3) fatty acids, and refined sugar, with hippocampal-dependent relational memory in prepubescent children.

Design: Participants aged 7-9 y (n = 52) reported their dietary intake by using the Youth-Adolescent Food-Frequency Questionnaire and completed memory tasks designed to assess relational (hippocampal-dependent) and item (hippocampal-independent) memory. Performance on the memory tasks was assessed with both direct (accuracy) and indirect (eye movement) measures.

Results: Partial correlations adjusted for body mass index showed a positive relation between relational memory accuracy and intake of omega-3 fatty acids and a negative relation of both relational and item memory accuracy with intake of SFAs. Potential confounding factors of age, sex, intelligence quotient, socioeconomic status, pubertal timing, and aerobic fitness (maximal oxygen volume) were not significantly related to any of the dietary intake measures. Eye movement measures of relational memory (preferential viewing to the target stimulus) showed a negative relation with intake of added sugar.

Conclusions: SFA intake was negatively associated with both forms of memory, whereas omega-3 fatty acid intake was selectively positively associated with hippocampal-dependent relational memory. These findings are among the first to show a link between habitual dietary intake and cognitive health as pertaining to hippocampal function in childhood. The Fitness Improves Thinking Kids (FITKids) and FITKids2 trials were registered at www.clinicaltrials.gov as NCT01334359 and NCT01619826, respectively.

FIGURE 1.

Test. A: Single-trial progression in the study (top) and test (bottom) phases. Durations of each trial component are specified in milliseconds. B: Example study and test trials from the Relational condition (top) and Item condition (bottom).

FIGURE 2.

Response locked eye-movement time courses depicting viewing to selected creatures during the test phase of the memory task (n = 52). The x-axis indicates onset of each 500-ms time bin. The vertical dotted line indicates the timing of behavioral response. Error bars indicate SEMs. Black asterisks indicate a significant pairwise difference in t tests at P < 0.05 (Bonferroni corrected). Gray asterisks indicate a significant pairwise difference at P < 0.05 (uncorrected). Gray shading indicates PDV—an eye-movement outcome measure assessed before behavioral response. PDV, preferential disproportionate viewing.

FIGURE 3.

Scatterplots depicting relations between intake of omega-3 (n−3) fatty acids (A and C) and SFAs (B and D) with Relational and Item memory accuracy (n = 52). Statistical relations were determined by using bivariate correlations (Pearson's r) with a significance threshold of P < 0.05. Each dietary intake measure is expressed as milligrams per kilocalorie consumed per day.