Dietary saturated fat and monounsaturated fat have reversible effects on brain function and the secretion of pro-inflammatory cytokines in young women

Background Previous literature suggests that a higher ratio of palmitic acid (PA)/oleic acid (OA) in the diet induces inflammation, which may result in deficient brain insulin signaling, and, secondarily, impaired physical activity, sleep efficiency, and cognitive functioning. Objective We hypothesized that lowering the typical dietary PA/OA would affect the activation of relevant brain networks during a working memory task and would also lower secretion of pro-inflammatory cytokines. Design In 12 female subjects participating in a randomized, cross-over trial comparing 3-week high PA diet (HPA) and low PA and a high OA diet (HOA), we evaluated functional magnetic resonance imaging (fMRI) using an N-back test of working memory, cytokine secretion by lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC), and plasma cytokine concentrations. Results Brain activation during the HPA diet compared to the HOA diet was increased in regions of the basal ganglia including the caudate and putamen (p < 0.005). In addition, compared to the HOA diet, during the HPA diet, the plasma concentrations of IL-6 (p = 0.04) and IL-1β (p = 0.05) were higher, and there was a higher secretion of IL-18 (p = 0.015) and a trend for higher IL-1β secretion (p = 0.066) from LPS-stimulated PBMCs. Conclusions The HPA diet resulted in increased brain activation in the basal ganglia compared to the HOA diet as well as increased secretion of pro-inflammatory cytokines. These data provide evidence that short-term (2 week) diet interventions impact brain network activation during a working memory task and that these effects are reversible since the order of the study diets was randomized. These data are consistent with the hypothesis that lowering the dietary PA content via substitution with OA also could affect cognition.