How the Dietary Saturated/Monounsaturated Fatty Acid Ratio Modulates Brain Function in Older Adults

Abstract

Palmitic acid (PA) and oleic acid (OA) are, respectively, the most prevalent saturated and monounsaturated fatty acids (SFAs, MUFAs) in the human diet. The objective of this brief review is to explore how this ratio affects brain function. In two double-masked crossover trials in young adults, physical activity was greater and systemic inflammatory tone was diminished under a diet with a lower dietary PA/OA ratio compared to that of the typical North American Diet, and anger and total mood disturbance were diminished under the low- compared to the higher-PA/OA diet. In another diet trial in young women, functional magnetic resonance imaging showed that lowering the dietary PA/OA ratio decreased brain activation in regions of the basal ganglia, suggesting that brain function was reversibly altered by the dietary PA/OA ratio. Recently, a crossover trial in older adults showed that a lower dietary PA/OA ratio decreased systemic inflammatory tone and caused the greater activation of a working memory network. As people age, there are declines in cognition that impact functional abilities and independence, but the preservation of structural aspects of the brain in normal aging implies that there is the possibility of slowing, stopping, or reversing cognitive changes that impact daily life. Reducing pro-inflammatory cytokine secretion by lowering habitual PA intake for even brief periods of time may be one modality to improve cognitive function in older adults, not only in those with typical cognitive aging but in those with dementia as well.

Keywords: brain function; cytokines; inflammatory tone; monounsaturated fat; oleic acid; palmitic acid; saturated fat.

Figure 1

Dietary PA/OA ratio: metabolic and immunologic effects in human subjects.

Figure 2

Mechanisms by which the dietary PA/OA ratio affects brain function.