Polyunsaturated fatty acids and blood circulation in the forebrain during a mental arithmetic task.

The effects of polyunsaturated fatty acids on human cerebral blood oxygenation have yet to be extensively investigated. In this study, healthy participants (14 men, 40 women) aged between 20 and 49 years were recruited. All female participants entered the trial at the start of their menstrual cycle. Blood was sampled before measuring cerebral blood oxygenation in the prefrontal cortex (PFC) and prior to administering two kinds of questionnaires, the Profile of Mood States (POMS) and a questionnaire regarding participants' arousal level. Blood oxygenation in the PFC was continuously monitored immediately before and during the Uchida-Kraepelin Performance (UKP) test as a mental arithmetic task. Changes in the tissue oxygenation index (the ratio of oxyhemoglobin to oxyhemoglobin+deoxyhemoglobin; TOI, a simplified index for cerebral blood circulation) were measured by near-infrared spectroscopy. Multiple regression analysis was performed with sex, age, smoking and drinking as confounding factors. Eicosapentaenoic acid (EPA) was positively associated with TOI, which was positively associated with arousal level and inversely associated with negative mood (POMS). EPA and docosahexaenoic acid were inversely associated with depression-dejection (POMS) and positively associated with arousal level and overall performance in the UKP test. We suggest that EPA might increase the oxygenation level in the PFC, in turn improving various psychological parameters and performance.