The effects of bioavailable omega-3 polyunsaturated fatty acids, delivered at bedtime, on brain function, sleep, cognition and mood in healthy adults

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) are ‘essential’ fatty acids that cannot be manufactured de novo within the body and must be obtained via the diet, with the n-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) previously being found to have a wide range of bioactive properties within the body and particularly on brain function. However, in the UK and several other western nations, n-3 PUFA intake is found to fall below government and health organisation guidelines. Although previous research into the effects of n-3 PUFA intake and physiological and psychological outcomes is extensive, the previous research can be criticised for several methodological limitations relating to supplementation lengths, population samples, formulations of the supplements and placing little focus on the bioavailability and uptake of the fatty acids across the supplementation period. Therefore this thesis aimed to address the previous limitations identified within the research area to more accurately examine the effects of both a DHA- and EPA-rich supplement on measures of cerebral blood flow, sleep, memory consolidation, cognition and mood. Chapter 3 describes an intervention study that employs a near-infrared spectroscopy (NIRS) neuroimaging technique capable of measuring gross changes in cerebral haemodynamics across a 26 week supplementation period, a factor missing from the previous research conducted thus far. Chapter 4 describes a 26 week intervention study that measured parameters of sleep via subjective rating scales, actigraphy watches and urinary 6sulphatoxymelatonin (aMT6s). Chapter 5 describes a novel 26 week intervention study that aimed to measure overnight memory consolidation via completion of learning and recall tasks before and after sleeping. Finally, Chapter 6 describes a 26 week intervention study measuring aspects of episodic memory, working memory, information processing speed, executive function, attention and global cognition. The intervention studies that comprise this thesis include the first investigations that administer self-micro-emulsifying delivery system (SMEDS) formulated DHA- and EPA-rich supplements, designed to increase fatty acid bioavailability, dosed at bed-time, in healthy, young adults aged 25-49. Notably, there is evidence to suggest that supplementation with both the DHA-rich and EPArich treatments show a trend towards reducing the quantities of oxygenated haemoglobin during completion of serial subtraction tasks, interpreted as an increase in neural efficiency. N-3 PUFAs, particularly DHA, also improved objective measurements of sleep whilst the EPArich treatment improved global cognitive function and improved reaction times during both executive functioning and episodic memory tasks. Taken together, these findings suggest that 26 weeks’ n-3 PUFA supplementation is beneficial for a number of psychological and physiological brain parameters in healthy, young adult samples