The effect of phospholipid supplementation on cognitive performance across the lifespan

Phospholipids (PLs) are found abundantly in mammalian cell membranes and support cellular health and function. Their composition and shape promotes asymmetry within membrane bilayers and affects membrane physiological properties. PLs have the potential to facilitate cognitive function. A systematic review identified ten PL supplementation studies, including two acute and eight chronic (≥ 2 week) interventions. Cognitive benefits, mainly memory enhancement, were reported for a single PL, phosphatidylserine, and a bovine milk-derived PL composite, which was used in the supplementation studies reported in this thesis. The quality of the empirical studies reviewed was compromised by poor study designs and/or analytical approach. Moreover, the review highlighted a lack of empirical studies considering PL supplementation in children and adolescents. The focus of this thesis was to investigate the potential for bovine milk-derived PLs to promote cognitive function. Study 1 (n=70) was the first randomised placebo-controlled trial of the effects of PLs on cognitive performance in school-aged children (6-8 years). This was a six week intervention trial during which the children were tested every 3 weeks on measures of memory, motor skills, executive function and processing speed. Subjective evaluations of appetite, mood, motivation and mental alertness were also measured. The impact of the supplement on cognitive performance was limited. There was also no discernible effect on subjective state. Study 2 (n=50) extended limited existing evidence to examine effects of PL supplementation in middle-aged/older adults with a subjective memory complaint. This randomised placebo controlled trial investigated the acute and chronic effects of PL supplementation over 12 weeks on cognitive measures of memory and executive function and self-reports on the Cognitive Failures Questionnaire. Cognitive performance and the frequency of cognitive failures was measured at week 0 (acute), week 6 and week 12 (chronic). Few effects on cognitive performance following both acute and chronic supplement consumption were observed. Cognitive failures were reduced in participants who received the active supplement and reported greater cognitive failures at baseline. Across both studies, participants’ demographic characteristics and baseline performance had a greater impact on cognitive performance than the active supplement. Overall, the findings from the PL intervention studies presented in this thesis add to the existing heterogeneous evidence of the potential for PLs to moderate cognitive performance. Despite strong mechanistic data suggesting PLs could confer beneficial and/or protective effects on cognition, this thesis did not find clear evidence of a benefit of PLs for cognition. Further examination of the potential benefits of PLs in other formulations for cognitive function in young and old samples is warranted.