Effects of egg yolk choline intake on cognitive functions and plasma choline levels in healthy middle-aged and older Japanese: A Randomized double-blinded placebo-controlled parallel-group study

Background: Choline, as a neurotransmitter acetylcholine precursor, is reportedly associated with cognitive function. Although there are several cohort and animal studies on choline-containing foods and cognitive function, only a few interventional studies were reported. This study aimed to investigate the effect of consuming 300 mg of egg yolk choline per day on cognitive function of Japanese adults. Egg yolk is a rich source of choline containing different chemical forms such as phosphatidylcholine, lysophosphatidylcholine, and a-glycerophosphocholine. Methods A 12-week, randomized, double-blind, placebo-controlled, parallel-group study was conducted in 60 middle-aged and elderly males and females (46.7% female) aged ≥ 60 years and ≤ 80 years without dementia. Participants were randomly assigned to the placebo and choline groups. The choline group received a supplement containing egg yolk choline (300 mg/day), and the placebo group received an egg yolk supplement free from choline for 12 weeks. Assessments of Cognitrax, Trail Making Tests A and B, the MOS 36-Item Short-Form Health Survey, the Simplified Japanese Version of the WHO-Five Well-Being Index, and plasma choline levels were performed before and 6 and 12 weeks after supplement intake. Results The analysis excluded 19 subjects (9 in the placebo group and 10 in the choline group) who met the criteria for discontinuation and participant compliance. and the results revealed significantly higher verbal memory scores and verbal memory test-correct hit (delay) in the choline group compared with the placebo group at 6 and 12 weeks. The plasma-free choline level was significantly higher in the choline group compared with the placebo group at 6 weeks. Conversely, the choline group showed significantly lower Cognitrax processing speed scores, symbol digit coding testing correct responses, and SF-36 physical quality of life summary scores compared to the placebo group at 6 weeks. No significant differences were found for the other parameters between two groups. Conclusions The results showed the possibility that continued intake of egg yolk choline improved verbal memory, which is a part of cognitive functions. To confirm observed effects of egg yolk choline more well-designed, large-scale studies are warranted. Trial registration: Study protocols were pre-registered in the Clinical Trials Registration System (UMIN-CTR) (UMIN 000045050).