Egg Consumption Alters Lutein Transport in the Circulation and Enhances Macular Pigment Density in Older Adults

Background: Lutein, a dietary carotenoid, is selectively taken up into the retina (measured as macular pigment optical density, MPOD) and brain. Thus, MPOD and brain lutein content are positively associated with cognition in older adults. However, the relationship between serum lutein and cognition is inconsistent. Therefore, serum lutein, which is carried primarily by high-density lipoproteins (HDLs) and to a lesser extent by low-density lipoproteins (LDLs) and very low-density lipoproteins (VLDLs), may not accurately reflect neural lutein levels. Eggs, which modulate circulating lipoproteins, are particularly effective at enriching lutein in neural tissue even when the serum lutein response is small. Methods: This study conducted post hoc analyses of a randomized controlled trial to test the effects of consuming 2 eggs vs. 4 oz. of egg whites daily for 6 months on lutein transport in the circulation, and the subsequent relationship to MPOD and cognitive function in older adults (50–85 years old; 20 women, 21 men). The primary outcome of determine the relationship between lutein contained in HDL and MPOD. A secondary outcome evaluated the relationship between HDL-contained lutein and cognitive function. Blood draws, MPOD measurements, and cognitive assessments were performed at baseline and after 6 months. Results: The change from baseline for MPOD was significant for the egg group (p < 0.05) but not for the egg white group (0.09 ± 0.04 OD vs. 0.02 ± 0.05 OD, respectively). Similarly, the change in the proportion of serum lutein carried by the HDL (LDL+VLDL) was significant in the egg group (59 ± 11% to 67 ± 18%; p < 0.05) but not in the egg white group (67 ± 22 to 60 ± 24%) after 6 months. However, there were no significant differences between groups. When evaluating only participants who increased the proportion of serum lutein carried by HDL in response to egg consumption (n = 14), a trend between this proportion and MPOD was observed (p = 0.07). An increase in the proportion of serum lutein on the HDL was also associated with improved visual memory and learning (p < 0.04). Conclusions: In this study, the relative distribution of serum lutein between the HDL and LDL reflected lutein accumulation in neural tissue and cognitive status in older adults. Thus, further investigation into the effects of eggs on promoting cognitive health by enhancing lutein delivery to the brain is warranted. Clinical Trial Registration: This study was registered at ClinicalTrials.gov (NCT01621646, https://clinicaltrials.gov/study/NCT01621646).