Written by Angeline A. De Leon, Staff Writer. Compared to the control group, supplementation with lutein and zeaxanthin significantly improved macular pigment optical density and cognitive function in the participating community-dwelling older adults.
Aging involves a gradual degradation of structural and functional neural connectivity. From a dietary perspective, the correlation between lower levels of antioxidant intake and higher levels of oxidative stress in the brain 1 suggests that larger-scale loss of white matter integrity, for example, seen in older adults also involves peroxidation of brain lipids at an earlier stage 2. Researchers have identified certain key dietary antioxidants, namely lutein and zeaxanthin (carotenoids involved in protecting and maintaining healthy vision), that may be capable of reducing age-related oxidative stress in the brain and potentially even stimulate neurogenesis 3. In younger adults, studies have associated lutein and zeaxanthin with increased levels of brain-derived neural growth factor 4 and improved visual processing speed 5, which researchers estimate may be due to the antioxidants’ capacity to promote brain connectivity and neural efficiency 6. When combined with the omega-3 fatty acid DHA, supplementation with lutein and zeaxanthin can also improve verbal fluency, memory, and learning rate 7. Considering evidence of lutein and zeaxanthin to improve cognitive function, investigators at the University of Georgia (2017) extended basic findings to older adults, examining whether intake of lutein and zeaxanthin might benefit cognitive performance in seniors.
A total of 51 healthy, community-dwelling older adults (mean age = 73.7 years) were enrolled in a double-blind, randomized, placebo-controlled trial. Participants were randomly allocated to ingest either 10 mg of lutein and 2 mg of zeaxanthin or a visually identical placebo once daily for 12 months. Macular pigment optical density (MPOD) was measured as a biomarker of cortical lutein and zeaxanthin levels, and at baseline, Month 4, Month 8, and Month 12, cognitive function was assessed using a computerized test battery (CNS Vital Signs) evaluating verbal memory, visual memory, reasoning ability, executive function, psychomotor speed, cognitive flexibility, and neurocognitive index.
Analyses indicated that from baseline to 12-month follow-up, MPOD significantly increased for the lutein and zeaxanthin group (from 0.52 +/- 0.19 to 0.59 +/- 0.22, p < 0.03), but not placebo. Relative to placebo, the active supplement group also demonstrated significantly improved performance on complex attention (p < 0.02) and cognitive flexibility (p < 0.04), with an observed trend for executive function (p = 0.073). MPOD was shown to be significantly correlated to performance in the reasoning domain at the 12-month time point (r = 0.45, p = 0.04). In male subjects, supplementation with lutein and zeaxanthin was also seen to boost composite memory (p = 0.04).
Based on findings, the cognitive benefits of carotenoid supplementation are evident in the older adult population. Year-long intake of lutein and zeaxanthin proved effective in improving several aspects of cognitive function in older adults, as confirmed by correlations between MPOD and cognitive test scores. The study’s use of a control group whose daily dietary intake already regularly included lutein and zeaxanthin (i.e., convenience sampling) may be considered a limitation of the study. Future studies would benefit from examining the effects of carotenoid intake on subjects with relative deficiencies in lutein and zeaxanthin. Gender differences in the impact of lutein and zeaxanthin on cognition should also be further explored, both in younger and older population groups.
Source: Hammond Jr. BR, Miller SL, Bellow MO, et al. Effects of lutein/zeaxanthin supplementation on the cognitive function of community dwelling older adults: a randomized, double-masked, placebo-controlled trial. Frontiers in Aging Neuroscience. 2017; 9(254). DOI: 10.3389/fnagi.2017.00254.
Copyright © 2017 Hammond, Miller, Bello, Lindbergh, Mewborn and Renzi-Hammond. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.
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Posted October 22, 2018.
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