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Abstract
A growing literature emphasizes the importance of lifestyle factors such as nutrition in successful aging. The current study examined if one year of supplementation with lutein (L) and zeaxanthin (Z), two nutrients with known antioxidative properties and cognitive benefits, impacted structural brain outcomes in older adults using a double-blind, randomized, placebo-controlled trial. Participants (20 male, 27 female) aged 65 – 87 years (M = 71.8 years, SD = 6.04 years) were randomized into supplement (N = 33) and placebo groups (N = 14). L and Z were measured as retinal and blood serum concentrations and structural brain outcomes, focusing on global and frontal-temporal lobe regions, were acquired using both MRI and DTI technologies. It was hypothesized that the supplement group would increase, maintain, or show attenuated loss in hypothesized regions-of-interest (ROIs) while the placebo group would show age-related declines in brain structural integrity over the course of the trial. While results showed age-related declines for frontal and temporal gray and white matter volumes and fornix white matter microstructure across both groups, only minimal differences were found between the supplement and placebo groups. However, exploratory analyses showed that individuals who responded better to supplementation (i.e., showed greater increases in retinal L & Z concentrations) showed less decline in global and prefrontal gray matter volume than supplement “non-responders.” While results suggest that one year of L and Z supplementation has limited effects on structural brain outcomes, it is likely not harmful and appears to provide benefits for other aspects of cognitive and brain health that could improve or extend quality of life for older adults. Additionally, there may be a sub-sample of individuals for whom supplementation of L and Z provides greater benefits.