Lutein and its isomer zeaxanthin (L/Z) are dietary carotenoids that cross the blood brain barrier and exclusively accumulate in the macular region of the retina, where they are referred to as macular pigment (MP). MP density (MPD) has been reported to be significantly related to decreased risk of age-related macular degeneration as well as cognitive function in both young and older adults. Studies in non-human primates and humans find that MPD is significantly related to lutein brain concentrations. MPD, a non-invasive measure, is thus a biomarker for brain concentrations of L/Z. This may be of interest given the report that L/Z concentrations in the older adult brain are positively related to a variety of pre mortem cognitive measures. Furthermore, L/Z supplementation was found to significantly improve verbal fluency scores in healthy older adults. Pistachios are a bioavailable source of L/Z. L/Z are transported in the circulation primarily on high density lipoproteins (HDL) and HDL levels were found to be significantly related to MPD. Thus, increasing dietary intake of L/Z as well as changing lipoprotein levels may impact MPD. This is of interest given that a pistachio enriched diet has been reported to improve lipid profile in healthy and mild hypercholesterolemic patients. Based on the sum of these findings, the objective of this study was to investigate the effect of a long-term pistachio intervention on MPD.~The overall goal of the proposal is to determine whether the consumption of pistachios is a practical way to increase L/Z status. This will primarily be accomplished by performing a nutritional study to demonstrate that pistachios are a bioavailable source of L/Z to neural tissue (i.e., MP). Cross-sectional and intervention studies report a significant relationship between L/Z levels and ocular and cognitive health. Current L/Z intakes in the U.S. are lower than levels associated with health. This randomized, parallel study will test the efficacy of pistachios on increasing L/Z neural status (i.e., MPD).
Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss as people age. Studies have shown that lutein and zeaxanthin, nutrients found in green leafy vegetables and egg yolks, can help protect against AMD in older adults. These nutrients form a pigment in the retina (macular pigment) that can help protect the retina from light damage. Pistachios are rich sources of both lutein and zeaxanthin; thus, dietary intake of pistachios could serve as a beneficial food source for eye health.