Abstract
BACKGROUND: Pistachios are a bioavailable source of the xanthophyll lutein. Along with zeaxanthin, these plant pigments are major components of macular pigment (MP) in the human retina. MP can be non-invasively measured and is referred to as MP optical density (MPOD). MPOD is modifiable with dietary interventions that include lutein and zeaxanthin (L/Z). Higher MPOD protects the eye from light damage and is positively associated with eye health. OBJECTIVES: This dietary intervention study aimed to evaluate the effect of pistachio consumption on MPOD. METHODS: This single-blinded, randomized controlled trial compared a 12-week pistachio intervention (2 oz/d) with usual diet (UD) on MPOD and serum L/Z in middle-aged to older healthy adults (n = 36) in a 1:1 randomization scheme. Participants were selected for habitually low L/Z intake and low baseline MPOD. MPOD was measured using heterochromatic flicker photometry at 4 retinal eccentricities during baseline, week 6, and week 12 study visits. Serum L/Z was analyzed using high-performance liquid chromatography. Primary statistical analysis was conducted on an intent-to-treat basis using repeated-measure analysis of variance. RESULTS: Compared with UD, MPOD of the participants in the pistachio intervention group (PIS) had significantly increased (P < 0.001) at all eccentricities over the initial 6-wk period. This increase was maintained at week 12. MPOD in the UD participants did not change during the 12-week period. Serum lutein concentration followed a similar pattern to MPOD; serum cis-lutein and zeaxanthin did not change in either group over the 12-wk intervention. CONCLUSIONS: The results of our study demonstrate that a dietary intervention with pistachios is efficacious in increasing MPOD in healthy adults selected for habitually low intake of L/Z and low baseline MPOD. This suggests that pistachio consumption could be an effective dietary strategy for preserving eye health. Future studies need to evaluate the generalizability of our findings to other populations. This trial was registered at clinicaltrials.gov as NCT05283941.