This prospective randomized double-masked study investigated the effects of 20 mg lutein supplementation with two different capsules (beeswax or glycerol fatty acid esters) for 6 months on the fellow eyes of 39 Japanese patients with unilateral age-related macular degeneration, and assessed the factors associated with baseline plasma lutein concentration via lifestyle interviews. Macular pigment optical density (MPOD), determined with the two-wavelength autofluorescence method, increased over time in the beeswax group (ANOVA, p = 0.0451), although the increase from 3 months to 6 months was only marginally significant. No significant increase was observed in the glycerol fatty acid esters group (ANOVA, p = 0.7396). Plasma lutein concentrations significantly increased at 3 and 6 months from baseline in both groups (both p < 0.01). In a multiple regression model, age was negatively associated with higher plasma lutein concentration (p = 0.0305), while consumption of green vegetables was positively associated with baseline plasma lutein concentration (p = 0.0322). In conclusion, a significant increase in MPOD was not fully confirmed with 6 months intake duration despite a significant increase in plasma lutein concentrations. Consumption of green vegetable was confirmed to be associated with plasma lutein concentration after adjusting for other potential factors including age.