Glycation is known as an important factor inducing human diseases, including diabetic complications. As oxidative stress contributes to procedures of glycation, antioxidants may inhibit glycation and delay the progression of diabetic complications. Our previous investigation of human aqueous humor after the intake of a lutein-containing supplement demonstrated increases in antioxidative activities and decreases in peroxidative products. This study enrolled 25 patients with diabetes (DM group) and 100 age-matched controls. Aqueous humor samples were collected during cataract surgery before and after 6 weeks of oral intake of the lutein-containing antioxidant supplement, Ocuvite + Lutein®. The carboxymethyl-lysine level (CML) was measured as an indicator of glycation. Levels of superoxide dismutase activities (SOD) and total hydroperoxide (TH) were measured as indicators of oxidation. Changes after intake and the differences between age-matched controls and the DM group were evaluated. CML decreased after intake among the DM group, while there were no changes among the age-matched controls. SOD was significantly lower and TH was significantly higher in the DM group as compared to the age-matched controls, both before and after intake. In line with the decreases in glycation, the intake of lutein-containing antioxidant supplements may inhibit diabetic complications in diabetic patients.