Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries in individuals over the age of 65. High intake of the dietary carotenoids lutein (L) and zeaxanthin (Z) is believed to reduce the risk of AMD. This study investigated the effects of long-term supplementation of primates with high doses of L or Z, and their 1:1 combination, and whether high supplemental doses cause ocular toxicity.

Eighteen female rhesus macaques were divided into 4 groups: control (n=3), L-treated (n=5, 9.34 mg/kg L and 0.66 mg/kg Z), Z-treated (n=5, 10 mg/kg Z), and L/Z-treated (n=5, L and Z each at 0.5 mg/kg). At 6 month intervals beginning at baseline, plasma samples were analyzed by HPLC for L, Z, and their metabolites. Carotenoid analysis of tissues, ocular examinations, and toxicity assays were performed.

High-dose supplementation of primates with L or Z significantly increased plasma, and ocular and other tissue concentrations of these carotenoids and their metabolites in most cases. Supplementation with a 1:1 dose of L and Z increased plasma concentrations of these carotenoids after 6 months, but baseline and month 12 levels in plasma and ocular tissues were not significantly different. Supplementation of primates with L or Z at high doses does not cause ocular or kidney toxicity.