Objective: To investigate whether nutritional factors and possible risk factors for cataract influence the lens optical density (LOD). Design: Three hundred seventy-six subjects, aged 18 to 75 years, were recruited. In a cross-sectional design, serum was analyzed for lutein, zeaxanthin, vitamin C, α-tocopherol, and cholesterol levels. Adipose tissue (n = 187) was analyzed for lutein level. The LOD and the macular pigment optical density (MPOD) were measured by spectral fundus reflectance. Results: The mean ± SD LOD at 420 nm was 0.52 ± 0.17. It showed a significant association with age (β=.008, P<001) and MPOD (β=-.096, P=.02). For subjects 50 years and younger (mean±SD LOD, 0.45±0.11), we found only a single significant β coefficient, for age (β=.006, P<001). For subjects older than 50 years (mean±SD LOD, 0.68±0.16), we found significant β coefficients for age (β=.011, P<.001) and MPOD (β=-.240, P=.005). Controlling for age, we found no associations between LOD and other possible risk factors for age-related cataract or serum or adipose tissue concentrations of carotenoids, vitamin C, and α-tocopherol. Conclusions: Macular pigment is composed of lutein and zeaxanthin, the only carotenoids found in human lenses. The inverse relationship between LOD and MPOD suggests that lutein and zeaxanthin may retard aging of the lens. Chemicals/CAS: alpha tocopherol, 1406-18-4, 1406-70-8, 52225-20-4, 58-95-7, 59-02-9; ascorbic acid, 134-03-2, 15421-15-5, 50-81-7; cholesterol, 57-88-5; xanthophyll, 127-40-2, 52842-48-5; zeaxanthin, 144-68-3; alpha-Tocopherol, 59-02-9; Ascorbic Acid, 50-81-7; beta Carotene, 7235-40-7; Cholesterol, 57-88-5; Lutein, 127-40-2; Retinal Pigments; Xanthophylls; zeaxanthin, 144-68-3