ABSTRACT
In primates, the fovea appears as a yellow spot, as noted already in 1762 by Buzzi [1]. A rst thought was that this represented a retinal hole [2] or was due to postmortem changes [3,4]. However, in particular, after Wald’s paper on the photochemistry of vision [5], it was clear that it is caused by a pigment, which is concentrated in the central area of the retina, the so-called macular pigment [6]. Its specic yellow color is caused by carotenoids [7], more in particular the stereo-isomers lutein and zeaxanthin [8,9] and the intermediate meso-zeaxanthin [10]. Humans are unable to synthesize these carotenoids and are therefore dependent upon dietary intake. Serum levels associated with the normal diet are far below the maximal levels achieved by supplementation. The normal Western diet contains 1.3-3 mg/day of lutein and zeaxanthin combined [11]. The highest concentration of lutein is found in food sources with yellow color, such as corn and egg yolk. Dark, leafy green vegetables, such as spinach and kale, are also good sources of lutein. The same is true for orange peppers, followed by egg yolk, corn, and orange juice for zeaxanthin [12-15]. In general, fruit and vegetables contain 7-10 times more lutein than zeaxanthin. Meso-zeaxanthin is virtually nonexistent in food sources originating from plants. Lutein serum levels and the amount of macular pigment correlate, in particular in men [16-20]. It has further been shown that the amount of macular pigment can be increased by a dietary modication [11,21-23] or by supplements [17,24-38] in healthy subjects as well as in subjects with a diseased macula [39-42]. Note that meso-zeaxanthin is primarily formed in the retina following conversion from lutein [10,43].
