The carotenoids lutein (L) zeaxanthin (Z) and meso-zeaxanthin (MZ) accumulate as macular pigment (MP) in the macula lutea, the central region of the retina responsible for central and fine detail vision. These carotenoids confer protection against age-related macular degeneration (AMD), the most common cause of blindness in the developed world. The light-filtering properties of MP may also improve visual performance and resolution. The first body of this work (referred to as the Meso-zeaxanthin Ocular Supplementation Trial, or the “MOST” Study) was to assess the serum and macular response to three different macular carotenoid formulations in normal subjects (n = 27) and in patients with AMD (n = 27). Subjects were randomly assigned to one of three interventions. Group 1: 20 mg L, 0.860 mg Z; Group 2: 10 mg L, 2 mg Z, 10 mg MZ; Group 3: 3 mg L, 2 mg Z, 17 mg MZ. Serum L, Z and MZ were quantified at baseline, 4 weeks, and 8 weeks using HPLC. MP optical density (MPOD) was assessed at baseline, 2, 4, 6, and 8 weeks at 0.25⁰, 0.5⁰, 1.0⁰ and 1.75⁰ of eccentricity using customised heterochromatic flicker photometry (cHFP). MP increased significantly at 0.25⁰, 0.5⁰, 1⁰ and 1.75⁰ of eccentricity in all Groups, with the exception of the 1.75⁰ eccentricity in Group 3. MP response was statistically similar for AMD versus normal subjects, with the exception of a significantly greater response for AMD subjects at 1.75⁰ eccentricity in Group 2. Serum L and Z increased significantly in Group 1 and Group 2, with no significant change in Group 3. Serum MZ increased significantly in Group 1, Group 2 and Group 3. While all three formulations achieved a significant and comparable increase in MPOD within eight weeks, the formulation containing L:MZ:Z in a 10:10:2 ratio (Group 2) was uniquely efficacious in terms of achieving maximum concentrations of circulating levels of all three carotenoids, thereby optimising the bioavailability of these compounds for capture by the target tissue (retina). The second body of this work (referred to as the Egg Xanthophyll Intervention Trial, or the “EXIT” Study) developed a novel, carotenoid-enriched hen egg as an alternative to traditional supplements to augment MP. This was achieved through the incorporation of oil-suspended carotenoids into the hen feed given to egg-laying hens. Yolk carotenoid concentrations were measured by HPLC. 568 ± 72 μg/yolk L and 732 ± 110 μg/yolk MZ were successfully incorporated into the egg yolks. Human macular and serum response to supplementation with carotenoid-enriched eggs were also investigated in an eight-week clinical study. The “enriched” group (n = 25) was supplemented with L:MZ eggs (described above) concurrently with a control group (n = 25) supplemented with standard hen eggs. Serum carotenoids and MP optical density were measured using HPLC and heterochromatic flicker photometry respectively. The novel carotenoid-enriched egg was successful in augmenting serum L, Z and MZ. It was not successful as a means to augment MP in the current study, likely due to the short eight-week study period. Further work is required to demonstrate a significant effect by this form of supplementation on MP levels.
|Publication status||Unpublished - 2015|
- Macular Carotenoids