Xanthophylls are the oxygenated carotenoids that are the most important filters of the blue light in the retina — they are the primary components of the macular pigment (along with the zeaxanthin, which is the other major xanthophyll in the macular pigment), and they are responsible for the optical density of the macular pigment and for the protection of the photoreceptors from the photo-oxidative damage that is caused by the high-energy blue light. The macular pigment is the yellow-coloured area in the centre of the macula (the fovea), where the visual acuity is the highest, and it is composed primarily of the two xanthophylls: the zeaxanthin and the meso-zeaxanthin (which are the predominant xanthophylls in the central fovea) and the lutein (which is the predominant xanthophyll in the peripheral macula). The xanthophylls are uniquely suited for their role in the macular pigment because they have the molecular structure that is optimal for the absorption of the blue light (they have the conjugated double bond system that absorbs the light in the 400-500 nm range, which is the blue light range) and because they have the antioxidant activity that protects the photoreceptors from the oxidative damage. Without adequate xanthophylls and macular pigment density, the blue light reaches the photoreceptors unfiltered, the photo-oxidative damage accumulates, and the age-related macular degeneration (AMD) develops — the hallmark of the xanthophyll deficiency and of the inadequate macular pigment protection. The typical dietary xanthophyll intake from the foods (particularly the leafy green vegetables, the corn, the eggs, and the oranges) is approximately 2-5mg daily (as the lutein and the zeaxanthin), and this is often insufficient to maintain the optimal macular pigment density and the adequate protection against the AMD — making the xanthophyll supplementation one of the most important and most evidence-based interventions for the prevention of the AMD.
Xanthophylls and the Blue Light Filtering
Xanthophylls protect the retina from the blue light primarily through their role as the primary filters of the blue light in the macular pigment — the macular pigment acts as a natural sunglasses that filters the high-energy blue light before it reaches the photoreceptors, and it is the density of the macular pigment (which is determined primarily by the xanthophyll intake and the xanthophyll status) that determines how effectively the blue light is filtered and how well the photoreceptors are protected. The xanthophylls (particularly the lutein and the zeaxanthin) absorb the blue light at the wavelengths of approximately 430-480 nm, and this absorption prevents the blue light from reaching the photoreceptors and from causing the photo-oxidative damage that is the primary driver of the AMD. The xanthophylls also protect the retina through their antioxidant activity — they are potent scavengers of the singlet oxygen and of the other reactive oxygen species that are generated by the high-energy blue light, and they therefore prevent the oxidative damage to the photoreceptor membranes and to the retinal pigment epithelium (RPE) cells. This dual mechanism of action (blue light filtering plus antioxidant activity) makes the xanthophylls the most effective and most specific nutrients for the prevention of the AMD — and it explains why the xanthophyll supplementation has been shown to be one of the most effective interventions for the reduction of the AMD risk and for the slowing of the AMD progression in multiple large clinical trials.
The clinical importance of the xanthophylls for the AMD prevention is underscored by the AREDS2 trial (Age-Related Eye Disease Study 2), which found that the supplementation with the lutein and the zeaxanthin (at 10mg and 2mg daily, respectively) significantly reduced the risk of the progression to the advanced AMD (by 20-25%) in people with the intermediate AMD — making the xanthophyll supplementation one of the most important and most evidence-based interventions for the AMD prevention that has ever been identified in the eye disease research.
Practical Application
For general xanthophyll supplementation for the macular pigment and for the AMD prevention, the evidence-based approach is to supplement with 10-20mg of lutein daily and 2-4mg of zeaxanthin daily (as the xanthophylls from the marigold flower extract or from the lutein-rich foods, taken with the meals that contain some fat to enhance the absorption). The xanthophylls should be taken with the omega-3 fatty acids (which support the macular health and which work synergistically with the xanthophylls for the retinal protection — the combination of the xanthophylls and the omega-3 fatty acids is one of the most effective and most comprehensive approaches for the AMD prevention and for the maintenance of the visual function). The xanthophylls are generally well-tolerated with no significant adverse effects at the doses that are used for the AMD prevention (up to 40mg daily of lutein and up to 10mg daily of zeaxanthin), and they do not have any known drug interactions or contraindications. For comprehensive macular pigment and AMD prevention, xanthophylls pair well with the omega-3 fatty acids (which are the primary structural components of the photoreceptor membranes and which have complementary anti-inflammatory and anti-angiogenic effects on the retina — the combination of the xanthophylls and the omega-3 fatty acids is one of the most effective approaches for the AMD prevention), with the vitamin C and the vitamin E (which are antioxidants that protect the retina from the oxidative damage and which work synergistically with the xanthophylls for the prevention of the photo-oxidative damage — the combination of the xanthophylls, the vitamin C, and the vitamin E is one of the most effective combinations for the retinal antioxidant defence), with the zinc (which is a cofactor for the superoxide dismutase enzyme and which supports the retinal antioxidant defence — the zinc deficiency is associated with an increased risk of the AMD, and the combined zinc and xanthophyll supplementation is one of the most effective approaches for the AMD prevention), and with the bilberry extract (which is a potent antioxidant that protects the retina from the oxidative damage and which works synergistically with the xanthophylls for the retinal protection — the combination of the xanthophylls and the bilberry is one of the most effective combinations for the AMD prevention and for the maintenance of the visual function).
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