Astaxanthin is the marine carotenoid that is the most potent antioxidant in the nature — it is found in high concentrations in the wild salmon, the trout, the shrimp, the krill, the lobster, and the yeast (Phaffia rhodozyma), and it is responsible for the characteristic pink-red colouration of these marine organisms. The astaxanthin is unique among the carotenoids because it has a polar ionone ring at each end of the molecule and a long carbon chain in the middle — this unique structure gives the astaxanthin a much higher antioxidant potency than the other carotenoids (such as the beta-carotene, the lutein, and the zeaxanthin) and gives it the ability to span the entire cell membrane (with one ionone ring at the inner membrane surface and the other at the outer membrane surface), thereby providing the comprehensive antioxidant protection to the entire cell membrane. The astaxanthin is approximately 100 times more potent as an antioxidant than the beta-carotene, approximately 10 times more potent than the vitamin E, and it is one of the few carotenoids that does not act as a pro-oxidant (which is a problem with the beta-carotene at high doses, particularly in the smokers). Without adequate astaxanthin and antioxidant protection, the oxidative damage accumulates in the membranes, the proteins, and the DNA, the visual function declines (particularly in the retina, which is one of the most oxidative-stress-exposed tissues in the body), and the ageing accelerates — the hallmark of the astaxanthin deficiency and of the low-carotenoid diet. The typical dietary astaxanthin intake from the wild salmon is 0.5-2mg daily, and the therapeutic doses for the antioxidant and anti-inflammatory effects are 4-12mg of the astaxanthin supplement daily — making the astaxanthin supplementation one of the most evidence-based interventions for the antioxidant defence and for the healthy ageing.
Astaxanthin and the Visual Function
Astaxanthin is particularly important for the visual function because it is one of the few carotenoids that crosses the blood-retinal barrier and accumulates in the retina — where it provides the potent antioxidant protection to the photoreceptors, the retinal pigment epithelium, and the choroid. The retina is one of the most metabolically active and most oxidative-stress-exposed tissues in the body — the photoreceptors have a very high rate of the oxidative metabolism, they are exposed to the high-intensity light (particularly the blue light), and they are rich in the polyunsaturated fatty acids (which are highly susceptible to the lipid peroxidation). The astaxanthin protects the retina from the oxidative damage primarily through its potent antioxidant effects (scavenging the reactive oxygen species that are generated by the phototransduction cascade, by the mitochondrial oxidative metabolism, and by the photo-oxidation of the rhodopsin), through its anti-inflammatory effects (inhibiting the NF-kappaB and the VEGF, which are the key mediators of the diabetic retinopathy and of the age-related macular degeneration), and through its anti-apoptotic effects (protecting the photoreceptors from the apoptosis that is induced by the oxidative stress and by the retinal detachment). The astaxanthin also improves the ocular blood flow (by relaxing the ciliary arteries and by reducing the oxidative stress in the vascular endothelium), thereby improving the oxygen and nutrient delivery to the retina and the optic nerve.
The clinical importance of the astaxanthin for the visual function is underscored by the observation that the astaxanthin supplementation improves the visual function and reduces the eye fatigue in people with the digital eye strain and in people with the early age-related macular degeneration. A study in 40 adults with the eye strain found that the astaxanthin supplementation at 6mg daily for 4 weeks significantly improved the visual function (by 15-20%, as measured by the contrast sensitivity and the accommodation amplitude) and reduced the eye fatigue (by 30-40%, as measured by the Visual Analogue Scale) — demonstrating the potent visual-protective effect of the astaxanthin in humans.
Practical Application
For general astaxanthin supplementation for the antioxidant and visual support, the evidence-based approach is to supplement with 4-12mg of astaxanthin daily (as the astaxanthin from the Haematococcus pluvialis algae, which is the most bioavailable and the most stable form of the astaxanthin). The astaxanthin should be taken with the meals that contain the fats (to enhance the absorption, because the astaxanthin is a fat-soluble carotenoid), and it should be taken consistently for at least 4-8 weeks (to achieve the maximum tissue levels, which take time to accumulate due to the long half-life of the astaxanthin in the tissues). The astaxanthin is generally well-tolerated with no significant adverse effects at doses up to 40mg daily, and it does not cause the vitamin A toxicity (because it is not converted to the retinol like the beta-carotene is). For comprehensive antioxidant and visual support, astaxanthin pairs well with the omega-3 fatty acids (which are essential for the retinal function and which work synergistically with the astaxanthin for the anti-inflammatory and antioxidant effects in the retina), with the lutein and the zeaxanthin (which are the other major carotenoids in the retina and which work synergistically with the astaxanthin for the macular pigment protection), with the bilberry extract (which is rich in the anthocyanins and which has complementary visual-protective effects), and with the CoQ10 (which is required for the mitochondrial energy production in the photoreceptors and which works synergistically with the astaxanthin for the mitochondrial antioxidant defence).
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