Research confirms that the potent antioxidant astaxanthin may reduce oxidative stress, reduce lipid peroxidation, reduce the risk of chronic diseases including cancer and cardiovascular disease, modulate the immune system, lower inflammatory markers including C-reactive protein (CRP), reduce the risk of neurodegenerative diseases, block oxidative DNA damage, lower triglyceride levels and increase high density lipoprotein (HDL) cholesterol.[1,2]
However, one of astaxanthin’s most exciting roles is in promoting and protecting the health of the eyes. The pathogenesis of a range of eye disorders has been attributed to cellular oxidative damage from singlet oxygen and free radical generation. These contributing factors indicate the potential benefits of astaxanthin as an antioxidant supplement for eye health.
An extensive range of clinical trials and in vitro research have investigated the effects of astaxanthin in the prevention and treatment of eye diseases, as well as maintaining healthy eye function. The benefits of astaxanthin range from reducing eye strain to having a potential role in the treatment of age-related macular degeneration. Its ability to cross the blood-retinal brain barrier and accumulate in the retina adds to astaxanthin’s benefits in the treatment of eye diseases.
Age-related macular degeneration
One of the proposed mechanisms behind the development and progression of age-related macular degeneration (AMD) is the effect of oxidative stress on retinal pigment epithelial (RPE) cells resulting in degeneration, dysfunction and cell loss. Due to its strong antioxidant effects, astaxanthin has been investigated as a potential treatment to protect RPE cells from oxidative damage and to slow the progression of AMD.
A two-year study investigating the effects of an antioxidant supplement (including 4mg of astaxanthin) on AMD symptoms found that active treatment resulted in clinically meaningful stabilisations and improvements in visual acuity, contrast sensitivity and visual functioning, indicating that antioxidants may help to both delay the progression of AMD and improve visual performances.
In vitro research has shown that astaxanthin has a protective effect on RPE cells exposed to hydrogen peroxide. Astaxanthin was able to reduce hydrogen peroxide-induced cell death, apoptosis and intracellular generation of reactive oxygen species (ROS), with the researchers concluding that astaxanthin may provide a valuable therapeutic strategy for early AMD by protecting RPE cells from oxidative damage.
Eye fatigue, eye strain and visual sharpness
Japanese researchers have extensively studied the effect of astaxanthin supplementation on eye fatigue, eye strain, blurred vision and presbyopia, which is the inability to focus on near objects.
A dose of 9mg of astaxanthin per day was found to significantly improve eye strain in visual display terminal workers after four weeks of supplementation. A similar dose regime of 6mg of astaxanthin for four weeks resulted in improved pupillary constriction, and improved the symptoms of blurred vision, eye strain and difficulty to see near objects in individuals with presbyopia. In another trial, both a 4mg and 12mg dose of astaxanthin for four weeks significantly improved uncorrected far visual acuity.
Astaxanthin vs other antioxidants
Astaxanthin’s unique molecular structure accounts for the strength of its antioxidant activity, which is higher than other carotenoids such as zeaxanthin, lutein and betacarotene, and 100 to 550 times stronger than alpha-tocopherol.[9,10]
Astaxanthin contains polar ionone rings at each end which contain hydroxyl (OH) and keto (C=O) moieties. A non-polar zone consisting of conjugated carbon-carbon bonds joins the ionone rings and forms the backbone of astaxanthin. Both of these structural factors contribute to astaxanthin’s antioxidant activity and set it apart from other antioxidants. The polar-nonpolar-polar layout allows astaxanthin to span the cellular membrane and neutralise reactive molecular species both within the membrane’s nonpolar (hydrophobic) core and along its polar (hydrophilic) boundary zones giving superior overall antioxidant protection.
Carotenoids such as betacarotene may show pro-oxidant properties under certain conditions. Astaxanthin differs in this regard and is considered a pure antioxidant with no pro-oxidant capabilities.
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