Alzheimer’s disease (AD) is an advanced stage of dementia which progressively worsens with time and is associated with a high degree of mortality. The disease is not part of normal aging, and is likely caused by various processes that damage nerve cells. Many clinical symptoms are associated with AD, including cognitive decline, memory loss, disorientation, language impairment and so on plus AD also has a pronounced effect on the family or their caregivers. In 2010 in the US alone there were over five million cases and over twenty million worldwide. The cause of AD is not fully known but there
As we age many systems and senses begin changing. Often the changes in these senses result in some very significant alterations and decreases in quality of life. It is estimated that approximately half a million Canadians are living with significant vision loss that impacts their quality of life. Ocular aging relates to structural, mechanical, and functional impairments in any of the structures of the eye from the cornea, the covering of the outer eye that offers both protection and light refraction, to the macula, the center of the retina in which age-related degeneration occurs. Conditions that are attributed to aging eyes include age-related macular degeneration, glaucoma, cataracts, and diabetic retinopathy. Risk factors for ocular aging include natural aging and genetics, environmental factors such as oxidative stress from smoking, chemical irritants or UV light, screen and artificial light exposure, diet, and finally comorbidities such as diabetes and high blood. In addition to vision loss damage to eyes and surrounding structures can also have a significant impact on the master pacemaker, our circadian rhythm, which in turn disrupts hormone, cell cycle regulation, immune function and more. Of course, the impact of vision loss and ocular damage justifies the extensive research being conducted into low-risk interventions such as lifestyle and nutritional treatments.
Physical protection of our eyes is an important step to prevent accelerated ocular aging. Such measures were previously only thought to relate only to UV blocking sunglasses. However, the adverse impacts of exposure to blue light (or short wavelength light) emitted by electronics and energy-efficient lightbulbs over time on the cells of the retina is a growing concern as we move to an increasingly digital world. Thus, it is important to switch to warmer filters when looking at your screens in the dark, adjusting overhead fluorescent lighting and avoiding screens and ambient light before bed. It is also important to hold screens and devices further from your eye (about an arm’s length at least) to prevent fatigue and strain. Such activities slow aging by preserving the rods and cones of the eye and have also been shown to improve mood and circadian rhythm with activation of the suprachiasmatic nuclei (SCN). While lifestyle interventions largely center around restricting or blocking harmful types of light reaching the eye, an internal protective approach ensures further fortification and protection of the eyes. Hence, nutritional interventions are important to introduce alongside these lifestyle interventions.
Nutrients for aging eye health
Perhaps the most prolific study of nutritional supplemental interventions risk of developing age-related eye diseases are the Age-Related Eye Disease Studies (AREDS1 and AREDS2) by the National Eye Institute. Results of these large-scale studies (both >5000 participants over 5 years) led to development of the AREDS formula including vitamin C, vitamin E, beta carotene, zinc, copper and follow up included lutein zeaxanthin omega 3 fatty acids EPA and DHA.
Carotenoids are pigments found in a wide variety of plants and are the reason many vegetables have rich colours depending on the type of wavelength absorbed. Certain carotenoids are considered “macular pigments” which are particularly intriguing for eye health as these pigments absorb high energy, short wavelength light (UV and blue light) that damage photoreceptors.
Lutein and Zeaxanthin
Two carotenoids of particular interest include lutein and zeaxanthin as they are selectively absorbed and sequestered in the retina. These carotenoids are thought to have excellent antioxidant, blue light filtration, contrast sensitivity mitigation of glare.
Differences in the form and function between the two carotenoids is also synergistic, with zeaxanthin predominant where cone density is highest and risk of oxidative damage is greatest, meaning it has more potent antioxidant effects and prevents lipid peroxidation by UV light. While lutein is thought to be more effective at light filtering.
Astaxanthin is a member of the xanthophyll subcategory of carotenoids – organic pigments give the rich pink colour seen in shrimp and other sea life that consume astaxanthin producing algae. A 2020 review of literature relating to the ocular benefits of astaxanthin supplementation cites both preclinical and clinical research. The authors focused on the role of astaxanthin in the setting of retinal diseases, ocular surface disorders, uveitis, cataract and asthenopia. Patients with AMD treated in combination with lutein/zeaxanthin and astaxanthin over a two-year period found significant improvement in visual acuity, contrast sensitivity and vision-related functions. Finally, the beneficial effects of astaxanthin in mitigating eye fatigue were demonstrated in at least one double-blind randomized clinical trial. Astaxanthin showed benefits for eye muscle endurance and objective eye fatigue scales as soon as 28 days after supplementation.
Benfotiamine (vitmain B1)
Benfotiamine is a lipid-soluble thiamine derivative and is thought to be particularly effective against vascular damage related to hyperglycemia. Hyperglycemia can increase risk of developing Advanced Glycation End-products (AGEs), warped cellular proteins that have been damaged by sugar which cause the lens to appear cloudy.
L-carnosine is a key antioxidant that minimizes and removes damaging free radicals inside our cells. It protects cells and helps maintain healthy cellular function, getting rid of damaged proteins that make cells old and dysfunctional. L-carnosine also protects against the formation of AGE’s. L-carnosine has been well studied in the treatment of cataracts with many participants experiencing a full resolution of their cataracts avoiding surgery. Studies with supplementation have shown individuals had clearer vision and less glare during night driving. 90% of patients in the treated group had improved visual acuity, and 89% showed improved glare sensitivity.
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Giannaccare G, Pellegrini M, Senni C, Bernabei F, Scorcia V, Cicero AFG. Clinical Applications of Astaxanthin in the Treatment of Ocular Diseases: Emerging Insights. Mar Drugs. 2020;18(5):239. Published 2020 May 1. doi:10.3390/md18050239
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Jia YP, Sun L, Yu HS, et al. The Pharmacological Effects of Lutein and Zeaxanthin on Visual Disorders and Cognition Diseases. Molecules. 2017;22(4):610. Published 2017 Apr 20. doi:10.3390/molecules22040610
Tosini, G.; Ferguson, I.; Tsubota, K. Effects of blue light on the circadian system and eye physiology. Mol. Vis. 2016, 22, 61–72.