Walnuts for the eye and vision

Abstract

The increase in lifespan with the consequent expansion of the aging of the world population has become an important challenge for public health. In recent decades, there has been a progressive increase in the incidence of debilitating diseases related to aging, including neurodegenerative disorders and eye diseases. Oxidative stress and inflammation are believed to play a critical role in several eye disorders, such as age‐related macular degeneration (AMD), diabetic retinopathy (DR), and cataracts, the leading causes of visual loss and blindness worldwide. Neurodegenerative events were also related to AMD and DR.Nutrients such as n‐3 polyunsaturated fatty acids (n‐3 PUFA) and antioxidants, specifically polyphenols, carotenoids, and vitamins C and E, may play a role in preventing both cognitive decline and retinal degenerative processes. Nuts have been described as a “superfood”, containing a notable variety of natural components that may have additive and/or synergistic properties for health and may prevent some pathologies. Nuts in general and walnuts in particular have a rich matrix of these bioactive components and through additive effects, have the potential to beneficially impact neuronal function in the brain and retina. Among different nuts, walnuts contain n‐3 PUFAs, specifically α‐linolenic acid (ALA; C18:3n‐3). It is believed that ALA may improve brain health indirectly through conversion to docosahexaenoic acid (DHA; C22:6n‐3), which has the ability to modulate brain plasticity and counteracts neuroinflammation in experimental studies. Other bioactive compounds in walnuts, such as arginine, tocopherols, folate, melatonin and polyphenols, also support neurological health and cognitive well‐being by modulating blood pressure, HDL function, glucoregulation, endothelial vasodilator function, oxidative status and vascular dysfunction. Polyphenols (including ellagitannins) have high antioxidant and prebiotic properties, which can regulate the gut microbiome, which is related to the increased risk of several inflammatory diseases. There is growing evidence that walnuts may contribute positively to eye disorders such as AMD, DR, and cataract prevention.