Aging: an important factor for the pathogenesis of neurodegenerative diseases.

Aging is a natural process that is defined as a progressive deterioration of biological functions after the organism has attained its maximal reproductive competence. Aging leads to the accumulation of disabilities and diseases that limit normal body functions and is a major risk factor for neurodegenerative diseases. Many neurodegenerative diseases share oxidative stress and nitrosative stress as common terminal processes. According to free radical theory of aging, an elevation in reactive oxygen species (ROS) and reactive nitrogen species (RNS) damages neural membranes and induces oxidative and nitrosative stress. The increase in oxidative and nitrosative stress is accompanied by the concomitant decline in cognitive and motor performance in the elderly population, even in the absence of neurodegenerative diseases. Markedly increased rates of oxidative and nitrosative stress are the major factors associated with the pathogenesis of neurodegenerative diseases. Diet is a key environmental factor that affects the incidence of chronic neurodegenerative diseases. Dietary supplementation with polyphenols, resveratrol, ginkgo biloba, curcumin, ferulic acid, carotenoids, flavonoids, and n-3 fatty acids exerts beneficial effects not only through the scavenging of free radicals, but also by modulating signal transduction, gene expression, and restoring optimal neuronal communication.