Flavonoids and the aging brain.

Like in all other organs, the functional capacity of the human brain deteriorates over time. Pathological events such as oxidative stress, due to the elevated release of free radicals and reactive oxygen or nitrogen species, the subsequently enhanced oxidative modification of lipids, protein, and nucleic acids, and the modulation of apoptotic signaling pathways contribute to loss of brain function. The identification of neuroprotective food components is one strategy to facilitate healthy brain aging. Flavonoids were shown to activate key enzymes in mitochondrial respiration and to protect neuronal cells by acting as antioxidants, thus breaking the vicious cycle of oxidative stress and tissue damage. Furthermore, recent data indicate a favorable effect of flavonoids on neuro-inflammatory events. Whereas most of these effects have been shown in vitro, limited data in vivo are available, suggesting a rather low penetration of flavonoids into the brain. Nevertheless, several reports support the concept that flavonoid intake inhibits certain biochemical processes of brain aging, and might thus prevent to some extent the decline of cognitive functions with aging as well as the development or the course of neurodegenerative diseases. However, more data are needed to assess the true impact of flavonoids on brain aging.