Phytochemical Supplementation Regulates Immune Function and Modulates Cell Survival Signaling, Enhancing Neuroprotection and Cognitive Functions in Aging

Phytochemicals present in plant sources, including fruits and vegetables, both fresh and processed, have been known for their positive effects on human health. Phytochemical supplementation regulates immune functions through immunomodulation, controls cell survival signaling through its antioxidant properties, and acts as a selective modulator of signal transduction. Their roles may be stimulatory or suppressive, depending on the quantity of phytochemicals consumed. Phytochemicals in green tea can improve both cellular and humoral immune responses. Resveratrol exhibits anti-inflammatory and immunomodulatory properties. Carotenoids boost both specific and nonspecific immune activity. Flavonoids have antioxidant, antiallergic, anti-inflammatory, antithrombotic, antibacterial, antiviral, amyloidogenic, hepatoprotective, neurotrophic protective, anticarcinogenic, and immunomodulatory properties. Quercetin and curcumin, which are dietary polyphenols, significantly impact the modulation of numerous cell signaling networks and promote healthy aging. The critical signaling pathways that increase the prolonged existence of the organism in aging are AMPK, Sirtuin 1 (SIRT1), mTOR, Akt, IGF, SKA, and PKA. The phytochemicals modulated growth factors and proteins involved in inflammatory pathways and apoptosis, including NF-κB, Bad, caspase 9, Fast, and Bcl-2. Aging is a risk factor for most diseases, and phytochemicals act as immunomodulators by diminishing immunosenescence and enhancing antioxidant activity. They also help decrease oxidative stress on cells and modify cellular senescence, ultimately reducing the rate of diseases associated with aging and promoting healthy aging. This review will concentrate on the different sources of phytochemicals, their properties, and the defensive mechanisms of aging.