NAD+ is a coenzyme for oxidation and reduction reactions. It is central to energy metabolism. This enzyme influences many key cellular functions directly and indirectly, including metabolic pathways, DNA repair, chromatin remodeling, cellular aging-associated and immune cell function. This decline in NAD+ levels is causally linked to numerous aging-associated diseases, including cognitive decline, cancer, metabolic disease, sarcopenia, and frailty. NAD+ plays an integral role in mitochondrial function by accepting electrons from substrates and transferring them to the electron transport chain (ETC). This process generates ATP, which powers the cell. NAD+ serves as a substrate for sirtuins, which modify proteins in the mitochondria to help ensure optimal mitochondrial function.