NAD+ (Nicotinamide Adenine Dinucleotide) is an essential coenzyme present in every living cell, playing a central role in cellular energy production, DNA repair, and metabolic regulation. NAD+ levels naturally decline with age, contributing to fatigue, cognitive slowdown, and reduced cellular resilience. NAD+ is widely studied in longevity, cognitive health, and metabolic optimization research for its ability to support mitochondrial efficiency and cellular regeneration.