nicotinamide adenine dinucleotide (NAD+), a coenzyme found in all living cells and crucial for fundamental biological processes. NAD+ helps drive cellular energy production by shuttling electrons in metabolic pathways like glycolysis and the Krebs cycle, ultimately enabling ATP synthesis for cell function. Beyond its metabolic role, NAD+ also participates in DNA repair and cell signaling, making it essential for maintaining cellular health and viability. Natural NAD+ levels decline progressively with age; by middle age, tissues may contain roughly half the NAD+ they had in youth. This age-related NAD+ depletion has prompted interest in NAD+ supplementation strategies to support cellular metabolism and possibly counteract aspects of aging.