NAD+ (nicotinamide adenine dinucleotide) is a vital coenzyme found in every living cell, essential for energy production, cellular repair, and metabolic function, and increasingly recognized in longevity and anti-aging research for its role in supporting mitochondrial health and regulating key biological processes; NAD+ functions as a critical electron carrier in cellular respiration, enabling the conversion of nutrients into ATP (cellular energy), while also activating important enzymes such as sirtuins and PARPs that are involved in DNA repair, gene expression, and cellular stress resistance; as NAD+ levels naturally decline with age, this reduction has been linked to fatigue, decreased metabolic efficiency, and signs of aging, driving growing interest in NAD+ supplementation and precursor compounds like nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) to help restore optimal levels; research suggests that increasing NAD+ availability may support improved energy levels, cognitive function, metabolic health, and cellular resilience, while also playing a role in muscle recovery and overall vitality; widely used in wellness and biohacking communities through intravenous therapies, injections, and oral supplements, NAD+ has become a cornerstone molecule in modern longevity science due to its foundational role in maintaining cellular health and optimizing biological performance.