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NAD+ (Nicotinamide Adenine Dinucleotide) is a coenzyme present in every living cell, acting as a critical helper molecule in hundreds of metabolic reactions. It sits at the center of how your cells convert food into usable energy and how they respond to and repair DNA damage. The problem is that NAD+ levels decline steadily with age — dropping by roughly 50% between your 20s and 50s — which researchers believe contributes to fatigue, cognitive decline, and many age-related health changes.
NAD+ works in two main ways: it shuttles electrons during energy metabolism (essentially acting as a rechargeable battery inside cells), and it fuels a family of longevity-linked proteins called sirtuins and PARP enzymes that govern DNA repair, inflammation control, and cellular stress responses. Because NAD+ itself is poorly absorbed when taken orally, most supplements use precursor molecules — NMN or Nicotinamide Riboside (NR) — that the body converts into NAD+ once inside the cell. IV delivery bypasses digestion entirely, flooding cells with NAD+ directly.
IV infusions (250–1000 mg per session) offer the fastest and most complete delivery and are used in addiction recovery clinics and longevity medicine. Oral NR (typically 250–500 mg/day) and NMN (250–500 mg/day) are the most researched oral routes and are widely available. Sublingual and nasal spray forms exist but have less clinical data. Direct oral NAD+ supplements are sold but likely rely on gut conversion rather than direct absorption.
NAD+ was first identified by biochemists Arthur Harden and William Young in 1906 while studying fermentation. Its central role in cellular metabolism was mapped through much of the 20th century. Clinical interest in NAD+ as a therapeutic tool accelerated in the 2000s when researchers discovered its role in activating sirtuins — proteins linked to longevity — and its dramatic age-related decline. IV NAD+ therapy gained traction in addiction medicine in the 1960s through the work of South African physician Dr. William Hitt and was later popularized in the U.S. wellness and longevity medicine space.
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