NAD+ Precursors (NMN and NR): They Raise a Biomarker, Not Proven to Slow Aging

Summary

NAD+ precursors — nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) — are sold as anti-aging pills, and the biomarker they move is real: NAD+ genuinely declines with age, and both compounds reliably raise blood NAD+ in humans across double-blind trials, a legitimate and replicated pharmacodynamic effect, with a few scattered surrogate signals (muscle insulin signalling, a muscle NAD+ metabolome shift, an anti-inflammatory transcriptomic signature) — yet the outcome that is actually marketed, slowing aging or extending healthspan and lifespan, has never been shown in a single hum