NAD+ Precursors (NR & NMN)

What it is

NAD⁺ (nicotinamide adenine dinucleotide) is a coenzyme essential for energy metabolism and a substrate for the sirtuin (SIRT1–7) and PARP enzyme families that regulate stress response, DNA repair, and chromatin state. Tissue NAD⁺ levels decline with age. NR (nicotinamide riboside) and NMN (nicotinamide mononucleotide) are precursors taken orally to raise NAD⁺.

Why it’s of interest

In pre-clinical work, restoring NAD⁺ improves mitochondrial function, stem-cell maintenance, and metabolic flexibility in aged mice. Human trials reliably show that supplementation raises blood NAD⁺, but downstream endpoint effects (insulin sensitivity, muscle function, frailty) have been inconsistent.

Mechanism

NAD⁺ serves as cofactor for >500 enzymatic reactions. Boosting it is proposed to:

• restore sirtuin activity (deacetylation of metabolic and chromatin substrates);
• support DNA-damage repair via PARPs without depleting cellular NAD;
• maintain redox balance in mitochondria.

Human evidence

• Multiple RCTs show NR/NMN raise circulating NAD⁺ in older adults.
• Effects on insulin sensitivity, blood pressure, and muscle endurance are small and mixed.
• No long-term mortality or healthspan data in humans.

Safety

Generally well-tolerated in short-term trials (up to ~1 g/day). Long-term safety profile is less established. Theoretical concerns include fuelling existing tumours (some cancers are highly NAD-dependent).

Related entries

See also: Mitochondrial dysfunction, Deregulated nutrient-sensing, David Sinclair.