NAD+

Background

NAD+ (nicotinamide adenine dinucleotide) is one of the most abundant non-protein molecules in living cells. It exists in oxidized (NAD+) and reduced (NADH) forms and is essential for hundreds of enzymatic reactions, most centrally in glycolysis, the citric acid cycle, and electron transport.

Cellular NAD+ declines with age — by some measures 30–50% from young to old adulthood — and this decline is one of the better-replicated molecular features of aging. The decline drives reduced sirtuin and PARP activity, which feeds back into the broader aging phenotype.

NAD+ is included in peptide catalogs primarily because injectable NAD+ is sold and used in similar clinical and research contexts as peptides. Pharmacologically, however, it is a nucleotide coenzyme, not a peptide.

Mechanism in depth

NAD+ has two main functional roles:

1. Redox cofactor — accepts and donates electrons (NAD+ ↔ NADH) in metabolic reactions. This is essential but largely catalytic; the pool size matters less than the ratio.
2. Substrate — consumed by NAD+-consuming enzymes including sirtuins (which cleave NAD+ as part of their deacetylation reaction) and PARPs (which use NAD+ for poly-ADP-ribosylation during DNA repair). For this role, absolute pool size matters.

It is the second role that drives most of the "boost NAD+" thinking. Raising NAD+ raises substrate availability for sirtuins and PARPs, both of which have anti-aging functional signatures.

Human evidence

Almost all robust human evidence is for precursors, not direct NAD+:

• Multiple controlled trials of oral NR (250–1000 mg/day) raise blood NAD+ by 30–50%, are well-tolerated for months, and show small effects on inflammatory markers and blood pressure.
• Oral NMN at 250–500 mg/day raises NAD+ similarly in healthy and prediabetic adults; one trial in prediabetic women showed improved muscle insulin sensitivity.
• Direct IV/SC NAD+ studies are smaller, mostly observational, and dominated by subjective endpoints (energy, mood, recovery).

The honest summary: precursor supplementation raises NAD+ reliably and has a clean safety profile; functional benefits in healthy adults are modest and variable. Direct NAD+ infusion is well-known anecdotally but poorly characterized in controlled trials.

Animal evidence

Extensive. In rodent models:

• NAD+ precursor supplementation rescues mitochondrial function in aged muscle, liver, and brain.
• Sirtuin activation is dose-dependent on NAD+ availability.
• Some longevity extension in lower organisms (C. elegans, yeast); modest or context-dependent in mice.

A growing concern is the bidirectional cancer effect: NAD+ is required for proliferation, and several preclinical studies show precursor supplementation accelerating tumor growth in established cancer models. This is the principal source of the caution flag.

Stack synergy

Common pairings:

• MOTS-c, 5-Amino-1MQ, urolithin A — overlapping mitochondrial / sirtuin / mitophagy programs
• Resveratrol or pterostilbene — sirtuin activators; rationale-driven rather than evidence-driven combination
• Methyl donors (TMG, B12) — sometimes co-administered to support methylation when high-dose NR/NMN burdens methylation pathways

Avoid stacking high-dose NAD+ with active sirtuin-inhibitor or PARP-inhibitor therapy.

Open questions

• Does intact NAD+ enter cells, or is it degraded at the membrane and re-synthesized? This determines whether direct administration offers any advantage over oral precursors.
• Why is the subjective response to IV NAD+ so strong if precursor pharmacology is similar?
• What is the long-term cancer risk of chronic NAD+ elevation in older adults — the population most likely to use it?
• Is there an optimal NAD+/NADH ratio target, or only an absolute pool target?