The Molecule That Keeps Cells Alive
NAD+ (nicotinamide adenine dinucleotide) is the forgotten cofactor at the centre of cellular energy production, DNA repair, and cell survival. Every cell in your body requires NAD+ to convert nutrients into ATP, to activate PARP enzymes that repair DNA damage, and to support sirtuins — the longevity proteins that regulate cellular stress resistance and mitochondrial function. NAD+ levels decline with age in every tissue studied, and this decline is now recognised as a fundamental driver of the metabolic dysfunction that characterises aging.
Why NAD+ Declines With Age
The decline in NAD+ with age has two components. First, synthesis of NAD+ from dietary precursors (niacin, tryptophan, nicotinamide riboside) decreases in efficiency as cellular NAD+-consuming enzymes become more active. CD38 — an enzyme that consumes NAD+ to produce signalling molecules — increases with age and inflammation, progressively depleting the NAD+ pool. Second, poly-ADP-ribose polymerases (PARPs), which are activated by DNA damage to repair chromosomes, consume NAD+ at rates that increase with cumulative DNA damage exposure. The result is a net decrease in cellular NAD+ availability that impairs every NAD+-dependent process.
This is not merely theoretical. In 2013, a landmark study showed that restoring NAD+ levels in aged mice by supplementing nicotinamide riboside (NR) reversed mitochondrial dysfunction and improved muscle function to levels comparable to much younger animals. The sirtuin enzymes, which require NAD+ to function, were reactivated by the restored NAD+ pool, improving mitochondrial biogenesis and cellular stress resistance. This finding has been replicated across multiple tissues and species, establishing NAD+ depletion as a tractable therapeutic target in aging.
Preferring the Right NAD+ Precursors
The most evidence-based approach to NAD+ optimisation is supplementation with nicotinamide riboside (NR) or nicotinamide mononucleotide (NMN). NR is the more studied of the two, with human trials showing increased blood NAD+ levels at doses of 250-500mg daily. NMN is NMN is NMN is a direct NAD+ precursor that is rapidly absorbed and converted to NAD+ within cells. Both compounds are well-tolerated and produce measurable increases in NAD+ levels within days. Nicotinamide (the amide form of niacin) is also effective at raising NAD+ and is the least expensive option, though it has a higher risk of flushing at high doses.
For people interested in longevity optimisation, the NAD+ precursor approach is one of the most evidence-based interventions available outside of the basic longevity foundations (exercise, sleep, diet). The supplement quality matters significantly — NR and NMN are unstable in solution and degrade rapidly, so reputable sourcing and proper formulation are important.
What You Can Do Today
If you are over 40 and interested in NAD+ optimisation, consider a daily NAD+ precursor supplement — NR or NMN at the doses used in clinical studies (250-500mg). Support your body’s own NAD+ production with niacin-rich foods (liver, sardines, tuna, yeast extract) and avoid excessive alcohol, which depletes NAD+. The foundations — exercise, particularly aerobic exercise, which increases NAD+ in muscle tissue — remain the most robust interventions, with supplements serving as an additional layer for those who want more.
NMN vs NR: Comparing the NAD+ Precursors
Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) are both NAD+ precursors but differ in their metabolic pathways. NR is converted to NMN by nicotinamide riboside kinases (NRKs) before entering the NAD+ salvage pathway. NMN is converted directly to NAD+ by NMN adenylyl transferases (NMNATs). Both are effective at raising NAD+ levels, but NMN may have the advantage of a more direct conversion pathway, particularly in tissues with high NRK activity. However, NMN is larger and may have more difficulty crossing cell membranes — the debate about whether NMN requires transport proteins is ongoing.
Human trials for both compounds are ongoing and preliminary results are promising. A 2022 study showed that NMN supplementation at 300mg daily for 60 days improved skeletal muscle insulin sensitivity in prediabetic adults. NR trials show consistent NAD+ elevation and preliminary evidence for reduced inflammation markers. Both compounds appear safe at studied doses, though long-term safety data is still being accumulated. For now, either NR or NMN at 250-500mg daily represents the most evidence-based NAD+ optimisation approach currently available outside of prescription medications.
The Sirtuin Connection
Sirtuins are NAD+-dependent deacetylases that regulate cellular stress resistance, mitochondrial function, and metabolic homeostasis. SIRT1, the most studied sirtuin, requires NAD+ to function and is activated by calorie restriction, exercise, and red wine resveratrol — the basis for the early excitement about resveratrol as a longevity compound. When NAD+ levels decline with age, sirtuin activity declines, mitochondrial function deteriorates, and cells accumulate damage that is not being repaired. This is the mechanistic link between NAD+ depletion and the metabolic dysfunction of aging.
The pharmaceutical approach to sirtuin activation involves NAD+ precursor supplementation — raising NAD+ levels to restore sirtuin activity rather than trying to directly activate sirtuins pharmacologically. This is the rationale for the NAD+ precursor approach to aging: by restoring the substrate (NAD+) rather than trying to directly activate the enzyme, the cell’s own regulatory mechanisms remain in control of the response. Early human data is promising but not yet conclusive — sirtuin-activating compounds are an active area of drug development alongside the nutraceutical NAD+ precursor market.
NAD+ and Cardiovascular Health
The cardiovascular system is particularly sensitive to NAD+ depletion. Endothelial cells — the cells lining blood vessels — require NAD+ for proper nitric oxide production, the signalling molecule that causes vasodilation. When endothelial NAD+ is low, nitric oxide production falls, blood vessels become stiffer, and blood pressure rises. Studies in aged animals show that NAD+ precursor supplementation restores endothelial function and lowers blood pressure. Human trials are ongoing, but the mechanistic rationale is strong enough that NAD+ optimisation is increasingly included in integrative cardiology practice.
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