Nicotinamide adenine dinucleotide (NAD+) is a coenzyme present in every cell of your body, essential for hundreds of metabolic reactions including energy production, DNA repair, and cellular signalling. NAD+ levels decline with age, and this decline is associated with many hallmarks of ageing. The question driving a multibillion-dollar supplement industry is whether restoring NAD+ levels can influence the ageing process itself.
NAD+ Biology and Function
NAD+ functions as an electron carrier in metabolic reactions, shuttling electrons between molecules in processes like glycolysis and the citric acid cycle. Without adequate NAD+, cellular energy production falters.
Beyond energy metabolism, NAD+ is a required substrate for sirtuins, a family of proteins involved in DNA repair, inflammation regulation, and stress response. It is also consumed by PARPs (poly-ADP ribose polymerases) during DNA damage repair. This dual demand, from both energy metabolism and cellular maintenance, creates a competition for a finite resource that becomes scarcer with age.
Age-Related NAD+ Decline
Research consistently shows that NAD+ levels decrease with age across multiple tissues. By middle age, NAD+ levels may be 50% lower than in youth. This decline is driven by increased consumption by PARPs responding to accumulated DNA damage, decreased synthesis through the salvage pathway, increased activity of CD38, an enzyme that degrades NAD+, and chronic inflammation that accelerates NAD+ turnover.
The correlation between declining NAD+ and ageing-related dysfunction has led to the hypothesis that boosting NAD+ levels could slow or partially reverse aspects of ageing.
NMN vs NR as Precursors
The two primary NAD+ precursors available as supplements are nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR). Both are converted to NAD+ through different metabolic pathways.
NMN is one step closer to NAD+ in the biosynthetic pathway and has been championed by David Sinclair's research at Harvard. Animal studies show promising results for metabolic health, cognitive function, and exercise capacity. Human clinical trials are ongoing, with early data suggesting oral NMN can increase blood NAD+ levels and improve some biomarkers.
NR has a longer track record in human research, with Charles Brenner's work establishing its bioavailability and safety profile. Multiple human trials have demonstrated that NR supplementation raises NAD+ levels in blood and muscle tissue. However, the functional outcomes of this increase are less clear in humans than in animal models.
Current Evidence Limitations
The honest assessment of NAD+ supplementation in 2026 is that the biology is compelling, the animal data is encouraging, and the human evidence is early-stage. Most human trials to date are small, short-duration, and focused on biomarker changes rather than hard clinical endpoints.
The gap between raising NAD+ levels in a blood test and demonstrating meaningful changes in ageing outcomes is significant. NAD+ precursors reliably increase circulating NAD+, but whether this translates to intracellular increases in the tissues that matter most, and whether those increases produce functional benefits, remains an active area of investigation.
Practical Considerations
For people interested in NAD+ optimisation, the evidence-based approach includes foundational strategies first: exercise (which naturally boosts NAD+ through AMPK activation), caloric management, adequate sleep, and managing chronic inflammation through diet. Supplementation as an adjunct, not a replacement, with realistic expectations about current evidence. Regular monitoring through blood work and functional markers rather than assuming a supplement is working.
The dose, form, and duration of NAD+ precursor supplementation that optimises human health outcomes is not yet established with certainty. What is established is that the lifestyle interventions, nutrition, exercise, sleep, and stress management, produce measurable benefits regardless of supplement use.
Frequently Asked Questions
Should I take NMN or NR? Neither has been definitively shown to be superior in human studies. NMN has more recent research momentum; NR has a longer human safety record. Both raise NAD+ levels. The choice is less important than ensuring foundational health behaviours are in place.
What dose of NAD+ precursors is effective? Human trials have used 250mg to 1,000mg daily for NMN and 300mg to 1,000mg for NR. Optimal dosing is not established. Starting at the lower end and monitoring response is a reasonable approach.
Can I boost NAD+ without supplements? Yes. Exercise, particularly high-intensity and resistance training, activates AMPK and upregulates NAD+ synthesis. Caloric restriction and time-restricted eating also appear to influence NAD+ metabolism. These interventions have robust evidence for health benefits independent of their effects on NAD+.
Our Longevity Programme includes advanced supplementation protocol design based on your individual biomarker data. Learn more about biological age measurement.
