If you have spent any time reading about longevity, you have encountered NAD+. It is one of the most researched molecules in ageing science, and for good reason. But the gap between what the research shows and what the marketing claims is worth understanding.
What is NAD+?
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme found in every cell of your body. It is essential for hundreds of metabolic processes, including:
- Energy production. NAD+ is a key player in the mitochondrial electron transport chain, the process that converts food into cellular energy (ATP).
- DNA repair. Enzymes called PARPs use NAD+ to repair damaged DNA. Without adequate NAD+, DNA damage accumulates.
- Sirtuin activation. Sirtuins are a family of proteins linked to longevity, inflammation regulation, and metabolic health. They require NAD+ to function.
- Cellular signalling. NAD+ participates in calcium signalling and immune cell function.
In short, NAD+ is not optional. It is fundamental to how your cells operate.
Why do levels decline?
NAD+ levels drop significantly with age. By middle age, most people have roughly half the NAD+ they had in their twenties. The decline is driven by:
- Increased activity of CD38, an enzyme that consumes NAD+
- Chronic inflammation, which accelerates NAD+ depletion
- Reduced production of NAD+ precursors
- Accumulated DNA damage requiring more NAD+ for repair
This decline correlates with many hallmarks of ageing: mitochondrial dysfunction, impaired DNA repair, metabolic slowdown, and increased inflammation.
What does supplementation do?
NAD+ itself is poorly absorbed orally. Clinical approaches focus on precursors that your body converts into NAD+:
- NMN (Nicotinamide Mononucleotide). The most direct precursor. Research in Science and Cell Metabolism has shown NMN supplementation restores NAD+ levels in aged tissues and improves metabolic function in animal models. Human trials are ongoing but early results are promising.
- NR (Nicotinamide Riboside). Another precursor with good oral bioavailability. Human trials have confirmed it raises blood NAD+ levels, though functional outcomes are still being studied.
IV NAD+ infusions bypass the absorption issue entirely and are used in some clinical settings.
What the evidence supports
The preclinical evidence for NAD+ restoration is strong. Animal studies consistently show improvements in:
- Mitochondrial function and energy metabolism
- Insulin sensitivity and glucose tolerance
- Cognitive function and neuroplasticity
- Exercise capacity and muscle function
- DNA repair efficiency
Human evidence is catching up. Several clinical trials have confirmed that NMN and NR raise NAD+ levels in humans. The question now is whether the functional benefits seen in animal models translate at clinically meaningful levels.
A measured perspective
NAD+ supplementation is not a miracle cure. It is one piece of a larger picture. The most honest assessment is this: the science is promising and the mechanism is well understood. But we are still learning the optimal dosing, timing, and patient selection criteria.
What we can say with confidence is that NAD+ decline is real, it matters, and addressing it is a reasonable component of a comprehensive longevity strategy, particularly under clinical supervision where dosing and response can be monitored.