NAD+ and Ageing: What the Science Actually Says in 2026

NAD+ has gone from an obscure biochemistry term to the centrepiece of the global longevity movement. Researchers at Harvard, Stanford and the National Institutes of Health are publishing papers on it. David Sinclair, one of the world's most prominent longevity scientists, has built much of his work around it. But what does the science actually say?

As a practising doctor who has followed this research closely, I want to cut through the hype and give you an accurate picture of what NAD+ is, what we know with confidence, and where the science is still developing.

The Biology of NAD+

NAD+ (Nicotinamide Adenine Dinucleotide) is a coenzyme — a small molecule that enables enzymes to do their jobs. It's found in every single cell in your body and is involved in over 500 enzymatic reactions.

Its most critical roles include:

• Cellular respiration: NAD+ is a core component of the Krebs cycle and oxidative phosphorylation — the processes by which your mitochondria convert food into ATP energy
• Sirtuin activation: Sirtuins are proteins often called "longevity genes." They regulate gene expression, DNA repair, inflammation, and metabolism — but they can only function when NAD+ is available
• PARP activation: PARP (Poly ADP-ribose polymerase) enzymes use NAD+ to detect and repair DNA damage. Every time your DNA is damaged by UV radiation, toxins, or normal metabolic processes, PARP consumes NAD+ to fix it
• CD38 activity: CD38 is an enzyme that consumes NAD+ as part of immune function. Notably, CD38 activity increases significantly with age — contributing to the age-related decline in NAD+

The NAD+ Decline with Age

Here is the central problem: NAD+ levels decline dramatically as we age. Studies have measured NAD+ levels in human tissue and found that by middle age, levels may be less than half of what they were in young adulthood. By older age, the decline is even more pronounced.

This matters because as NAD+ falls:

• Mitochondrial function declines, reducing cellular metabolism production
• Sirtuin activity drops, impairing gene regulation and stress responses
• DNA repair becomes less efficient, allowing damage to accumulate
• Inflammation increases as regulatory mechanisms weaken

This cascade of effects is not just theoretically linked to ageing — it maps closely onto the biological changes we observe in ageing organisms, including humans.

Can Supplementation Reverse This Decline?

Multiple human trials have now confirmed that NAD+ precursor supplementation can meaningfully raise blood and tissue NAD+ levels. A 2023 trial involving 80 healthy adults found dose-dependent increases in NAD+ with NMN supplementation at 300mg, 600mg and 900mg per day. Participants also reported improvements in energy levels and physical performance.

Earlier trials with NR (nicotinamide riboside) similarly showed significant NAD+ elevation. Critically, elevated NAD+ appears to translate into measurable biological changes — not just higher NAD+ numbers on a blood test.

The most compelling evidence comes from research showing that raising NAD+ activates sirtuins, which in turn influence hundreds of genes associated with metabolic health, stress resistance and longevity.

The 4-in-1 Approach: Why Our NAD+ Complex is Different

Most NAD+ supplements take a single-ingredient approach. Our NAD+ Complex combines four complementary components:

• Liposomal NAD+ — direct NAD+ in a liposomal delivery system for enhanced absorption
• Nicotinamide Riboside (NR) — an additional NAD+ precursor providing a second pathway to raise levels
• Trans-Resveratrol — activates SIRT1 and SIRT3 sirtuins, amplifying the effect of raised NAD+ levels
• Magnesium Glycinate — supports mitochondrial function and over 300 other enzymatic processes

By targeting NAD+ production through two precursor pathways while simultaneously activating the sirtuins that NAD+ powers, this formula is designed for people who want comprehensive longevity support rather than a single-ingredient supplement.

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Written by Dr Chun Tang, MBChB, MRCGP — founder of Little Ox and UK GP with 26 years of clinical experience.