If you have been feeling more fatigued than you once did, slower to recover from exercise, or simply not quite as sharp as you used to be — there is a good chance your cells are quietly running low on one of the most important molecules in your body.
NAD+ (nicotinamide adenine dinucleotide) sits at the centre of your body's ability to produce energy, repair DNA damage, and fight the biological processes that drive ageing. It is not a supplement trend. It is fundamental biochemistry — and it has been studied for over a century.
What Exactly is NAD+?
NAD+ stands for nicotinamide adenine dinucleotide. It is a coenzyme — a molecule that assists enzymes in performing chemical reactions — found inside every living cell in your body. It exists in two forms:
- NAD+ (the oxidised form) — the active version involved in energy production, DNA repair, and cellular signalling
- NADH (the reduced form) — produced when NAD+ accepts electrons during metabolism
Scientists first identified NAD+ in 1906 while studying fermentation in yeast. More than 100 years of research later, it is now understood to be involved in over 500 enzymatic reactions — making it one of the most widely used molecules in human biology.
You cannot absorb NAD+ directly from food. Your body manufactures it from precursor molecules — primarily nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) — derived from vitamin B3. This is why supplementing with NR or NMN is the most evidence-backed way to raise NAD+ levels.
The Two Core Roles of NAD+
1. Powering your cellular energy production
Every time you move, think, or breathe, your cells convert nutrients into usable energy in the form of ATP (adenosine triphosphate). NAD+ sits at the heart of this process. During glycolysis and the TCA cycle in your mitochondria, NAD+ acts as an electron carrier — accepting hydrogen ions and electrons to generate NADH, which then drives the electron transport chain to produce ATP.
When NAD+ is depleted, your mitochondria — the powerhouses of the cell — cannot sustain efficient energy output. The result is the kind of persistent, low-grade fatigue that sleep alone does not fix.
2. Activating your body's repair and longevity pathways
NAD+ is the essential fuel for two protein families directly tied to healthy ageing:
- Sirtuins (SIRT1–SIRT7): Often called "longevity proteins," sirtuins regulate gene expression, reduce inflammation, coordinate DNA repair, and manage how cells respond to stress. They cannot function without NAD+.
- PARPs: These enzymes detect and repair broken DNA strands. Every repair cycle consumes NAD+. More DNA damage with age = more PARP activity = faster NAD+ depletion.
Professor David Sinclair of Harvard Medical School describes the NAD+–sirtuin relationship as an engine and its fuel: "Sirtuins are the engine; NAD+ is the fuel. An excellent engine is useless without sufficient fuel."
Why Does NAD+ Decline With Age?
Your body is constantly producing and consuming NAD+. In youth, production keeps pace with demand. As you get older, that balance breaks — and faster than most people realise.
Several mechanisms drive this:
Increased NAD+ consumption
Accumulating DNA damage activates PARP enzymes, which consume large amounts of NAD+ during repair. CD38 — an immune enzyme — also becomes overexpressed with age, breaking down NAD+ rapidly. Research has found CD38 activity increases dramatically in aged tissues, becoming a major driver of depletion independent of how much you produce.
Reduced biosynthesis
Your body becomes less efficient at converting precursor nutrients — tryptophan, vitamin B3 — into NAD+ as you age. The enzymes responsible for these conversions slow down, reducing the rate of new NAD+ production at precisely the time demand increases.
Lifestyle factors compound the decline
Poor sleep, chronic stress, excess alcohol, a sedentary lifestyle, and high-calorie diets all accelerate NAD+ depletion independently of age. Even at 35, these factors can suppress NAD+ to levels normally associated with people decades older.
What Happens When NAD+ Levels Fall?
Because NAD+ underpins so many fundamental processes, its decline has broad effects. Common signs of sub-optimal NAD+ levels include:
- Persistent fatigue and low energy, even after adequate sleep
- Slower recovery from exercise or physical effort
- Brain fog, difficulty concentrating, reduced mental sharpness
- Reduced metabolic efficiency and changes in body composition
- More frequent illness as immune function declines
- Slower healing and greater sensitivity to physical stress
These are not inevitable consequences of ageing. They are, at least in part, a consequence of cellular energy deficiency and impaired repair capacity — both driven by declining NAD+.
Taking NR daily has had a substantial effect over the past two years. Initially I didn't notice a drastic difference but, over time, I noticed my overall energy levels were solid, I was recovering much quicker and didn't seem to catch as many colds.
How Can You Restore NAD+ Levels?
The most direct and evidence-backed approach is to supplement with NAD+ precursors — molecules your body readily converts into NAD+ inside the cell. Two are particularly well studied:
Nicotinamide Riboside (NR)
A form of vitamin B3 that converts efficiently into NAD+ via the salvage pathway. Multiple randomised controlled trials in humans have confirmed NR supplementation raises blood NAD+ levels by 40–90% within four to eight weeks. NADBio's Liposomal NR Capsules use an advanced delivery system that significantly improves absorption compared to standard oral capsules.
Nicotinamide Mononucleotide (NMN)
One step closer to NAD+ in the biosynthesis pathway than NR. NMN is absorbed via dedicated transporters and converted rapidly. Human trials have confirmed NMN increases NAD+ levels and is well tolerated, with studies showing improvements in muscle metabolism, insulin sensitivity, and aerobic capacity in older adults.
High-intensity interval training (HIIT), intermittent fasting, and reducing alcohol intake all support NAD+ production and conservation — and work synergistically with precursor supplementation.
Not All NAD+ Supplements Are Equal
The UK supplement market has grown rapidly, but quality varies enormously. Independent testing has found that a significant proportion of NAD+ products contain far less active ingredient than their labels claim — in some cases less than 1% of the stated dose.
At NADBio, every product is independently tested by SGS — one of the world's leading testing and certification organisations — to verify purity, potency, and safety. Certificates of analysis are published on every product page. We believe complete transparency is non-negotiable.
