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Pillar 1: NAD+ & Cellular Energy — Longevity Protocol UK (2026) | Vitality Supplements
The Vitality Longevity Protocol
Pillar One of Five

NAD+ & Cellular Energy

The coenzyme at the centre of longevity biology. What NAD+ is, why published research documents its decline with age, the enzymes that consume it and how precursor molecules like NMN and NMNH relate to it as food supplement ingredients.

Last updated · Written by Vitality Supplements Editorial Team · 12 min read · 10 studies cited

12 min read 10 studies cited Not health claims
Quick Answer

What is NAD+ and why does it matter for longevity?

NAD+ (Nicotinamide Adenine Dinucleotide) is a coenzyme present in every living cell, participating in over 500 enzymatic reactions. Published research consistently documents that NAD+ levels decline with age across multiple human tissue types. This decline is driven by two converging factors: reduced biosynthesis, and increased consumption by PARP enzymes (activated by age-related DNA damage) and CD38 (whose expression increases with age). NMN is the most studied NAD+ precursor food supplement ingredient — a 2023 systematic review of 10 RCTs with 437 participants confirmed consistent NAD+ elevation at 250-900mg/day.

Key Takeaways
  • NAD+ participates in over 500 enzymatic reactions — it is fundamental to cellular energy production, DNA repair and sirtuin activation
  • Published research documents NAD+ decline with age across liver, skeletal muscle, heart and brain tissue
  • PARP enzymes consume NAD+ during DNA repair — DNA damage accumulates with age, increasing PARP activation
  • CD38 expression increases with age and is identified as a primary driver of NAD+ decline in aged tissue
  • NMN is one step from NAD+ via NMNAT enzymes — the most studied NAD+ precursor with 30+ human studies
  • NMN has no authorised health claim under UK food supplement regulations
The Fundamentals

What is NAD+?

NAD+ stands for Nicotinamide Adenine Dinucleotide. It is a coenzyme — a small molecule that enables enzymatic reactions — present in every living cell of every organism on earth. It was first identified in by Arthur Harden and William John Young during research into yeast fermentation.

Over a century of subsequent research has established NAD+ as one of the most fundamental molecules in biology. It participates in over 500 enzymatic reactions and has two primary roles: as an electron carrier in cellular energy production, and as a substrate and signalling molecule for a family of regulatory enzymes including sirtuins, PARP enzymes and CD38.

NAD+ exists in two interconverting forms: NAD+ (the oxidised form) and NADH (the reduced form). During the breakdown of nutrients, NAD+ accepts electrons to become NADH. NADH then donates those electrons to the mitochondrial electron transport chain to generate ATP — the cell's primary energy currency. The NAD+/NADH ratio is an important indicator of cellular metabolic state.

Without adequate NAD+, cells cannot produce energy efficiently, cannot repair DNA damage effectively and cannot activate several critical classes of regulatory enzymes. It is not optional — it is fundamental to cellular life. See our related guide: What is NAD+? — complete science guide →

NAD+ participates in over 500 enzymatic reactions. Without it, cells cannot produce energy or activate critical repair pathways.
Year identifiedHarden & Young
500+
Enzymatic reactionsNAD+ participates in
7
Sirtuin enzymesNAD+-dependent in humans
~50%
Decline documentedin some tissues with age
The Core Problem

Why NAD+ declines with age

One of the most consistently documented findings in ageing biology is that NAD+ levels decline with age across multiple human tissue types. This has been confirmed in peer-reviewed studies covering liver, skeletal muscle, heart and brain tissue — reproduced across independent research groups. See our Longevity Protocol overview and research references →

The decline is not simply a matter of the body producing less NAD+ as it ages. It results from two converging problems: reduced biosynthesis — the body's ability to produce NAD+ becomes less efficient with age — and dramatically increased consumption by NAD+-consuming enzymes that become more active with age.

Understanding which enzymes consume NAD+ — and why their activity increases with age — is central to understanding the entire NAD+ longevity research field. Both PARP enzymes and CD38 are covered in depth in the next section.

NAD+ decline is driven by both falling production and rising consumption — a combination that accelerates with every decade.

The practical consequence is that cells have progressively less NAD+ available for energy production, DNA repair signalling and sirtuin enzyme activation as they age. This is why NAD+ metabolism has become one of the most active research areas in longevity biology. For full details on sirtuins and their NAD+ dependence, see Pillar 2: Sirtuins & Gene Regulation →

Important note: The above describes what peer-reviewed research has documented about NAD+ levels and ageing biology. This is not a health claim for any food supplement product. All Vitality Supplements products are food supplements — not medicines — and are not intended to diagnose, treat, cure or prevent any disease.

The NAD+ Consumers

PARP enzymes & CD38

Two categories of NAD+-consuming enzymes are particularly relevant to understanding NAD+ decline in ageing: PARP enzymes and CD38. Understanding both is essential to understanding the research rationale behind NAD+ precursor supplementation.

PARP Enzymes

Poly ADP-Ribose Polymerases
PARP enzymes are activated by DNA damage and play a critical role in DNA repair. They consume substantial amounts of NAD+ in the process. DNA damage accumulates with age — environmental exposure, replication errors and oxidative stress all contribute. As DNA damage accumulates, PARP enzymes are increasingly activated, consuming increasing quantities of NAD+. This creates a vicious cycle: ageing causes DNA damage, DNA damage activates PARPs, PARPs consume NAD+, reduced NAD+ impairs cellular function, impaired cellular function accelerates ageing.
Major NAD+ consumer · Activated by DNA damage

CD38

Cyclic ADP-Ribose Hydrolase
CD38 is an NAD+-consuming enzyme expressed on immune cells and many other cell types. Published research has documented that CD38 expression increases significantly with age and has described it as a primary driver of NAD+ decline in aged tissue. Some researchers have estimated CD38's contribution to NAD+ decline as greater than that of PARP enzymes. Apigenin — a botanical flavone found in chamomile and parsley — has been studied in relation to CD38 inhibition, which is why it features in some longevity formulas alongside NMN.
Increases with age · Primary NAD+ consumer in aged tissue
The NAD+ Consumption & Decline Model
Ageing → DNA damage → PARP activation
Ageing
→
DNA Damage ↑
→
PARP Activation
→
NAD+ Consumed
Ageing → CD38 expression → NAD+ consumed
Ageing
→
CD38 Expression ↑
→
NAD+ Consumed
Result — downstream consequences of NAD+ decline
NAD+ Decline
→
Sirtuin Activity ↓
→
Energy Production ↓
→
DNA Repair ↓
The Supplement Approach

NAD+ precursors — the research rationale

Published supplementation research has focused on precursor molecules rather than NAD+ itself. This is because the NAD+ molecule is relatively large and does not easily cross cell membranes — making direct supplementation less effective than supplying smaller molecules the body can use to produce NAD+ via existing biosynthetic pathways.

Three NAD+ precursors have been studied as food supplement ingredients. Each has a different structure, a different route to NAD+ and a different published research base. For a detailed comparison of NMN and NR, see our NMN vs NR guide. For dosing details, see our NMN dosage guide →

NMN

Nicotinamide Mononucleotide
Most studied
Steps to NAD+
1 step — NMN → NAD+ via NMNAT enzymes
Human research
30+ peer-reviewed studies · Systematic review of 10 RCTs · 437 participants (Yi et al. 2023)
Natural sources
Edamame, broccoli, avocado (trace amounts)
Vitality purity
>99% β-NMN · verified every batch by ISO/IEC 17025

NR

Nicotinamide Riboside
Established
Steps to NAD+
2 steps — NR → NMN → NAD+
Human research
20+ peer-reviewed studies · Older research base than NMN
Natural sources
Milk (trace amounts)
Note
Not available from Vitality Supplements. Compare NMN vs NR →

NMNH

Dihydronicotinamide Mononucleotide
Newer
Steps to NAD+
1 step — reduced form of NMN · distinct pathway
Human research
Developing · Active ongoing research · Newer ingredient
Form
Reduced form — nicotinamide ring in reduced state
Vitality purity
>99% · verified every batch · 500mg per serving. NMN vs NMNH guide →
Published Research

What the research actually shows

The following summarises the published research landscape for NAD+ and NMN supplementation — not as health claims, but as accurate descriptions of what peer-reviewed studies have investigated and documented. All Vitality Supplements products are food supplements with no authorised health claims under UK regulations. Full references at research-references →

Systematic Review

Yi et al. 2023 — NMN and NAD+ elevation — 10 RCTs, 437 participants

A systematic review published in covering 10 randomised controlled trials with 437 participants documented that oral NMN supplementation consistently elevated blood NAD+ levels across all studies, at doses from 250 to 900mg per day. The review found a strong safety profile with no significant adverse events reported across studies. This is the highest quality level of published evidence — a systematic review of randomised controlled trials.

Human Studies

NAD+ decline in human tissue — documented across tissue types

Multiple independent peer-reviewed studies have documented declining NAD+ levels in human tissue samples with age. The finding has been confirmed in liver, skeletal muscle, heart and brain tissue across independent research groups. The magnitude of decline varies by tissue type and individual.

Human Research

CD38 as a primary driver of NAD+ decline

Published research has documented that CD38 expression increases significantly with age and has proposed CD38 as a primary driver of NAD+ decline in aged tissue. Research exploring CD38 inhibition as a strategy to support NAD+ levels — including the study of compounds like apigenin — is an active area of investigation.

Mechanistic Research

PARP activation and NAD+ consumption

Extensive published mechanistic research has documented the relationship between DNA damage, PARP activation and NAD+ consumption. PARP enzymes are estimated to consume a substantial fraction of cellular NAD+ when activated. The accumulation of DNA damage with age — and consequent PARP activation — is considered a significant contributor to age-related NAD+ decline.

FAQ

Common questions

NAD+ is a coenzyme present in every living cell, participating in over 500 enzymatic reactions. It plays a central role in cellular energy production, DNA repair signalling and sirtuin enzyme activation. Published research has documented that NAD+ levels decline with age across multiple human tissue types — one of the most consistently reproduced findings in longevity biology. This decline is the primary reason NAD+ metabolism has become a major focus of longevity research. Read the complete NAD+ guide →
NAD+ decline results from two converging factors: reduced biosynthesis and increased consumption. PARP enzymes — activated by DNA damage, which accumulates with age — consume significant NAD+. CD38 — an NAD+-consuming enzyme whose expression increases with age — is documented as a primary driver of NAD+ decline. The combination of reduced production and increased consumption accelerates NAD+ decline with each decade.
NAD+ is the coenzyme itself — present in every cell. NMN is a biosynthetic precursor — a smaller molecule the body uses to produce NAD+ via the salvage pathway using NMNAT enzymes. NAD+ itself does not easily cross cell membranes, which is why published supplementation research has focused on smaller precursor molecules like NMN. Read the full NMN guide →
CD38 is an NAD+-consuming enzyme whose expression increases significantly with age. Published research has described it as a primary driver of NAD+ decline in aged tissue. Apigenin — a botanical flavone found in chamomile — has been studied in relation to CD38 inhibition. This is why apigenin appears alongside NMN in some longevity formulas, including Vitality Supplements NMN Complete 1350mg.
A systematic review of 10 randomised controlled trials with 437 participants (Yi et al. 2023) documented that oral NMN supplementation consistently elevated blood NAD+ levels across all studies, at doses from 250 to 900mg per day, with a strong safety profile and no significant adverse events. This is the highest quality level of published evidence for any NAD+ precursor. As a food supplement, NMN has no authorised health claims under UK regulations. See our NMN dosage guide for the full study breakdown.
NMNH is the reduced form of NMN — its nicotinamide ring is in a reduced state. It is a newer NAD+ precursor ingredient with an active but developing research base. Like NMN, it enters NAD+ production via a one-step pathway but through a distinct mechanism. Vitality Supplements provides NMNH at >99% purity, UK manufactured, independently tested every batch. Read the NMN vs NMNH guide →

Shop NAD+ precursor supplements

NMN Complete 1350mg · NMNH 500mg · NMN + Trans-Resveratrol 1100mg. UK manufactured. Every batch independently tested by ISO/IEC 17025-accredited laboratory. >99% β-NMN purity. CoA on request.

Shop NMN Complete → View full range

This page is part of The Vitality Longevity Protocol — an educational resource covering published peer-reviewed research. Not medical advice. All Vitality Supplements products are food supplements regulated under UK food supplement legislation — not medicines. Not intended to diagnose, treat, cure or prevent any disease. Consult a qualified healthcare professional before starting any supplement. Contact: info@vitality-supplements.co.uk · 12 Deer Park Road, London SW19 3TL