Nicotinamide adenine dinucleotide (NAD) is a vital coenzyme present in every cell of the body, essential for energy production and cellular function. NAD+ levels naturally decline with age, prompting interest in supplementation with precursors such as nicotinamide riboside (NR). Whilst research suggests potential benefits for metabolic health, DNA repair, and cellular ageing, clinical evidence in humans remains limited and preliminary. In the UK, NR is an authorised novel food with specific usage conditions, whilst nicotinamide mononucleotide (NMN) is not currently authorised. This article examines what NAD is good for, exploring the evidence, safety considerations, and regulatory status of NAD+ supplementation.

What Is NAD and How Does It Work in the Body?

Nicotinamide adenine dinucleotide (NAD) is a coenzyme found in every living cell, playing a fundamental role in cellular metabolism and energy production. This molecule exists in two forms: NAD+ (oxidised) and NADH (reduced), which work together in redox reactions essential for converting nutrients into cellular energy through processes such as glycolysis and the citric acid cycle.

NAD+ serves multiple critical functions beyond energy metabolism. It acts as a substrate for several enzyme families, including sirtuins, poly(ADP-ribose) polymerases (PARPs), and CD38/CD157. Sirtuins regulate gene expression, DNA repair, and cellular stress responses, whilst PARPs are involved in DNA damage repair and genomic stability. These enzymes consume NAD+ to perform their functions, making adequate NAD+ levels essential for cellular function and stress responses.

Research suggests NAD+ levels naturally decline in tissues throughout the body with age, with studies showing significant reductions between youth and middle age. This decline has been associated with various age-related physiological changes, though the precise causal relationships remain under investigation. Factors contributing to NAD+ depletion include increased consumption by DNA repair enzymes in response to accumulated cellular damage, reduced biosynthesis, and enhanced degradation by CD38, an enzyme whose activity tends to increase with age.

The body synthesises NAD+ through multiple pathways, including the de novo pathway from tryptophan and the salvage pathway from nicotinamide (a form of vitamin B3). The salvage pathway is particularly important in mammals, recycling nicotinamide back into NAD+ through the enzyme nicotinamide phosphoribosyltransferase (NAMPT). Understanding these mechanisms has led to interest in NAD+ precursor supplementation, though it's important to note that mechanistic understanding does not necessarily translate to proven clinical benefits in humans.

Health Benefits: What Is NAD Good For?

Cellular Energy and Metabolic Health

NAD+ supplementation has been investigated for its potential to support metabolic health, typically through precursors such as nicotinamide riboside (NR). It's important to note that in the UK, NR is an authorised novel food with a maximum permitted daily intake of 300 mg for adults, while nicotinamide mononucleotide (NMN) is not currently authorised as a novel food in Great Britain or the EU. Preclinical studies suggest that boosting NAD+ levels may improve insulin sensitivity, enhance mitochondrial function, and support healthy glucose metabolism. Some human trials have shown modest improvements in metabolic markers in specific populations, though results remain inconsistent across studies and clinical significance is not yet established.

Cardiovascular and Neuroprotective Potential

Emerging research indicates that NAD+ may play a role in cardiovascular health by supporting endothelial function and reducing oxidative stress. Animal studies have demonstrated improvements in blood vessel elasticity and cardiac function with NAD+ precursor supplementation. Regarding neurological health, NAD+ is essential for neuronal energy metabolism and may support cognitive function, though human evidence remains preliminary and limited. There is ongoing investigation into whether NAD+ supplementation might offer neuroprotective benefits, but no clinical outcomes have been established.

DNA Repair and Cellular Ageing

One of the most compelling theoretical benefits relates to DNA repair mechanisms. NAD+ is required for PARP enzymes to repair DNA damage that accumulates with age and environmental exposures. Maintaining adequate NAD+ levels may theoretically support genomic stability, though whether supplementation translates to meaningful clinical benefits in humans requires further investigation. Currently, there are no authorised health claims in the UK or EU regarding NAD+ precursors and ageing or disease prevention.

Exercise Performance and Recovery

Some athletes and active individuals use NAD+ precursors to potentially enhance exercise capacity and recovery. The rationale centres on NAD+'s role in mitochondrial energy production and muscle cell metabolism. Whilst some small studies suggest possible benefits for endurance and muscle function, robust clinical evidence supporting performance enhancement remains limited. It is important to note that no major sporting or regulatory body has established definitive guidance on NAD+ supplementation for athletic performance, and supplements should not be marketed with performance enhancement claims.

Potential Side Effects and Safety Considerations

Common Adverse Effects

Nicotinamide riboside (NR), an authorised novel food in the UK with a maximum permitted adult daily intake of 300 mg, is generally well-tolerated in clinical trials. The most commonly reported side effects are mild and include nausea, fatigue, headache, diarrhoea, and abdominal discomfort. These effects are typically dose-dependent and often resolve with continued use or dose reduction. Some individuals report flushing, though this is less common with NR compared to high-dose niacin (nicotinic acid).

Drug Interactions and Contraindications

Whilst significant drug interactions have not been extensively documented, theoretical concerns exist. Individuals taking any regular medications should consult their GP or pharmacist before starting NAD+ precursor supplements, as individual risk assessment is important. Those with pre-existing medical conditions, particularly liver or kidney impairment, should seek medical advice before supplementation. There is currently insufficient evidence regarding safety in pregnancy and breastfeeding, so supplementation is not recommended in these populations.

Long-term Safety and Regulatory Status

Long-term safety data for NAD+ precursor supplementation in humans remains limited, with most trials lasting weeks to months rather than years. In the UK, nicotinamide riboside is regulated as an authorised novel food with specific conditions of use, while nicotinamide mononucleotide (NMN) is not currently authorised as a novel food in Great Britain or the EU. NAD+ precursors are typically sold as food supplements rather than licensed medicines, meaning they are not subject to the same rigorous pre-market safety and efficacy evaluation required by the Medicines and Healthcare products Regulatory Agency (MHRA). Quality and purity can vary between manufacturers.

When to Seek Medical Advice

Stop taking the supplement and seek immediate medical attention (call 999 or go to A&E) if you experience signs of a severe allergic reaction such as wheezing, facial/throat swelling, or collapse. Contact your GP promptly if you develop jaundice (yellowing of skin/eyes), dark urine, severe abdominal pain, or unexplained bruising/bleeding. Also seek medical advice for persistent gastrointestinal symptoms or unexplained fatigue after starting supplementation. Any suspected adverse reactions should be reported via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

It's worth noting that intravenous NAD+ infusions are not MHRA-licensed medicines in the UK, have limited evidence for benefit, and may carry additional risks.

Who Should Consider NAD Supplementation?

Individuals Who May Benefit

Whilst research is ongoing, the evidence for clinical benefits from NAD+ precursor supplementation remains preliminary and limited. Anyone considering supplementation should first discuss this with their GP or pharmacist, particularly as nicotinamide riboside (NR) is the only NAD+ precursor currently authorised as a novel food in the UK, with a maximum permitted daily intake of 300 mg for adults. Nicotinamide mononucleotide (NMN) is not currently authorised as a novel food in Great Britain or the EU.

Some researchers are investigating whether older adults experiencing age-related metabolic changes might benefit from NAD+ precursor supplementation, though this remains theoretical. Individuals with metabolic concerns might be interested in NAD+ precursors as an adjunct to lifestyle modifications, but these supplements should not replace evidence-based interventions such as diet, exercise, and prescribed medications.

It is important to emphasise that there is no established link between NAD+ supplementation and prevention of specific diseases in humans, and no authorised health claims exist for these supplements in the UK or EU.

Who Should Exercise Caution or Avoid Supplementation

Certain groups should avoid NAD+ supplementation or only proceed under medical supervision. These include pregnant or breastfeeding women and those with severe liver or kidney impairment. Individuals with current or previous cancer should seek specialist advice before use, as there are theoretical concerns about the effects of NAD+ on rapidly dividing cells, though evidence is limited. Children and adolescents should not take NAD+ supplements outside of specific medical guidance, as safety and appropriate dosing have not been established in paediatric populations.

Evidence-Based Approach and UK Guidance

Currently, NICE has not issued specific guidance on NAD+ supplementation, reflecting the early stage of human clinical evidence. The Food Standards Agency (FSA) regulates nicotinamide riboside as a novel food with specific conditions of use in the UK.

Individuals should prioritise evidence-based lifestyle interventions known to support healthy ageing, including regular physical activity, a balanced Mediterranean-style diet, adequate sleep, stress management, and avoidance of smoking and excessive alcohol consumption. The NHS provides comprehensive resources on these lifestyle factors through its Live Well programme. NAD+ supplementation, if pursued, should be viewed as a potential complement to, rather than replacement for, these established health behaviours. Consultation with a GP or registered dietitian can help determine whether supplementation is appropriate for individual circumstances and health goals.

Frequently Asked Questions