Few molecules in modern longevity science have generated as much excitement, and controversy, as NAD+.
Over the past decade, nicotinamide adenine dinucleotide, better known as NAD+, has moved from the pages of biochemistry journals into mainstream discussions about ageing, metabolic health and human performance. However, this rise in visibility has been accompanied by growing debate, particularly around intravenous NAD+ therapy and the expanding market for NAD+ precursor supplements such as NMN and NR.
“For anyone trying to make sense of the longevity field, the real challenge is not deciding whether NAD+ matters,” says Iain De Havilland, CEO of New Yorkbased NADclinic Group. “The biological evidence is indisputable. The real challenge lies in distinguishing proven science from speculation and understanding where the future of evidence-based longevity medicine is truly heading,” he continues.
“The future will not be defined by single interventions alone but by integrated systems that combine diagnostics, personalised protocols and continuous data feedback”
Iain De Havilland
WHY NAD+ MATTERS
At its core, NAD+ is a coenzyme present in every living cell. It plays a central role in energy metabolism and mitochondrial function, helping cells convert nutrients into usable energy. Beyond energy, it is a master regulator, participating in DNA repair and signalling pathways that manage stress responses and the ageing process.
One of the most critical findings in longevity research is that NAD+ levels decline with age. This depletion has been directly linked to mitochondrial dysfunction, heightened oxidative stress and impaired cellular repair mechanisms.
In practical terms, declining NAD+ levels may contribute to the gradual loss of metabolic efficiency we experience over time. This has led researchers to become interested in whether supporting NAD+ pathways can help preserve cellular resilience and metabolic health over time.
THE DEBATE AROUND NAD+ THERAPY
As interest in NAD+ has grown, so too has the number of therapeutic approaches aimed at restoring or supporting NAD+ levels. Among these, intravenous NAD+ therapy has emerged as one of the most visible interventions.
Currently used in specialist clinics for everything from addiction recovery and neurological support to elite performance medicine, the treatment is not without its sceptics. Some academic commentators continue to question its mechanism, specifically, how effectively NAD+ molecules delivered intravenously can enter the cells directly.
The current academic debate rests on a technicality: the possibility that NAD+ must first be broken down into precursor molecules before the body can fully utilise it, raising questions about whether direct infusion is the most efficient delivery method.
“These criticisms are part of a healthy scientific process,” says De Havilland, who has dedicated his career to turning longevity science into data-driven reality. “Medicine has always evolved through a continuous cycle of debate, experimentation and refinement. In the pursuit of longevity, it is vital to distinguish between genuine scientific uncertainty and the false assumption that a therapy must therefore be ineffective,” he explains.
“In many areas of medicine, clinical application often precedes a complete map of the underlying biological pathways,” De Havilland continues. “Observed outcomes in patients often guide the next phase of research, rather than the other way round.”
THE RISE OF NAD+ PRECURSORS
At the same time, the supplement industry has embraced NAD+ precursors such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). These compounds act as biological building blocks that the body can convert into functional NAD+ through established metabolic pathways.
In laboratory models these molecules have shown extraordinary promise in enhancing mitochondrial function and cellular metabolism. Human trials have also demonstrated that certain precursors can raise NAD+ levels in blood and tissues.
However, translating these findings into meaningful clinical outcomes remains complex. Bioavailability varies significantly between individuals. Dosage is critical and external factors, including metabolic health, lifestyle and biological age, all play a role in the result.
“What is truly transformative is the emerging evidence from recent preclinical and clinical research regarding the restorative effects of NAD+ on heart and brain health”
Dr Sinead Sheridan
“Consumers are now faced with a market flooded with supplements that promise dramatic longevity benefits, often sold online with little transparency regarding quality, dosage or clinical validation,” says De Havilland. “The reality is that not all products are created equal, and many claims remain ahead of the evidence. This is where critical evaluation becomes essential.”
WHY EVIDENCE MATTERS
Throughout De Havilland’s work in longevity medicine, one principle has always been straightforward: follow the science.
Innovation is essential in any emerging field, but without the ballast of evidence, it quickly dissolves into noise. For that reason, De Havilland has always believed that therapeutic interventions, no matter how promising, must be paired with measurable outcomes. This is where modern diagnostics have become transformative.
Advances in biomarker testing, metabolic analysis and physiological diagnostics now allow clinicians to measure how the body is responding to specific interventions. Rather than relying purely on anecdotal outcomes, physicians can observe changes in metabolic function, inflammation markers, cardiovascular performance and other indicators of biological health. “For me, diagnostics are just as important as the interventions themselves,” De Havilland says.
“Over the years, I have chosen to work alongside several leading diagnostic organisations that are pioneering new ways to measure human performance and biological ageing,” he continues. “These technologies enable practitioners to move beyond the guesswork of traditional wellness and towards a far more precise and evidence-led approach to preventative medicine.
“In many ways this is where longevity medicine is heading. The future will not be defined by single interventions alone but by integrated systems that combine diagnostics, personalised protocols and continuous data feedback.”
EXPANDING ACCESS TO LONGEVITY SCIENCE
Another profound shift is the growing public interest in taking a more proactive role in health optimisation. Longevity medicine, once confined to specialist clinics and research environments, is moving into the mainstream. Today, there is a growing movement of individuals who want to understand their biology, track their biomarkers and explore evidence-based strategies for improving long-term vitality.
Some describe this as the emergence of a “DIY longevity” culture. While it raises legitimate questions around regulation and product quality, it also reflects a broader change in how people think about their health. In De Havilland’s view, this trend represents the early stages of the democratisation of longevity science.
“If the goal of this field is ultimately to improve human healthspan on a meaningful scale, the knowledge and tools developed within specialist environments must eventually become accessible to all,” he says. That does not mean abandoning scientific standards, if anything, it makes those standards more critical than ever. “The responsibility of clinicians, researchers and leading organisations is to help guide this shift, by supporting innovation while maintaining a strong commitment to evidence, transparency and measurable outcomes,” De Havilland observes.
A BALANCED PERSPECTIVE
NAD+ is not a miracle molecule, but neither is it a passing trend. It is a fundamental component of human metabolism whose role in cellular health is indisputable. The question is no longer whether NAD+ matters, but how best to support its pathways in ways that are scientifically credible and clinically meaningful As research continues to evolve, the field will inevitably refine its understanding of the most effective delivery systems, optimal dosages and clinical applications, a process that will take time.
In the meantime, the most productive path forward is neither blind enthusiasm nor blanket scepticism. Longevity medicine will advance through careful research, honest debate and the responsible application of emerging science.
“Ultimately, the goal is simple,” De Havilland says. “To move from hype toward evidence, and from speculation toward measurable improvements in human healthspan. And that is where the real promise of this field lies.”
THE HEART–BRAIN CONNECTION
As the field continues to mature, the central question evolves: how do these deep-seated scientific insights translate into measurable impacts on human health? Preventive Medicine Consultant and CEO of Previty Healthcare Dr Sinead Sheridan cites the study “Pharmacologic reversal of advanced Alzheimer’s disease in mice and identification of potential therapeutic nodes in human brain” (Cell Reports Medicine, January 2026) as suggesting that by fortifying the energy-producing systems of the heart and the brain against deficits, we are safeguarding the very engines of human vitality.
“If restoring NAD+ pathways can preserve cellular function at the source,” notes Sheridan, “it may provide a vital shield for the organs most dependent on a continuous, high-performance energy supply, namely the heart and the brain.”
THE BODY’S CORE ENERGY CURRENCY
NAD+ is the fundamental currency of human energy. Its depletion occurs when the demand from vital cellular processes outpaces the body’s ability to produce it, a state often driven by ageing, chronic inflammation and metabolic stress.
This drastic decline in NAD+ levels as we age has been identified as a key driver in the progression of various age- and lifestyle-related conditions, particularly cardiovascular and neurodegenerative diseases.
Both the heart and the brain are exceptionally sensitive to these energy deficits; consequently, low NAD+ levels are a consistent hallmark in patients facing heart failure and Alzheimer’s disease.
RESTORING VITALITY FROM WITHIN
“What is truly transformative is the emerging evidence from recent preclinical and clinical research regarding the restorative effects of NAD+ on heart and brain health,” says Sheridan, a PhD in clinical exercise physiology and cardiovascular disease.
The study “Effect of nicotinamide adenine dinucleotide on heart failure caused by ischemic cardiomyopathy” (American Journal of Cardiovascular Drugs, September 2025) found that intravenous NAD+ improved cardiovascular function in patients with heart failure, enabling the heart to pump more effectively.
“The success of this study demonstrates that increasing NAD+ bioavailability intravenously can have immediate, systemic benefits for our most energy-demanding organs,” says Sheridan. She draws attention to the neuroprotective effects of NAD+ outlined in a study published late last year in the journal Cell reporting the prevention and reversal of Alzheimer’s disease in mice by restoring brain NAD+ levels. While these findings are currently preclinical, they offer a profound signal for human health: the possibility of preventing or reversing cognitive decline by simply restoring the body’s natural energy reserves.
WELLNESS TIPS
Why evidence and diagnostics matter
- Look for clinics that pair interventions with diagnostics: biomarkers, metabolic testing and
other measures of cardiovascular and brain function over time. - Be wary of products promising sweeping longevity benefits without transparent dosing, quality control or published human data.
What to ask before you try anything
- What specific outcome are we tracking (energy, cognition, cardiovascular health, recovery), and how will we measure change?
- How does this NAD+ protocol fit with my overall health picture — existing conditions, medications, sleep, exercise and nutrition — rather than replace those foundations