Inside every one of the roughly 37 trillion cells in your body, a tiny molecule is working without pause. It shuttles electrons, fuels the production of ATP (your cellular energy currency), helps repair broken strands of DNA, and coordinates hundreds of metabolic reactions. That molecule is NAD+, short for nicotinamide adenine dinucleotide, and it may be one of the most consequential compounds in human biology that most people have never heard of.

It has no smell, no flavour, no colour. You cannot point to it on a label at a pharmacy. Yet over the past decade, a global research effort has quietly established NAD+ as a master regulator of cellular health — and its inevitable decline with age as a possible explanation for why we slow down, why our memories fade, and why our risk of diseases like Alzheimer's and Parkinson's rises as the decades pass.

This report explains what NAD+ is at a biological level, how the regulatory landscape in the United States and internationally has evolved, and what the most significant events of 2025 and 2026 mean for scientists, doctors, and anyone paying attention to the future of healthy ageing.

What is NAD+?

NAD+ stands for nicotinamide adenine dinucleotide — a coenzyme found in every living cell on Earth, from bacteria to blue whales. A coenzyme is a molecule that helps enzymes do their work; without it, the enzyme simply cannot function.

In cellular biology, NAD+ acts primarily as an electron carrier. When your body breaks down glucose or fats for energy, NAD+ accepts electrons and becomes NADH. NADH then donates those electrons to the mitochondrial machinery that produces ATP — the universal energy currency of life. This cycle repeats thousands of times every second in every cell.

But NAD+ is far more than just an energy shuttle. It is an essential cofactor for three critically important classes of proteins:

The central problem is one of scarcity over time. Humans produce NAD+ from dietary precursors — mainly tryptophan and various forms of niacin (vitamin B3). But the enzymes that degrade NAD+, particularly CD38, become more active as we age, while biosynthesis slows. The result is a progressive and measurable depletion.

The science: what research actually shows

For most of the twentieth century, NAD+ was studied in the narrow context of pellagra — the niacin-deficiency disease that plagued poor communities in the American South and southern Europe. The explosion of interest in NAD+ as an anti-ageing target began in the early 2000s, when researchers discovered that feeding NAD+ precursors to yeast and mice extended their lifespan and improved metabolic health.

Animal studies

The animal data is compelling and consistent. In mice, restoring NAD+ levels through supplementation has been shown to improve muscle endurance, enhance memory and cognitive function, reverse some aspects of vascular ageing, and extend healthy lifespan. Similar results have been observed in worms, flies, and rats. These findings established the scientific rationale for human trials.

Human clinical trials

The human evidence is younger and more cautious. Multiple small-to-medium trials have confirmed that oral supplementation with NAD+ precursors — particularly nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) — reliably raises NAD+ levels in blood and certain tissues. What those elevated levels actually do for human health outcomes is still being established.

A 24-week clinical trial conducted at Massachusetts General Hospital tested whether boosting NAD+ through NR supplementation could improve cognitive function and ease symptoms in people with long COVID. The study, involving 58 participants, found early signals that NR may reduce fatigue and brain fog — some of the most debilitating features of post-viral illness — though researchers emphasised that larger trials are needed to confirm the findings.

A separate large observational study by the United States Department of Veterans Affairs confirmed that nicotinamide — a closely related form of vitamin B3 and a simpler NAD+ precursor — may offer significant protection against certain skin cancers, adding a preventive medicine angle to the NAD+ conversation.

The 2026 Nature Aging landmark review

The most authoritative statement to date on NAD+ and ageing came on 24 March 2026, when researchers from the University of Oslo, Akershus University Hospital, and more than two dozen international collaborators published a comprehensive expert review in Nature Aging — one of the most prestigious journals in the field.

The review, which synthesised data from hundreds of studies, reached several important conclusions. It identified NAD+ augmentation as a genuinely promising avenue for slowing the progression of both Alzheimer's and Parkinson's disease — not as a cure, but as a preventive and disease-modifying strategy. The mechanism: NAD+ is essential for mitochondrial health in neurons, and mitochondrial dysfunction is now understood to be a core feature of both diseases. Maintaining higher NAD+ levels may dampen this dysfunction and reduce the neuroinflammation that drives neurodegeneration.

Crucially, the review also called for more rigorous, large-scale clinical trials — a sign that, while the field is maturing, definitive proof of benefit in humans remains a work in progress.

Regulation: FDA, NMN, and a three-year battle

Understanding how NAD+ supplements are regulated requires distinguishing between the molecule itself and its precursors — the compounds the body uses to synthesise it.

NAD+ itself is not sold in significant quantities as an oral supplement, because the molecule is broken down in the gut before it reaches the bloodstream. What people actually take are precursors: mainly niacin (plain vitamin B3), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN). Each follows different pathways in the body, and each has had its own regulatory story.

NR: well-established and uncontroversial

Nicotinamide riboside, sold under brand names such as Tru Niagen by Niagen Bioscience (formerly ChromaDex), has been commercially available as a dietary supplement since 2013 without regulatory challenge. The compound has GRAS (Generally Recognised As Safe) status and a robust safety profile from human trials. As of 2026, it remains the most legally clear-cut of the NAD+ precursors.

NMN: a three-year regulatory saga

Nicotinamide mononucleotide had a far more turbulent journey. In May 2022, one manufacturer's NMN received the first New Dietary Ingredient Notification (NDIN) acknowledgement from the FDA. But in November 2022, the agency reversed course — declaring that NMN could not be lawfully marketed as a dietary supplement, because it had been investigated as a pharmaceutical drug (under the designation MIB-626) prior to being marketed as a supplement. This invoked the "drug preclusion clause" of the Dietary Supplement Health and Education Act (DSHEA), which prevents an ingredient from being sold as a supplement if it was first investigated as a drug.

The decision was purely regulatory — the FDA never declared NMN unsafe. Nevertheless, several major retailers including Amazon pulled NMN products from their platforms. The Natural Products Association (NPA) and the Alliance for Natural Health USA filed a formal citizen petition challenging the FDA's interpretation, followed by a federal lawsuit.

After nearly three years of petitions, court proceedings, and advocacy, the FDA reversed its position on 29 September 2025, confirming that NMN is lawful for use in dietary supplements in the United States. In December 2025, the agency issued formal letters reinstating the New Dietary Ingredient status for NMN suppliers.

The IV NAD+ question

Intravenous NAD+ infusions — offered at longevity clinics and wellness centres, sometimes at significant cost — sit in a distinct regulatory category. They are not dietary supplements and are not FDA-approved drugs. They are compounded preparations, regulated by state medical boards and requiring prescriber oversight. In 2024, the FDA issued enforcement actions against clinics operating outside these requirements, though these targeted non-compliant facilities, not the compound itself. IV NAD+ therapy remains legal when administered by licensed practitioners following state telehealth statutes.

No FDA-approved NAD+ drug

It is worth being clear on one point: no NAD+ precursor has been approved by the FDA as a pharmaceutical drug for any disease indication. NR, NMN, and related compounds are regulated as dietary supplements in the United States — meaning they can be sold without pre-market approval, but manufacturers are prohibited from making disease treatment claims. Researchers continue to investigate them as potential drug candidates for specific conditions, but that process is at an early stage.

The key NAD+ precursors compared

2026: a year of milestones

Aside from the Nature Aging review, 2026 has seen a cluster of significant developments that reflect how seriously the mainstream scientific and institutional world now takes NAD+ biology.

In March 2026, the inaugural NAD for Health: Opportunities and Challenges scientific conference took place at the Royal Danish Academy of Sciences and Letters in Copenhagen, hosted by the University of Copenhagen and sponsored by Niagen Bioscience. The gathering, attended by leading researchers from across Europe and North America, was devoted entirely to the therapeutic potential and scientific challenges of NAD+ augmentation — a sign of the field's growing institutional weight.

Also in 2026, researchers published new comparative data on three different NAD+ boosters and their differential effects on circulatory NAD levels and microbial metabolism in human participants — addressing longstanding questions about which precursor is most effective in practice and for whom.

In parallel, the market for NAD+ products has continued to expand rapidly. Niagen Bioscience, which acquired additional patents covering NR and its salt forms from Queen's University Belfast in early 2026, also expanded the availability of its flagship Tru Niagen supplement through HSA (Health Savings Account) and FSA (Flexible Spending Account) channels in the United States — a move that signals growing recognition of NAD+ supplementation as a legitimate health product rather than a fringe wellness commodity.

Not all the sentiment in the field is uniformly bullish, however. Some leading researchers have urged caution. The enthusiasm from the longevity and biohacking communities — with celebrities and wellness influencers paying hundreds or thousands of pounds for IV infusions on the basis of limited human outcome data — has prompted scientists to distinguish clearly between what the mechanistic and animal evidence shows and what has been proven in randomised clinical trials in humans. The headline of a major NPR investigation published in May 2026 captured the tension neatly: the market for NAD+ products is booming, and the optimism has legitimate scientific roots, but the definitive human evidence has not yet arrived to match the excitement.

The bottom line

NAD+ is not a fad. It is a molecule whose fundamental importance to cellular life has been established beyond doubt over decades of rigorous biochemistry. The decline of NAD+ with age is real, measurable, and linked to processes that drive disease. The precursors available to boost it are, in 2026, legally clear-cut in the United States, affordable, and backed by a growing body of human safety data.

What remains genuinely open is the question of how much benefit healthy humans receive from supplementation — and at what doses, using which precursors, and for which specific health outcomes. That is the work now underway in dozens of clinical trials around the world. The March 2026 Nature Aging review, authored by more than 25 scientists from leading institutions, represents the field placing its institutional weight behind NAD+ augmentation as a legitimate scientific priority — not a cure-all, but a frontier worth taking seriously.

The molecule at the heart of your cells' energy production has, after decades in biochemistry textbooks, arrived in public consciousness. Whether it arrives in clinical practice as a treatment for Alzheimer's, Parkinson's, long COVID fatigue, or the general infirmities of ageing will depend on the trials now being run. In the meantime, the science is more credible — and more watched — than at any point in history.