NMN (nicotinamide mononucleotide) has become one of the most talked-about supplements in anti-ageing circles, largely thanks to research from Harvard scientist David Sinclair and a wave of interest from the longevity community. The basic premise is straightforward: as we age, levels of a molecule called NAD+ decline in our cells, and NMN serves as a precursor that can potentially restore those levels.

But here’s where things get complicated. Most of the exciting research on NMN has been conducted in mice, not humans. And while the mouse studies show genuinely impressive results, translating rodent findings to human biology is notoriously unreliable. I’ll walk through what the evidence actually shows—both the promising bits and the considerable gaps in our knowledge.

What is NMN?

NMN (nicotinamide mononucleotide) is a derivative of vitamin B3 (niacin) and serves as a building block for NAD+ production in the body. Chemically speaking, it’s a bioactive nucleotide formed when a phosphate group combines with a nucleoside containing ribose and nicotinamide 1.

The molecule exists in two forms (alpha and beta), with the beta form being biologically active. It has a molecular weight of 334.221 g/mol.

You can actually get small amounts of NMN from food. Vegetables like cauliflower and cabbage contain roughly 0.25 to 1.12 mg per 100 grams. Avocados are among the richer sources at 0.36 to 1.6 mg per 100 grams, while beef contains considerably less at 0.06 to 0.42 mg per 100 grams. However, these amounts are minuscule compared to supplement doses, which typically range from 250 mg to 1000 mg daily.

Other common NAD+ precursors include niacin, nicotinamide, and nicotinamide riboside (NR). Each takes a slightly different pathway to NAD+ production, and there’s ongoing debate about which is most effective.

What is NAD+ and why does it matter?

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in every living cell. It’s required for over 500 enzymatic reactions and plays essential roles in metabolism, DNA repair, mitochondrial function, and gene expression 2.

The ageing connection comes from consistent observations that NAD+ levels decline with age across multiple tissues and organs. This decline has been associated with various age-related conditions including type 2 diabetes, obesity, heart failure, Alzheimer’s disease, and impaired cellular energy production.

The theory behind NMN supplementation is that by providing the body with more raw material to produce NAD+, we might slow or partially reverse some aspects of cellular ageing. Whether this theory holds up in humans is still being actively researched.

What are the evidence-based benefits of NMN?

1. May improve physical function in older adults

One of the more robust human studies comes from a randomised, double-blind, placebo-controlled trial involving 108 participants over 65 years of age. After 12 weeks of NMN supplementation at 250 mg daily, researchers observed improvements in lower extremity function and reduced drowsiness compared to placebo 3.

This matters because physical function decline is a significant predictor of falls, hospitalisation, and mortality in older adults. The World Health Organisation projects that by 2050, the number of people aged 60 and over will exceed 2.1 billion—making interventions that preserve physical function increasingly important from a public health perspective.

That said, this is a single study with a relatively small sample size. The results are encouraging but hardly definitive. More research with larger populations and longer follow-up periods would strengthen the case considerably.

2. May enhance aerobic endurance in athletes

A randomised, double-blind, placebo-controlled trial examined NMN’s effects on 48 healthy amateur runners over 6 weeks. Participants were divided into four groups receiving either placebo, low-dose (300 mg), medium-dose (600 mg), or high-dose (1200 mg) NMN daily 4.

The medium and high-dose groups showed greater improvements in oxygen uptake and ventilation thresholds compared to placebo. The researchers suggested this improvement stemmed from enhanced oxygen utilisation in skeletal muscle.

For anyone interested in endurance performance, this is worth noting—though the practical magnitude of improvement and whether it would make a noticeable difference for recreational exercisers remains unclear. If you’re already taking CoQ10 or fish oil for exercise performance, NMN might work through complementary mechanisms.

3. May improve muscle insulin sensitivity

A study in overweight or obese women with prediabetes found that 10 weeks of NMN supplementation (250 mg daily) increased muscle insulin sensitivity, improved muscle insulin signalling, and promoted muscle remodelling 5.

Skeletal muscle accounts for roughly 40% of total body weight and plays a crucial role in glucose metabolism. Improved insulin sensitivity in muscle tissue could theoretically help with blood sugar control, though this study was conducted in a very specific population (postmenopausal women with metabolic dysfunction).

Whether these findings extend to other groups—younger people, men, those without prediabetes—isn’t yet established.

4. Shows promise for liver fibrosis (animal studies only)

Liver fibrosis develops in response to chronic liver damage from alcohol, viral hepatitis, autoimmune conditions, or fatty liver disease. An animal study found that NMN supplementation inhibited the activation of hepatic stellate cells (the cells responsible for producing scar tissue) and prevented liver fibrosis progression 6.

I want to be clear here: this is animal research only. Liver fibrosis is a serious condition, and anyone dealing with it should work with a hepatologist rather than self-treating with supplements. The finding is interesting from a mechanistic standpoint but has no proven clinical application yet.

5. Anti-ageing effects (mostly theoretical)

The anti-ageing claims for NMN rest primarily on two mechanisms observed in animal studies:

Telomere maintenance: Telomeres are protective caps at the ends of chromosomes that shorten with each cell division. When they become too short, cells enter senescence or die. Animal research suggests NMN may help maintain telomere length and reduce DNA damage 7.

Sirtuin activation: NMN appears to increase activity of SIRT1, one of the sirtuin proteins involved in cellular stress responses, metabolism, and longevity pathways 8.

These mechanisms sound compelling, but remember that dozens of compounds activate sirtuins or protect telomeres in laboratory settings. Resveratrol, for instance, was once touted as a miracle anti-ageing compound based on similar reasoning. The translation to measurable human lifespan extension hasn’t materialised for most of these substances.

6. May support blood sugar regulation (animal studies)

Animal studies have shown that NMN can enhance liver insulin sensitivity through SIRT1 activation and restore gene expression patterns related to oxidative stress and circadian rhythm, ultimately improving glucose tolerance 9.

This connects to the muscle insulin sensitivity findings mentioned earlier, suggesting NMN might have metabolic benefits through multiple pathways. However, the animal-to-human translation problem applies here as well. People with diabetes or prediabetes should continue following evidence-based treatments rather than substituting NMN supplements.

For those interested in natural approaches to blood sugar support, the vitamin B complex family (of which NMN is derived) has better-established roles in metabolism.

7. Shows neuroprotective effects in Alzheimer’s models (animal studies)

In a rat model of Alzheimer’s disease, NMN treatment improved neuronal survival, enhanced energy metabolism, and reduced accumulation of reactive oxygen species 10.

Alzheimer’s disease affects tens of millions of people worldwide and remains without effective disease-modifying treatments. Any compound showing neuroprotective effects warrants investigation. But—and this is a significant but—countless substances have shown promise in animal Alzheimer’s models only to fail in human trials.

What are the side effects of NMN?

One of the more reassuring aspects of NMN research is its safety profile, though data remains limited.

Human safety data: A study examining single oral doses of 100 mg, 250 mg, and 500 mg found no changes in heart rate, blood pressure, blood oxygen levels, or body temperature after 5 hours. No major adverse reactions occurred 11.

Animal toxicity studies: Rodent studies using doses of 375, 750, and 1500 mg/kg/day for 90 days showed NMN to be safe. Acute toxicity trials found no deaths or treatment-related adverse effects at doses up to 2666 mg/kg 12.

Long-term animal safety: A year-long study in rodents using 100 or 300 mg/kg/day found no significant toxicity, serious side effects, or increased mortality 13.

Theoretical cancer concerns: Because NMN promotes angiogenesis (blood vessel formation), there’s been theoretical concern it might accelerate tumour growth. However, rodent studies have not shown NMN affecting tumour cell proliferation 14. This remains an area requiring more research.

The honest answer is that we don’t have long-term human safety data for NMN. Most supplement users are essentially participating in an uncontrolled experiment. If you’re considering NMN, starting with lower doses and monitoring for any adverse effects makes sense.

Dosage and practical considerations

Most human studies have used doses between 250 mg and 1200 mg daily. The sweet spot for many people seems to be 250-500 mg, though optimal dosing hasn’t been established.

NMN supplements come in various forms including capsules, powders, and sublingual tablets. Some manufacturers claim sublingual administration improves bioavailability, though rigorous comparative studies are lacking.

Quality varies significantly between manufacturers. Because supplements aren’t regulated as strictly as pharmaceuticals, third-party testing for purity and potency is worth seeking out.

Who should avoid NMN?

Given the limited safety data, certain groups should exercise particular caution:

Pregnant or breastfeeding women (no safety data)
People with active cancers (theoretical angiogenesis concerns)
Those taking medications that affect NAD+ metabolism
Anyone with significant liver or kidney disease

If you’re taking medications or managing chronic conditions, discussing NMN with your healthcare provider before starting supplementation is sensible—they can help assess potential interactions specific to your situation.

What this means for you

NMN sits in an interesting position: there’s genuine scientific rationale for its potential benefits, some promising early human data, and a reasonable safety profile—but we’re still far from being able to confidently recommend it for anti-ageing or specific health conditions.

The most honest assessment is that NMN might provide modest benefits for energy metabolism, physical function in older adults, and possibly exercise performance. The grander claims about reversing ageing or preventing age-related diseases remain unproven in humans.

If you’re curious about NMN, the risks appear low for most healthy adults. But managing expectations is important. This isn’t a fountain of youth, and the dramatic results seen in mouse studies may never translate to humans. Boring fundamentals like regular exercise, adequate sleep, and a nutrient-dense diet have far more evidence supporting their anti-ageing effects than any supplement currently available.

For those interested in the broader NAD+ and longevity space, comparing NMN with other approaches like astaxanthin for antioxidant support or intermittent fasting (which also affects NAD+ metabolism) might provide useful perspective.