What are NMN supplements and will they really help with longevity? Doctors explain

There's no shortage of supplements promising to slow the ageing process, but few have generated quite as much buzz as NMN. 

Touted as a shortcut to boosting levels of NAD+ (a coenzyme linked to cellular repair and energy), it's become a go-to among the celebrity wellness crowd. Names including Gwyneth Paltrow, Hailey Bieber and Jennifer Aniston have all been linked to NAD+ therapies, while Kim Kardashian has reportedly been taking NMN supplements for over a year, influenced by longevity research from Dr. David Sinclair.

It's not just a celebrity fixation. Interest in 'biological age' is steadily growing, with more of us looking to extend our healthspan – not just how long we live, but how well we live. 

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According to Boots' 2026 trend report, 60% of consumers now prioritise healthy ageing, with more people turning to biohacking tools (such as collagen supplements and NAD+ boosters) in an effort to optimise how their bodies function at a cellular level. But can a daily supplement really turn back the clock, or is NMN simply another longevity trend outpacing the science?

What is NMN and how does it work in the body?

NMN (nicotinamide mononucleotide) is a naturally occurring molecule that acts as a direct precursor to NAD+ (nicotinamide adenine dinucleotide) – a coenzyme that is essential for life. "NAD+ is central to energy metabolism, DNA repair and the activity of proteins called sirtuins, which play a key role in cellular ageing," explains Alice Mackintosh, registered nutritional therapist and co-founder of Equi London.

Like collagen, NAD+ levels naturally decline over time. Research suggests they peak in our twenties and can fall by as much as 50% by midlife. "This decline is one of the reasons ageing is often associated with lower energy, slower recovery and increased vulnerability to disease," says Dr. Cherry Lo, a longevity researcher specialising in pathology and immunity at Manapura.

By acting as a building block for NAD+, it's thought that supplementing with NMN could help restore levels and support the body's natural repair systems. The aim isn't to "reverse ageing", but to help cells function more optimally for longer – although, as with many areas of longevity science, the extent of its real-world impact is still being explored.

Do NMN supplements actually work? 

Despite the buzz, experts are careful not to overstate what NMN can do. "As a clinician, I'm always cautious when a supplement becomes a cultural moment before the science has caught up," says Mackintosh. "The excitement largely began with animal studies (particularly in mice) which showed some remarkable results around energy, muscle function and metabolic health. But the human trials we have so far are small, short-term and haven’t consistently replicated those outcomes in a meaningful way."

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That doesn't mean NMN is without potential. At a biological level, the rationale is strong, and early findings are encouraging. "Emerging clinical trials suggest NMN supplementation can safely raise NAD+ levels and may improve markers linked to muscle function, insulin sensitivity and fatigue," says Dr Lo. However, while NMN appears to increase NAD+ levels in the blood, it's still unclear how this plays out in humans – largely because the long-term data isn't there yet. As Mackintosh puts it: "That's where the evidence is still catching up."

Can you boost NAD+ levels naturally?

When it comes to longevity, there's no such thing as a "quick fix". Supplements may have a role to play, but they're not a substitute for the fundamentals. "Foods rich in niacin and tryptophan (think eggs, oily fish, chicken, dairy, legumes and wholegrains) support the body's own NAD+ synthesis pathways," says Mackintosh.

There's also growing interest in plant compounds. "Flavonoids such as apigenin, found in parsley, celery and chamomile tea, and quercetin, found in onions and apples, appear to inhibit an enzyme called CD38," she explains. "This enzyme essentially acts as a drain on NAD+ levels, and its activity increases as we age." While it's unclear whether the amounts found in food are enough to have a measurable effect, it's another reason to prioritise a varied, plant-rich diet.

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Lifestyle factors can make a difference, too. Exercise, particularly resistance training and higher-intensity cardio, is one of the most well-evidenced ways to support NAD+ production, thanks to its role in mitochondrial health and energy metabolism. Sleep, too, plays a critical role in the cellular repair processes that NAD+ underpins, while chronic overeating has been linked to depleted levels.

"The more sophisticated thinking in this space is moving away from single-ingredient solutions and towards a whole-systems approach," says Mackintosh. "In almost fifteen years of clinical practice, I've rarely found that a single molecule is the answer."

Is NMN safe – and who should take it? 

NMN may be most suited for those noticing changes in energy, focus or recovery. "Symptoms such as persistent fatigue, brain fog, disrupted sleep and a sense that your body just isn't bouncing back the way it used to are very common," says Mackintosh. But those symptoms aren't always as straightforward as they seem. "Before attributing them to NAD+ decline, I'd want to rule out things such as iron deficiency, thyroid dysfunction, low B12, poor sleep quality, blood sugar dysregulation or chronic stress," she explains. 

That's especially true for women navigating perimenopause and menopause, where hormonal changes have wide-reaching effects on energy, metabolism and cognition. "NMN is not going to touch any of that if someone is under-eating protein, running on too little sleep, or on a blood sugar rollercoaster," Mackintosh adds. Instead, the focus should remain on the fundamentals – nutrition, resistance training, sleep and stress management.

From a safety perspective, NMN appears to be well tolerated in the short term, and for most healthy adults, it's unlikely to cause harm. That said, long-term data in humans is still limited, so it's worth approaching with caution. Pregnant or breastfeeding women, those on medication, or anyone with underlying health conditions should speak to a healthcare professional before taking it.

For those considering it, NMN is best viewed as one potential piece of the longevity puzzle, rather than a standalone solution. As Dr. Lo notes, it may be most relevant for those experiencing age-related declines in energy, metabolic health or recovery – but the science is still evolving.

What should you look for in an NMN supplement? 

"Transparency and purity are extremely important in the NMN market," says Dr Lo. Look for products that are third-party tested, with clear information on sourcing, manufacturing and stability. "High-purity NMN, ideally verified by independent testing, is key," she says, along with the active β-form – the version the body can use.

Manufacturing also matters. Enzymatic synthesis is often considered the gold standard, as it avoids harsh chemical solvents. Be wary of red flags: products that promise dramatic "anti-ageing" results, lack transparency or come at unusually low price points. "NMN is an exciting area of research, but it should not be positioned as a miracle supplement or a shortcut to healthy ageing," Dr. Lo adds.

Try these supplements as part of your healthy living routine...

Charava NMN+ 1200, £59.99 for 30 capsules

A well-rounded formula that combines NMN with resveratrol and pterostilbene, this is a good option if you're looking to support energy and focus alongside broader cellular health.

Manapura Pure NMN, £63 for 30 capsules

A high-strength, no-frills option, one capsule delivers 500mg of bioactive NMN in a micronised form to support absorption. Take two every morning for a targeted NAD+ boost.

Youth & Earth NMN Capsules, £24.99 for 60 capsules

Clean, plant-based and made with 99% NMN, this is a fuss-free option designed to support energy, metabolism and overall cellular function.

ARTAH Enhanced NAD+ Complex, £60 for 30 capsules

This supplement blends NAD+ precursors with phytonutrients (such as resveratrol and luteolin) to support both NAD+ production and recycling. It’s ideal for cognitive clarity and sustained energy.

Nuchido TIME+, £65 for 30 capsules

Designed to work with your circadian rhythm, this blend of NAD+ precursors and antioxidants supports steady energy throughout the day – without the peaks and crashes.