Longevity: The Science of Slowing Biological Ageing
What Longevity Science Actually Studies
Longevity science is not about living forever. It is about compressing the period of decline at the end of life, and extending the years spent in full health. The distinction between lifespan (total years alive) and healthspan (years of functional, disease-free life) sits at the centre of every serious research programme in this field.
Most people spend the last decade or more of their lives managing chronic disease. Longevity science asks whether that has to be true, and whether the biological processes driving decline can be slowed, or in some cases reversed.
In 2013, a landmark paper in Cell identified nine hallmarks of ageing: the molecular and cellular changes that accumulate over time and eventually cause the body to fail. These have since been expanded, but the core framework holds. Among the most clinically relevant are NAD+ decline, senescent cell accumulation, mitochondrial dysfunction, telomere attrition, and loss of proteostasis (the cell's ability to maintain protein quality). These are not separate problems. They are interconnected, and they amplify one another.
This page maps the key mechanisms, explains what the evidence currently supports, and describes how a targeted supplement stack addresses them.
NAD+ Decline as a Central Driver of Ageing
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme found in every cell in the body. It is involved in over 500 enzymatic reactions, making it one of the most critical molecules in human biology. The problem is that NAD+ levels fall steadily with age. By the time most people reach 60, their NAD+ has dropped roughly 50% compared to levels in their 30s.
This matters for several reasons. First, NAD+ is required by sirtuins, a family of proteins that regulate DNA repair, inflammation control, and mitochondrial function. Without adequate NAD+, sirtuins cannot do their jobs. Second, NAD+ is consumed by PARP enzymes, which detect and repair DNA strand breaks. As DNA damage accumulates with age, PARP activity increases, depleting the remaining NAD+ further. This creates a cycle: ageing reduces NAD+, which impairs the repair systems that would otherwise slow ageing.
NMN (nicotinamide mononucleotide) is the most direct dietary precursor to NAD+. When you take NMN orally, it is converted to NAD+ in tissues within minutes. Of the available NAD+ precursors, NMN enters cells via a dedicated transporter (Slc12a8) and bypasses several of the rate-limiting steps that make other precursors less efficient in certain tissues.
Supplementing with NMN is currently the most studied approach to raising NAD+ in adults. NMN Bio's 500mg NMN capsules use stabilised, third-party tested NMN with no fillers or proprietary blends.
Senescent Cells and Why They Matter
Cellular senescence is the process by which a damaged or stressed cell stops dividing but does not die. These cells are sometimes called zombie cells: they linger in tissues, metabolically active but no longer functional, and they cause damage to the cells around them.
The mechanism driving this damage is the senescence-associated secretory phenotype, or SASP. Senescent cells secrete a mix of inflammatory cytokines, proteases, and other signalling molecules that degrade the surrounding tissue environment. In small numbers, senescent cells play useful roles in wound healing and tumour suppression. The problem is that they accumulate with age, because the immune system becomes less efficient at clearing them. As senescent cell burden rises, so does chronic low-grade inflammation, one of the most consistent features of biological ageing.
Senolytics are compounds that selectively clear senescent cells. The most studied are quercetin and fisetin, both polyphenols found in plants. In animal models, senolytic treatment has consistently improved physical function, reduced inflammatory markers, and extended healthspan. Human trials are still early, but the mechanistic rationale is well established.
Quercetin also inhibits CD38, an enzyme that degrades NAD+. This means quercetin may support NAD+ levels through a different pathway than NMN, making the two compounds complementary rather than redundant.
Mitochondrial Function and the Energy of Ageing
Mitochondria generate the ATP that powers every cell in the body. When mitochondria decline, cells lose the energy they need to carry out repair, signalling, and normal function. Mitochondrial dysfunction is consistently present in aged tissue and is one of the hallmarks with the broadest downstream consequences.
Several processes drive mitochondrial decline with age. Mitochondrial DNA accumulates mutations more readily than nuclear DNA, because it lacks protective histones and sits close to the site of reactive oxygen species production. The network of mitochondria within cells also becomes fragmented and less efficient at quality control, allowing damaged mitochondria to persist rather than being cleared.
NAD+ is essential to mitochondrial respiration. It acts as an electron carrier in the electron transport chain, and without it, cells cannot generate ATP efficiently. Restoring NAD+ via NMN supplementation has been shown to improve mitochondrial markers in human trials. A 2021 study published in Cell Metabolism found that NMN supplementation improved muscle physiology and physical performance in older adults, with improvements in markers directly related to mitochondrial function.
Sirtuins, particularly SIRT3, also regulate mitochondrial health. SIRT3 deacetylates and activates key enzymes in the electron transport chain, and its activity depends entirely on available NAD+. This creates a direct line from NAD+ status to mitochondrial efficiency.
The Sirtuin Pathway
Sirtuins are a family of seven proteins (SIRT1 through SIRT7), often described as longevity proteins because of their role in regulating the cellular responses to stress, nutrient availability, and damage. Every sirtuin requires NAD+ as a cofactor to function. They are not enzymes that use NAD+ as a substrate incidentally: they consume it with each catalytic cycle.
SIRT1 is the most studied. It regulates DNA repair, suppresses inflammatory gene expression via NF-kB inhibition, and governs mitochondrial biogenesis through PGC-1alpha activation. Reduced SIRT1 activity is associated with metabolic dysfunction, neurodegeneration, and impaired DNA repair.
SIRT3 is localised to mitochondria and maintains the efficiency of the electron transport chain. SIRT6 plays a critical role in telomere maintenance and DNA repair at double-strand breaks.
Caloric restriction activates sirtuins by increasing NAD+ availability. When cells are in an energy-restricted state, NADH is oxidised more readily, raising the NAD+/NADH ratio and giving sirtuins more substrate to work with. NMN supplementation achieves the same biochemical outcome by restoring total NAD+ levels without requiring caloric restriction. This is part of why David Sinclair's lab, among others, has focused heavily on NMN as a caloric restriction mimetic.
The Role of Methylation
Methylation is one of the most important regulatory processes in biology. It controls gene expression through epigenetic modification of DNA and histones, governs neurotransmitter synthesis (including dopamine, serotonin, and adrenaline), and is central to the methylation cycle that supports detoxification, cardiovascular health, and immune function.
The epigenetic clock, developed by Steve Horvath at UCLA, measures biological age through patterns of DNA methylation across the genome. Methylation patterns shift predictably with age, and they do so faster when the body is under stress, nutritional deficiency, or chronic inflammation. Maintaining healthy methylation capacity is therefore one mechanism by which biological age can diverge from chronological age.
Here, there is a specific and important interaction with NMN. The conversion of NMN to NAD+ generates nicotinamide as a byproduct. Nicotinamide is cleared from the body primarily through methylation, consuming methyl groups in the process. At higher doses of NMN, this can place additional demand on the body's methyl pool.
TMG (trimethylglycine, also called betaine) is the most efficient dietary methyl donor. It donates methyl groups directly in the methionine cycle, replenishing S-adenosylmethionine (SAMe), the universal methyl donor for hundreds of biochemical reactions. Taking TMG alongside NMN ensures that methyl group demand from NMN metabolism does not deplete the pool needed for DNA methylation and neurotransmitter synthesis.
This is why NMN Bio formulates NMN and TMG together. The combination supports NAD+ restoration without compromising methylation capacity.
Autophagy and Cellular Housekeeping
Autophagy is the process by which cells break down and recycle their own damaged or dysfunctional components. Misfolded proteins, worn-out organelles, and pathological aggregates are sequestered into autophagosomes and delivered to lysosomes for degradation. The resulting components are then recycled as building materials.
This is not a secondary cleanup function. Autophagy is essential to cell survival under stress, to immune defence, and to the prevention of the protein aggregates that underlie neurodegenerative diseases. Loss of proteostasis, one of the hallmarks of ageing, is in part a consequence of declining autophagic flux.
Autophagy is regulated primarily through the AMPK and mTOR pathways. AMPK, which is activated when cellular energy is low, promotes autophagy. mTOR, which is activated when nutrients are abundant, suppresses it. Fasting and caloric restriction drive autophagy by shifting this balance toward AMPK activation. Exercise does the same.
NAD+ restoration also activates autophagy, in part through SIRT1. SIRT1 deacetylates and activates key components of the autophagy machinery, including Beclin-1 and Atg5. This means that NMN supplementation, by restoring NAD+ and supporting sirtuin activity, may improve autophagic flux in aged tissue.
Dr Seranova's doctoral research at the University of Birmingham focused on autophagy and stem cell biology, which informs NMN Bio's emphasis on this pathway.
The NMN Bio Longevity Stack
No single compound addresses every hallmark of ageing. The goal of a longevity stack is to cover multiple mechanisms simultaneously, with ingredients that are complementary rather than redundant.
NMN Bio's core stack is built around four compounds, each targeting a distinct but interconnected pathway.
| Compound | Primary Target | Mechanism |
|---|---|---|
| NMN 500mg | NAD+ decline, sirtuins, mitochondria | Restores intracellular NAD+ as the direct precursor; activates SIRT1/SIRT3; supports mitochondrial respiration |
| TMG | Methylation, epigenetic clock | Replenishes methyl groups consumed during NMN metabolism; supports SAMe production and DNA methylation |
| Quercetin | Senescent cells, NAD+ preservation | Senolytic activity against SASP-producing cells; CD38 inhibition to reduce NAD+ degradation |
| Fisetin | Brain senescence, neuroinflammation | Crosses the blood-brain barrier; clears senescent cells in neural tissue; reduces neuroinflammatory signalling |
NMN 500mg capsules form the foundation of the stack. For those starting with a single product, this is the most direct way to address NAD+ decline. The Morning Bundle combines NMN with TMG and additional longevity compounds in a single daily protocol, designed around the mechanisms described on this page.
Dosing is straightforward. NMN and TMG are taken in the morning, with or without food. There are no known interactions with common medications at standard doses, though anyone on blood thinners or immunosuppressants should consult their GP before starting.
What the Human Research Shows
Most longevity research is preclinical. This is worth stating clearly: the evidence that NMN extends lifespan in mice is strong and consistent. Whether the same effects translate to humans at equivalent doses is still being established. The human data on NMN is growing, and it is more promising than sceptics often acknowledge, but it is not yet the size of the clinical evidence base for statins or metformin.
What the human trials do show:
- Yoshino et al. (Cell Metabolism, 2021): A randomised, placebo-controlled trial in postmenopausal women with prediabetes found that 250mg/day of NMN for 10 weeks significantly increased muscle NAD+ levels and improved insulin signalling, with upregulation of genes involved in muscle remodelling and energy metabolism.
- Imai et al. (Science, 2022): A double-blind trial in older adults found that 250mg/day of NMN improved physical performance, particularly in the muscles' ability to use oxygen during exercise. This is consistent with improved mitochondrial function and is one of the most cited pieces of human NMN evidence to date.
- Japanese safety trials (2020, 2022): Multiple trials conducted in Japan have confirmed that NMN is safe and well-tolerated in humans at doses ranging from 100mg to 1200mg/day, with no serious adverse events recorded.
- Plasma NAD+ elevation: Several trials have confirmed that oral NMN supplementation reliably raises NAD+ levels in blood, meaning it is absorbed and converted as expected. The question is no longer whether it works biochemically, but what the clinical outcomes are at the doses people actually take.
The honest summary is this: the mechanistic case for NMN is well supported. The human safety data is solid. The efficacy data in humans is promising but still accumulating. Anyone who tells you NMN is proven to extend human lifespan is ahead of the evidence. Anyone who dismisses it as unproven ignores the depth of the mechanistic and early clinical literature.
Who This Is For
Longevity interventions make most sense for people who are far enough from acute disease to focus on prevention, but close enough to the inflection point of biological decline to act before it compounds.
That typically means people in their mid-30s to 60s who are already paying attention. People who have read Lifespan by David Sinclair, or Peter Attia's Outlive. People who track their blood work, think about their VO2 max, and treat their biology as something to be managed rather than endured. Founders and executives who understand that cognitive and physical performance are assets, and that protecting them is not vanity: it is strategy.
This is not a supplement line for people looking for a shortcut to health they have not otherwise worked for. Sleep, training, diet, and stress management remain the largest levers. What NMN, TMG, quercetin, and fisetin do is address the cellular-level processes that lifestyle alone cannot fully reach, and which are already declining by the time most people notice.
If you are 35 and wondering whether to start, the research suggests earlier is better. NAD+ decline is already measurable in your 30s. The compounding returns of maintaining mitochondrial and sirtuin function are greater when you begin from a higher baseline.
If you are 50 and have not started, you have not missed the window. Human trials showing benefit have largely recruited participants in their 50s and 60s. There is still meaningful ground to recover and protect.
Start with NMN 500mg. Pair it with TMG. Add quercetin and fisetin when you are ready to address senescence directly.
