What NAD biology explains — and what human trials have yet to establish.

When an ingredient is described as supporting cellular energy, it is easy to imagine a noticeable change: a clearer morning, an easier workout, fewer afternoons spent running on empty. NMN has attracted attention partly because its biology seems to offer a route to those experiences. The connection is more complicated than the phrase suggests.

NMN participates in the production of NAD⁺, a molecule essential to cellular metabolism. Human trials show that supplementation can change NAD-related measurements. Whether those changes consistently improve daily energy, physical performance or long-term health is a different question. Understanding that distinction is the best place to begin. [1, 7]

What NMN Actually Is

NMN stands for nicotinamide mononucleotide. It is a nucleotide involved in the body's pathways for making nicotinamide adenine dinucleotide, usually written as NAD⁺. Enzymes called NMN adenylyltransferases convert NMN into NAD⁺. The body also makes and recycles NAD⁺ through other routes, so this is a regulated metabolic network rather than a single reservoir waiting to be topped up. [1]

NAD⁺ and its reduced form, NADH, help transfer electrons during reactions that extract energy from nutrients. Those reactions connect to mitochondrial ATP production. ATP supplies usable energy for cellular work. NAD⁺ also serves as a substrate for enzymes involved in processes such as DNA repair and cellular signaling. None of this means that an NMN capsule directly supplies ATP, repairs a person's DNA or produces an immediate feeling of energy. [1]

NR, or nicotinamide riboside, is another NAD⁺ precursor. NMN and NR are related, but they are not interchangeable ingredients. A trial of NR cannot establish the effects of NMN, and a trial of one NMN preparation does not automatically establish the effects of every commercial formulation. [1, 7]

Why Aging Researchers Study It

Research has documented changes in NAD⁺ metabolism with aging in experimental models and in some human tissues. These changes have prompted scientists to test whether altering precursor availability can influence cellular function. However, tissue, health status and measurement method matter; age alone does not establish that someone has a clinically meaningful NAD⁺ deficiency. [1]

The distinction between compartments is also important. A blood measurement is not a direct reading of NAD⁺ inside every muscle cell or within its mitochondria. Higher circulating or blood-cell NAD-related values show a biological response, but they do not by themselves demonstrate better stamina, younger cells or a longer life. [1, 7]

What the Human Trials Found

A Small Metabolic Trial

In a randomized, double-blind trial published in Science in 2021, researchers studied postmenopausal women with prediabetes who were overweight or obese over ten weeks. NMN supplementation was associated with changes in insulin-stimulated glucose disposal and skeletal muscle insulin signaling. The study used specialized metabolic testing rather than relying only on routine fasting blood measurements. [2]

This is a meaningful research observation in a defined population. It is not evidence that NMN treats diabetes, prevents progression from prediabetes, causes weight loss or produces the same response in healthy men and women. The study was short and was not designed to answer those clinical questions. [2]

Exercise Results Need Their Training Context

A 2021 trial enrolled 48 recreational runners for six weeks. Participants received placebo or 300, 600 or 1,200 mg of NMN per day while following an exercise-training program. The medium- and higher-dose groups improved more on some ventilatory-threshold measures, which describe how the body responds as exercise intensity rises. However, the study did not show corresponding between-group advantages in maximal oxygen uptake or peak power. [3]

All groups trained. The result therefore concerns NMN in that training setting, not a capsule replacing exercise. With only 12 participants per group and predominantly male runners, the findings are also too narrow to predict the response of a sedentary older adult. The doses describe the experiment; they are not personal dosing recommendations. [3]

A Walking and Sleep Study With a Null Primary Outcome

A 2024 randomized trial assigned 60 older adults to 250 mg of NMN daily or placebo for 12 weeks. Its primary stepping-test outcome did not differ significantly between groups. Some secondary measures favored NMN, including four-meter walking time, NAD-related blood measurements and selected sleep-questionnaire scores. [4]

That combination deserves a careful reading. The positive secondary findings suggest questions for further study, but they do not erase the null primary outcome. Questionnaire scores also cannot establish that NMN treats insomnia. When a trial examines many outcomes, replication and the prespecified analysis become especially important. [4]

What the Broader Evidence Adds

A 2025 systematic review and meta-analysis evaluated NMN and NR studies involving adults whose mean ages were above 60. For NMN, pooled results did not show significant improvements in skeletal muscle index, handgrip strength, gait speed or the five-chair-stand test. The review does not prove that every possible NMN intervention is ineffective, but it argues against presenting muscle preservation as an established benefit. [5]

A July 2026 review included 15 trials of oral NMN or NMN-related preparations, with ten contributing to safety analyses. Study durations ranged from 14 days to 24 weeks. It found no significant pooled effects on body weight, BMI, fasting glucose, HbA1c or lipid profiles. A small diastolic blood-pressure signal was exploratory and did not establish NMN as a blood-pressure treatment. The included populations and preparations varied. [6]

A separate 2026 review of 113 human and rodent studies reached a compatible conclusion: biochemical responses to NAD-related interventions were more consistent than functional or broader health outcomes in people. Its total included 33 human intervention studies, not 113 human trials. [7]

How to Think About Safety and Product Claims

The 2026 safety analysis found no clear short-term increase in reported adverse events or measured liver-enzyme abnormalities. That is useful information within the studied conditions, not proof of safety over years. Small studies cannot reliably rule out uncommon adverse effects, and their results do not establish safety during pregnancy or breastfeeding or with every medication. [6]

An ingredient's purity, dose, formulation and storage conditions are separate questions from its proposed biology. A certificate of analysis can help document what is in a product; it cannot establish that the product improves health. Likewise, a higher dose on a label does not establish a larger benefit.

For someone reading the science, three questions are more useful than a promise of cellular rejuvenation: What was measured? In whom? Compared with what? NMN remains an active area of research. The most defensible interpretation is that it can alter NAD biology under studied conditions, while reliable improvements in everyday function and long-term outcomes remain unsettled. [5–7]

References

1. Covarrubias AJ et al. NAD⁺ metabolism and its roles in cellular processes during ageing. Nature Reviews Molecular Cell Biology. 2021;22(2). doi.org/10.1038/s41580-020-00313-x
2. Yoshino M et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547). doi.org/10.1126/science.abe9985
3. Liao B et al. Nicotinamide mononucleotide supplementation enhances aerobic capacity in amateur runners. Journal of the International Society of Sports Nutrition. 2021;18(1). doi.org/10.1186/s12970-021-00442-4
4. Morifuji M et al. Ingestion of β-nicotinamide mononucleotide increased blood NAD levels, maintained walking speed, and improved sleep quality in older adults. GeroScience. 2024;46(5). PubMed
5. Prokopidis K et al. The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis. Journal of Cachexia, Sarcopenia and Muscle. 2025;16(3). PMC
6. Yang W et al. Safety and Metabolism-Related Outcomes of Oral Nicotinamide Mononucleotide Supplementation in Adults. Nutrients. 2026;18(14).
7. Gallagher C et al. NAD⁺ supplementation for anti-aging and wellness: A PRISMA-guided systematic review. Ageing Research Reviews. 2026;116.

A closer look at mitophagy, muscle trials and the limits of the evidence.

Mitochondria are often described as the power plants of a cell. Less attention goes to the maintenance work around them: identifying damage, replacing components and removing structures that no longer function well. Urolithin A has become a subject of longevity research because of its connection to that maintenance process.

The human evidence is interesting, but it does not support every claim that has grown around the ingredient. Several trials report changes in muscle tests or molecular measurements. Important primary outcomes have also been negative, and the studies have generally been small and short. Both parts belong in the story. [1–7]

What Urolithin A Is and Where It Comes From

Urolithin A, abbreviated UA, is a metabolite that certain gut microbes can produce from dietary ellagitannins and ellagic acid. Foods such as pomegranates, walnuts and some berries provide these precursor compounds. Eating those foods does not deliver a standardized supplement dose of UA. Conversion depends in part on the person's gut microbial community, and people differ in their capacity to produce it. [1, 4]

Supplement studies generally administer UA itself. That bypasses the need to produce the same quantity from food precursors, but it does not make food and supplementation equivalent. A pomegranate study and a purified-UA study answer different questions. Nor does variation in microbial production establish that a low producer needs a supplement. [1, 2]

What Mitophagy Means

Mitophagy is a selective form of autophagy through which cells remove mitochondria. In this process, cellular machinery identifies mitochondria for disposal and routes material toward lysosomal degradation. It is part of mitochondrial quality control, alongside other processes such as repair, division, fusion and the generation of new mitochondrial components. [1]

In a foundational 2016 study, UA induced mitophagy in experimental systems, extended lifespan in the worm C. elegans and improved aspects of muscle function in rodents. These were preclinical findings. They did not demonstrate human lifespan extension or show that a person can reverse aging by taking UA. [1]

Measuring the mechanism in people is more difficult than the housekeeping metaphor makes it sound. More of a protein associated with mitophagy is not the same as directly measuring the rate at which damaged mitochondria are removed. A molecular signature can support a hypothesis without proving the full sequence of events in living human muscle. [2, 4]

What the Human Trials Found

The First Human Studies Focused on Tolerability and Biomarkers

A first-in-human trial published in Nature Metabolism in 2019 assessed single doses and repeated dosing over four weeks in healthy, sedentary older adults. Safety was the primary focus. At 500 and 1,000 mg daily, researchers also observed changes in plasma acylcarnitines and skeletal muscle mitochondrial gene expression. [2]

Those results showed that oral UA was bioavailable and could affect measured biological pathways. They did not establish improvements in everyday mobility or long-term health. [2]

The Older Adult Muscle Trial

In a 2022 JAMA Network Open trial, 66 adults aged 65–90 received 1,000 mg of UA daily or placebo for four months. The primary outcomes were six-minute walking distance and maximal ATP production in hand muscle. Neither showed a statistically significant advantage for UA over placebo. [3]

Secondary endurance tests in hand and leg muscles favored UA at two months. These tests measured repeated contractions until fatigue; they were not measures of overall strength or the ability to manage every daily activity. The participants were predominantly women and all were White, which limits generalization; the study also involved investigators with company ties. [3]

What the Middle-Aged Adult Trial Adds

The 2022 ATLAS trial randomized 88 adults aged 40–64 to placebo or 500 or 1,000 mg of UA daily for four months. Certain hamstring strength measures improved relative to placebo, but peak power output, the prespecified primary outcome, did not. [4]

The frequently repeated "12% stronger" figure came from a particular hamstring measurement in the 500-mg group. It was not a universal gain in whole-body strength. Muscle biopsy analyses found changes in proteins associated with mitochondrial pathways, but did not directly quantify mitophagy flux. ATLAS was funded by Amazentis, with several authors affiliated with the company. [4]

Immune Cell Research Is a Different Kind of Evidence

A Nature Aging trial published in October 2025 studied 50 healthy adults over four weeks using 1,000 mg of UA daily or placebo. It reported changes in some T-cell populations and immune-cell metabolic measurements. These are laboratory and cellular findings, not proof that participants developed fewer infections or experienced clinically reversed immune aging. [5, 6]

What the Pooled Evidence Says

A July 2026 systematic review identified five randomized trials involving 236 participants. Only the six-minute walk test could be quantitatively pooled, using two trials. The pooled estimate favored UA by about 17 meters, but its 95% confidence interval crossed zero. The authors rated that evidence as low certainty. [7]

What This Means When Reading a Label

The doses above describe research protocols, not a recommended regimen. UA research is most useful when we keep the questions separate: Does it enter the circulation? Does it change a pathway? Does it change performance? Does it improve long-term health? A positive answer to one does not settle the others. [2–7]

References

1. Ryu D et al. Urolithin A induces mitophagy and prolongs lifespan in C. elegans and increases muscle function in rodents. Nature Medicine. 2016;22(8). doi.org/10.1038/nm.4132
2. Andreux PA et al. The mitophagy activator urolithin A is safe and induces a molecular signature of improved mitochondrial and cellular health in humans. Nature Metabolism. 2019;1(6). doi.org/10.1038/s42255-019-0073-4
3. Liu S et al. Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults. JAMA Network Open. 2022;5(1). PMC
4. Singh A et al. Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults. Cell Reports Medicine. 2022;3(5). PMC
5. Denk D et al. Effect of the mitophagy inducer urolithin A on age-related immune decline. Nature Aging. 2025;5(11). doi.org/10.1038/s43587-025-00996-x
6. Denk D et al. Author Correction. Nature Aging. 2026;6(2).
7. Dao T et al. Effects of Urolithin A supplementation on muscle health outcomes in humans from randomized controlled trials. Frontiers in Nutrition. 2026;13.

What research reveals about hormone changes and the health of our cells.

BY RESETTA EDITORIAL

A night interrupted by heat. Less energy for a familiar workout. A growing concern about muscle or bone health. During the menopause transition, these changes can prompt a larger question: what is happening beneath the symptoms?

Research offers part of an answer. Changes in ovarian hormones can affect cellular processes, and some health interventions improve specific functions in postmenopausal women. But the evidence does not establish a single chain in which menopause accelerates every aspect of cellular aging and an anti-aging treatment reverses the consequences. The findings depend on the tissue, the intervention, and what researchers actually measured. [1–9]

Understanding those distinctions makes the science more useful. It helps explain why sleep, physical activity, and appropriate menopause care deserve attention, while keeping emerging longevity treatments in perspective.

What Cellular Aging Means in This Discussion

Several different biological processes appear under the label of cellular aging. Mitochondria help cells produce usable energy. Mitophagy is a quality-control process that removes damaged mitochondria. Cellular senescence describes a state in which cells stop dividing and can release signals that affect nearby tissue, including inflammatory signals. Senescence also has protective functions, so eliminating it indiscriminately is not the goal. [3–5]

Biological-age estimates are different again. An epigenetic clock calculates an age-related pattern from chemical marks on DNA. It does not directly count senescent cells or measure how well a muscle produces energy. A change in one of these measurements cannot automatically stand in for a change in all the others. [2]

This matters when reading a headline. A study reporting a blood biomarker has answered a narrower question than a study showing fewer fractures, better physical function, or longer life.

The Connection Begins Before the Final Menstrual Period

Cellular maintenance can help shape reproductive aging itself. In a 2021 Nature study, Ruth and colleagues examined genetic variation in roughly 200,000 women of European ancestry and identified 290 genetic determinants associated with the timing of natural menopause. Their analyses highlighted pathways involved in the response to DNA damage. [1]

This places ovarian aging within a broader biological context: how cells respond to damage can influence reproductive lifespan. It also complicates the idea that menopause simply starts an otherwise unrelated aging process. Shared biology may contribute to both. Genetic associations and accompanying experimental work do not, however, show that a supplement can preserve human ovarian function or safely delay menopause. [1]

A separate 2016 PNAS study by Levine and colleagues analyzed epigenetic age across four observational cohorts. Earlier menopause and a longer time since menopause were associated with greater epigenetic age acceleration in blood; bilateral ovary removal was also associated with this measure. [2]

These findings support a connection between reproductive history and biological-age markers. They do not fully resolve its direction. Hormonal changes may contribute, while shared genetics, health exposures, and other differences may also influence both menopause timing and aging. An epigenetic association is not proof that menopause makes every organ age at a uniform rate. [2]

A Muscle Study Identifies a Possible Causal Pathway

A study by Uebo and colleagues, published online in November 2025 and in the January 2026 issue of Experimental Gerontology, examined estrogen deficiency in mice and cultured human skeletal muscle cells. These were laboratory models, not a clinical trial in menopausal women. [3]

In the cultured cells, estrogen-deficient conditions reduced mitophagy and expression of Rab9, a protein involved in an alternative cellular recycling pathway. Mitochondrial function and muscle-cell differentiation deteriorated, while senescence increased. Experimentally increasing Rab9 improved these outcomes. [3]

Because the researchers altered the pathway and observed a rescue, this is stronger mechanistic evidence than a simple correlation. It suggests that impaired mitochondrial maintenance can help connect estrogen deficiency with muscle dysfunction in these models. The study also tested NMN in mice, but neither that result nor the cell experiment demonstrates that NMN prevents muscle loss in menopausal women. [3]

Bone Research Shows Why the Pathway Is Not Universal

A 2019 study by Farr and colleagues reached a different conclusion in bone. In young adult mice, removal of the ovaries caused bone loss without increasing the measured senescence markers. A strategy designed to eliminate certain senescent cells did not prevent that estrogen-deficiency-related bone loss. [4]

The researchers also examined bone biopsies from older postmenopausal women. Three weeks of estrogen treatment in 10 women, compared with 10 untreated women, did not alter the measured senescence markers or senescence-associated secretory signals. [4]

The small sample and brief treatment period limit what can be concluded. Even so, the results challenge a universal sequence of estrogen loss, senescent-cell accumulation, and tissue damage. In these experiments, estrogen deficiency and cellular senescence acted through separable routes. Menopause care and treatments aimed at senescent cells therefore cannot be assumed to be interchangeable. [4]

Hormone Therapy Can Influence Some Biomarkers

Human intervention evidence adds another layer. A 2020 analysis of 109 participants in the randomized Kronos Early Estrogen Prevention Study compared blood proteins after 36 months of oral conjugated estrogens, transdermal estradiol, or placebo. The proteins were associated with senescence and inflammation. [5]

The oral-estrogen group had lower levels of several measured proteins than placebo. Results were less consistent for transdermal estradiol, and one marker, MIP1α, showed no significant treatment effect. These findings support an effect of the assigned treatment on selected circulating markers, with differences between regimens. [5]

Blood proteins are not a direct census of senescent cells. The analysis did not demonstrate whole-body rejuvenation or establish that changing these markers prevents age-related disease. [5]

Hormone therapy has established uses for bothersome menopause symptoms and can protect against bone loss. Whether it is appropriate depends on individual symptoms, medical history, age, timing, and treatment formulation. A discussion with a clinician should focus on those benefits and risks; the biomarker study alone is not a reason to start hormone therapy for anti-aging. [10]

Health Management Can Change Specific Cellular and Metabolic Functions

The practical question is whether women can influence functions that matter during and after this transition. Exercise and sleep studies provide useful evidence, even though neither establishes reversal of cellular aging.

Aerobic Training in Early Postmenopause

In a 2017 study in The Journal of Physiology, 20 premenopausal and 16 recently postmenopausal women completed 12 weeks of aerobic training at high intensity. Researchers observed vascular and skeletal-muscle mitochondrial adaptations, including increases in several mitochondrial respiratory-chain proteins in the postmenopausal group. Some adaptations were greater in that group. [6]

The study was small, compared groups before and after training, and did not include an inactive control group. It nevertheless shows that muscle remains responsive to training in early postmenopause. It does not establish a reversal of biological age or mean that everyone should begin with high-intensity exercise. [6]

Sleep Restriction and Insulin Sensitivity

Sleep has also been tested experimentally. In a 2023 randomized crossover trial, Singh and colleagues compared habitual sleep with four nights of restricted sleep in postmenopausal women. Fourteen entered the trial and nine were included in the reported analysis. Time in bed averaged approximately 8.4 hours during habitual sleep and 5.0 hours during restriction. [7]

Insulin sensitivity declined during sleep restriction. Because the same women experienced both conditions in randomized order, this supports a short-term causal effect of insufficient sleep on metabolic function in this small sample. The trial did not measure senescent-cell burden or demonstrate that improving sleep reverses aging. It gives a concrete reason to take persistent sleep disruption seriously. [7]

Emerging Longevity Interventions Have Narrower Evidence

Research on cellular pathways naturally raises interest in supplements and senolytics, treatments intended to selectively eliminate senescent cells. Human results require close attention to the population and the endpoint.

NMN in a Metabolic Trial

In a 2021 randomized, double-blind trial published in Science, 25 postmenopausal women with prediabetes and overweight or obesity received NMN or placebo for 10 weeks. The NMN group received 250 mg daily and showed improvement in muscle insulin sensitivity. [8]

That is a specific metabolic finding in a selected population. It does not establish relief of hot flashes, treatment of diabetes, delayed menopause, or reversal of cellular aging. The study regimen is a research detail, not a dosing recommendation. [8]

A Senolytic Trial in Bone

A 2024 phase 2 randomized trial in Nature Medicine tested intermittent dasatinib plus quercetin in 60 postmenopausal women. The trial did not meet its primary endpoint: the change in a blood marker of bone resorption at 20 weeks was not significantly different from control. An early improvement in a bone-formation marker was not sustained at 20 weeks. [9]

Exploratory findings suggested that women with higher baseline levels of a senescence-associated marker might respond differently. That is a question for further trials, not proof of broad benefit. The combination included a prescription drug; its results cannot be transferred to quercetin alone or to other marketed longevity supplements. [9]

Putting the Findings Into Everyday Care

A useful plan begins with observable health needs. Discuss persistent sleep disruption and troublesome menopause symptoms with a clinician. Build regular aerobic and muscle-strengthening activity at a level suited to your health and current ability. Review bone health, blood pressure, and other relevant risk factors during routine care. Adequate nutrition, including calcium and vitamin D, belongs in that discussion. These are established health priorities; the studies above do not establish them as a unified treatment that slows whole-body cellular aging. [10,11]

Most of the intervention studies described here enrolled women after menopause. Their results should not automatically be applied to all women in perimenopause, whose hormonal patterns and symptoms can differ.

References

Primary research is listed in references 1 to 9. References 10 and 11 provide clinical and patient education context.

1. Ruth KS et al. Genetic insights into biological mechanisms governing human ovarian ageing. Nature. 2021;596:393–397. doi.org/10.1038/s41586-021-03779-7
2. Levine ME et al. Menopause accelerates biological aging. Proceedings of the National Academy of Sciences. 2016;113(33):9327–9332. doi.org/10.1073/pnas.1604558113
3. Uebo S et al. Disruption of Rab9-dependent mitophagy contributes to menopause-induced sarcopenia. Experimental Gerontology. 2026;213:112970. Published online November 20, 2025. doi.org/10.1016/j.exger.2025.112970
4. Farr JN et al. Independent Roles of Estrogen Deficiency and Cellular Senescence in the Pathogenesis of Osteoporosis: Evidence in Young Adult Mice and Older Humans. Journal of Bone and Mineral Research. 2019;34(8):1407–1418. doi.org/10.1002/jbmr.3729
5. Faubion L et al. Effect of menopausal hormone therapy on proteins associated with senescence and inflammation. Physiological Reports. 2020;8(16):e14535. doi.org/10.14814/phy2.14535
6. Nyberg M et al. Leg vascular and skeletal muscle mitochondrial adaptations to aerobic high-intensity exercise training are enhanced in the early postmenopausal phase. The Journal of Physiology. 2017;595(9):2969–2983. doi.org/10.1113/JP273871
7. Singh P et al. Effect of sleep restriction on insulin sensitivity and energy metabolism in postmenopausal women: A randomized crossover trial. Obesity. 2023;31(5):1204–1215. doi.org/10.1002/oby.23739
8. Yoshino M et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547):1224–1229. doi.org/10.1126/science.abe9985
9. Farr JN et al. Effects of intermittent senolytic therapy on bone metabolism in postmenopausal women: a phase 2 randomized controlled trial. Nature Medicine. 2024;30:2605–2612. doi.org/10.1038/s41591-024-03096-2
10. The Menopause Society. Hormone Therapy. Patient education. Accessed October 22, 2026. menopause.org
11. National Institutes of Health. Menopause. Patient education. Accessed October 22, 2026. health.nih.gov

What research shows about sleep and everyday routines.

BY RESETTA EDITORIAL

The morning after a poor night can feel different before anything has happened. Concentration takes more effort. A familiar walk feels less inviting. We often describe this as a lack of energy, but the biology reaches beyond how awake we feel. Experiments in people show that restricting sleep can change how cells respond to insulin, how muscle mitochondria function and how the body maintains its proteins. [2,3,4]

That is why sleep belongs at the center of a conversation about cellular health. It helps shape the conditions in which the body manages energy and maintains tissue. Spermidine and PQQ enter this conversation because they are studied for cellular recycling and mitochondrial biology, and because both have human sleep research. To understand their potential, it helps to begin with what sleep itself is doing.

Sleep Helps Organize the Daily Work of Cells

"Cellular health" is a broad term. Here, it means the ability of cells to use nutrients, maintain functional components and respond appropriately to stress. These functions depend on coordinated activity over time. They cannot be reduced to a single ingredient, blood marker or morning energy score.

A human experiment published in PNAS helps make that coordination visible. Twenty-six participants completed a week of restricted sleep and a week of sufficient sleep, averaging approximately 5.7 and 8.5 hours per night. Subsequent blood sampling identified changes in the expression of 711 genes, including genes involved in metabolism, inflammatory responses and biological timing. Fewer genes retained a daily rhythmic pattern after insufficient sleep. These were changes in gene activity, not mutations in the participants' DNA. [1]

The finding suggests that sleep influences when and how cellular work is organized. Recovery therefore involves more than the number of hours spent motionless. Sleep duration and the body's daily timing systems interact, and a disrupted night can leave a measurable biological signature after waking. [1]

Energy Depends on How Cells Use Fuel

Food supplies energy, but cells still have to respond to metabolic signals and convert fuel into a usable form. Insulin is one of those signals. In a small randomized crossover study, seven healthy adults spent four nights with either 4.5 or 8.5 hours available for sleep. Fat cells collected after restricted sleep responded less effectively to insulin, and whole-body insulin sensitivity also declined. Food intake and physical activity were controlled. The experiment connected sleep loss directly to altered signaling inside human cells. [2]

Mitochondria are another part of this picture. They help produce ATP, the molecule that powers much of a cell's work. A study of 24 healthy young men compared five nights with eight hours in bed, four hours in bed, or four hours plus interval exercise. The sleep-restriction group showed reduced mitochondrial respiratory function in muscle and poorer glucose tolerance. The same changes were not observed in the group that exercised. This was a short experiment in young men, but it demonstrates that sleep availability can affect energy metabolism in tissue. [3]

These findings give "energy" a more precise meaning in longevity research. Feeling tired is a personal experience; mitochondrial respiration and insulin signaling are measurements of specific biological functions. They may be related, but a fatigue score alone cannot reveal which cellular process has changed.

Sleep Also Matters for Maintaining Tissue

Cells continually replace proteins that form structures, carry signals and perform chemical reactions. Maintaining tissue requires both the production of useful proteins and the handling of material that is no longer functioning well. This ongoing maintenance is one reason recovery matters even on days without strenuous exercise.

In a randomized crossover experiment involving 13 healthy young adults, one night of total sleep deprivation reduced the following day's measured rate of muscle protein synthesis by 18% compared with normal sleep. Researchers measured protein production after eating, making the result relevant to how the body uses nutritional resources. It was an acute change in synthesis, not an 18% loss of muscle mass. [4]

The practical implication is that nutrition and sleep work within the same physiology. Providing protein does not make the conditions for using it irrelevant. This study does not tell us what every interrupted night does over decades, but it helps explain why a discussion of physical recovery should include sleep alongside diet and activity. [4]

Sleep Loss Can Alter Inflammatory and Antioxidant Responses

Inflammation is part of the body's normal defense system. The relevant question for cellular health is how that response is regulated. In a study of 14 healthy adults, partial sleep deprivation increased the next morning's activity of NF-kB, a regulator of inflammatory gene expression, in blood immune cells. The increase was detected in women but not men in this small sample. After recovery sleep, activity was similar to baseline. The finding identifies a responsive cellular pathway, rather than showing that a single poor night causes chronic disease. [5]

Oxidative stress concerns the balance between reactive molecules and the defenses that manage them. A 2023 randomized crossover study examined this balance in 35 healthy women. After six weeks of sleeping about 1.5 hours less than usual, cells collected from the lining of blood vessels showed increased oxidative stress without a corresponding increase in their antioxidant response. [6]

That design matters because it examined repeated, modest sleep curtailment over several weeks. The results suggest that insufficient sleep can affect the cell's own protective response, making the relationship more complex than simply "needing more antioxidants." They strengthen the case for protecting sleep itself; the experiment did not test whether a supplement could reverse these changes. [6]

Brain Fluid Movement and Cellular Recycling Are Distinct

Sleep research also reaches beyond metabolism. In a 2019 study of 13 people, researchers recorded brain activity and rapid MRI signals during sleep. During non-REM sleep, slow electrical waves were followed by coordinated changes in blood-related signals and cerebrospinal fluid flow. The brain was showing an organized pattern of activity and fluid movement while participants slept. [7]

These observations are relevant to research on fluid exchange and waste clearance in the brain. However, this experiment measured fluid dynamics, not the amount of a specific toxin removed or a reduction in dementia risk. It should also be distinguished from autophagy, which is the breakdown and recycling of material within cells. Brain fluid movement and intracellular recycling operate at different biological levels. [7,8]

This distinction becomes useful when discussing spermidine. A compound associated with autophagy cannot automatically be described as "cleaning the brain during sleep." The more informative question is whether a defined intervention changes a cellular process and whether that change is accompanied by better sleep in people.

Why This Leads to Spermidine and PQQ

The human evidence establishes several routes from insufficient sleep to altered cellular physiology. Researchers are also exploring the other direction: whether changing cellular maintenance or metabolism can influence sleep. Animal work, including experiments involving spermidine and age-related sleep patterns, supports investigating that possibility. Its translation to people still needs direct testing. [9]

Spermidine is relevant to the recycling of cellular components. PQQ is relevant to mitochondrial biology and responses to oxidative stress. These are plausible points of investigation because sleep loss affects related processes. Plausibility becomes more useful when paired with human trials that ask whether people actually sleep better. The two ingredients have reached that stage, although their results and study designs differ.

Spermidine and Cellular Maintenance

Spermidine is a naturally occurring polyamine involved in cell function. A foundational 2009 study found that supplementation promoted autophagy in several experimental organisms and in cultured human cells. Autophagy allows cellular material to be broken down and its components reused; it is part of how cells maintain their internal environment. Effects in cultured human cells remain laboratory evidence, distinct from a trial in people taking a supplement. [8]

A 2022 fruit-fly study added a more direct sleep connection. Spermidine attenuated changes in sleep patterns that normally appeared with early aging in the flies. This gives researchers a reason to examine cellular maintenance and sleep together, while leaving the relevant mechanism and clinical benefit in humans to be established. [9]

A positive human result was published online in Current Urology on September 30, 2026. In a randomized, double-blind, placebo-controlled trial, 60 men with impaired sperm production received either a spermidine-enriched supplement providing 4 mg daily or placebo for three months, alongside standard treatment. The published abstract reports significantly better sleep-quality outcomes with supplementation, assessed using the Pittsburgh Sleep Quality Index. This questionnaire captures several aspects of a person's recent sleep experience. [10]

The result gives spermidine a direct human sleep finding. Its relevance is currently limited to the population, formulation and treatment setting studied. It does not establish comparable benefits for healthy adults, women or people with chronic insomnia, and the reported findings do not demonstrate that increased autophagy caused the sleep improvement. [10]

A larger, earlier trial provides necessary context. In the 2022 SmartAge study, 100 older adults with subjective cognitive decline were randomized to a wheat-germ supplement providing 0.9 mg of spermidine daily or placebo for 12 months. No significant sleep-quality benefit was found; sleep was a secondary outcome. Differences in dose, formulation and participants could contribute to the contrast, but these separate trials cannot identify an effective sleep dose. [11]

PQQ and Mitochondrial Biology

Pyrroloquinoline quinone, usually shortened to PQQ, is studied for redox activity, meaning its participation in reactions involving the transfer of electrons, and for effects on mitochondrial biology. In mouse-derived cells, a 2010 study found that PQQ increased mitochondrial DNA content, oxygen consumption and other measures associated with mitochondrial biogenesis. The experiments implicated CREB and PGC-1α, regulators involved in building the cell's mitochondrial machinery. [12]

This is relevant to the earlier sleep-restriction research because mitochondrial function is one of the measurable processes affected by sleep loss. It creates a testable hypothesis for recovery research. It does not establish that oral PQQ restores mitochondria after poor sleep in people.

PQQ's human sleep evidence includes a 2012 study in which 17 adults took 20 mg daily for eight weeks. Participants reported improvements in questionnaire measures of falling and staying asleep, sleep duration and sleepiness on waking; fatigue ratings also improved. These outcomes speak to both the night and the following morning. [13]

The study had no placebo group and participants knew they were taking PQQ. Expectations or natural symptom changes could therefore explain some or all of the improvement. The lead author was affiliated with the ingredient manufacturer. The findings support further investigation, with controlled replication needed to determine how much benefit PQQ itself provides. [13]

A separate 2013 report offers early human evidence related to cellular metabolism. In research involving 10 adults, a short experiment using 0.3 mg of PQQ per kilogram of body weight daily found lower CRP and IL-6 inflammatory markers and changes in urinary metabolites associated with mitochondrial metabolism after 76 hours. These were exploratory biomarker findings, rather than direct measurements of new mitochondria or a demonstrated explanation for better sleep. [14]

What Would Strengthen the Connection

A more complete trial would measure sleep and cellular outcomes in the same people, compare the intervention with placebo and test whether the biological changes explain the sleep result. Sleep questionnaires are valuable because the person's experience matters. Overnight recordings or validated activity monitoring can add information about sleep timing, continuity and physiology. Each measure answers a different question.

The current findings do not establish that combining spermidine and PQQ adds benefit, that bedtime dosing works better, or that either ingredient extends human lifespan through improved sleep. Nor can results from one tested supplement automatically be transferred to a finished formula containing different ingredients. The useful evidence is specific to what was studied.

References

1. Möller-Levet CS, et al. Effects of insufficient sleep on circadian rhythmicity and expression amplitude of the human blood transcriptome. PNAS. 2013;110(12):E1132–E1141. doi.org/10.1073/pnas.1217154110
   Human sleep-restriction experiment
2. Broussard JL, et al. Impaired insulin signaling in human adipocytes after experimental sleep restriction: a randomized, crossover study. Annals of Internal Medicine. 2012;157(8):549–557. doi.org/10.7326/0003-4819-157-8-201210160-00005
   Human crossover trial with fat-cell sampling
3. Saner NJ, et al. Exercise mitigates sleep-loss-induced changes in glucose tolerance, mitochondrial function, sarcoplasmic protein synthesis, and diurnal rhythms. Molecular Metabolism. 2021;43:101110. doi.org/10.1016/j.molmet.2020.101110
   Human experimental study with three groups
4. Lamon S, et al. The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment. Physiological Reports. 2021;9:e14660. doi.org/10.14814/phy2.14660
   Human randomized crossover experiment
5. Irwin MR, et al. Sleep loss activates cellular inflammatory signaling. Biological Psychiatry. 2008;64(6):538–540. doi.org/10.1016/j.biopsych.2008.05.004
   Human partial sleep-deprivation experiment
6. Shah R, et al. Mild sleep restriction increases endothelial oxidative stress in female persons. Scientific Reports. 2023;13:15360. doi.org/10.1038/s41598-023-42758-y
   Human randomized crossover study
7. Fultz NE, et al. Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep. Science. 2019;366(6465):628–631. doi.org/10.1126/science.aax5440
   Human EEG and MRI study
8. Eisenberg T, et al. Induction of autophagy by spermidine promotes longevity. Nature Cell Biology. 2009;11:1305–1314. doi.org/10.1038/ncb1975
   Mechanistic research in model organisms and cultured cells
9. Huang S, et al. A brain-wide form of presynaptic active zone plasticity orchestrates resilience to brain aging in Drosophila. PLOS Biology. 2022;20(12):e3001730. doi.org/10.1371/journal.pbio.3001730
   Fruit-fly research
10. Qian D, et al. A randomized controlled trial investigating the effect of spermidine-enriched dietary supplementation on fertility-related outcomes and sleep quality in men with spermatogenic failure. Current Urology. Published online September 30, 2026. doi.org/10.1097/CU9.0000000000000375
    Human randomized trial
11. Schwarz C, et al. Effects of Spermidine Supplementation on Cognition and Biomarkers in Older Adults With Subjective Cognitive Decline: A Randomized Clinical Trial. JAMA Network Open. 2022;5(5):e2213875. doi.org/10.1001/jamanetworkopen.2022.13875
    Human randomized trial; sleep was a secondary outcome
12. Chowanadisai W, et al. Pyrroloquinoline Quinone Stimulates Mitochondrial Biogenesis through cAMP Response Element-binding Protein Phosphorylation and Increased PGC-1α Expression. Journal of Biological Chemistry. 2010;285(1):142–152. doi.org/10.1074/jbc.M109.030130
    Laboratory cell study
13. Nakano M, et al. Effects of Oral Supplementation with Pyrroloquinoline Quinone on Stress, Fatigue, and Sleep. Functional Foods in Health and Disease. 2012;2(8). doi.org/10.31989/ffhd.v2i8.81
    Human open-label study
14. Harris CB, et al. Dietary pyrroloquinoline quinone (PQQ) alters indicators of inflammation and mitochondrial-related metabolism in human subjects. Journal of Nutritional Biochemistry. 2013;24(12):2076–2084. doi.org/10.1016/j.jnutbio.2013.07.008
    Exploratory human metabolic studies
15. Centers for Disease Control and Prevention. About Sleep. Accessed October 7, 2026. cdc.gov/sleep/about
    Public health guidance

A closer look at NAD⁺, mitochondrial recycling and cellular senescence.

There is a moment on a hiking trail when a familiar incline feels harder than you remember. Your legs ask for a pause. It is tempting to read that moment as a message from aging cells. But a slower climb cannot tell you what is happening inside your mitochondria, or whether you need a supplement.

That distinction matters when we talk about longevity. Researchers can measure a change inside a cell without demonstrating a change in how someone feels or functions. Understanding the difference makes the science more interesting—and the claims around it easier to judge.

Here is a closer look at several processes behind the conversation, with particular attention to what the studies actually measured. This is a discussion of research, not evidence that any RESETTA product reproduces these findings.

NAD⁺ and Cellular Energy

NAD⁺, short for nicotinamide adenine dinucleotide, participates in reactions that help cells obtain energy from nutrients. It also supports enzymes involved in DNA repair. Researchers study how NAD⁺ metabolism changes with age, but it is too simple to assume that everyone develops the same deficiency or that restoring a blood measurement will restore youthful function. [1, 2]

NR, or nicotinamide riboside, and NMN, or nicotinamide mononucleotide, are precursors used in NAD⁺ synthesis. In a 2016 mouse study, NR affected mitochondrial and stem-cell function and increased lifespan — findings in mice, not evidence that NR extends human life. [3]

The human evidence is more measured. A systematic review published in 2026 identified 113 intervention studies, including 33 in humans. Oral NR and NMN generally increased measured NAD-related metabolites, while effects on physical function, metabolism and other health-related outcomes varied and were frequently absent or limited to particular measurements. [1]

A higher NAD-related blood measurement tells researchers that an intervention reached a biological target. Whether someone will feel less tired, climb more easily or live longer is a separate question. The review did not establish those benefits as reliable outcomes. [1]

Mitophagy and Mitochondrial Recycling

Mitochondria help produce the ATP that powers many cellular activities. Cells also maintain these structures, including through mitophagy, a process that removes damaged mitochondria. Urolithin A is studied in relation to that process. Gut microbes can produce it from compounds found in foods such as pomegranates and walnuts, although production varies between people. [4]

A 2022 trial assigned 88 adults aged 40–64 to urolithin A or placebo for four months. Some hamstring strength measures improved relative to placebo, but the primary outcome, peak power output, did not. The often-quoted 12% figure concerned a specific strength measure in one dose group, not overall strength or everyday stamina. [4]

A separate trial, published in Nature Aging in 2025, studied 50 adults for four weeks and reported changes in certain immune-cell populations and metabolic measures. It did not establish fewer infections, longer life or clinically reversed immune aging. [5, 6]

Senescence and the Limits of the Cleanup Metaphor

Cellular senescence is a state in which cells stop dividing but remain metabolically active. Some senescent cells release signals that affect surrounding tissue. Senescence also has useful biological roles, including limiting the replication of damaged cells, so describing every senescent cell as waste to be removed misses part of the picture. [7]

Senolytics are studied for their ability to selectively eliminate certain senescent cells. Fisetin, a plant flavonoid, showed activity in laboratory experiments and mice in a 2018 study. The screen of ten flavonoids was a laboratory comparison — not a trial showing fisetin was the best supplement for people. [7]

A 2025 mouse study reported better grip strength and frailty measures in older animals, with no corresponding effects in young mice, and no increase in skeletal muscle mass. These results support further investigation; they do not demonstrate that fisetin supplements preserve human muscle or extend human life. [8]

Spermidine and Autophagy

Spermidine belongs in a related but distinct conversation. It is a naturally occurring polyamine investigated for effects on autophagy, the broader process through which cells recycle internal components. Autophagy is not the same as eliminating whole senescent cells. [9]

A prospective study linked higher dietary spermidine intake with lower mortality. Because participants were observed rather than randomly assigned to a supplement, the study cannot establish that spermidine caused the difference or that a capsule would reproduce it. [10]

In the 2022 SmartAge trial, 100 older adults with subjective cognitive decline were assigned to a spermidine-rich extract or placebo for 12 months. The intervention did not significantly improve the primary memory outcome. Adverse events were balanced between groups. [11]

How to Read a Longevity Claim

The mechanisms are worth understanding. They are not a shopping list. Before drawing a conclusion from a study, ask: Was the intervention tested in people, animals or cells in a laboratory? Did it change a biomarker, a meaningful measure of function or a long-term health outcome? Did it meet its prespecified primary outcome, against the control group? Does the product match the studied formulation, dose and population — and has the result been independently repeated?

The answers usually require looking beyond the label. Even a randomized human trial answers a specific question under specific conditions; it does not settle every claim attached to an ingredient.

Back on the trail, the harder incline remains a personal experience, not a diagnosis of a cellular problem. We can be curious about what our cells are doing without assuming that a supplement is the missing piece. That is the kind of curiosity worth keeping: interested in the possibility, attentive to the evidence.

References

1. Gallagher C, Emmanuel OO. NAD⁺ supplementation for anti-aging and wellness. Ageing Research Reviews. 2026;116:103057.
2. Martens CR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD⁺ in healthy middle-aged and older adults. Nature Communications. 2018;9:1286. doi.org/10.1038/s41467-018-03421-7
3. Zhang H, et al. NAD⁺ repletion improves mitochondrial and stem cell function and enhances life span in mice. Science. 2016;352(6292):1436–1443. doi.org/10.1126/science.aaf2693
4. Singh A, et al. Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults. Cell Reports Medicine. 2022;3(5):100633. PMC
5. Denk D, et al. Effect of the mitophagy inducer urolithin A on age-related immune decline. Nature Aging. 2025;5:2309–2322. doi.org/10.1038/s43587-025-00996-x
6. Denk D, et al. Author Correction. Nature Aging. 2026.
7. Yousefzadeh MJ, et al. Fisetin is a senotherapeutic that extends health and lifespan. EBioMedicine. 2018;36:18–28. doi.org/10.1016/j.ebiom.2018.09.015
8. Murray KO, et al. Intermittent Supplementation With Fisetin Improves Physical Function and Decreases Cellular Senescence in Skeletal Muscle With Aging. Aging Cell. 2025;24(8):e70114. doi.org/10.1111/acel.70114
9. Madeo F, Eisenberg T, Pietrocola F, Kroemer G. Spermidine in health and disease. Science. 2018;359(6374):eaan2788. doi.org/10.1126/science.aan2788
10. Kiechl S, et al. Higher spermidine intake is linked to lower mortality. American Journal of Clinical Nutrition. 2018;108(2):371–380. doi.org/10.1093/ajcn/nqy102
11. Schwarz C, et al. Effects of Spermidine Supplementation on Cognition and Biomarkers in Older Adults With Subjective Cognitive Decline. JAMA Network Open. 2022;5(5):e2213875. doi.org/10.1001/jamanetworkopen.2022.13875

A personal note from RESETTA's founder on what it actually meant to start paying attention.

When Trying Harder Stopped Working

For a while, I thought the answer was to try harder.

On mornings when I felt slow, I told myself to get moving. When my focus disappeared in the afternoon, I reached for another coffee or forced myself through the work in front of me. If I woke up tired after what should have been enough sleep, I assumed I had done something wrong the day before.

None of this felt serious enough to call a problem. It was simply a collection of small frustrations: rereading the same paragraph, losing momentum earlier than expected, or reaching the end of the day without feeling that I had fully arrived in it. I treated these moments as failures of discipline.

I had always been someone who trusted effort. Difficult problem? Work longer. Busy week? Become more organized. Low energy? Build a better routine. That approach had served me well for a long time. So when it stopped working, my first instinct was not to question the approach. It was to question myself.

Perhaps I was becoming less resilient. Perhaps this was just part of getting older. Perhaps everyone felt this way and was simply better at hiding it.

I cannot point to one dramatic event that changed my thinking. It was more gradual than that. I began noticing that the difficult moments were not entirely random. The same parts of the day often felt difficult in similar ways. Mornings had one kind of heaviness. Afternoons had another. Rest did not always leave me feeling restored.

The more closely I paid attention, the less useful it became to describe all of it with a single word like "tired." That was the beginning of a different question. Instead of asking how I could push through the feeling, I began asking what might be behind it.

Paying Attention Before Passing Judgment

I started reading about sleep, metabolism, cellular health, and the many biological processes that influence how we feel throughout the day and over time. I was not looking for a shortcut to youth. I still am not.

What interested me was the possibility that some of the changes we casually blame on age—or on ourselves—might deserve more curiosity than resignation. Learning more did not give me one simple explanation. If anything, it reminded me how complex the human body is. Energy, sleep, nutrition, movement, stress, and age do not operate independently. They affect one another, and individual experiences can vary considerably.

Oddly, that complexity was reassuring. It meant I did not need to reduce every difficult afternoon to a flaw in my character. I could observe it without immediately judging it. I could become more curious about my own patterns and more thoughtful about the choices I made in response.

The shift was subtle, but it changed the way I approached my health. I stopped thinking of wellness as a demand to perform perfectly every day. I began seeing it as an ongoing practice of paying attention, learning, adjusting, and beginning again.

The Question That Stayed With Me

As I continued learning, one question kept returning: What would it look like to support the body with greater respect for its changing needs and rhythms?

I did not have a complete answer. I still do not believe responsible wellness begins with pretending that one answer will work for everyone. But I believed the question was worth pursuing. That pursuit eventually became RESETTA.

RESETTA did not begin with a promise to stop time. It began with my desire to understand it better—and to create something grounded in curiosity, consistency, and respect for the body rather than fear of aging. Those principles continue to shape how we think about what we make, what we communicate, and what we choose not to claim.

There are many things we are still learning. I consider that an important part of building this brand honestly. Science evolves. People are different. Trust has to be earned through transparency and through actions that remain consistent over time.

"Feeling different does not always mean that you have failed. Sometimes it is an invitation to pay closer attention."

What I can share with certainty is the personal realization that started it all: feeling different does not always mean that you have failed. Sometimes it is an invitation to pay closer attention.

If you have experienced your own version of the slow morning, the unfocused afternoon, or the night of sleep that did not feel like enough, I will not pretend to know exactly what it means for you. But I hope you will meet that experience with curiosity before criticism. That is what I eventually learned to do. And that is where RESETTA began.

— Jennifer S. HAN, Founder, RESETTA

Keep reading: The Mechanism · Our Ingredients · The Longevity Newsletter

This is a personal reflection, not medical advice. It does not describe the effects of any RESETTA product. Consult a qualified healthcare professional about changes in your energy, sleep, or health.