Nicotinamide riboside, or NR, is biologically active in people: repeated human trials show that oral NR can raise NAD+ and related metabolites in blood and cells. Clinical benefits are more selective. A 2024 randomized trial found better six-minute walking performance in people with peripheral artery disease. Newer cognition, blood-pressure and long-COVID trials, alongside detailed metabolic studies, show a mix of promising biological signals and neutral functional results. [1][12][14][16][17]
For a healthy woman in midlife, that distinction matters. NR has a convincing human record for engaging NAD+ metabolism. It has also produced real benefits in a few defined clinical settings. The broader everyday-benefit profile is much less consistent across energy, weight control, memory, blood pressure and exercise performance in healthy adults.
The most useful way to read the NR research is therefore by outcome. Which effects repeat across studies? Which have appeared in one population? Which are still biomarkers rather than changes you would notice in daily life?
If you want the molecule and pathway first, start with our guide to what nicotinamide riboside is. This page stays focused on the human benefits evidence.
CELLSHE EVIDENCE MAP
NR benefits in human studies, at a glance
| Outcome | Best current reading | Human evidence | What it means in midlife |
|---|---|---|---|
| NAD+ and related metabolites | Most repeatable effect | Multiple controlled trials show higher whole-blood or cellular NAD-related measures after oral NR. [3][4][5][17] | NR reliably reaches the pathway it is taken to support. The size of the rise depends on dose, study and biological compartment. |
| Walking capacity | Positive clinical result in PAD | In 90 people with peripheral artery disease, six months of NR improved six-minute walk distance by 17.6 m versus placebo. [12] | This is a meaningful functional result, but it comes from people with PAD rather than healthy adults. |
| Blood pressure and vascular function | Mixed | An early midlife/older-adult trial produced exploratory blood-pressure and arterial-stiffness signals. In a 2025 hypertension pilot, daytime systolic blood-pressure changes were similar whether supervised walking included NR or placebo. [5][14] | Cardiovascular research remains active, and the blood-pressure findings are mixed. |
| Brain and cognition | Strong target engagement, clinical benefit still being tested | NR has changed brain-related NAD measures and Alzheimer's-related biomarkers in small studies. Randomized trials in cognitive impairment have produced biomarker changes without a consistent cognitive improvement. [9][10][13][17] | Human brain research now shows target engagement, while a repeatable cognitive benefit remains unconfirmed. |
| Muscle and mitochondrial biology | Biological effects are clearer than performance effects | Trials have changed muscle NAD-related metabolites, acetylcarnitine metabolism and gene-expression patterns, without a consistent improvement in mitochondrial function or physical performance in generally healthy participants. [7][8] | Muscle target engagement is clearer than evidence for better strength or exercise performance. |
| Insulin sensitivity, glucose and weight | No consistent metabolic benefit in the main NR trials | Controlled studies in obesity or insulin resistance have produced largely neutral insulin-sensitivity, glucose-handling and broad metabolic outcomes despite biochemical activity. [6][8] | Evidence for weight loss or better glucose control is much weaker than the evidence for NAD+ target engagement. |
| Inflammatory markers | Repeated signal in selected studies | Several studies report changes in circulating or cellular inflammatory markers, including work in older adults and neurological populations. [2][7][10] | For now, this is a biological research signal rather than a reliable symptom or functional outcome. |
| Short-term tolerability | Generally favorable at studied doses | Randomized studies from 100 mg/day to 3,000 mg/day have generally reported similar short-term adverse-event rates to placebo in the populations studied. [4][11][17] | The human safety record is reassuring over weeks to months. A high research dose is not a personal dosing recommendation. |
CELLSHE synthesis: based on randomized human trials and current reviews. The evidence map separates biochemical target engagement from functional or clinical outcomes. [1][2][18]
Raising NAD+ is the most consistent human result
NR entered human research because the body can use it in NAD+ metabolism. That finding now extends across multiple trials showing that oral NR raises NAD+ or related metabolites in blood, immune cells and selected tissues. A 2026 systematic review of NAD-boosting interventions reached the same broad conclusion for oral NR and NMN: biochemical target engagement is consistent, while health outcomes vary by endpoint and population. [1]
The dose-response study by Conze and colleagues is one of the clearest examples. In 140 healthy overweight adults aged 40 to 60, 100, 300 and 1,000 mg/day of nicotinamide riboside chloride increased whole-blood NAD+ by 22%, 51% and 142%, respectively, within two weeks. The increases were maintained through eight weeks. [4]
A 2018 crossover trial in healthy middle-aged and older adults also found clear stimulation of NAD+ metabolism with 1,000 mg/day for six weeks. [5] In a 2026 phase II pilot in older adults with amnestic mild cognitive impairment, whole-blood NAD+ rose from an estimated 23.36 to 48.52 micromolar after 12 weeks of NR, while the placebo group stayed close to baseline. [17]
Why this matters: Human trials show that NR functions as an NAD+ precursor in people and can change measured NAD+ biology. The harder question is which of those biochemical changes translate into better function or health.
That is also why the popular idea that one blood NAD+ number can tell you how well you are aging deserves care. NAD+ varies by tissue and measurement method. Our NAD+ levels by age analysis covers that evidence in depth.
Where NR has produced a measurable functional benefit
The strongest recent example is walking performance in peripheral artery disease, or PAD. PAD reduces blood flow to the legs and can make walking progressively difficult.
In the 2024 NICE randomized trial, 90 people with PAD received NR, NR plus resveratrol, or placebo for six months. The NR-only group improved its six-minute walk distance by 7.0 m from baseline, while the placebo group declined by 10.6 m. The between-group difference was 17.6 m at six months. [12]
That study matters because walking distance is a functional endpoint. It also illustrates why NR benefits should be tied to the people who were actually studied. PAD is a vascular disease with impaired walking capacity, so the practical relevance is strongest for people with PAD. Healthy-adult walking performance remains a separate question.
A second positive clinical signal came from a 2025 crossover trial in people with Werner syndrome, a rare genetic disorder associated with accelerated aging. NR at 1,000 mg/day improved cardio-ankle vascular index and reduced skin-ulcer area during 26-week treatment periods. [15] It is useful evidence that NR can affect more than a biomarker in humans, but Werner syndrome is a highly distinct clinical population.
Brain benefits: human target engagement is ahead of cognitive results
NR research has now moved well beyond blood measurements into brain-related biology. In Parkinson's disease, the 2022 NADPARK phase I trial found a variable increase in cerebral NAD measured by magnetic resonance spectroscopy after 30 days of 1,000 mg/day NR. The study also reported changes in cerebral metabolism and inflammatory markers. [10]
A separate study in 22 healthy older adults found higher NAD+ in plasma extracellular vesicles enriched for neuronal origin after six weeks of NR, along with changes in several neurodegeneration-related biomarkers. [9]
The next step is cognition itself. Two newer randomized studies make the picture clearer.
In 2025, 46 adults over 55 with subjective cognitive decline or mild cognitive impairment entered an eight-week NR trial. Plasma pTau217 moved favorably versus placebo, but the main cognitive measure did not improve between groups. [13]
In 2026, a 12-week phase II pilot randomized 52 older adults with amnestic mild cognitive impairment. NR nearly doubled blood NAD+ among completers. Cognitive performance, total cerebral blood flow and blood pressure did not improve versus placebo, although an exploratory analysis found a regional blood-flow signal in the left hippocampus. [17]
CELLSHE interpretation: NR is reaching human NAD+ biology in neurological research. Brain-related biomarkers and imaging signals justify continued study. Cognition remains an open clinical endpoint despite clear target engagement.
Muscle and metabolism: NR changes biology more reliably than performance
Muscle is especially relevant in midlife because maintaining strength, activity and metabolic health becomes more important with age. The NR literature includes several detailed muscle studies, but the results are easier to understand when biochemical changes are separated from functional changes.
In 12 older men, 1,000 mg/day of NR for 21 days changed the skeletal-muscle NAD+ metabolome and gene-expression patterns, while mitochondrial bioenergetics did not improve. The study also found lower circulating inflammatory cytokines. [7]
In 13 healthy overweight or obese men and women, six weeks of 1,000 mg/day increased markers of NAD+ synthesis in muscle and changed acetylcarnitine metabolism. The study also reported a small increase in fat-free mass and sleeping metabolic rate, while insulin sensitivity, mitochondrial function, liver and intramuscular fat, ambulatory blood pressure and plasma inflammatory markers were unchanged. [8]
A larger 12-week trial in 40 obese, insulin-resistant men used 2,000 mg/day. Insulin sensitivity did not improve. [6]
This makes NR a poor candidate for turning a cellular mechanism directly into a weight-loss, glucose-control or exercise-performance claim. The human muscle studies show clear biological activity, but the functional payoff depends on the outcome and population.
What about energy, fatigue and sleep?
NAD+ is central to cellular energy metabolism, which is why NR is often marketed around “energy.” Day-to-day energy has not emerged as a repeatable clinical NR endpoint in healthy adults.
The 2025 long-COVID randomized trial offers a useful stress test of that claim. Fifty-eight participants received 2,000 mg/day NR or placebo during the controlled phase. NAD+ increased about 2.6-fold to 3.1-fold after five to ten weeks in the NR group, yet there were no significant between-group improvements in fatigue, sleep, cognition, anxiety or depression. [16]
Because the participants had long COVID, the result applies most directly to that population. It also shows that biomarker response and symptom response can diverge.
Blood pressure: an early signal met a tougher newer test
Cardiovascular findings are a good example of why newer studies matter. In the 2018 trial of healthy middle-aged and older adults, NR produced exploratory signals for lower systolic blood pressure and arterial stiffness, with the strongest changes appearing in people who entered with higher blood pressure. [5]
A 2025 pilot then tested NR in a more targeted setting: 54 sedentary adults aged 55 or older with daytime systolic blood pressure of at least 130 mmHg. Sixty-one percent were women. Adding 1,000 mg/day NR to supervised walking did not lower daytime systolic blood pressure more than walking plus placebo over six weeks. [14]
Taken together, the vascular studies leave a promising early signal, but blood-pressure lowering has not become a reproducible NR effect.
CELLSHE DATA
Landmark human NR trials: dose, duration and what actually changed
| Study | Population | NR dose | Duration | Main useful result |
|---|---|---|---|---|
| Conze 2019 [4] | 140 healthy overweight adults, ages 40 to 60 | 100, 300 or 1,000 mg/day | 8 weeks | Whole-blood NAD+ rose 22%, 51% and 142% at the three doses within two weeks and remained elevated. |
| Martens 2018 [5] | Healthy middle-aged and older adults | 1,000 mg/day | 6 weeks | Raised NAD+ metabolism; exploratory blood-pressure and arterial-stiffness signals. |
| Dollerup 2018 [6] | 40 obese, insulin-resistant men, ages 40 to 70 | 2,000 mg/day | 12 weeks | No improvement in insulin sensitivity or glucose disposal. |
| Elhassan 2019 [7] | 12 older men | 1,000 mg/day | 21 days | Changed muscle NAD-related metabolites and inflammatory signatures; mitochondrial bioenergetics did not improve. |
| Remie 2020 [8] | 13 overweight/obese men and women | 1,000 mg/day | 6 weeks | Changed muscle NAD-related and acetylcarnitine metabolism; no improvement in insulin sensitivity or mitochondrial function. |
| McDermott 2024 [12] | 90 adults with peripheral artery disease | 1,000 mg/day | 6 months | Six-minute walking distance improved by 17.6 m versus placebo. |
| Wu 2025 [13] | Adults over 55 with subjective cognitive decline or MCI | 1,000 mg/day | 8 weeks | pTau217 moved favorably; no between-group cognitive improvement. |
| Lin 2025 [14] | 54 sedentary adults 55+ with elevated daytime systolic BP; 61% women | 1,000 mg/day | 6 weeks | NR plus walking did not lower daytime systolic BP more than walking plus placebo. |
| Martens 2026 [17] | Older adults with amnestic MCI; 63% of participants who started treatment were women | 1,000 mg/day | 12 weeks | Whole-blood NAD+ nearly doubled; cognition, total cerebral blood flow and blood pressure did not improve versus placebo. |
Source: primary human trials. See references 4 to 8, 12 to 14 and 17.
What do the NR studies mean for women in midlife?
Women are represented in several important NR trials. The eight-week dose-response study included healthy overweight men and women aged 40 to 60. [4] The 2025 hypertension pilot was 61% female. [14] The 2026 amnestic MCI study also enrolled more women than men. [17]
Women are represented, but the NR evidence base has not yet been designed around perimenopause or menopause outcomes such as hot flashes, menopausal sleep disruption or body-composition change across the transition.
For a woman considering NR for healthy aging, the evidence supports a simple hierarchy:
- Most certain: oral NR can raise NAD+ and related metabolites in humans.
- Most encouraging functional result: improved walking capacity in a randomized PAD trial.
- Active research areas: brain biology, vascular function and inflammatory signaling.
- Less dependable expectations: weight loss, better glucose control, a noticeable energy surge, lower blood pressure or sharper memory in otherwise healthy adults.
This is a more useful standard than asking whether NR is “good” or “bad.” The molecule has clear biological activity. The benefit depends on the endpoint you care about.
How much NR has been studied?
Human studies have used a wide range of doses. Controlled trials include 100, 300 and 1,000 mg/day in healthy overweight adults, 1,000 mg/day in several older-adult studies, 2,000 mg/day in obesity and long-COVID studies, and 3,000 mg/day for four weeks in a Parkinson's disease safety trial. [4][6][11][16]
These are research doses. A study dose tells you what investigators tested under that protocol. Choosing a personal dose is a different question.
Duration matters too. Some studies measured NAD-related changes within days or two weeks. Trials looking for functional or disease-related outcomes have run from several weeks to six months. A measurement at week two, six or twelve marks when researchers checked an endpoint. Personal time-to-effect is a separate question.
What side effects have NR trials reported?
Across controlled trials, NR has generally been well tolerated over the study periods tested. In the 140-person eight-week trial, adverse-event rates were similar across placebo and the 100, 300 and 1,000 mg/day groups. [4]
A four-week phase I Parkinson's disease study also found 3,000 mg/day was well tolerated in 20 participants, with no moderate or severe adverse events. [11] In the 2026 amnestic MCI trial, no serious adverse events occurred. Nausea, diarrhea and mild headaches were among the more frequently reported events in the NR group, but similar event types and frequencies occurred with placebo. [17]
The safety evidence is strongest for the doses, populations and durations that have actually been studied. Most healthy-aging trials remain measured in weeks or months rather than years. For a broader route-by-route safety review, see Can NAD+ Be Harmful?
How does NR compare with NMN?
NR and NMN are both NAD+ precursors, and both raise circulating NAD+ in human studies. The comparison deserves its own evidence review because pathway position alone is insufficient to rank them for an individual. Our NMN vs NR guide covers the direct 2026 head-to-head studies, while our NR vs NMN vs niacin comparison places the main oral precursors side by side.
So, what are the real benefits of nicotinamide riboside?
NR has moved past the stage of being interesting only in animals. In people, it repeatedly raises NAD+ and related metabolites, reaches muscle and brain-related biology, and has produced meaningful functional results in selected clinical populations. The 2024 PAD walking trial is the clearest recent example. [12]
For healthy women in midlife, the strongest current conclusion is more focused: NR is a credible NAD+ precursor with demonstrated human target engagement and an expanding clinical research base. The next generation of trials needs to show which functional benefits repeat in healthy adults, which are disease-specific, and which matter enough to be felt in everyday life.
Scientific references
- Gallagher C, Emmanuel OO. 2026. NAD+ supplementation for anti-aging and wellness: A PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Research Reviews. PMID: 41655607. PubMed.
- Damgaard MV, Treebak JT. 2023. What is really known about the effects of nicotinamide riboside supplementation in humans. Science Advances. PMID: 37478182. PubMed.
- Trammell SAJ, et al. 2016. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nature Communications. PMID: 27721479. PubMed.
- Conze D, Brenner C, Kruger CL. 2019. Safety and Metabolism of Long-term Administration of NIAGEN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, Placebo-controlled Clinical Trial of Healthy Overweight Adults. Scientific Reports. PMID: 31278280. PubMed.
- Martens CR, et al. 2018. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nature Communications. PMID: 29599478. PubMed.
- Dollerup OL, et al. 2018. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. American Journal of Clinical Nutrition. PMID: 29992272. PubMed.
- Elhassan YS, et al. 2019. Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures. Cell Reports. PMID: 31412242. PubMed.
- Remie CME, et al. 2020. Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans. American Journal of Clinical Nutrition. PMID: 32320006. PubMed.
- Vreones M, et al. 2023. Oral nicotinamide riboside raises NAD+ and lowers biomarkers of neurodegenerative pathology in plasma extracellular vesicles enriched for neuronal origin. Aging Cell. PMID: 36515353. PubMed.
- Brakedal B, et al. 2022. The NADPARK study: A randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease. Cell Metabolism. PMID: 35235774. PubMed.
- Berven H, et al. 2023. NR-SAFE: a randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson's disease. Nature Communications. PMID: 38016950. PubMed.
- McDermott MM, et al. 2024. Nicotinamide riboside for peripheral artery disease: the NICE randomized clinical trial. Nature Communications. PMID: 38871717. PubMed.
- Wu CY, et al. 2025. Cognitive and Alzheimer's disease biomarker effects of oral nicotinamide riboside supplementation in older adults with subjective cognitive decline and mild cognitive impairment. Alzheimer's & Dementia: Translational Research & Clinical Interventions. PMID: 39817194. PubMed.
- Lin Y, et al. 2025. Nicotinamide riboside combined with exercise to treat hypertension in middle-aged and older adults: a pilot randomized clinical trial. GeroScience. PMID: 40770531. PubMed.
- Shoji M, et al. 2025. Nicotinamide Riboside Supplementation Benefits in Patients With Werner Syndrome: A Double-Blind Randomized Crossover Placebo-Controlled Trial. Aging Cell. PMID: 40459998. PubMed.
- Wu CY, et al. 2025. Effects of nicotinamide riboside on NAD+ levels, cognition, and symptom recovery in long-COVID: a randomized controlled trial. eClinicalMedicine. PMID: 41357333. PubMed.
- Martens CR, et al. 2026. A phase-II randomized controlled pilot study of nicotinamide riboside supplementation in older adults with amnestic mild cognitive impairment. Alzheimer's & Dementia. DOI: 10.1002/alz.71605. DOI.
- Freeberg KA, et al. 2023. Dietary Supplementation With NAD+-Boosting Compounds in Humans: Current Knowledge and Future Directions. Journals of Gerontology: Series A. PMID: 37068054. PubMed.
