What to know
- Raising NAD or changing an aging marker does not by itself demonstrate a health benefit.
- Small trials suggest some specific effects, but results vary by population and outcome.
- Long-term safety, disease prevention and lifespan benefits remain unestablished.
01
Have NMN or NR been shown to slow human aging?
Human trials have not established that nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR) broadly slow aging, extend lifespan or prevent the diseases of aging. They do show that these compounds can affect NAD-related biology, and some studies report benefits for a particular metabolic or functional outcome. Those narrower findings deserve attention without being expanded into a general longevity claim.
A 2025 clinical review emphasized limited evidence for efficacy and gaps in understanding age-related NAD changes in humans. A 2026 systematic review likewise found more consistent changes in NAD-related biomarkers than in clinical outcomes. The research is active, but biological plausibility and a marketable anti-aging treatment are different stages of evidence.
02
Why does NAD attract interest?
NAD is a molecule involved in energy metabolism and other cellular processes. NMN and NR are precursors that the body can use in pathways that produce NAD. This makes supplementation a plausible research strategy, but it does not establish that a low measurement is the cause of aging or that increasing it will improve health.
Measurements in blood also cannot be assumed to describe every organ. A trial can demonstrate that an intervention reaches a biological target while leaving the clinical question unanswered. To establish benefit, researchers still need suitable comparisons and outcomes such as physical function, disease events or survival.
03
What selected human trials found
The trials below answer different questions. They should not be combined as if every result measured the same anti-aging effect, and findings for NR should not automatically be attributed to NMN. A positive result in one selected population needs confirmation before being applied to healthy adults generally.
| Study | Main finding relevant here | Limit of the inference |
|---|---|---|
| NR, 2018 crossover trial | Six-week treatment periods increased NAD-related measures in healthy middle-aged and older adults. | Target engagement and short-term tolerability do not demonstrate longer life. |
| NMN, 2021 trial | In 25 postmenopausal women with overweight or obesity and prediabetes, 10 weeks improved muscle insulin sensitivity. | A selected metabolic effect is not proof of diabetes prevention or an effect in all adults. |
| NR, 2025 cognition trial | The trial randomized 46 people; 37 completed it. Eight-week comparisons did not show a significant cognitive advantage on the primary assessment. | Changes in an Alzheimer-related blood marker did not establish a cognitive benefit. |
| NR, 2024 NICE trial | A six-month trial in peripheral artery disease found a walking-distance signal favoring NR. | The result used a preliminary one-sided testing threshold and needs confirmation. |
04
A promising walking result needs its statistical context
The NICE trial randomized 90 people with peripheral artery disease to NR, NR plus resveratrol, or placebo. At six months, the NR-only group had a 17.6-meter advantage over placebo in six-minute walking distance. This was a functional outcome, not merely a laboratory marker, and is a reason to keep investigating the intervention in this population.
However, the trial prespecified a one-sided significance threshold of 0.10. The reported one-sided p-value was 0.08; its one-sided 90% confidence interval had a lower bound of 1.8 meters and no finite upper bound. This should not be presented as meeting a conventional two-sided 0.05 threshold. Adding resveratrol did not improve the primary result, and the authors called for a larger confirmatory trial. A possible walking benefit in peripheral artery disease does not establish slower aging across healthy people.
Understand p-values and prespecified testing thresholds
Sources for this section: [5]
05
Do better biomarkers or aging clocks mean rejuvenation?
A small 2023 trial in 20 older adults with mild cognitive impairment illustrates the gap. NR increased blood NAD, but cognition did not improve over 10 weeks. Exploratory aging-clock results varied by clock, and within-group paired tests did not show significant changes. A headline about a younger biological age would therefore overstate what that trial established.
The 2025 cognition trial also found a change in an Alzheimer-related blood marker without a significant advantage in its cognitive assessment. Biomarkers can help test mechanisms or select future studies, but their meaning depends on validation for the outcome being claimed. Changing a clock score or a blood protein does not by itself show that dementia was prevented, daily life improved or lifespan increased.
06
What remains uncertain about safety?
Short, small trials can provide useful tolerability information, but they are poorly suited to finding uncommon harms or effects that emerge after years. The reviewed human evidence does not establish long-term safety for broad anti-aging use across people with different illnesses, medicines and supplement combinations.
Oral NMN, oral NR and NAD infusions are different interventions. Evidence for one should not be used to advertise another route or mixture. A 2026 review found no eligible intravenous or intramuscular NAD anti-aging or wellness outcome trials under its criteria; that is a limit of the evidence reviewed, not a claim that no NAD infusion has ever been studied.
NCCIH advises discussing supplements with a health care professional because products can interact with medicines and quality can vary. Take the product label and medication list to that conversation. These early findings do not justify replacing established care or paying for a product on the assumption that a higher NAD measurement proves it is extending life.
07
What evidence would strengthen the case?
This focused narrative synthesis draws on selected clinical reviews, randomized human trials and official supplement guidance checked on September 8, 2026. Accessible full texts and abstracts were used; the paywalled 2025 Nature Metabolism review was assessed through its abstract. This is not an exhaustive systematic search, a new meta-analysis or an independent clinical review. Mouse findings were not treated as proof of human efficacy.
- Look for replication of a meaningful clinical outcome, not just a rise in NAD.
- Check the compound, route, population, follow-up and prespecified primary outcome.
- Read the uncertainty and correction for multiple tests alongside any positive finding.
- Require longer follow-up and adequate safety monitoring for long-term prevention claims.
At present, NMN and NR are scientifically interesting interventions with some specific human signals and substantial unanswered questions. The supported conclusion is that broader anti-aging benefits remain unproven; it is neither a guarantee of benefit nor proof that every future clinical application will fail.
Sources
- Vinten et al. — NAD+ precursor supplementation in human ageing: clinical evidence and challengesNature Metabolism · 2025Source accessed: DOI 10.1038/s42255-025-01387-7
- Martens et al. — Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adultsNature Communications · 2018Source accessed: DOI 10.1038/s41467-018-03421-7
- Yoshino et al. — Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic womenScience · 2021Source accessed: DOI 10.1126/science.abe9985
- Cognitive and Alzheimer’s disease biomarker effects of oral nicotinamide riboside supplementation in older adults with subjective cognitive decline and mild cognitive impairmentAlzheimer's & Dementia: Translational Research & Clinical Interventions · 2025Source accessed: DOI 10.1002/trc2.70023
- McDermott et al. — Nicotinamide riboside for peripheral artery disease: the NICE randomized clinical trialNature Communications · 2024Source accessed: DOI 10.1038/s41467-024-49092-5
- A randomized placebo-controlled trial of nicotinamide riboside in older adults with mild cognitive impairment2023Source accessed: PMID 37994989
- Using Dietary Supplements WiselyNational Center for Complementary and Integrative HealthSource accessed:
- Gallagher and Emmanuel — NAD+ supplementation for anti-aging and wellness: A PRISMA-guided systematic review of preclinical and clinical evidenceAgeing Research Reviews · 2026Source accessed: DOI 10.1016/j.arr.2026.103057
Revision history
- Initial article prepared with automated assistance and sources checked at 2026-09-07T16:27:46Z (UTC). The publication timestamp 2026-08-28T01:23:47Z (UTC) was assigned retrospectively at the publisher's request; it is separate from preparation and source checking. This is a narrative evidence review. No independent clinical review is recorded. Date displays and this explanation use UTC; the recorded instants are unchanged.