Research Watch: What Recent Studies Say About NAD+ and Longevity (Early July 2026)

A few things landed on my desk in the last couple of weeks that I thought were worth sharing. The NAD+ space moves quickly, and June 2026 brought a handful of peer-reviewed publications that paint a more nuanced picture than the headlines usually admit. Here is what I found, and what I think it means for anyone thinking about NAD+ precursors as part of a longevity-focused routine. As always, this is not medical advice, and you should speak with a healthcare provider before starting any new supplement.

Quick Answer: Recent 2024-2025 research confirms that NMN and NR reliably raise blood NAD+ levels in humans, but whether those elevated levels translate into meaningful benefits for muscle strength, cognitive recovery, or slower aging is still an open question. The science is promising, especially for cellular energy metabolism and cardiovascular markers, but the human evidence remains preliminary and cautious optimism is warranted rather than certainty.

Study 1: A Major Review Asks Whether the Human Evidence Actually Holds Up

One of the most important papers of the year comes from Vinten, Tretowicz, Coskun, and colleagues, published in Nature Metabolism in 2025. The review, titled "NAD+ precursor supplementation in human ageing: clinical evidence and challenges," synthesizes the current clinical landscape across neurodegeneration, vision, hearing, inflammation, and musculoskeletal conditions.

What they found: The authors note that evidence for an age-related decline in NAD+ levels in humans has been consistently observed only in a limited number of tissues, primarily skin, liver, and brain. Other tissues show no clear decline. On the question of clinical efficacy, the picture is mixed: neurological and inflammatory conditions appear more receptive to NAD+ supplementation than musculoskeletal ones. The safety record, however, is very high, with minimal side effects reported across trials.

What it means: This is a useful corrective to the idea that NAD+ precursors are universally beneficial for all aging processes. The biology is real. The supplementation works at raising NAD+ levels. But the downstream effects depend heavily on which tissue, which condition, and which biomarker you are measuring.

Caveats: This is a narrative review, not a meta-analysis. Reviews summarize existing data and are shaped by which studies the authors choose to include. The conclusions reflect the current state of evidence, which the authors themselves describe as limited by small sample sizes, short durations, and heterogeneous outcome measures across trials.

Study 2: NR Shows Real Benefits for a Rare Accelerated-Aging Condition

A double-blind, randomized, crossover, placebo-controlled trial by Shoji and colleagues, published in Aging Cell in June 2025, tested nicotinamide riboside (NR) in patients with Werner syndrome, a rare hereditary condition that causes accelerated aging, often leading to age-associated diseases in the 20s and 30s and early mortality before 60.

What they found: Daily NR supplementation elevated blood NAD+ levels by approximately 140% compared to baseline. Beyond the biomarker change, the trial reported improved arterial stiffness (measured by cardio-ankle vascular index), a reduction in skin ulcer area, and a trend toward reduced heel pad thinning. These are meaningful clinical markers, not just numbers on a lab panel.

What it means: Werner syndrome patients have documented NAD+ depletion driven by a specific gene mutation (WRN), so this population may benefit more than healthy adults. Still, the fact that raising NAD+ levels produced measurable cardiovascular and skin improvements in humans, in a controlled trial, adds meaningful weight to the hypothesis that NAD+ status matters for tissue health.

Caveats: Werner syndrome is a rare disease with a very specific mechanism. The results should not be directly extrapolated to healthy aging populations. Sample sizes in rare disease trials are inherently small, which limits statistical power. This trial is best understood as proof-of-concept, not as confirmation that NR will produce the same results in people without the WRN mutation.

Study 3: NR Does Not Move the Needle on Long COVID Cognitive Symptoms in a Controlled Trial

A 2025 randomized controlled trial by Wu, Guzman-Velez, and colleagues at Mass General Brigham, published in eClinicalMedicine (a Lancet journal), tested high-dose NR supplementation in 58 non-hospitalized adults with persistent long COVID symptoms. Participants received either 2,000 mg per day of NR for 20 weeks or a placebo lead-in for 10 weeks followed by NR for 10 more weeks.

What they found: The researchers observed encouraging within-group improvements in fatigue, sleep quality, and mood among NR users. However, the trial did not reach statistical significance between the NR group and the placebo group on its primary cognitive endpoints. NR successfully raised NAD+ levels, confirming that absorption and bioavailability were not the bottleneck.

What it means: A null result is still a result. This trial suggests that raising NAD+ levels in adults with long COVID does not, by itself, reliably resolve cognitive impairment or post-viral fatigue in a controlled comparison. The within-group improvements may reflect placebo effect, natural recovery, or real but modest benefit that the trial was underpowered to detect.

Caveats: The sample size of 58 participants is small for detecting modest effects. Long COVID is a heterogeneous condition with varying symptom profiles, and the study population may not have been uniform enough to capture a signal. The authors call for larger, longer trials to reach definitive conclusions. This is a preliminary negative finding, not a final verdict.

Study 4: A 2025 Meta-Analysis Finds No Clear Muscle Benefit From NMN or NR Alone

Prokopidis and colleagues published a systematic review and meta-analysis in the Journal of Cachexia, Sarcopenia and Muscle in April 2025, pooling 10 randomized controlled trials that tested NMN or NR on skeletal muscle mass and function in adults aged 60 and older.

What they found: Across measures including skeletal muscle index, handgrip strength, and gait speed, the pooled analysis found no statistically significant differences between the supplementation and placebo groups. NMN did not improve knee extension strength, short physical performance battery scores, or thigh muscle mass compared to controls.

What it means: For anyone hoping that NMN or NR will act as a standalone muscle-building or sarcopenia-prevention supplement, this meta-analysis is a useful reality check. Pooling 10 trials is more informative than any single study, and the overall signal on muscle outcomes is currently flat.

Caveats: The authors highlight an important gap: most study participants were sedentary. Resistance training is the most powerful stimulus for muscle protein synthesis, and NAD+ metabolism plays a role in exercise adaptation. Whether NMN or NR might show benefits in combination with structured resistance training is a different question that these trials were not designed to answer. The authors themselves flag this as a priority for future research.

What This Means for Your Routine

The honest summary from this batch of research is that NAD+ precursors are safe and do what they are supposed to do at the biochemical level: they reliably raise blood NAD+ concentrations. Where the evidence gets murky is the next step, the question of whether higher NAD+ translates to measurable benefits in healthy adults over realistic supplementation periods.

A few practical takeaways from the current literature:

Pairing with lifestyle habits matters. The Prokopidis meta-analysis raises the pointed question of whether sedentary trial participants simply lacked the physiological stimulus to benefit. If you are thinking about NAD+ support, the research suggests that exercise, sleep, and caloric quality are not optional add-ons; they are likely co-factors for any supplementation effect.

Expect biomarker changes, not overnight transformations. What the science consistently delivers is elevated NAD+ in blood. What it has not yet consistently delivered is large-scale human evidence of reversed aging or dramatic functional improvement in healthy populations. Treat supplementation as one input among many, not a silver bullet.

The neurological and vascular angles look more promising than muscle. The Vinten review and the Shoji trial both point toward cardiovascular and brain tissue as areas where NAD+ support may have more traction than muscle. That is worth keeping in mind when reading marketing claims focused primarily on physical performance.

If you are curious about NAD+ precursor supplementation and want an option that carries a Health Canada Natural Product Number, the Live 5AM NAD+ Booster Complex is one to look at. Every NPN-licensed product has had its ingredients, doses, and intended use reviewed by Health Canada before it can be sold in Canada.

Frequently Asked Questions

Does NAD+ actually decline with age in humans?

The evidence is tissue-specific and less universal than earlier animal studies suggested. A 2025 Nature Metabolism review by Vinten et al. found that consistent age-related NAD+ decline in humans has been documented mainly in skin, liver, and brain. Other tissues show more variable patterns. Aging research in mice does not always replicate cleanly in humans, so this is an area where the science is still being refined.

What is the difference between NMN and NR?

Both NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) are precursors that the body converts into NAD+. NMN sits one step closer to NAD+ in the biosynthesis pathway. In practice, human trials have found that both compounds raise blood NAD+ levels effectively. The 2025 Prokopidis meta-analysis pooled trials of both compounds and found comparable outcomes on the measures studied, suggesting no clear clinical superiority of one over the other for the outcomes tested so far.

Are NMN and NR supplements safe?

The available human trial data suggests a favorable safety profile for both NMN and NR at commonly studied doses. The Vinten et al. 2025 review in Nature Metabolism notes that the safety record across model systems and human trials appears very high, with none or very limited side effects reported. That said, long-term safety data beyond 12 months in large human populations remains limited. If you have an existing health condition or take medications, consult a healthcare provider before starting.

Can NAD+ supplements help with muscle loss as you age?

Based on current evidence, the answer appears to be: not on their own in sedentary adults. A 2025 meta-analysis by Prokopidis et al., pooling 10 randomized controlled trials of NMN or NR in adults 60 and older, found no significant improvement in muscle mass, handgrip strength, or physical function compared to placebo. The authors note that most trial participants were not engaged in resistance training, which may be a key missing variable. This does not close the question, but it does temper expectations for supplementation alone.

What does the research say about NAD+ and brain or cardiovascular health?

These are among the more promising areas in current research. The Shoji et al. 2025 trial in Aging Cell found that NR supplementation significantly improved arterial stiffness markers in Werner syndrome patients, a finding with cardiovascular implications. The Vinten et al. review identified neurodegeneration and inflammation as areas where NAD+ supplementation appears more receptive than musculoskeletal outcomes. Results in long COVID cognitive symptoms were mixed in the 2025 Wu et al. trial, highlighting that evidence in this space is still early-stage and incomplete.

The Bottom Line

The NAD+ supplementation field is maturing, and the 2024-2026 wave of human trials is doing useful work in separating what the science actually shows from what the marketing sometimes claims. The core finding is consistent: oral NMN and NR raise NAD+ levels in humans. The contested question is what that elevation accomplishes clinically.

The most promising signals right now point toward cardiovascular tissue and neurological function, with the Shoji 2025 trial providing the first controlled human evidence of measurable vascular improvement from NR. The most sobering signal is the muscle meta-analysis by Prokopidis et al., which found no benefit across 10 RCTs for the older adults studied. The long COVID trial added a useful null result that keeps expectations appropriately calibrated.

None of this makes NAD+ precursors a bad idea. The safety profile is strong, the biochemical mechanism is well-established, and there are plausible reasons to think that longer trials with better-defined populations and combined lifestyle interventions will clarify the picture. For now, the honest framing is that NAD+ supplementation may support cellular energy metabolism as part of a broader health routine, with the understanding that the human evidence is still accumulating and no supplement works in isolation.

This post is for informational purposes only and does not constitute medical advice. The studies summarized here involve diverse populations, dose ranges, and outcome measures. Supplement responses vary between individuals. Consult a qualified healthcare provider before making changes to your supplement regimen. Health Canada has not evaluated these statements as a cure, treatment, or prevention for any disease or condition.

Sources

1. Vinten KT, Tretowicz MM, Coskun E, et al. "NAD+ precursor supplementation in human ageing: clinical evidence and challenges." Nature Metabolism. 2025;7(10):1974-1990. doi:10.1038/s42255-025-01387-7
2. Shoji S, et al. "Nicotinamide Riboside Supplementation Benefits in Patients With Werner Syndrome: A Double-Blind Randomized Crossover Placebo-Controlled Trial." Aging Cell. 2025. doi:10.1111/acel.70093
3. Wu CY, Guzman-Velez E, et al. "Effects of nicotinamide riboside on NAD+ levels, cognition, and symptom recovery in long-COVID: a randomized controlled trial." eClinicalMedicine. 2025. doi:10.1016/j.eclinm.2025.103633
4. 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. doi:10.1002/jcsm.13799