Written by the Nuvirox Research Team
Key Points
- A 2025 crossover trial gave older adults with cognitive decline 1 g/day of nicotinamide riboside (NR) for 8 weeks and found no significant change in cognitive test scores versus placebo.
- A separate 12-week trial in amnestic mild cognitive impairment found NR increased blood flow to the hippocampus but did not improve memory performance.
- Alzheimer's biomarker changes (tau, amyloid) have been mixed and mostly non-significant across trials so far — this is genuinely unsettled science, not a hidden win.
Short answer: two legitimate human trials have now tested an NAD+ precursor in people with cognitive decline, and neither found a clear memory benefit — though both found interesting downstream effects worth understanding. If you came here hoping for a clean "yes," the honest answer is more complicated, and that complexity is worth walking through rather than glossing over.
Why would NAD+ matter for the aging brain at all?
NAD+ is required for mitochondrial energy production and for enzymes that repair DNA and regulate inflammation in neurons. Brain NAD+ concentrations are lower in older adults than in younger ones, and this decline has been linked — mostly in mouse models — to the kind of cellular stress seen in Alzheimer's disease. That's the theoretical case for NAD+ precursors like nicotinamide riboside (NR): raise the fuel supply, support the repair machinery, and hope downstream neurons hold up better. It's a coherent hypothesis. It is not the same thing as a proven treatment.
What did the actual human trials find?
The most direct test came from a Massachusetts General Hospital team (Wu et al., 2025), who ran a crossover, double-blind, randomized, placebo-controlled trial in older adults with subjective cognitive decline and mild cognitive impairment. Participants took 1 g/day of NR for 8 weeks. The primary outcome — the RBANS cognitive battery — showed no significant treatment effect. Secondary blood biomarkers (phosphorylated tau 217, GFAP, neurofilament light) also did not differ significantly between NR and placebo.
A second, separate trial (Martens et al., University of Delaware, phase II pilot) gave 52 older adults with amnestic mild cognitive impairment 500 mg of NR twice daily for 12 weeks. Blood NAD+ rose as expected, and — notably — hippocampal blood flow (perfusion) increased on brain imaging. But memory performance itself did not significantly improve. The researchers were explicit that a larger, longer trial is needed before any conclusion about cognitive benefit can be drawn.
What about a separate nicotinamide (not NR) trial?
A different, earlier-stage proof-of-concept trial tested high-dose nicotinamide (not nicotinamide riboside) — 1,500 mg twice daily for 12 months — in 47 people with mild Alzheimer's disease. It found a significantly smaller decline on one clinical dementia rating scale (CDR-SB) compared to placebo, but no significant effect on the standard cognitive test (ADAS-Cog-13) or daily-living scale. This is a different compound, a different dose, and a mixed result — it doesn't resolve the question, but it's part of the honest picture and shows why researchers keep pursuing this line of work.
What this research doesn't tell you
None of these trials tell you whether NAD+ precursors prevent Alzheimer's, slow progression once diagnosed, or help earlier in life before any decline appears. They also don't establish a "right" dose for brain effects — the trials used 1 g/day and 500 mg twice daily, both higher than a typical maintenance dose, for relatively short periods (8–12 weeks). If you or someone you love has been diagnosed with mild cognitive impairment or Alzheimer's disease, this is a conversation for a neurologist, not a supplement aisle — cognitive decline has dozens of contributing causes, some reversible (medication side effects, thyroid problems, sleep apnea, depression, B12 deficiency) and worth ruling out before anything else.
Where this leaves someone without a diagnosis
If your interest is general brain-aging support rather than an existing diagnosis, it's worth knowing that NAD+'s broader role in cellular metabolism and its relationship to everyday brain fog are separate — and generally better-supported — questions than its role in diagnosed neurodegenerative disease. Similar honest caveats apply across NAD+ research in Parkinson's disease and multiple sclerosis, where trials also show biological activity without yet showing clear symptomatic benefit.
Why researchers keep pursuing this despite mixed results
It's worth understanding why this research area hasn't stalled out despite the disappointing headline results. Mouse studies of Alzheimer's disease models have repeatedly shown that NAD+ supplementation can normalize DNA damage responses and certain disease-associated features at the molecular level, and a separate line of research found that NR treatment increased NAD+ levels specifically within plasma extracellular vesicles enriched for neuronal origin, alongside favorable changes in several proteins associated with neurodegenerative pathology, in a small crossover trial of 22 healthy older adults. That's a genuinely different kind of evidence than a symptom-scale score — it's a biomarker signal in tissue closer to the source — and it's part of why researchers describe this as an unresolved question rather than a closed one. The gap between "we can move the biology" and "we can move the symptoms" is exactly where Alzheimer's drug development has struggled for decades, well beyond NAD+ precursors specifically, and it's a useful frame for reading any single trial's results with appropriate patience.
FROM NUVIROX
Because of the caveats above, we'd encourage you to read this as general background rather than a treatment plan. If you're curious about the ingredient at the center of this research, here's what's in ours, alongside clinician-routing guidance for anything beyond everyday support:
- 500 mg Nicotinamide Riboside Chloride (NR) — one of the two most-researched NAD+ precursors, within the dose range used in published human trials
- 150 mg trans-resveratrol + 50 mg quercetin — polyphenols studied alongside NAD+ pathways for cellular health support
- 10 mg fenugreek galactomannans to support absorption
- Backed by a 60-day money-back guarantee — long enough to actually evaluate it the way the research says you should
Frequently asked questions
Does NAD+ reverse memory loss?
No human trial has shown that. The two direct trials in cognitive decline found no significant memory improvement, though one found increased blood flow to the hippocampus, a finding researchers describe as intriguing rather than conclusive.
Is nicotinamide riboside the same as nicotinamide for brain health?
No. They're both NAD+ precursors but different molecules with different trial histories. The nicotinamide trial used much higher doses (3 g/day) over a full year and found mixed results on different outcome measures.
Should someone with a dementia diagnosis take an NAD+ supplement instead of prescribed treatment?
No. This research does not support replacing or delaying any prescribed treatment. Cognitive decline should be evaluated and managed by a physician, since many contributing causes are treatable.
Why did hippocampal blood flow increase without a memory benefit?
Researchers don't fully know. It's possible the 12-week trial was too short to translate a perfusion change into a measurable memory effect, or that perfusion isn't the limiting factor for memory in this population. It's an open question for future, larger trials.
Are longer or larger trials planned?
Yes — researchers involved in the amnestic mild cognitive impairment pilot trial explicitly stated a larger phase 3 trial is necessary before any conclusion about cognitive benefit can be drawn, and a separate dose-optimization trial (N-DOSE AD) is registered to test different NR doses specifically in Alzheimer's disease.
The bottom line: NAD+ precursors are biologically active in the aging brain — that much is well documented — but the leap from "biologically active" to "cognitively beneficial" hasn't been made yet in rigorous human trials. Anyone navigating a cognitive decline diagnosis deserves a fuller answer than a supplement bottle can honestly give.
References
- Wu CY, Kupferschmid AC, Chen L, et al. Cognitive and Alzheimer's disease biomarker effects of oral nicotinamide riboside (NR) supplementation in older adults with subjective cognitive decline and mild cognitive impairment. Alzheimers Dement (N Y). 2025;11(1):e70023. PMID: 39817194.
- Martens CR, Decker KP, DeConne TM, et al. A phase-II randomized controlled pilot and feasibility study of nicotinamide riboside supplementation in older adults with amnestic mild cognitive impairment. Alzheimers Dement. 2025. PMC12724761.
- Grill JD, et al. Proof-of-concept trial of high-dose nicotinamide in mild Alzheimer's disease. Presented at Alzheimer's Association International Conference (AAIC), 2023.
- Braidy N, Liu Y. Can nicotinamide riboside protect against cognitive impairment? Curr Opin Clin Nutr Metab Care. 2020;23(6):413-420. PMID: 32925178.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical advice.