Key Points
- NAD+ blood levels steadied after 2 weeks
- Brain NAD+ increased after 4 weeks
- Elevated NAD+ declined gradually after stopping
"Both NR and NMN showed excellent tolerability with no moderate or severe adverse events."
Overview of Study
Researchers designed a two-stage study following a 24-hour pilot in one individual.
In the first stage, six healthy adults (ages 43-47) completed a randomized crossover study with both NMN and NR phases separated by an 11-day washout period.
- NMN First: 8 days of 1,200 mg/day oral NMN (600 mg twice daily), followed by 1,200 mg/day oral NR (600 mg twice daily)
- NR First: 8 days of 1,200 mg/day oral NR (600 mg twice daily), followed by 8 days of 1,200 mg/day oral NMN (600 mg twice daily)
In a second stage of the study, 12 participants received:
- HC: 6 healthy individuals received 1,200 mg/day oral NR (600 mg twice daily) for 4 weeks
- PwP: 6 Parkinson's individuals received 1,200 mg/day oral NR (600 mg twice daily) for 4 weeks
Blood samples and brain scans were taken repeatedly throughout each phase to track changes in NAD+ levels over time.
NMN & NR Increased NAD+ Gradually and Sustainably
NAD+ levels did not spike immediately after supplementation, but instead increased steadily over time, stabilizing after about two weeks.
"In healthy individuals, NR induced a gradual increase in mean blood NAD levels over time which stabilized after approximately 2 weeks."
This shows that short-term dosing doesn't reflect full NAD+ effects and consistent intake over weeks is required to evaluate the benefits.
"Oral NR and NMN produce a gradual increase in blood and brain NAD levels that plateau only after approximately two weeks of supplementation."
After supplementation ended, NAD+ levels declined slowly rather than returning immediately to baseline.
"After treatment cessation, blood and brain NAD levels declined, requiring 2–3 weeks to return to baseline."
Brain NAD+ Also Increases with Continued Use
Brain NAD+ changes lagged behind blood, with increases seen after 4 weeks of supplementation, indicating precursors do reach the brain, but more slowly.
"Cerebral NAD+ levels increased measurably after four weeks of treatment."
Brain NAD+ increased nearly 40% above baseline, supporting the idea that neurological effects likely require sustained supplementation.
"In the brain, NR supplementation increased NAD levels over time in healthy individuals… reaching 39.73% above baseline after four weeks of treatment."
This aligns with broader research showing that NAD+ plays a central role in neuronal resilience, mitochondrial function, and DNA repair pathways in the brain.
NAD+ Response Was Consistent Across Groups
Importantly, NAD+ levels increased consistently across groups, with no significant differences in the level or rate of elevation.
"There were no differences between healthy individuals and PwPs with regard to baseline blood NAD+ levels, NAD+ response to NR supplementation, or return to baseline during washout."
These findings indicate that NAD+ precursors increase NAD+ levels consistently across populations, with similar responses regardless of biological sex or disease status, suggesting broad applicability.
Conclusion
This study provides one of the clearest human timelines for NAD+ biology.
Oral NMN and NR do work to increase NAD+, but the process is slow. NAD+ levels build over weeks before stabilizing and decline gradually after stopping.
"Blood NAD increased slowly, plateauing after approximately two weeks of treatment, and declined with similarly slow kinetics following treatment discontinuation."
"In the brain, NR supplementation increased NAD levels over time in healthy individuals, stabilizing after two weeks and reaching 39.73% above baseline after four weeks."
"PwPs exhibited a highly similar profile to the healthy individuals with progressively increasing blood NAD levels over time, stabilizing after two weeks."
Overall, this reinforces that consistency matters more than acute dosing, and NAD+ interventions should be evaluated over weeks, not days.
Clinical comparisons of NAD+ precursors provide important context for why these molecules are preferred for elevating NAD+ over time.
