BERGEN, NORWA, A phase III clinical trial has found that nicotinamide riboside, a popular longevity supplement that increases cellular NAD+ levels, did not improve clinical outcomes in people with early Parkinson’s disease.
The 52-week NOPARK trial found modestly worse average disease assessment scores among participants taking the supplement than among those receiving a placebo.
The findings challenge the assumption that increasing NAD+ levels necessarily improves neurological health.
Nicotinamide Riboside Fails Parkinson’s Trial
Nicotinamide riboside (NR) is a form of vitamin B3 that the body uses to produce nicotinamide adenine dinucleotide (NAD+). This molecule supports cellular energy production, metabolism, DNA repair and other processes that help cells function.
NAD+ levels and metabolism have attracted interest in ageing research. Scientists have investigated whether increasing NAD+ availability could protect nerve cells and improve outcomes in conditions associated with neurodegeneration, including Parkinson’s disease.
However, evidence that a supplement changes a biological marker does not establish that it improves symptoms or slows a disease. The NOPARK trial directly tested whether prolonged NR supplementation could improve clinical outcomes in people with early Parkinson’s disease.
The results, published in JAMA on October 8, 2026, did not support its use as a treatment to slow Parkinson’s disease. The findings were also reported by MedPage Today.
What the NOPARK Trial Examined
The NOPARK study was a randomized, double-blind, placebo-controlled phase III clinical trial conducted at 11 centres in Norway. Researchers screened 537 people and randomized 410 participants who met the eligibility criteria.
Participants had been diagnosed with Parkinson’s disease within the previous two years. They were at least 35 years old, had early-stage disease and were receiving stable dopaminergic treatment.
Researchers assigned participants to one of two groups:
- Nicotinamide riboside group: 500 milligrams twice daily for 52 weeks.
- Placebo group: A matching placebo over the same period.
Neither participants nor the study teams knew which treatment each participant received. This design helped reduce bias when measuring outcomes.
Of the 410 randomized participants, 393 were included in the primary analysis. Their mean age was 65.6 years, and 34% were women.
The researchers wanted to determine whether increasing NAD+ availability could improve symptoms, reduce disease burden or provide evidence of a disease-modifying effect. (Brakedal et al. 2026)
Primary Outcome Shows No Benefit
The trial’s primary endpoint was the change in the Movement Disorder Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Parts I to III after 52 weeks.
The scale assesses several aspects of Parkinson’s disease, including non-motor experiences of daily living, motor experiences of daily living and motor examination findings. Higher scores indicate greater disease severity.
At the end of the trial, the results were:
- Nicotinamide riboside: The average score worsened by 2.45 points.
- Placebo: The average score improved by 0.27 points.
- Adjusted difference: 2.72 points in favour of placebo.
The difference was statistically significant, with a 95% confidence interval of 0.47 to 4.98 points and a P value of 0.02.
These results indicate that participants receiving NR did not experience better clinical outcomes than those receiving placebo. The average outcome was modestly worse in the NR group.
Statistical Significance Versus Clinical Importance
A statistically significant result indicates that the observed difference is unlikely to be explained by random variation alone under the statistical model, assuming its underlying conditions hold. It does not automatically mean that the difference is large enough to matter clinically.
The trial authors cited minimum clinically important differences of 6.7 points for improvement and 5.2 points for worsening on the MDS-UPDRS total score.
The observed 2.72-point difference was below these thresholds. Therefore, although the primary endpoint favoured placebo statistically, the average difference was smaller than the cited thresholds for a clinically important change.
This distinction matters when interpreting the findings. The study did not demonstrate a clinically meaningful benefit from NR, and its results do not support using the supplement to slow Parkinson’s disease.
Non-Motor Symptoms Also Worsened
Parkinson’s disease affects more than movement. People may also experience sleep problems, constipation, fatigue, mood changes and other non-motor symptoms that interfere with daily life.
The NOPARK researchers assessed these symptoms using the Non-Motor Symptoms Scale, which measures the overall burden of non-motor problems.
At week 52, the adjusted difference between the NR and placebo groups was 4.22 points, with a 95% confidence interval of 1.07 to 7.37 points and a P value of 0.009. The result favoured placebo, indicating greater worsening of non-motor symptom burden in the NR group.
This was an important secondary finding. However, it should not be interpreted as proof that NR causes every non-motor symptom or that it accelerates Parkinson’s disease in every person who takes it.
Other Outcomes Did Not Show Clear Benefits
The researchers assessed five prespecified key secondary outcomes. Four did not show statistically significant differences between the groups.
These outcomes included individual MDS-UPDRS components and dopamine transporter imaging findings.
Brain imaging did not show evidence that NR slowed or accelerated changes in the brain’s dopamine system over the study period. However, the imaging method has limitations when detecting subtle changes over a relatively short period.
The findings therefore provide no convincing evidence that NR improved motor symptoms, daily functioning or the measured features of dopaminergic degeneration.
Did the Supplement Affect NAD+ Levels?
NAD+ plays a central role in cellular energy metabolism and supports several biological processes involved in maintaining cell function. Researchers had proposed that increasing NAD+ availability might help nerve cells cope with biological changes associated with Parkinson’s disease.
The trial confirmed that NR affected NAD metabolism. However, this biological effect did not translate into improved clinical outcomes.
This distinction highlights an important principle in medical research: a treatment can influence a biological pathway without producing a meaningful improvement in a patient’s health.
A rise in a biomarker does not establish that a supplement prevents disease, slows progression or improves quality of life. Those benefits require evidence from clinical outcomes.
The NOPARK results also show why findings from laboratory experiments and smaller early-stage studies must be confirmed in larger, well-controlled trials before treatments are recommended for specific diseases.
What the Safety Results Showed
The safety findings did not show a higher overall adverse-event rate with NR compared with placebo.
Serious adverse events occurred in 17 of 205 participants in the NR safety group, or 8.3%, compared with 29 of 205 participants in the placebo group, or 14.1%.
The researchers’ statistical analysis did not find a significant difference in the rate of serious adverse events between the groups. The study also did not identify a significant difference in the overall rate of adverse events.
These findings should be interpreted carefully. They do not prove that NR is harmless, nor do they establish its long-term safety in all populations. The trial evaluated a specific dose in people with early Parkinson’s disease over 52 weeks.
Importantly, the absence of a higher adverse-event rate does not offset the lack of clinical benefit. A supplement may be reasonably tolerated in a trial without being effective for the condition under investigation.
Limitations of the NOPARK Study
The NOPARK trial provides important evidence, but several limitations affect how its results should be interpreted.
Treatment Assessments Were Conducted On Medication
Participants were assessed while receiving their usual dopaminergic treatment. This may have reduced the sensitivity of some assessments to small differences in motor function.
The researchers noted that this limitation would generally be expected to make small treatment differences harder to detect rather than explain a clear benefit from NR.
No Washout Period Was Included
The study did not include a washout phase after treatment. As a result, the researchers could not fully separate possible short-term symptomatic effects from effects that might alter the underlying progression of Parkinson’s disease.
This limitation is relevant because a disease-modifying treatment should influence the course of the disease, not simply produce a temporary change in symptoms.
Imaging Has Limited Sensitivity
The dopamine transporter imaging method used in the trial has limited sensitivity for detecting subtle changes in neurodegeneration over one year. Therefore, the absence of a significant imaging difference cannot exclude every possible biological effect.
However, the imaging findings do not provide evidence that NR slowed changes in the dopamine system.
Despite these limitations, the primary clinical outcome did not show a benefit. The results also remained consistent with the overall conclusion that NR should not be used as a disease-modifying treatment for Parkinson’s disease. (Brakedal et al. 2026).
What the Findings Mean for Patients
The NOPARK findings are particularly relevant because NR is marketed as a longevity supplement and has attracted interest among people seeking to support healthy ageing.
The results do not support taking NR to slow Parkinson’s disease. The researchers also advised against using NR or other NAD-boosting supplements for this purpose outside controlled clinical studies.
People living with Parkinson’s disease should discuss supplements with their treating clinician, especially when taking prescription medication. They should not replace or alter prescribed treatment because of claims about NAD+ or longevity.
The trial does not establish whether NR benefits other conditions, nor does it determine whether the supplement affects healthy ageing in people without Parkinson’s disease. Those questions require separate, condition-specific clinical research.
Why Supplement Claims Need Clinical Evidence
Supplements can be promoted using evidence from laboratory studies, animal research or changes in biological markers. While these findings can help researchers develop hypotheses, they do not establish that a product improves health outcomes in people.
For a supplement to be recommended for a specific disease, clinical trials need to demonstrate meaningful benefits and assess potential risks.
The NOPARK trial illustrates this distinction. NR increased NAD-related measures, but the researchers did not observe an improvement in the primary clinical outcome.
The findings reinforce the need to evaluate longevity supplements using rigorous clinical evidence rather than relying on biological plausibility or marketing claims.
What Researchers Will Investigate Next
The researchers plan to examine the trial data further to understand the biological mechanisms behind the results and explore whether particular patient groups responded differently.
Future research may investigate how sustained NAD+ augmentation affects cellular processes in Parkinson’s disease, whether treatment effects differ across patient groups and how these findings relate to other neurological conditions.
Any proposed subgroup effects will need careful evaluation. A result observed in a small subgroup does not automatically establish that a supplement benefits that population.
Further studies will also need to distinguish changes in biomarkers from improvements in symptoms, daily functioning and disease progression.
The NOPARK findings do not rule out every possible future use of NAD-boosting treatments. They do, however, show that the specific NR regimen tested did not improve clinical outcomes in early Parkinson’s disease.
Conclusion
The NOPARK phase III trial found that nicotinamide riboside did not improve clinical outcomes in people with early Parkinson’s disease after 52 weeks. The primary outcome favoured placebo, and non-motor symptom burden also worsened more in the NR group.
Although NR increased NAD-related measures, this biological effect did not translate into clinical benefit. The observed difference in the primary outcome was statistically significant but below the cited threshold for a clinically important change.
The findings do not support NR as a treatment to slow Parkinson’s disease. People with the condition should seek advice from their treating clinician before using supplements for disease management, and future research must establish clinical benefits before NAD-boosting treatments can be recommended for this purpose.
Stay tuned with us for more health related topics.
Follow us on LinkedIn and Instagram for more.
