Major trial finds nicotinamide riboside ineffective for early Parkinson's disease

A year-long clinical trial of 410 people with early Parkinson's disease has delivered a sobering result: nicotinamide riboside, a compound designed to boost cellular energy metabolism, did not slow the disease's progression and may have made things slightly worse. The findings, published in JAMA, represent a significant setback for a treatment approach that had seemed biologically sound and had shown promise in smaller studies.

The NOPARK trial, led by Professor Charalampos Tzoulis at Haukeland University Hospital and the University of Bergen, was conducted across 11 Norwegian centers. Participants were randomly assigned to receive either 500 milligrams of nicotinamide riboside twice daily or an identical-looking placebo for 52 weeks. Neither the people taking the medication nor the research teams administering it knew who was receiving which treatment—the gold standard for eliminating bias in clinical research.

The study measured disease severity using the MDS-UPDRS scale, a standard tool where higher scores reflect more pronounced symptoms. After one year, those who received nicotinamide riboside had declined by an average of 2.45 points on this scale. The placebo group showed essentially no change. When adjusted for baseline differences, the gap widened to 2.72 points in favor of placebo. While the difference reached statistical significance, it fell below the threshold researchers typically consider clinically meaningful—the kind of change a patient would actually notice in their daily life.

The biological reasoning behind the trial was compelling. Nicotinamide adenine dinucleotide, or NAD, is fundamental to how cells produce energy and repair DNA, and it plays a role in controlling inflammation. Earlier laboratory work and small human studies had suggested that raising NAD levels might protect the nerve cells damaged in Parkinson's disease. That promise justified a large, rigorous Phase 3 trial to test the idea at scale. But the mechanism that worked in the lab did not translate to clinical benefit. Brain imaging revealed no evidence that nicotinamide riboside either slowed or accelerated the deterioration of the brain's dopamine system—the neurological hallmark of Parkinson's. The safety profile was comparable between groups, so the compound was not causing unexpected harm; it simply was not helping.

Tzoulis acknowledged the disappointment in a statement accompanying the results. The team had strong biological rationale, he noted, and earlier smaller studies had been encouraging. Nicotinamide riboside clearly did increase NAD metabolism in the body. But that biochemical change did not translate into clinical improvement. The researchers now advise against people with Parkinson's disease using nicotinamide riboside or other NAD-boosting supplements outside of controlled clinical trials. They emphasized, however, that the failure in Parkinson's does not rule out the possibility that NAD-boosting treatments could help in other diseases—effects vary between conditions and each requires its own rigorous testing.

The research team is continuing to examine the data in search of deeper understanding. They are analyzing whether certain subgroups of patients might have responded differently to the treatment, and they are investigating the biological mechanisms that explain why the compound failed to deliver the expected benefit. These analyses may inform the next generation of treatment strategies. For now, the trial has answered one important medical question with clarity: nicotinamide riboside is not the answer for slowing early Parkinson's disease. The work ahead lies in understanding why, and in identifying what might be.