12 OCT 2026 — Nicotinamide riboside, a compound that raises the body's levels of the energy molecule NAD, did not slow early Parkinson's disease in the largest trial yet of an NAD-boosting treatment in a neurological disorder. Patients who took it for a year did slightly worse than those given a placebo. The researchers do not recommend that people with Parkinson's take it, or other NAD-boosting supplements, outside controlled studies.
The NOPARK trial ran at 11 hospitals in Norway and was published in JAMA on 8 October.
What the trial tested
NAD is essential for how cells produce energy, and it also plays a part in DNA repair and regulating inflammation. Laboratory work and small early studies had suggested that raising it might protect the nerve cells that Parkinson's destroys. NOPARK was designed to test that idea in a large phase 3 trial.
The researchers enrolled 410 people aged 35 or over who had been diagnosed within the previous two years and whose loss of dopamine-producing nerve cells had been confirmed by a brain scan. Half took 500 mg of nicotinamide riboside twice a day and half a matching placebo, for 52 weeks. Neither the patients nor the study teams knew who was receiving which. The study, sponsored by Haukeland University Hospital and registered in 2018, enrolled patients between May 2020 and June 2024.
What it found
The main measure was the change in the Movement Disorder Society's Parkinson's disease rating scale, where a higher score means more severe disease. Over the year, scores rose by 2.45 points in the treatment group and fell by 0.27 points on placebo. After adjustment, the difference was 2.72 points in favour of placebo, and it was statistically significant.
Of five key secondary measures, four showed no difference, including the brain scans of the dopamine system. The fifth, a scale of non-motor symptoms, worsened more with the treatment.
How large the difference was
The gap is small. The trial set 5.2 points as the threshold for a clinically important worsening, and the difference of 2.72 points falls well below it. The University of Bergen's announcement describes it as "modest", and sums up the result as showing that the compound "provided no clinical benefit".
Serious adverse events were less common with the treatment: 17 of 205 patients, against 29 of 205 on placebo. The university says adverse events overall were similar in the two groups.
Why researchers hoped it would work
"We had a strong biological rationale for testing this treatment, and earlier, smaller clinical studies had produced encouraging findings," said Charalampos Tzoulis of Haukeland University Hospital and the University of Bergen, who led the trial. "NR clearly increased NAD metabolism, but this did not translate into clinical improvement."
The researchers say the result does not rule out a benefit from raising NAD in other diseases, which would need their own trials. They plan to examine whether particular groups of patients responded differently.
What it means for patients
The authors conclude that the findings "do not support nicotinamide riboside as a disease-modifying treatment for Parkinson disease". Treatments that ease symptoms are available, and new ones such as the recently approved tavapadon continue to reach patients. None has yet been shown to slow the disease itself, which is what NOPARK set out to test. Anyone with Parkinson's who is taking an NAD supplement should discuss it with their neurologist.
View author profile → · Editorial policy
