Nicotinamide riboside left Parkinson's patients slightly worse than placebo

A year of nicotinamide riboside (NR), a popular NAD-boosting supplement, did not slow early Parkinson's disease in a 410-person trial in Norway, and the people taking it ended up slightly worse than those on placebo. The results of the NOPARK trial were published in JAMA on October 8, 2026.

The finding lands awkwardly for the supplement's maker. In July 2025, before the results were out, Niagen Bioscience (formerly ChromaDex) licensed the Bergen data and rights to develop NR as a potential Parkinson's drug.

What the trial measured

NOPARK enrolled people with early Parkinson's at 11 centers across Norway. Half took 500 mg of NR twice a day for 52 weeks and half took a matching placebo, and neither the patients nor the study teams knew who got which.

The main yardstick was the MDS-UPDRS, a standard rating scale where a higher score means more severe symptoms. According to the University of Bergen, the NR group's score rose by an average of 2.45 points over the year, while the placebo group stayed roughly where it started. Adjusted for other factors, placebo came out ahead by 2.72 points.

That difference was statistically significant but small, the researchers said, and it falls below the threshold usually treated as clinically meaningful. Brain scans of the dopamine system showed no sign that NR slowed or sped up changes there, and side effects were similar in both groups.

The drug did what it was supposed to, chemically

The biochemistry worked. NR is meant to raise levels of NAD, a molecule cells use to make energy, and the trial's background cites earlier research suggesting that topping it up might protect nerve cells. Study leader Charalampos Tzoulis of Haukeland University Hospital said NR "clearly increased NAD metabolism, but this did not translate into clinical improvement."

The university describes NOPARK as the biggest test yet of any NAD booster against a disorder of the nervous system.

The team advises people with Parkinson's not to take NR or other NAD boosters outside controlled studies. The researchers stress that the result says nothing about whether NR helps in other diseases.

The commercial thread

The trial was paid for by public and foundation funders in Norway. ChromaDex, now part of Niagen Bioscience, supplied the NR and the placebo capsules, and the university says the funders had no role in the study or in the decision to publish.

When Niagen announced its exclusive license in 2025, it said the NOPARK data could support future European regulatory filings and that publication was expected by the end of that year. How the company will respond to a result that favors placebo was not stated in the university's release.

The researchers are still analyzing whether any subgroup of patients responded differently. Those results have not been published yet.