A year-long clinical trial called NOPARK found that nicotinamide riboside (NR), a supplement that raises levels of the cellular molecule NAD, did not slow Parkinson's disease — and patients who took it actually declined slightly more than those on placebo. The phase 3 trial, the largest and most rigorous test yet of an NAD-boosting supplement in Parkinson's, closes the door on a theory that has circulated in patient communities for years. Researchers at the University of Bergen in Norway ran the study after an earlier small trial raised hopes that boosting NAD could protect dopamine-producing brain cells. The new results, published in JAMA, show that hope didn't hold up under a larger, properly controlled test.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What the NOPARK trial actually tested
- What the results showed on the main measure of symptoms
- Did NR do anything measurable in the brain?
- Why this result contradicts earlier hope
- What this means if you're considering an NAD supplement
- Frequently Asked Questions
What the NOPARK trial actually tested
NOPARK was a phase 3 randomized, double-blind, placebo-controlled trial — the gold-standard design for testing whether a treatment works — conducted in 410 people with early Parkinson's disease across 11 centers in Norway over 52 weeks, according to the University of Bergen's findings reported via News-Medical. Double-blind means neither patients nor researchers knew who received the real supplement until the study ended, which prevents bias from affecting the results.
Half the participants received 500 mg of nicotinamide riboside twice a day (1,000 mg total daily), and half received a placebo. The trial is registered on ClinicalTrials.gov as NCT03568968 and is listed as completed. NR is sold commercially as an NAD-boosting supplement, including under the brand name Niagen, and has been marketed to people with Parkinson's and other conditions on the premise that restoring NAD — a molecule cells need to produce energy — might protect struggling neurons.
What the results showed on the main measure of symptoms
The trial's primary measure was the MDS-UPDRS, a standard scale clinicians use to score Parkinson's motor and daily-function symptoms, where higher scores mean worse disease. Over 52 weeks, the group taking NR worsened by an adjusted average of 2.45 points, while the placebo group actually improved slightly, by 0.27 points — a statistically significant 2.72-point difference favoring placebo, according to the JAMA findings summarized by News-Medical.
That gap was real in a statistical sense, but reporting from Inside Precision Medicine notes it falls below the threshold generally considered a clinically important difference — meaning it's unlikely to be a change a patient or doctor would actually notice day to day. Nonmotor symptoms, such as mood, sleep, or cognitive issues, worsened more in the NR group than in the placebo group. Four other prespecified secondary outcomes showed no significant difference between the two groups.
Did NR do anything measurable in the brain?
Researchers also tracked dopamine transporter (DAT) imaging, a brain scan that measures the loss of dopamine-producing neurons — the cells that progressively die off in Parkinson's disease. This imaging showed no significant difference between the NR and placebo groups, according to the University of Bergen's statement on the study. In plain terms, NR neither slowed nor sped up the underlying neurodegeneration that imaging can detect.
Lead investigator Charalampos Tzoulis, of Haukeland University Hospital and the University of Bergen, said NR clearly did raise NAD metabolism in participants' bodies, but that this biological change did not translate into any clinical improvement. He concluded, per the same university statement, that the results "do not support NR as a treatment to slow Parkinson's disease." One piece of reassurance: NR did not appear to make anyone less safe. Serious adverse events occurred in 17 of 205 participants (8.3%) taking NR, compared with 29 of 205 (14.1%) on placebo, according to data reported by MDLinx. The supplement wasn't more dangerous — it simply didn't help.
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Why this result contradicts earlier hope
The excitement around NAD-boosting supplements in Parkinson's traces back to a much smaller, open-label phase 1 study of roughly 30 patients, who took NR for just 30 days at doses up to 1,000 mg daily. That study reported raised brain NAD levels and was promoted by ChromaDex, the maker of the NR supplement Niagen, as evidence the approach held promise, according to a 2026 ChromaDex press release.
A short, unblinded study in 30 people can detect a biological change, like a rise in NAD, but it can't reliably show whether a treatment actually helps symptoms or slows disease — that requires a larger, placebo-controlled, year-long trial like NOPARK. The larger trial does not support the earlier claim of clinical promise.
What this means if you're considering an NAD supplement
Based on these results, the research team does not recommend that people with Parkinson's disease take nicotinamide riboside or other NAD-boosting supplements outside of a controlled clinical study, according to a University of Bergen update via News-Medical. That guidance applies specifically to Parkinson's; the researchers noted their findings don't rule out a benefit for NAD-boosting supplements in other diseases. If you're currently taking NR or a similar supplement for Parkinson's, a few points are worth raising with your neurologist:.
- The trial found no meaningful slowing of motor symptom progression over a full year.
- Nonmotor symptoms trended worse, not better, on NR compared with placebo.
- Brain imaging showed no protective effect on dopamine neurons.
- The supplement itself did not raise safety concerns at the doses tested.
- Any decision to start, stop, or continue a supplement should go through your own treatment team, since this trial doesn't address every formulation or dose on the market.
Frequently Asked Questions
What is nicotinamide riboside (NR)?
NR is a form of vitamin B3 that the body converts into NAD, a molecule cells need to produce energy; it's sold as an over-the-counter supplement, including under the brand Niagen.
Did the trial find NR unsafe?
No. Serious adverse events were actually less common in the NR group (8.3%) than in the placebo group (14.1%), according to data reported by MDLinx — the issue was lack of benefit, not safety.
Could a different dose or formulation work better?
The NOPARK trial tested one specific regimen, 500 mg twice daily for 52 weeks, in early-stage Parkinson's; its results don't address other doses, timing, or disease stages.
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