One year of nicotinamide riboside supplementation did not improve symptoms in early Parkinson's disease. Digest
Nicotinamide riboside (NR) can markedly raise blood levels of NAD, a molecule involved in cellular energy production that has been studied for its potential to protect nerve cells in Parkinson's disease. A new study tested whether it could improve symptoms when taken alongside Parkinson's medication.
Researchers randomly assigned 410 people diagnosed with Parkinson's disease in the previous two years to receive 500 milligrams of NR or placebo twice daily for 52 weeks, alongside Parkinson's medication. The main study outcome combined movement and nonmovement difficulties in daily life with a clinician's movement examination. Higher scores on the 0–236 scale meant worse impairment.
- The combined symptom score rose 2.45 points with NR and fell 0.27 points with placebo over 52 weeks. The difference was below commonly used thresholds for clinical importance.
- Symptoms unrelated to movement also worsened more with NR, with a 4.22-point difference from placebo on a separate 0–360 symptom scale.
- Brain imaging showed no clear difference between groups in the loss of dopamine-producing nerve connections affected by Parkinson's disease.
- Although NR markedly increased blood NAD levels, brain imaging provided no clear evidence that it increased NAD levels in the brain compared with placebo.
The lack of a clear difference in the brain NAD measurement, despite the strong blood response and promising findings from earlier short-term trials, could have several explanations. With prolonged treatment, brain cells may adjust by reducing NAD production or increasing its breakdown. The brain measurement may also have not been sensitive enough to detect modest changes that could have provided further insight. Neither possibility, however, has been shown to explain the difference in symptom scores. Whether that difference reflected an interaction with Parkinson's medication, other effects of prolonged NR supplementation, or unrelated factors remains uncertain.
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The trial challenges the idea that NR supplementation can make the brain more resilient to the underlying disease processes in Parkinson's disease. Whether different doses, treatment durations, or stages of the disease might produce different outcomes has yet to be determined.