iScienceMar 20, 2026

How oral NAD precursors change NAD levels in blood and brain over time

Longevity & Aging Weekly Brief ↗PubMed ↗DOI ↗

Updated Jun 27, 2026

Abstract

Essence

Oral NAD precursor supplementation appeared to raise blood NAD slowly and brain NAD after four weeks in healthy people and people with Parkinson's disease.

Evidence

A phase I pharmacokinetic trial studied 1,200 mg/day nicotinamide riboside or nicotinamide mononucleotide in 6 healthy individuals and 6 persons with Parkinson's disease.

Caveat

The study was very small and measured pharmacokinetics, not clinical benefit, with considerable interindividual variability.

Simplified

Nicotinamide adenine dinucleotide (NAD) augmentation therapy (NAD-AT) is increasingly explored in clinical trials across multiple indications, especially neurological diseases, yet its human pharmacokinetic profile remains incompletely defined. We report findings from a phase I pharmacokinetic trial assessing systemic and cerebral responses to oral NAD precursors in healthy individuals (= 6) and persons with Parkinson's disease (= 6) receiving 1,200 mg/day nicotinamide riboside or nicotinamide mononucleotide. Blood NAD increased slowly, plateauing after approximately two weeks of treatment, and declined with similarly slow kinetics following treatment discontinuation. Cerebral NAD levels increased measurably after four weeks of treatment. NAD-related metabolites showed faster increase and washout dynamics compared to NAD itself. Collectively, these data suggest that effective NAD-AT requires sustained oral administration over at least 2-4 weeks and that once-daily dosing is sufficient to maintain stable NAD levels. NAD responses exhibited considerable interindividual variability, but were not influenced by disease status or sex, indicating broad applicability. n n