Acute nicotinamide riboside supplementation increases human cerebral NAD⁺ levels in vivo

Purpose: The purpose of this study was to determine the effect of acute nicotinamide riboside (NR) supplementation on cerebral nicotinamide adenine dinucleotide (NAD⁺) levels in the human brain in vivo by means of downfield proton MRS (DF ¹H MRS). Methods: DF ¹H MRS was performed on 10 healthy volunteers in a 7.0 T MRI scanner with spectrally selective excitation and spatially selective localization to determine cerebral NAD⁺ levels on two back-to-back days: once after an overnight fast (baseline) and once 4 h after oral ingestion of nicotinamide riboside (900 mg). Additionally, two more baseline scans were performed following the same paradigm to assess test–retest reliability of the NAD⁺ levels in the absence of NR. Results: NR supplementation increased mean NAD⁺ concentration compared to the baseline (0.458 ± 0.053 vs. 0.392 ± 0.058 mM; p < 0.001). The additional two baseline scans demonstrated no differences in mean NAD⁺ concentrations (0.425 ± 0.118 vs. 0.405 ± 0.082 mM; p = 0.45), and no difference from the first baseline scan (F(2, 16) = 0.907; p = 0.424). Conclusion: These preliminary results confirm that acute NR supplementation increases cerebral NAD⁺ levels in healthy human volunteers and shows the promise of DF ¹H MRS utility for robust detection of NAD⁺ in humans in vivo.