The differential impact of three different NAD(+) boosters on circulatory NAD and microbial metabolism in humans

Christen S, Redeuil K, Goulet L, Giner MP, Breton I, Rota R · Nature Metabolism

The first head-to-head human comparison. NR and NMN roughly doubled whole-blood NAD+ and did so comparably — differences versus placebo of 49.4 µM (95% CI 39.5 to 59.3) for NR and 43.1 µM (32.7 to 53.4) for NMN, both p<0.001 — while plain nicotinamide did not (p=0.461). Ex vivo work traced the effect to gut microbial conversion of NR and NMN into nicotinic acid, which was the potent booster in whole blood; NMN, NR and nicotinamide were not.

Population

Healthy adults, four parallel arms

Intervention

14 days of nicotinamide riboside 1,000 mg/day, NMN 1,000 mg/day, or nicotinamide 500 mg/day

Comparator

Placebo (microcrystalline cellulose)

Limitations

Open-label, 14 days, healthy adults, biochemical endpoints only. Conducted at Nestlé Research by Nestlé scientists. The mechanistic conclusion — that the precursors work through a gut detour — is inferred from ex vivo fermentation rather than measured in vivo.