Evidence-graded · NAD+ precursors
Updated 2026-06-14 · Data sourced from ClinicalTrials.gov and PubMed
NAD+ (nicotinamide adenine dinucleotide) declines ~50% between ages 40 and 60. Restoring it is one of the most-studied longevity interventions. Three precursors dominate the market: NMN (nicotinamide mononucleotide), NR (nicotinamide riboside), and plain nicotinamide (niacinamide). They all raise NAD+ — but they differ in cost, bioavailability, evidence volume, and mechanism.
Below we compare them honestly on the evidence that exists, not the marketing. The verdict may surprise you.
Best evidence-to-cost ratio by far — often overlooked
confidence
Nicotinamide (niacinamide, flush-free) raises NAD+ comparably to NR in head-to-head blood studies, costs ~$0.10/day vs $1.50+/day for NMN/NR, and has Grade A evidence for skin cancer prevention (ONTRAC trial, n=386, Phase 3 RCT). At 500mg 2×/day, it's the most cost-effective NAD+ precursor with human proof-of-benefit.
Full Nicotinamide (Niacinamide) evidence →Best-validated premium option — more human RCTs than NMN
confidence
NR has more published human RCTs than NMN and is the most-studied premium NAD+ precursor. Tru Niagen (ChromaDex) is the clinical-grade form. Evidence is solid for raising blood NAD+; functional longevity outcomes in humans are still preliminary.
Full Nicotinamide Riboside (NR) evidence →Most-hyped, fastest-growing — evidence catching up but not yet ahead of NR
confidence
NMN is downstream of NR in the NAD+ biosynthesis pathway. Human trials are rapidly accumulating (David Sinclair's Harvard lab is a major driver of interest). Key trials show NAD+ elevation and some muscle endurance effects. Premium priced — currently no robust RCT demonstrates superiority to NR or nicotinamide.
Full NMN (Nicotinamide Mononucleotide) evidence →Evidence collection
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The honest answer: no human RCT has shown NMN produces meaningfully better NAD+ restoration or longevity outcomes than NR. NR has more clinical trials. NMN costs more. If price matters, try NR or nicotinamide first. If you specifically want to match David Sinclair's protocol, NMN. The biology is similar enough that the difference is unlikely to be clinically meaningful.
For raising blood NAD+, nicotinamide performs comparably to NR in head-to-head pilot studies, at a fraction of the cost. It also has a Phase 3 RCT proving it reduces non-melanoma skin cancer incidence — an outcome that NMN and NR don't yet have. The main limitation: at very high doses (>3g/day), nicotinamide may inhibit sirtuins. At 500–1,000mg/day, this concern doesn't apply.
NMN or NR + apigenin (inhibits CD38, which degrades NAD+) + TMG (provides methyl groups depleted by NAD+ synthesis) is a popular evidence-informed stack. Apigenin at 50–200mg/day and TMG at 500–1,000mg/day are reasonable adjuncts.
The trials have not demonstrated a need to cycle NMN, NR, or nicotinamide. Continuous daily use is the protocol in most clinical studies. Some practitioners suggest cycling 5 days on / 2 days off, but there is no clinical evidence supporting this as superior to continuous dosing.
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Informational only — not medical advice. Trial counts reflect ClinicalTrials.gov registry matches and PubMed publication-type filters and include all endpoints, not only longevity endpoints. Evidence grades are editorial assessments. See each ingredient page for sources.