NMN vs NR — Two Roads to the Same NAD+ Pool
NMN and NR use different transporters and enzymes on the way to NAD+.
- Slc12a8: NMN entry route (putative NMN transporter)
- Nucleoside: NR entry route (transporters, well characterized)
- NMN 334 / NR 255: Molecular weight (g/mol, approximate)
- Both OTC: Market status (sold as dietary supplements)
Placeholder: precursor structure and pathway entry
Placeholder text comparing NMN and NR entry pathways briefly.
Placeholder callout: neither precursor is FDA-approved as a drug.
Getting Past the Gut — Absorption and Bioavailability
Oral bioavailability limits how much precursor ever reaches circulation.
- Variable: Oral bioavailability (placeholder estimate range)
- Present: First-pass effect (gut and liver metabolism)
- Unclear: Food effect (placeholder, under study)
- ~30–60 min: Peak plasma time (placeholder estimate)
Placeholder: gut transport and first-pass metabolism
Placeholder text on absorption mechanics and dose-response saturation.
Placeholder callout: higher doses show diminishing absorption efficiency.
From Bloodstream to NAD+ — Enzymatic Conversion
NRK and NAMPT enzymes convert circulating precursor into cellular NAD+.
- NRK1/2: Key enzyme (NR) (nicotinamide riboside kinase)
- NAMPT: Key enzyme (NMN) (salvage pathway rate limiter)
- High: Tissue variability (placeholder, tissue-dependent)
- placeholder %: Blood NAD+ change (reported in small trials)
Placeholder: salvage pathway conversion steps
Placeholder text on enzymatic conversion to intracellular NAD+.
Placeholder callout: blood NAD+ rise does not confirm tissue-level benefit.
What Is Actually in the Bottle — Dosing Variability
Consumer supplement content often deviates from the label claim.
- Variable: Label accuracy (placeholder, brand-dependent)
- Inconsistent: Third-party testing (placeholder coverage)
- 125–500 mg: Typical capsule dose (placeholder common range)
- Limited: Regulatory oversight (dietary supplement category)
Placeholder: manufacturing and label accuracy
Placeholder text on batch-to-batch and brand-to-brand variability.
Placeholder callout: actual capsule content can differ from label claim.
The Open Question — Long-Term Human Safety
Most human trials are short-duration; chronic effects are still unclear.
- 6–12 wks: Typical trial length (placeholder, most studies)
- ~1 year: Longest human trials (placeholder, few exist)
- Sparse: High-dose chronic data (placeholder evidence gap)
- Supplement: Regulatory status (not drug-approved)
Placeholder: evidence gaps in chronic supplementation
Placeholder text on the state of long-term human safety evidence.
Placeholder callout: long-term high-dose safety remains unestablished.