Intervention
Nicotinamide riboside (NR)
Mechanism, regulatory status, and an honest, tiered evidence map.
▲ Human lifespan evidence: no healthy-aging lifespan RCT — human evidence is randomized RCTs with biomarker endpoints (raised NAD+; a blood-pressure/aortic-stiffness signal)
What it is
Class: NAD⁺ precursor
Also known as: NR, Niagen
Relationship to mitochondrial health: Nicotinamide riboside is a precursor the body converts to NAD+, a cofactor for oxidative phosphorylation and the substrate for sirtuins. The rationale is that NAD+ falls with age and that NR can restore it; the sirtuin/mTOR longevity biology overlaps mtorix.com.
Regulatory status
Sold as a dietary supplement (e.g. Niagen), with a US FDA GRAS notification; not an approved drug and not approved for any anti-aging indication.
Mechanism
Raises whole-blood NAD+ in human RCTs; downstream blood-pressure/arterial-stiffness signals are mixed. Sirtuin/NAD+ signalling is cross-referenced to mtorix.com. See /nad-metabolism.
Evidence — Human (randomized, placebo-controlled)
| Species / population | Healthy middle-aged and older adults (Martens 2018, n=24 crossover). |
| Exposure, route, schedule | Oral NR 500 mg twice daily (1000 mg/day) for 6 weeks. |
| Comparator / duration | Placebo-controlled, double-blind, randomized crossover. |
| Endpoint / numeric result | Well tolerated; roughly doubled whole-blood NAD+; a suggestive reduction in systolic blood pressure and aortic stiffness in a subgroup with elevated baseline. |
| What it did NOT establish | Biomarker-grade; the blood-pressure/stiffness signal was a secondary/subgroup finding, not a powered clinical outcome, and there is no lifespan evidence. |
Negative or null findings
- The blood-pressure/aortic-stiffness effect did not reach significance in the full cohort; a dedicated Phase 2 blood-pressure/stiffness RCT (NCT03821623) is separate and, as of the search date, still recruiting with no published results.
- No hard clinical outcome or lifespan endpoint.