Does nicotinamide riboside raise NAD+ and slow or reverse human aging?
Claim attributed to ChromaDex (Niagen / Tru Niagen) and Charles Brenner, NR researcher and ChromaDex Chief Scientific Officer , Brenner is ChromaDex's CSO, holds NR patents licensed to the company, owns its stock, and advises it: a substantial financial conflict. ChromaDex sells NR as Niagen/Tru Niagen and donated the study compound for most human NR trials through its External Research Program, while marketing frames NAD+ elevation as healthy aging.
Blood NAD+ goes up; human aging has never been measured. The NAD+ half is real and reproducible, but bundling it with "slows or reverses aging" extrapolates from a biomarker and rodent data to an outcome no human trial has tested, which tips the combined claim into misleading.
Raising a blood marker in weeks is not the same as living longer, and the trials hinting at benefit were largely supplied by the company that sells the pill.
What it’s supposed to target
- NAD+ (cellular energy cofactor)
- Sirtuins (SIRT1-7)
- Mitochondrial function
- DNA-repair (PARP) demand
NAD+ is a coenzyme every cell uses to turn food into energy and to run repair-and-signaling enzymes like the sirtuins and PARPs. NAD+ levels appear to fall with age, and the theory is that topping them back up should restore mitochondrial output and reactivate sirtuins, the same enzymes some researchers tie to the benefits of caloric restriction. Nicotinamide riboside (NR) is a form of vitamin B3 the body converts into NAD+, so the pitch is simple: take NR, raise NAD+, slow the metabolic slide of aging.
The first half is genuinely well supported: NR reliably and dose-dependently raises blood NAD+ in humans. What has not followed is the payoff. Trials looking for downstream benefits, on metabolism, strength, or blood pressure, have been mostly small, short, and null or modest, and none has measured aging itself. So NR clears the bar of “does it raise the marker” while leaving the real question, “does a higher marker make a person age more slowly,” unanswered, the recurring gap in NAD+ science.
Mechanism is theory, not proof. A plausible pathway explains why something might work, not whether it does. The verdict rests on the evidence below, not the elegance of the theory.
What would have to be true
Oral NR must raise NAD+ in humans: HOLDS, shown dose-dependently in blood across every RCT.
The NAD+ rise must reach and act in target tissues: PARTLY FAILS, muscle NAD+ did not significantly increase in Elhassan.
Raising NAD+ must translate into measurable functional or clinical benefit: LARGELY FAILS, grip strength, insulin sensitivity, mitochondrial function and blood pressure were null or unconfirmed.
Those benefits must extend to lifespan or healthspan: UNTESTED, no human aging-outcome trial exists.
What the evidence actually shows
The NAD+-raising half is solid; the muscle and function data are not
Across randomized human trials, oral NR reliably and dose-dependently raises NAD+ in whole blood and blood cells (Martens 2018; Elhassan 2019; Remie 2020). Elhassan, in aged men, confirmed a >2-fold blood NAD+ rise (p<0.001) yet found muscle NAD+ itself did not move (p=0.22), and every functional endpoint was null: grip strength p=0.96, plus no change in mitochondrial bioenergetics, insulin sensitivity, or muscle blood flow. The one repeatable signal was a modest drop in inflammatory cytokines, and even there TNF-alpha was not significant versus placebo after carryover correction. Remie, in overweight adults, likewise found 'no other metabolic health effects' and null insulin sensitivity.
The aging outcome has never been tested, and the headline benefit is unconfirmed
No human NR trial measures lifespan, healthspan, or a validated aging endpoint; the existing RCTs run 21 days to 3 months with 12 to 94 participants. Martens, the foundational study, reported only exploratory trends toward lower systolic blood pressure and aortic stiffness and explicitly urged 'future clinical trials' to test them. The dedicated phase IIa blood-pressure RCT built to do exactly that (n=94 planned) has only a published protocol, no primary results, so even the cardiovascular surrogate stays unconfirmed. An independent 2023 review concluded 'NR supplementation has very few clinically relevant effects' in humans.
Studies, graded, and who paid
Every human RCT to date shows a reliable rise; Elhassan reports a >2-fold blood increase (p<0.001).
Elhassan found muscle NAD+ itself did not rise (210 vs 197 pmol/mg; p=0.22), even as clearance metabolites climbed.
No trial measures lifespan, healthspan, or validated aging endpoints; tested clinical outcomes are mostly null.
| # | Study | Type | Size | Funding / COI | Key limitations |
|---|---|---|---|---|---|
| 24 | Martens 2018, healthy middle-aged/older adults | Double-blind placebo-controlled crossover RCT, 6 weeks | n=24 | Industry-funded ChromaDex-linked program supplied NIAGEN; NR-supportive Seals lab. | BP and aortic-stiffness signals exploratory only; authors called for future trials. Full disclosure sits in paywalled Nature text, not the PubMed page. |
| 12 | Elhassan 2019, aged men (median 75y) | Double-blind placebo-controlled crossover RCT, 21 days | n=12 | Industry-funded ChromaDex provided NR/placebo; Brenner discloses patents, stock and advisory role. | Blood NAD+ rose >2-fold but muscle NAD+ did not (p=0.22); all functional endpoints null (grip p=0.96); cytokine drop partly baseline-relative. |
| 13 | Remie 2020, healthy overweight/obese adults | Double-blind placebo-controlled crossover RCT, 6 weeks | n=13 | Mixed Dutch Heart Foundation and EU Horizon 2020 funded; ChromaDex supplied NIAGEN with no design role. | Insulin sensitivity and mitochondrial function null; only minor body-composition and acetylcarnitine shifts; 'no other metabolic health effects.' |
| 30 | Brakedal 2022, NADPARK, newly diagnosed Parkinson's | Double-blind placebo-controlled phase I RCT, 30 days | n=30 | Independent Academic Norwegian trial, no industry sponsor. | Raised cerebral NAD+ but only a subset showed 'mild' clinical change; explicitly hypothesis-generating, not disease modification or anti-aging proof. |
| 94 | Freeberg 2022, phase IIa blood-pressure trial (protocol only) | Protocol for double-blind placebo-controlled phase IIa RCT, 3 months | n=94 planned | Mixed NIH grants fund the work; ChromaDex supplied NIAGEN via material transfer agreement. | Only the protocol is published; no primary results located, so the cardiovascular claim remains untested at the outcome level. |
The split is structural: the well-supported finding (NAD+ rises) is repeatedly substituted for the unproven one (aging slows), so the marketing inherits credibility the aging claim has not earned.
Unproven ≠ disproven
The aging claim is unproven, not disproven: no trial has measured lifespan or healthspan. What has been tested, short-term clinical and functional endpoints, has mostly come back null.
Where claim and evidence diverge
Human aging outcomes need very large, multi-year trials that have never been funded for NR; every existing RCT is weeks to months long with surrogate endpoints, and even the dedicated blood-pressure trial has no published results.
The money trail
ChromaDex sells NR as Niagen/Tru Niagen and donated NR/placebo for most human trials via its External Research Program; CSO Charles Brenner holds NR patents, owns stock and advises the company (disclosed in Elhassan 2019).
Counterweight: the independent 2023 Science Advances review (Damgaard & Treebak, University of Copenhagen) declared no competing interests and found very few clinically relevant effects.
The honest read
NR is a safe, well-tolerated vitamin-B3 derivative that genuinely raises blood NAD+. Calling that 'slowing or reversing aging' is a marketing leap the human evidence does not support.
What would change this verdict
A large, long-duration, independently funded RCT showing NR improves a validated aging or healthspan endpoint (incident age-related disease, physical function, mortality) versus placebo.
Published primary results from an adequately powered trial showing reproducible, clinically meaningful gains in a hard endpoint such as blood pressure or insulin sensitivity.
Sources
- Martens CR, Denman BA, Mazzo MR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun. 2018;9:1286. PMID 29599478.
- Elhassan YS, Kluckova K, Fletcher RS, et al. Nicotinamide riboside augments the aged human skeletal muscle NAD+ metabolome and induces transcriptomic and anti-inflammatory signatures. Cell Rep. 2019;28(7):1717-1728. PMID 31412242.
- Remie CME, Roumans KHM, Moonen MPB, et al. Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans. Am J Clin Nutr. 2020;112(2):413-426. PMID 32320006.
- Brakedal B, Dolle C, Riemer F, et al. The NADPARK study: a randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease. Cell Metab. 2022;34(3):396-407. PMID 35235774.
- Freeberg KA, et al. Nicotinamide riboside supplementation for treating elevated systolic blood pressure and arterial stiffness in midlife and older adults (study protocol). Front Cardiovasc Med. 2022. PMID 35620522; PMC9127073. NCT03821623.
- Damgaard MV, Treebak JT. What is really known about the effects of nicotinamide riboside supplementation in humans. Sci Adv. 2023;9(29):eadi4862. PMC10361580.
People also ask
- Does nicotinamide riboside actually raise NAD+ levels?
- Yes, in blood. Every human RCT to date shows a reliable, dose-dependent rise, with one study reporting a more than two-fold blood increase. The blood NAD+ effect is real and reproducible; that is the strongest part of the claim.
- Does NR raise NAD+ inside muscle tissue?
- Not clearly. One trial found muscle NAD+ itself did not rise significantly (210 vs 197 pmol/mg), even as clearance metabolites climbed. So a blood increase does not necessarily mean more NAD+ reaches the tissues that matter.
- Does nicotinamide riboside slow or reverse aging in humans?
- No trial has shown this. None measures lifespan, healthspan, or validated aging endpoints, and the tested clinical outcomes are mostly null. Raising a blood marker over weeks is not the same as slowing aging.
- Is nicotinamide riboside safe to take?
- It is described as a safe, well-tolerated vitamin-B3 derivative. The concern is not safety but overstated benefit: most human trials were supplied by the company that sells NR, and an independent 2023 review found very few clinically relevant effects.
Part of our guide: Longevity supplements, fact-checked
Compare head to head: NMN vs NR: which NAD+ booster has the better evidence?
Caveat is journalism, not medical advice. We check public claims against published evidence; we don’t diagnose, treat, or tell you what to take.