Two of the most prominent NAD+ precursors on the market today include nicotinamide riboside (NR), the most popular being patented Niagen®, and NMN (nicotinamide mononucleotide). Both are available as dietary supplements, but they may not be equal when it comes to clinical evidence, product quality, and how efficiently they raise NAD+ levels.

In recent years, NAD+ has come to the forefront of research on aging, health, and disease. However, the popularity of NAD+ research has also opened the door for misinformation about NAD+ and NAD+ precursors. So, what are NAD+ supplements? They’re products designed to raise your body's NAD+ levels — but not all of them do so with the same efficiency or scientific backing.

For example, different forms of vitamin B3 are NAD+ precursors, which are “building blocks” for the cell to build NAD+. However, due to the phosphate group on NMN, when it’s consumed, it’s technically a precursor to nicotinamide riboside and must be converted to NR before it can pass through the cell membrane. Once inside the cell, the NR converts to NMN and then to NAD+. Given that NR can enter cells, this distinction is important to make when it comes to efficiency.

So, which one should you trust? The evidence favors Niagen, but here’s a breakdown to adequately assess both NAD+ precursors in detail.

What Is Nicotinamide Riboside (NR)?

Nicotinamide riboside (NR) is a precursor to NAD+ (nicotinamide adenine dinucleotide). So, what is NAD+? It’s a coenzyme found in every cell of your body that plays a central role in hundreds of metabolic processes, including DNA repair and cellular health.⁽¹⁾

As we age, NAD+ levels naturally decline. This decline is linked to many hallmarks of aging, from slower cellular repair to mitochondrial dysfunction. NR works by providing your cells with a readily absorbable building block they can use to produce more NAD+. Once inside the cell, NR is converted to NMN by an enzyme called NR kinase, and then NMN is converted to NAD+.⁽¹⁾

Niagen® is the patented, clinically studied form of NR. Unlike generic NR ingredients, Niagen is backed by 40+ human clinical studies and undergoes rigorous quality testing. It’s the form of NR that most researchers choose for their clinical trials, and it’s the active ingredient in Tru Niagen®.

What Is Nicotinamide Mononucleotide (NMN)?

Nicotinamide mononucleotide (NMN) is also a precursor to NAD+. Structurally, NMN is almost identical to NR. The only difference is one additional phosphate group attached to the molecule.⁽²⁾

That extra phosphate group is the crux of the NR vs. NMN discussion. Research has shown that NMN is too large to cross cell membranes on its own. Before it can enter a cell, that phosphate group must be stripped off, effectively converting NMN into NR. Once inside the cell as NR, it’s then converted back to NMN by NR kinase, and finally to NAD+.⁽²⁾

In other words, NMN takes an indirect route to boost NAD+. It has to become NR first. This is one of the central reasons many researchers and consumers prefer NR over NMN for supporting cellular nutrition.

What Are the Differences Between NR vs. NMN?

When comparing NR vs. NMN, the differences come down to five areas: molecular structure, conversion pathway, bioavailability, clinical research, and regulatory status. Here’s a closer look at each:

Molecular Structure
NR and NMN are nearly identical molecules. The sole difference is that NMN carries one phosphate group, which increases its molecular weight. The phosphate is what prevents NMN from entering cells directly.⁽²⁾

Conversion Pathway
NR enters cells directly, where it’s converted to NMN by NR kinase, and then to NAD+. NMN must first lose its phosphate group outside the cell (converting to NR), enter the cell as NR, then convert back to NMN before finally becoming NAD+. NR’s pathway is more direct.⁽²⁾

Bioavailability
Because NR can cross cell membranes without modification, it has a more efficient route to raising intracellular NAD+ levels. NMN’s extra conversion step outside the cell introduces an additional variable in terms of absorption and bioavailability.⁽²⁾ Learning how to support your mitochondrial health starts with choosing an efficient precursor.

Clinical Research
Niagen has been used in more than 40 published human clinical studies. The depth and breadth of Niagen research gives it a significant advantage in terms of proven safety and efficacy in humans.

Regulatory Status
Niagen has been successfully notified to the FDA as Generally Recognized as Safe (GRAS), and has been successfully reviewed by the FDA in 2015 and 2018 under its New Dietary Ingredient (NDI) notification program. 

Does NR or NMN Have More Clinical Evidence?

According to Clinicaltrials.gov, a government-sponsored database of human clinical studies, as well as the World Health Organization (WHO) International Clinical Trials Registry, there are 74 ongoing or completed studies involving NR versus 65 for NMN, where only NR or NMN was used with no combination of ingredients.

These numbers show double the growing amount of research behind Niagen over NMN to investigate the various health benefits of raising NAD+ levels in humans.

Niagen has 20 published human clinical studies demonstrating that it effectively increases NAD+ and/or NAD+ flux. 

The continued use of Niagen in these trials further reflects the trust that the precursor commands in the scientific community.

Understanding Clinical Study Terminology

Crossover design
A crossover trial is one in which all subjects receive all the interventions in the study, but the order in which they are given the intervention is randomized. For example, 10 subjects in an 8-week study might be randomized to receive NR for 4 weeks and then receive a placebo for the next 4 weeks after a predetermined length of time off the treatment. Another set of 10 subjects would experience the opposite order.

Randomized, Double blind
A randomized double-blind study is a clinical trial in which neither the patient nor the researcher(s) know whether an experimental treatment, standard treatment, or placebo is being administered. Only those directing the study know which patients receive which treatments. This prevents bias when scientists evaluate outcomes and improves the reliability of the trial’s results.

Parallel-group design
A parallel study is probably the most common study design. Treatments each have an ”arm,” which might include a particular dosage, a placebo, or another type of care. In parallel studies, participants are randomly assigned to each arm and remain in that arm throughout the study duration. These studies are usually randomized and double-blinded.

Pharmacokinetics
Pharmacokinetics is the study of the movement of a substance into, through, and out of the body—the complete time course of its absorption, distribution, metabolism, and excretion (ADME).⁽³⁾

Clinical Evidence Supporting NR's Safety and Efficacy as an NAD Precursor

The body of clinical research behind Niagen is extensive and continues to grow. Below is a summary of published human studies that demonstrate Niagen’s ability to safely and effectively raise NAD+ levels across a range of populations and dosages.

First Human Niagen Study That Demonstrates Effectiveness:

A study published in Nature Communications in 2016 reports that single oral doses of 100mg, 300mg, and 1,000mg of Niagen can safely elevate NAD+ levels.⁽⁴⁾ Researchers investigated the effects of NR supplementation in 12 healthy men and women, establishing both its safety and efficacy as an NAD+ precursor in humans. 

Second Human Niagen Study That Demonstrates Effectiveness:

A study published in PLOS One in 2017 monitored the effects of Niagen with a gradual increase in dosage.⁽⁵⁾ The study administered 250mg of Niagen to eight healthy volunteers on Days 1 and 2, then gradually administered higher doses each subsequent day. On days 7 and 8, the study administered a peak dose of 1,000mg twice daily. The study concluded on Day 9, showing oral administration of Niagen to be well tolerated in humans with no adverse effects.⁽⁶⁾

Third Human Niagen Study That Demonstrates Effectiveness:

A study published in Nature Communications in 2018 shows that Niagen supplementation is well tolerated and effectively elevates NAD+ in a group of healthy middle-aged and older adults.⁽⁷⁾ The subject cohort was comprised of 60 healthy men and women between the ages of 55 and 79. The study administered a dosage of 500mg twice per day for six weeks in a randomized, placebo-controlled, and crossover-designed trial. 

Fourth Human Niagen Study That Demonstrates Effectiveness:

A study published in the American Journal of Clinical Nutrition in 2018 concluded that 2,000mg of daily Niagen supplementation over a period of 12 weeks is safe. In addition, the subjects showed an increase in NAD+ metabolites in urine samples.⁽⁸⁾

The researchers administered 1,000mg of Niagen twice daily over a period of 12 weeks in a randomized, placebo-controlled, double-blind, parallel-group designed trial. The subjects consisted of 40 healthy, obese men ranging in ages from 40-70. 

Fifth Human Niagen Study That Demonstrates Effectiveness:

A clinical trial published in Scientific Reports in 2019 concludes Niagen both safely and effectively increases NAD+ levels in a dose-dependent manner in healthy overweight adults.⁽⁹⁾ The study used an eight-week randomized, double-blind, placebo-controlled trial to conduct its evaluation. After two weeks, the study results are as follows:

Sixth Human Niagen Study That Demonstrates Effectiveness:

A study published in Cell Reports in 2019 investigated the effects of Niagen on skeletal muscle. The study supplemented 12 marginally overweight older men with 1,000mg of Niagen daily for 21 days. The study used a randomized, double-blind, placebo-controlled, crossover-designed trial and concluded, “oral nicotinamide riboside increased human skeletal muscle NAAD, a sensitive marker of increased NAD+ metabolism.”⁽¹⁰⁾ 

Seventh Human Niagen Study That Demonstrates Effectiveness:

A study published in The American Journal of Clinical Nutrition in 2020 investigated the effects of Niagen on metabolic health, muscle metabolism, and mitochondrial function. The study was a randomized, double-blind, placebo-controlled, crossover trial of 13 healthy overweight and obese adults. Similar to the previous study, NR supplementation significantly increased markers of enhanced NAD+ metabolism in human skeletal muscle.⁽¹¹⁾

Eighth Human Niagen Study That Demonstrates Effectiveness:

A pilot study published in Molecular Systems Biology in 2020 investigated the pharmacokinetics of Niagen in combination with other supplements. The study combined NR with L-serine, N-acetyl-L-cysteine, and L-carnitine for their potential benefits in humans, particularly those with higher liver fat content. Mathematical modeling results showed increased fat metabolism, decreased glucose metabolism, and increased synthesis/turnover of NAD+, carnitine, and glutathione.⁽¹²⁾

Ninth Human Niagen Study That Demonstrates Effectiveness:

An ex vivo and pilot clinical study published in the Journal of Clinical Investigation investigated mitochondrial dysfunction in peripheral blood mononuclear cells (PBMCs, or white blood cells). The study showed that NR increased whole blood NAD+ levels and the mitochondrial respiration rate of PBMCs.⁽¹³⁾

Tenth Human Niagen Study That Demonstrates Effectiveness:

A study published in The Journal of Physiology investigated the effects of Niagen supplementation on whole-body metabolism and exercise-induced mitochondrial signaling in skeletal muscle. The study showed increased markers of NAD+ flux, demonstrating the skeletal muscle bioavailability of NR supplementation.⁽¹⁴⁾ 

Eleventh Human Niagen Study That Demonstrates Effectiveness:

A 2022 study explored the effects of NR on monocytes (a type of white blood cell) taken from both healthy subjects and subjects with systemic lupus. The study included analyses of the mechanism behind NR’s effects, as well as a randomized, double-blind, placebo-controlled pilot study of 35 healthy participants who were given 1,000mg of NR for seven days. NR was shown to increase whole-body NAD+ levels along with levels of related NAD+ metabolites. Increasing NAD+ via NR supplementation reduced type-I interferon (IFN) signaling, which plays an important role in immune response.⁽¹⁵⁾

Twelfth Human Niagen Study That Demonstrates Effectiveness:

Another 2022 study assessed the tolerability, safety, and cerebral penetration of NR therapy (1,000mg per day for 30 days) in humans. They also sought to determine if NR has an impact on neurometabolic profiles and on motor function. NR supplementation significantly increased cerebral NAD+ levels and altered metabolic patterns in the brain. Patients experienced a mild but significant clinical improvement that correlated with these pattern changes, with no adverse effects.⁽¹⁶⁾

Thirteenth Human Niagen Study That Demonstrates Effectiveness:

Another study in humans assessed the safety and tolerability of NR at 2,000mg/day for 12 weeks. Exploratory end points included identifying changes in functional capacity and heart function. High-dose NR supplementation was safe and well tolerated, nearly doubled whole-blood NAD+ levels, and increased PBMC mitochondrial respiration.⁽¹⁷⁾

Is NR or NMN better at raising NAD+ levels?

In a 2026 independent peer-reviewed, head-to-head NR vs. NMN study published in iScience, a Cell Press journal, it was found that NR is better at raising NAD+ levels compared to NMN. In this study, healthy human adults, which consisted of the same participants, same dose, and same controlled conditions, had their blood NAD+ levels increase by 161% after 8 days of supplementing with 1,200 mg/day, compared to an increase in blood NAD+ of 67% for NMN at the same dose in the same participants. The researchers of this study were based at the University of Bergen in Norway, conducting the study completely independent of any commercial interest.

Why is NR better at raising NAD+ levels than NMN? One advantage nicotinamide riboside has over NMN is that it can enter cells directly, while NMN cannot because it requires an extra metabolic step. And, because NMN has a higher molecular weight than NR, it provides fewer molar equivalents of the compound for a given mass.

Another study (published in Nature Communications in 2016) on NMN’s metabolism in mammalian cells concluded that NMN cannot directly enter the cell. Simply put, NR enters cells directly; NMN does not.⁽¹⁹⁾

However, a study published in Nature Metabolism in 2019 claimed to have identified a transport protein for NMN in the small intestine of mice.⁽²⁰⁾ But researchers Mark S. Schmidt and Charles Brenner questioned the validity of this claim, stating there is an absence of evidence for this NMN transporter.⁽²¹⁾

NR vs. NMN FAQs

Is NR or NMN better?

Both NR and NMN are NAD+ precursors, and both can contribute to raising NAD+ levels. That said, NR has a clear advantage in several areas. It enters cells directly without needing to be converted first, it’s backed by significantly more human clinical research, and Niagen — the patented form of NR — has earned regulatory authorizations across multiple countries. NMN may still offer benefits, but the weight of the evidence and the quality standards behind Niagen give NR the edge in the NR vs. NMN comparison.

Are NAD+ supplements as effective as NR?

Similarly, NAD+ supplementation provides no advantage over nicotinamide riboside because NAD+ is too large and contains 2 phosphate groups. NAD+ must be broken down into individual components before entering the cell; then, it reforms back into NAD+. For a more comprehensive understanding of how this process works, have a look at this post.

What NAD+ boosting supplements are better quality?

While NMN products may be more ubiquitous in the marketplace, that doesn’t mean all are of good quality. Our R&D team conducted testing on a variety of NMN products ordered via Amazon. Most of them did not even contain NMN, or did not meet their label claims.

Niagen, on the other hand, undergoes rigorous testing, and has an extensive research program behind it.⁽²²⁾ Niagen is a patented form of NR (and we also own the patents), so it’s far more reliable in terms of safety, potency, and consistency. Tru Niagen and Niagen undergo 19 different tests before they are released to the market. And Niagen is manufactured in an ISO-accredited facility under GMP conditions.

The fact that Niagen is the chosen form of NR that many researchers use also attests to its quality. While NMN studies are out there, they aren’t done with a consistent brand or source.

Niagen bears the NSF Certified for Sport seal, but no NMN products do.
Tru Niagen® Pro 1,000mg and Tru Niagen® 300mg Stick Packs, our consumer product that features Niagen, bear the NSF Certified for Sport® seal.

The NSF Certified for Sport seal includes a certification that Tru Niagen is made to current Good Manufacturing Practice (cGMP) standards.⁽²³⁾ It has been tested to confirm that the level of Niagen in the product is consistent with the amount claimed on the label, and that it is absent of over 270 banned substances and harmful contaminants.

Does Niagen have International Regulatory Acceptance as a Top-Quality Supplement?

Yes, Niagen has been:

• Successfully notified to the FDA as a New Dietary Ingredient two times and has been notified to the FDA as Generally Recognized as Safe
• Authorized as a permissible ingredient for use in complementary medicines by the Australian Therapeutic Goods Administration (TGA)
• Authorized as a novel food for use in supplements, foods for special medical purposes, total diet replacement for weight control, and meal replacements for the adult population by the European Commission
• Authorized for use in foods for special medical purposes by Food Standards Australia New Zealand (FSANZ)
• Authorized as a natural health product by Health Canada (Tru Niagen)
• Authorized for use in medical foods by the Brazilian Health Regulatory Agency (ANVISA)
• Authorized for use in dietary supplements by the Ministry of Agriculture and Forestry in Turkey

NMN has gained some regulatory ground. Natural health products with NMN have been authorized for use in Canada, and the FDA now permits NMN to be sold as a dietary supplement in the U.S. after reversing its earlier exclusion. Still, Niagen’s regulatory acceptance is far broader and more established.

Wrapping Up: Why NR Is the Recommended NAD+ Precursor

When you look at the clinical evidence, cellular efficiency, quality standards, and global regulatory acceptance, NR stands out as the preferred NAD+ precursor. Niagen is the most studied form of NR available, backed by 40+ human clinical trials and authorized by regulatory bodies around the world.

NMN is now available as a dietary supplement, and it offers some benefits. But its path to NAD+ is less direct, its research base is smaller, and quality control across NMN products remains inconsistent. When choosing between NR vs. NMN, the evidence favors NR.

If you’re ready to support your NAD+ levels with a precursor you can trust, Tru Niagen delivers Niagen in a convenient daily supplement backed by science and rigorous quality standards. It’s also an excellent complement to other healthy habits that support your circadian rhythm, energy levels, and overall well-being. And for those interested in NAD+ for skin benefits, NR’s ability to raise NAD+ levels may also support skin health at the cellular level.