NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) are the two NAD+ precursors that have attracted the most research attention and supplement market interest. They’re often discussed interchangeably — they shouldn’t be. This post covers the precise biochemical and clinical differences. Informational only — not medical advice.*

The NAD+ Biosynthesis Pathways

Understanding the difference between NMN and NR requires understanding where they each sit in the NAD+ biosynthesis network:

• NAD+ is the end product — the coenzyme cells need for energy metabolism and sirtuin function*
• NMN is one step away from NAD+ — converted to NAD+ by NMNAT enzymes (NMN adenylyltransferases)*
• NR is two steps away — converted first to NMN by NRK enzymes (nicotinamide riboside kinases), then to NAD+ by NMNATs*

This means NMN is “closer” to NAD+ in the biosynthetic pathway — but whether this proximity translates to a meaningful bioavailability advantage in humans is an active research question.*

The Absorption Controversy

A significant scientific debate has emerged around how orally supplemented NMN is actually absorbed. Grozio et al. (2019, Nature Metabolism) identified a specific NMN transporter (Slc12a8) in the small intestine of mice, suggesting NMN could be absorbed intact and converted to NAD+ in cells directly.* However, other researchers have challenged whether NMN is absorbed intact in humans or is first broken down to nicotinamide (NAM) in the gut before absorption — which would then be converted through a different pathway.* A 2023 paper by Shats et al. suggested that most orally ingested NMN may be converted to NAM before reaching the bloodstream.*

The practical implication: if NMN is converted to NAM before absorption, the distinction between NMN and NR (which follows a similar NAM-producing metabolic fate) may be less significant than the biosynthetic pathway difference implies.* The human data is still accumulating.*

Human Clinical Evidence: NR vs NMN

NR Clinical Trials

NR has the larger human clinical trial base. Trammell et al. (2016, Nature Communications) demonstrated that oral NR supplementation raises whole-blood NAD+ in humans — the first demonstration of NAD+ elevation with an oral precursor in a clinical trial.* Subsequent trials have examined NR in cardiovascular aging, kidney function, skeletal muscle, and metabolic health.* The overall picture shows consistent NAD+ elevation with favorable safety profiles.*

NMN Clinical Trials

NMN human trials are more recent. Imai et al. (2022, Science) conducted a 10-week trial in older men, finding that NMN supplementation raised muscle NAD+ levels and improved muscle insulin sensitivity — a functional outcome beyond biomarker change.* Yoshino et al. (2021, Science) found NMN improved muscle insulin sensitivity in postmenopausal women with prediabetes.* Safety profiles in both trials were favorable.*

The Current State of the Evidence

Both NMN and NR appear to raise circulating NAD+ in humans.* Neither has established superiority over the other in head-to-head human trials — this comparison hasn’t been formally studied at scale.* The functional outcome data for NMN is promising from recent well-designed trials; NR’s clinical evidence base is broader by virtue of a longer research history.* Both compounds continue to be actively studied.*

Our NMN Cellular Performance is manufactured at our cGMP facility to the same quality standard as our full range. Related: NMN and NAD+: What the Research Explores | Acetyl-L-Carnitine vs L-Carnitine

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Informational only — research citations are for educational purposes. Not medical advice. Consult your healthcare provider before use.