NMN and NAD+

What It Does

Cells can build NAD+ from tryptophan or from nicotinic acid, but most of it is recycled. NAD+-consuming enzymes (sirtuins, PARPs, and CD38) release nicotinamide, which the enzyme NAMPT converts to NMN and then back to NAD+. NR enters the same pathway one step earlier. In aging mice, NAD+ declines in several tissues, partly because CD38 activity rises, and NMN or NR restores it with improvements in metabolism and muscle function. David Sinclair's laboratory at Harvard popularized the idea, and his 2019 book Lifespan brought NMN to a general audience.

Human trials confirm the first step and little else. NR raises whole-blood NAD+ in a dose-dependent way (Trammell 2016). In 30 healthy middle-aged and older adults, 1,000 mg of NR daily for six weeks raised NAD+ by about 60% without significant changes in clinical measures (Martens 2018). In 40 obese men, 2,000 mg daily for 12 weeks did not improve insulin sensitivity or mitochondrial function (Dollerup 2018). For NMN, 250 mg daily for ten weeks improved muscle insulin signaling in 25 prediabetic postmenopausal women but did not change body composition, blood pressure, liver fat, or lipids (Yoshino 2021). MIB-626, a crystalline NMN formulation from a company Sinclair co-founded, raised blood NAD+ and its metabolites over 14 days in 32 middle-aged and older adults in a trial first published in 2022 (Pencina 2023). That trial measured levels, not outcomes.

The one NAD+ precursor with a positive outcome trial is the cheapest. In 386 people with prior skin cancers, nicotinamide 500 mg twice daily for a year reduced new nonmelanoma skin cancers by about a quarter (Chen 2015). That result applies to that population and that endpoint, not to aging.

Forms and Bioavailability

Absorption ratings are broad tiers. Head-to-head human trials rarely support a finer ranking among well-absorbed forms.

NMN and NR both end up partly as nicotinamide before they reach tissues, and whether NMN enters cells intact is disputed. Oral NAD+ itself is largely broken down in the gut. Nicotinamide raises NAD+ through the same salvage pathway at a small fraction of the cost, though at high concentrations it inhibits sirtuins in cell studies and doses of several grams daily have caused liver toxicity. Nicotinic acid (niacin) also raises NAD+ but causes flushing. NMN's legal status as a US supplement ingredient has been contested since 2022, because it was studied as a drug first.

Typical Dosing

Human trials used 250-1,000 mg NMN or 250-2,000 mg NR daily, mostly for 2-12 weeks. These doses raise blood NAD+ metabolites; no dose has been shown to improve a clinical outcome.

What to Look For

If you choose to try a precursor, NR (Niagen) has the most human pharmacokinetic data, and NMN has a little more metabolic data. Doses of 250-1,000 mg daily match the trials. NMN is sold by many small brands; ask for a certificate of analysis from an independent lab.

Do not expect to feel anything. The trials did not find consistent changes in energy, body composition, or performance, and there are no long-term human safety data. Because cancer cells also depend on NAD+, people with a cancer history should discuss these products with their oncologist.

Red flags: sublingual or oral NAD+ sold at a premium, IV NAD+ drips marketed for longevity or addiction without controlled data, and "longevity stacks" that combine precursors with resveratrol. Green flags: a single named precursor, milligrams per serving, and independent purity testing.

Products on Titrate

200 of the 214,745 labels in the NIH Dietary Supplement Label Database list NMN and NAD+ as an active ingredient (144 on market). 121 are sold as NMN and NAD+ products by name.

Top on-market labels, ranked by label completeness and simplicity:

1. NMN BulkSupplements.com · 250 mg as niacinamide
2. NMN BulkSupplements.com · 250 mg as niacinamide
3. NMN BulkSupplements.com · 250 mg as niacinamide
4. NMN (Nicotinamide Mononucleotide) BulkSupplements.com · 250 mg as niacinamide
5. NMN 1 g Nutricost · 1 g as niacinamide

Open supplement search

NMN and NAD+ does not have its own search category yet. Each product above links to its full label in the NIH database.

Related Tools

• Nicotinamide vs Nicotinamide Riboside
• Nicotinamide vs NMN
• Nicotinamide Riboside vs NMN
• Nicotinamide vs Oral NAD+
• Nicotinamide Riboside vs Oral NAD+
• NMN vs Oral NAD+
• All NMN and NAD+ form comparisons
• All supplement guides

References

Chen AC, Martin AJ, Choy B, et al. A phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention. N Engl J Med. 2015;373(17):1618-1626.

Trammell SA, Schmidt MS, Weidemann BJ, et al. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nat Commun. 2016;7:12948.

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(1):1286.

Dollerup OL, Christensen B, Svart M, et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. Am J Clin Nutr. 2018;108(2):343-353.

Yoshino M, Yoshino J, Kayser BD, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547):1224-1229.

Pencina KM, Lavu S, Dos Santos M, et al. MIB-626, an oral formulation of a microcrystalline unique polymorph of beta-nicotinamide mononucleotide, increases circulating nicotinamide adenine dinucleotide and its metabolome in middle-aged and older adults. J Gerontol A Biol Sci Med Sci. 2023;78(1):90-96.