Oral NAD+ Capsules

Nicotinamide adenine dinucleotide is not absorbed intact in any useful quantity. Extracellular NAD+ is cleaved by surface ectoenzymes to nicotinamide mononucleotide and then to nicotinamide riboside and nicotinamide, and it is those smaller fragments that cells take up.

Why the intact molecule does not arrive

NAD+ is a 663 Da dinucleotide carrying two phosphate groups, so it is large, charged and a poor candidate for passive absorption. More decisively, ectoenzymes including CD38 and CD73 degrade extracellular NAD+ stepwise, and the cell membrane has no established transporter for the intact dinucleotide in mammals. Whatever survives gastric and intestinal conditions is therefore processed to precursors before uptake. Selling the dinucleotide itself is a more expensive route to the same precursors the body would produce anyway.

Why plasma is the wrong readout

Even with a precursor that is genuinely absorbed, plasma concentration is a weak surrogate. The functional pool is intracellular, and the standard way to show a change is whole blood NAD+ measurement or tissue sampling, reported with a validated mass spectrometry method. A rise in plasma nicotinamide after a dose tells you absorption occurred, not that cellular NAD+ increased. Human studies with nicotinamide riboside used whole blood NAD+ as the endpoint for exactly this reason.

Where precursors stand

Nicotinamide riboside and nicotinamide mononucleotide are the two precursors with the most human data, and both have shown increases in blood NAD+ measures in controlled studies. Their regulatory status differs by market and has moved, including an amended FDA position on nicotinamide mononucleotide in dietary supplements following citizen petitions. A formulation program should confirm current status in each target market rather than rely on a general statement. Formulators should also treat nicotinamide mononucleotide as a hygroscopic material, since moisture uptake in a capsule or sachet degrades it during shelf life and will be read as poor delivery when it is actually poor packaging.

What a delivery claim needs

Three elements: a stability-indicating assay showing the precursor survives shelf life, an absorption result for the intact precursor by mass spectrometry, and a whole blood or tissue NAD+ endpoint with a comparator. Anything less is a formulation description, not a delivery claim. Anything less is a formulation description. Where a partner wants a defensible claim, the stability work comes first, because a precursor that decomposes on the shelf cannot be absorbed at any rate.

Key facts

• Extracellular NAD+ is degraded by CD38 and CD73 to nicotinamide mononucleotide, nicotinamide riboside and nicotinamide before cellular uptake (Nikiforov et al. 2011, J Biol Chem 286:21767)
• No established transporter for intact NAD+ across the mammalian plasma membrane has been identified (Nikiforov et al. 2015, Crit Rev Biochem Mol Biol 50:284)
• Oral nicotinamide riboside raised whole blood NAD+ in healthy adults, with whole blood rather than plasma as the endpoint (Trammell et al. 2016, Nat Commun 7:12948)
• FDA amended its position on nicotinamide mononucleotide in dietary supplements following citizen petitions (FDA citizen petition response, 2025)

Building an NAD precursor product? Ask for the stability and endpoint plan.

Related reading

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