Slc12a8 does not solve the bioavailability problem for NMN Capsules

This research was published in January 2019 that found an enzyme named Slc12a8 that can transport a small quantity of Nicotinamide Mononucleotide (NMN) directly into some cells.

However, this enzyme is only prevalent in the small intestine of older, sicker animals and humans.

The Slc12a8 enzyme was just discovered because it plays a very minor role, and does not transport a large enough quantity of NMN to have been noticed earlier. More about Slc12a8 below.


All NAD+ supplements can restore NAD+ in the Liver but this does not solve NAD+ deficiency throughout the body.

This research shows that ALL NAD+, NMN and NR are metabolized by CD38 in the liver to NAM, and ONLY NAM is excreted to the rest of the body

“orally delivered NR and NMN are converted into NAM before reaching the systemic circulation“

“we found that neither compound was able to enter the circulation intact in substantial quantities when delivered orally“

“IV administration of either compound results in its detection within the circulation, proving that the route of delivery has a profound effect on the ability of these precursors to reach target tissues”

* the above are direct quotes from the research

Quantitative Analysis of NAD Synthesis-Breakdown Fluxes (Liu, 2018)

Providing NAD+ or its immediate precursor, NMN, directly to the bloodstream may be much more effective than dropping large quantities of NAM or NR into the liver and trying to force it to produce more NMN and NAD to the bloodstream.

There is research now being conducted to quantify how much NMN and NAD+ are absorbed by sublingual delivery in humans, but none have yet been published.


Only A Small Quantity of NMN Capsules can sometimes bypass the liver

It has long been noticed that a small quantity of NMN can reach the bloodstream in minutes. The answer on how this happens was revealed in a  study published Jan 2019 that shows the newly identified Slc12a8 protein can transport NMN to NAD+ in the small intestine, avoiding digestion to NAM.

It is not a significant amount

The study  does not publish results showing  HOW MUCH NMN the Slc12a8 enzyme can transport, but all previous studies such as the Liu research  could not find evidence of any NAD+ at all that was created through this pathway.

 According to the authors:

It is important to note that the discovery of an NMN transporter by no means diminishes the importance of uptake via dephosphorylation

It must also be noted that Slc12a8 transporter is most prominent in the small intestine, but does not have a pathway to the rest of the body.  

There is hope Slc12a8 can be useful in future products

Future products may soon hit the market that target this pathway to help solve the bioavailability problem of NMN capsules. According to the study:

“Dr Imai’s lab already has identified small molecules that can stimulate production of the Slc12a8 NMN transporter, applied for patents, and licensed this technology to a company in Japan”

For now though, you can avoid having your NAD+ or NMN get digested by taking it sublingually – more about sublingual delivery –

All of our NAD+and NMN products are designed for sublingual use.

We discontinued selling capsules in 2017 when we found that sublingual delivery was more effective.


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