How is NAD+ an Effective Supplement if it isn’t bioavailable?
When NAD is digested in the stomach, the first step is to NMN.
NMN is digested to NR.
Then, NR to NAM.
So its a silly misconception that NR or NMN better survive digestion. It is simply not possible.
Research is clear now that orally, NAD+, NMN, and NR are ALL almost entirely digested to Nam in digestive system.
More bioavailable delivery methods like sublingual or liposomal are required to get more than 5% to the bloodstream intact.
Once in the bloodstream, NAD+ has several pathways to enter cells intact, or, be metabolized to NMN by the CD73 enzyme that is ubiquitous on the cell membrane, so it restores intracellular NAD+ levels as effectively as NR and NMN.
The advantage of NAD+ itself in the bloodstream is it is very stable. NR is quickly degraded to NAM in the blood, with NMN somewhere in the middle.
So, NAD+ makes a very effective supplement.