Why is it advantageous to take precursors rather than NAD+ itself?
We don’t believe there is any benefit to taking precursors instead of NAD+ itself. I have long believed that when taken as a supplement or injected, there are some benefits from NAD+ that are not found with NR or NMN. Recent research agrees with this.
It has long been known that NAD+ does not survive digestion in stomach and intestines.
With NR and NMN, it was hoped that they would be more effective at reaching the bloodstream where they can be taken up by cells and converted to NAD+.
But evidence continues to mount that NMN and NR are digested in the stomach, intestines, and liver, with very little escaping into the bloodstream.
Of course, NAD+ is digested to NMN then on to NR and NAM, so they are very similar when taken in a capsule that is not protected from digestion.
By when injected, or taken with an enhanced delivery method like Sublingual, Liposomal, Intranasal, or Transdermal, more will make it intact to the bloodstream.
Once in the bloodstream, elevated NAD+/NADH serves as a signal that increases SIRTUINS like SIRT1, which have a host of benefits such as preventing blindness as shown in this recent study.
This makes perfect sense, as systemic NAD+ levels drop as we age, but are increased with exercise or caloric restriction.
Systemic NAD+/NADH ratio is a master signaling molecule.
Besides serving as a signaling molecule, this recent study shows NAD+ can:
enter cells directly
convert to NMN and then enter cells by slc12a8
be degraded to NR to enter cells, and then be upgraded to NMN by NRk1.
NAD+ supplements are digested to NMN and NR in the stomach, and in the bloodstream. Any NAD+ that makes it intact to the bloodstream has beneficial effects as NAD+ before it is degraded to NMN and NR.