Bryan_S - for you mainly - what do you think of this post, posted in another blog and why:
Do you find taking niacinamide plus ribose as effective as commercial NR?
It's more effective. For NAD+, supplements appear to be effective in the following sequence: nicotinic acid < nicotinamide < NR < nicotinamide + ribose
Note that nicotinamide is the same as niacinamide, and nicotinic acid is the same as niacin.
Nicotinamide + a greater than stoichiometric dose of ribose should be more effective than NR, as NR must be enzymatically broken down into nicotinamide + ribose to be absorbed. Since some ribose will be lost, not all will be recombined, and there is a several hour delay before it reaches its maximum effect for that same reason. Thus the 2 g nicotinamide + 5 g ribose dose I'm using should be equivalent to > 4 g NR.
See the following paper--
Perfused or intact intestine rapidly hydrolyzed NMN to nicotinamide riboside, which accumulated, but was not absorbed. It was slowly cleaved by an enzyme associated with the mucosal cells to nicotinamide, which was the major if not the only labeled compound absorbed.