Nicotinamide and Sirt1
It is the general belief that nicotinamide inhibits sirt1. However the authors of this paper argue that while NAM is a sirt1 inhibitor at larger concentrations. At 5mM it is an activator.
"In the cells pulsed with 5 mM NAM, cellular NAD+ concentration increased by close to 40% in 12 h, and this increase was maintained throughout the 21 days of the investigation."
"NAM at 5 mM but Not at Higher Concentrations Causes the Activation of SIRT1 and the Decrease of Mitochondrial Content"
"NAM at a 10 or 20 mM dose caused an increase of [NAD+] to the levels almost identical to that in the cells treated with 5 mM NAM but resulted in an inhibition of SIRT1 activity during the early time period."
It seems the sensible thing would be to aim for a body concentration of 5mM. Now how does 5mM NAM invitro convert to an appropriate dosage per kg of bodyweight?