Figure 1: The NAD+ metabolome.
From: Nicotinamide riboside is uniquely and orally bioavailable in mice and humans
NAD+ is synthesized by salvage of the vitamin precursors, NA, Nam and NR, or from tryptophan in the de novo pathway. NAD+ can be reduced to NADH, phosphorylated to NADP+ or consumed to Nam. Nam can also be methylated and oxidized to waste products. NAAD was not thought to be a precursor of NAD+ from NR.
