Want to know the differences and details of all of the NAD+ precursors?

 

Trp (Tryptophan), NA (Nicotinic Acid), NAM (Nicotinamide), and NR (Nicotinamide Riboside)? They are surprisingly different:

Balancing NAD+ deficits with nicotinamide riboside: therapeutic possibilities and limitations 2022 https://link.springer.com/article/10.1007/s00018-022-04499-5

Nicotinic Acid still looks like the best option to my High School educated brain.