L-citrulline is an excellent nitrogen donor. The best I know of. Food for improved microcirculation.

Arginine is a cheaper NO donor, but not as specific. But - its still good. the difference is that Citrulline is turned into arginine in the body where THAT arginine will be the easiest to convert to NO. The NO cycle is a complicated and very important interaction.

Citrulline, I think, is far better in disease states for various reasons related to that. As you get healthier, then it might be reasonable to then take more arginine and less citrulline.

Citrulline also tastes much better. You may find you take more of it for that reason. However, its pricey. If you are on a budget you may not be able to afford it as easily as arginine.

Also make sure you are getting enough folic acid (for Bh4)

One place you can read about all that is here:

http://www.ajcn.org/search?fulltext=...it=yes&x=0&y=0

Another is here:
http://www.ncbi.nlm.nih.gov/sites/en...crocirculation